PowerPoint Lecture Slides prepared by Meg Flemming Austin Community College C H A P T E R 8. The Nervous System Pearson Education, Inc.

Transcription

1 PowerPoint Lecture Slides prepared by Meg Flemming Austin Community College C H A P T E R 8 The Nervous System

2 Chapter 8 Learning Outcomes Describe the anatomical and functional divisions of the nervous system. Distinguish between neurons and neuroglia on the basis of structure and function. Describe the events involved in the generation and propagation of an action potential. Describe the structure of a synapse, and explain the mechanism of nerve impulse transmission at a synapse. Describe the three meningeal layers that surround the central nervous system.

3 Chapter 8 Learning Outcomes Discuss the roles of gray matter and white matter in the spinal cord. Name the major regions of the brain, and describe the locations and functions of each. Name the cranial nerves, relate each pair of cranial nerves to its principal functions, and relate the distribution pattern of spinal nerves to the regions they innervate. Describe the steps in a reflex arc. Identify the principal sensory and motor pathways, and explain how it is possible to distinguish among sensations that originate in different areas of the body.

4 Chapter 8 Learning Outcomes Describe the structures and functions of the sympathetic and parasympathetic divisions of the autonomic nervous system. Summarize the effects of aging on the nervous system. Give examples of interactions between the nervous system and other organ systems.

5 The Nervous System and the Endocrine System (Introduction) The nervous system and endocrine system coordinate other organ systems to maintain homeostasis The nervous system is fast, short acting The endocrine system is slower, but longer lasting The nervous system is the most complex system in the body

6 Functions of the Nervous System (8-1) Monitors the body's internal and external environments Integrates sensory information Coordinates voluntary and involuntary responses

7 Divisions of the Nervous System (8-1) Anatomical divisions are: The central nervous system (CNS) Made up of the brain and spinal cord Integrates and coordinates input and output The peripheral nervous system (PNS) All the neural tissues outside of the CNS The connection between the CNS and the organs

8 Divisions of the Nervous System (8-1) Functional divisions are: The afferent division Includes sensory receptors and neurons that send information to the CNS The efferent division Includes neurons that send information to the effectors, which are the muscles and glands

9 Efferent Division of the Nervous System (8-1) Further divided into: The somatic nervous system (SNS) Controls skeletal muscle The autonomic nervous system (ANS) Controls smooth and cardiac muscle, and glands Has two parts 1. Sympathetic division 2. Parasympathetic division

10 Figure 8-1 A Functional Overview of the Nervous System. CENTRAL NERVOUS SYSTEM Information processing PERIPHERAL NERVOUS SYSTEM Sensory information within afferent division Motor commands within efferent division includes Somatic nervous system Autonomic nervous system ParasympatheticSympathetic division division Receptors Somatic sensory receptors (monitor the outside world and our position in it) Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Effectors Skeletal muscle Smooth muscle Cardiac muscle Glands

11 Checkpoint (8-1) 1. Identify the two anatomical divisions of the nervous system. 2. Identify the two functional divisions of the peripheral nervous system, and describe their primary functions. 3. What would be the effect of damage to the afferent division of the PNS?

12 Neurons (8-2) Cells that communicate with one another and other cells Basic structure of a neuron includes: Cell body Dendrites Which receive signals Axons Which carry signals to the next cell Axon terminals Bulb-shaped endings that form a synapse with the next cell

13 Neurons (8-2) Have a very limited ability to regenerate when damaged or destroyed Cell bodies contain: Mitochondria, free and fixed ribosomes, and rough endoplasmic reticulum Free ribosomes and RER form Nissl bodies and give the tissue a gray color (gray matter) The axon hillock Where electrical signal begins

14 Figure 8-2 The Anatomy of a Representative Neuron. Dendrite Cell body Mitochondrion Golgi apparatus Axon hillock Collateral Axon terminals Nucleus Axon (may be myelinated) Nucleolus Nerve cell body Nucleolus Nissl bodies Nucleus Axon hillock Nissl bodies Nerve cell body LM x 1500

15 Structural Classification of Neurons (8-2) Based on the relationship of the dendrites to the cell body Multipolar neurons Are the most common in the CNS and have two or more dendrites and one axon Unipolar neurons Have the cell body off to one side, most abundant in the afferent division Bipolar neurons Have one dendrite and one axon with the cell body in the middle, and are rare

16 Figure 8-3 A Structural Classification of Neurons. Multipolar neuron Unipolar neuron Bipolar neuron

17 Sensory Neurons (8-2) Also called afferent neurons Total 10 million or more Receive information from sensory receptors Somatic sensory receptors Detect stimuli concerning the outside world, in the form of external receptors And our position in it, in the form of proprioceptors Visceral or internal receptors Monitor the internal organs

18 Motor Neurons (8-2) Also called efferent neurons Total about half a million in number Carry information to peripheral targets called effectors Somatic motor neurons Innervate skeletal muscle Visceral motor neurons Innervate cardiac muscle, smooth muscle, and glands

19 Interneurons (8-2) Also called association neurons By far the most numerous type at about 20 billion Are located in the CNS Function as links between sensory and motor processes Have higher functions Such as memory, planning, and learning

20 Neuroglial Cells (8-2) Are supportive cells and make up about half of all neural tissue Four types are found in the CNS 1. Astrocytes 2. Oligodendrocytes 3. Microglia 4. Ependymal cells Two types in the PNS 1. Satellite cells 2. Schwann cells

21 Astrocytes (8-2) Large and numerous neuroglia in the CNS Maintain the blood brain barrier

22 Oligodendrocytes (8-2) Found in the CNS Produce an insulating membranous wrapping around axons called myelin Small gaps between the wrappings called nodes of Ranvier Myelinated axons constitute the white matter of the CNS Where cell bodies are gray matter Some axons are unmyelinated

23 Microglia (8-2) The smallest and least numerous Phagocytic cells derived from white blood cells Perform essential protective functions such as engulfing pathogens and cellular waste

24 Ependymal Cells (8-2) Line the fluid-filled central canal of the spinal cord and the ventricles of the brain The endothelial lining is called the ependyma It is involved in producing and circulating cerebrospinal fluid around the CNS

25 Figure 8-4 Neuroglia in the CNS. Gray matter White matter CENTRAL CANAL Ependymal cells Gray matter Neurons Myelinated axons Microglial cell White matter Myelin (cut) Axon Node Internode Oligodendrocyte Astrocyte Capillary Basement membrane

26 Neuroglial Cells in PNS (8-2) Satellite cells Surround and support neuron cell bodies Similar in function to the astrocytes in the CNS Schwann cells Cover every axon in PNS The surface is the neurilemma Produce myelin

27 Figure 8-5 Schwann Cells and Peripheral Axons. Nodes Neurilemma Axons Schwann cell nucleus Myelin covering internode Schwann cell nucleus Myelinated axon TEM x 14,048 A myelinated axon in the PNS is covered by several Schwann cells, each of which forms a myelin sheath around a portion of the axon. This arrangement differs from the way myelin forms in the CNS; compare with Figure 8-4. Unmyelinated axon TEM x 14,048 A single Schwann cell can encircle several unmyelinated axons. Every axon in the PNS is completely enclosed by Schwann cells.

28 Organization of the Nervous System (8-2) In the PNS: Collections of nerve cell bodies are ganglia Bundled axons are nerves Including spinal nerves and cranial nerves Can have both sensory and motor components

29 Organization of the Nervous System (8-2) In the CNS: Collections of neuron cell bodies are found in centers, or nuclei Neural cortex is a thick layer of gray matter White matter in the CNS is formed by bundles of axons called tracts, and in the spinal cord, form columns Pathways are either sensory or ascending tracts, or motor or descending tracts

30 Figure 8-6 The Anatomical Organization of the Nervous System. PERIPHERAL NERVOUS SYSTEM GRAY MATTER Ganglia Collections of neuron cell bodies in the PNS WHITE MATTER Nerves Bundles of axons in the PNS RECEPTORS CENTRAL NERVOUS SYSTEM GRAY MATTER ORGANIZATION Neural Cortex Gray matter on the surface of the brain Nuclei Collections of neuron cell bodies in the interior of the CNS Centers Collections of neuron cell bodies in the CNS; each center has specific processing functions Higher Centers The most complex centers in the brain WHITE MATTER ORGANIZATION Tracts Bundles of CNS axons that share a common origin, destination, and function Columns Several tracts that form an anatomically distinct mass EFFECTORS PATHWAYS Centers and tracts that connect the brain with other organs and systems in the body Ascending (sensory) pathway Descending (motor) pathway

31 Checkpoint (8-2) 4. Name the structural components of a typical neuron. 5. Examination of a tissue sample reveals unipolar neurons. Are these more likely to be sensory neurons or motor neurons? 6. Identify the neuroglia of the central nervous system. 7. Which type of glial cell would increase in number in the brain tissue of a person with a CNS infection? 8. In the PNS, neuron cell bodies are located in and surrounded by neuroglial cells called cells.

32 The Membrane Potential (8-3) A membrane potential exists because of: Excessive positive ionic charges on the outside of the cell Excessive negative charges on the inside, creating a polarized membrane An undisturbed cell has a resting membrane potential measured in the inside of the cell in millivolts The resting membrane potential of neurons is 70 mv

33 Factors Determining Membrane Potential (8-3) Extracellular fluid (ECF) is high in Na + and CI Intracellular fluid (ICF) is high in K + and negatively charged proteins (Pr ) Proteins are non-permeating, staying in the ICF Some ion channels are always open Called leak channels Some are open or closed Called gated channels

34 Factors Determining Membrane Potential (8-3) Na + can leak in But the membrane is more permeable to K + Allowing K + to leak out faster Na + /K + exchange pump exchanges 3 Na + for every 2 K + Moving Na + out as fast as it leaks in Cell experiences a net loss of positive ions Resulting in a resting membrane charge of 70 mv

35 Figure 8-7 The Resting Potential Is the Membrane Potential of an Undisturbed Cell. EXTRACELLULAR FLUID mv K + leak channel Na + leak channel Plasma membrane Sodium potassium exchange pump CYTOSOL Protein KEY Sodium ion (Na + ) Protein Protein Potassium ion (K + ) Chloride ion (Cl )

36 Changes in Membrane Potential (8-3) Stimuli alter membrane permeability to Na + or K + Or alter activity of the exchange pump Types include: Cellular exposure to chemicals Mechanical pressure Temperature changes Changes in the ECF ion concentration Result is opening of a gated channel Increasing the movement of ions across the membrane

37 Changes in Membrane Potential (8-3) Opening of Na + channels results in an influx of Na + Moving the membrane toward 0 mv, a shift called depolarization Opening of K + channels results in an efflux of K + Moving the membrane further away from 0 mv, a shift called hyperpolarization Return to resting from depolarization: repolarizing

38 Graded Potentials (8-3) Local changes in the membrane that fade over distance All cells experience graded potentials when stimulated And can result in the activation of smaller cells Graded potentials by themselves cannot trigger activation of large neurons and muscle fibers Referred to as having excitable membranes

39 Action Potentials (8-3) A change in the membrane that travels the entire length of neurons A nerve impulse If a combination of graded potentials causes the membrane to reach a critical point of depolarization, it is called the threshold Then an action potential will occur

40 Action Potentials (8-3) Are all-or-none and will propagate down the length of the neuron From the time the voltage-gated channels open until repolarization is finished: The membrane cannot respond to further stimulation This period of time is the refractory period And limits the rate of response by neurons

41 Membrane potential (mv) Figure 8-8 The Generation of an Action Potential SPOTLIGHT FIGURE 8-8 The Generation of an Action Potential Sodium channels close, voltage-gated potassium channels open, and potassium ions move out of the cell. Repolarization begins. Axon hillock First part of axon to reach threshold D E P O L A R I Z A T I O N Resting potential Threshold 1 A graded depolarization brings an area of excitable membrane to threshold ( 60 mv). 3 R E P O L A R I Z A T I O N Potassium channels close, and both sodium 2 and potassium channels return to their Voltage-gated sodium normal states. channels open and sodium ions move into the cell. The membrane potential 4 rises to +30 mv. REFRACTORY PERIOD During the refractory period, the membrane cannot respond to further stimulation. 0 Time (msec) mv Resting Potential 1 Depolarization to Threshold 60 mv +10 mv 2 Activation of Sodium Channels and Rapid Depolarization 3 Inactivation of Sodium Channels and Activation of Potassium Channels +30 mv 4 Closing of Potassium Channels 90 mv 70 mv Resting Potential Local current The axon membrane contains both voltage-gated sodium channels and voltage-gated potassium channels that are closed when the membrane is at the resting potential. = Sodium ion = Potassium ion The stimulus that begins an action potential is a graded depolarization large enough to open voltage-gated sodium channels. The opening of the channels occurs at a membrane potential known as the threshold. When the voltage-gated sodium channels open, sodium ions rush into the cytoplasm, and rapid depolarization occurs. The inner membrane surface now contains more positive ions than negative ones, and the membrane potential has changed from 60 mv to a positive value. As the membrane potential approaches +30 mv, voltage-gated sodium channels close. This step coincides with the opening of voltagegated potassium channels. Positively charged potassium ions move out of the cytosol, shifting the membrane potential back toward resting levels. Repolarization now begins. The voltage-gated sodium channels remain inactivated until the membrane has repolarized to near threshold levels. The voltage-gated potassium channels begin closing as the membrane reaches the normal resting potential (about 70 mv). Until all have closed, potassium ions continue to leave the cell. This produces a brief hyperpolarization. As the voltage-gated potassium channels close, the membrane potential returns to normal resting levels. The action potential is now over, and the membrane is once again at the resting potential.

42 Figure 8-8 The Generation of an Action Potential Sodium channels close, voltagegated potassium channels open, and potassium ions move out of the cell. Repolarization begins D E P O L A R I Z AT I O N 3 R E P O L A R I Z AT I O N 40 Resting potential 60 Threshold 70 1 A graded depolarization brings an area of excitable membrane to threshold ( 60 mv). 2 Voltage-gated sodium channels open and sodium ions move into the cell. The membrane potential rises to +30 mv. Potassium channels close, and both sodium and potassium channels return to their normal states. REFRACTORY PERIOD During the refractory period, the membrane cannot respond to further stimulation. 4 0 Time (msec) 1 2

43 Figure 8-8 The Generation of an Action Potential Resting Potential 70 mv Depolarization to Threshold Activation of Sodium Channels and Rapid Depolarization 60 mv +10 mv The axon membrane contains both voltage-gated sodium channels and voltage-gated potassium channels that are closed when the membrane is at the resting potential. = Sodium ion = Potassium ion Local current The stimulus that begins an action potential is a graded depolarization large enough to open voltage-gated sodium channels. The opening of the channels occurs at a membrane potential known as the threshold. When the voltage-gated sodium channels open, sodium ions rush into the cytoplasm, and rapid depolarization occurs. The inner membrane surface now contains more positive ions than negative ones, and the membrane potential has changed from 60 mv to a positive value.

44 Figure 8-8 The Generation of an Action Potential Inactivation of Sodium Channels and Activation of Potassium Channels +30 mv Closing of Potassium Channels 90 mv 70 mv Resting Potential As the membrane potential approaches +30 mv, voltage-gated sodium channels close. This step coincides with the opening of voltagegated potassium channels. Positively charged potassium ions move out of the cytosol, shifting the membrane potential back toward resting levels. Repolarization now begins. The voltage-gated sodium channels remain inactivated until the membrane has repolarized to near threshold levels. The voltage-gated potassium channels begin closing as the membrane reaches the normal resting potential (about 70 mv). Until all have closed, potassium ions continue to leave the cell. This produces a brief hyperpolarization. As the voltage-gated potassium channels close, the membrane potential returns to normal resting levels. The action potential is now over, and the membrane is once again at the resting potential.

45 Propagation of an Action Potential (8-3) Occurs when local changes in the membrane in one site: Result in the activation of voltage-gated channels in the next adjacent site of the membrane This causes a wave of membrane potential changes Continuous propagation Occurs in unmyelinated fibers and is relatively slow Saltatory propagation Is in myelinated axons and is faster

46 Figure 8-9 The Propagation of Action Potentials over Unmyelinated and Myelinated Axons. Action potential propagation along an unmyelinated axon Action potential propagation along a myelinated axon Stimulus depolarizes membrane to threshold EXTRACELLULAR FLUID Stimulus depolarizes membrane to threshold EXTRACELLULAR FLUID Myelinated Myelinated Myelinated Internode Internode Internode Plasma membrane CYTOSOL Plasma membrane CYTOSOL Myelinated Myelinated Myelinated Internode Internode Internode Local current Repolarization (refractory period) Myelinated Myelinated Myelinated Internode Internode Internode Local current Repolarization (refractory period)

47 Checkpoint (8-3) 9. What effect would a chemical that blocks the voltage-gated sodium channels in a neuron's plasma membrane have on the neuron's ability to depolarize? 10. What effect would decreasing the concentration of extracellular potassium have on the membrane potential of a neuron? 11. List the steps involved in the generation and propagation of an action potential. 12. Two axons are tested for propagation velocities. One carries action potentials at 50 meters per second, the other at 1 meter per second. Which axon is myelinated?

48 The Synapse (8-4) A junction between a neuron and another cell Occurs because of chemical messengers called neurotransmitters Communication happens in one direction only Between a neuron and another cell type is a neuroeffector junction Such as the neuromuscular junction or neuroglandular junction

49 A Synapse between Two Neurons (8-4) Occurs: Between the axon terminals of the presynaptic neuron Across the synaptic cleft To the dendrite or cell body of the postsynaptic neuron Neurotransmitters Stored in vesicles of the axon terminals Released into the cleft and bind to receptors on the postsynaptic membrane PLAY ANIMATION Neurophysiology: Synapse

50 Figure 8-10 The Structure of a Typical Synapse. Axon of presynaptic cell Axon terminal Mitochondrion Synaptic vesicles Presynaptic membrane Postsynaptic membrane Synaptic cleft

51 The Neurotransmitter ACh (8-4) Activates cholinergic synapses in four steps 1. Action potential arrives at the axon terminal 2. ACh is released and diffuses across synaptic cleft 3. ACh binds to receptors and triggers depolarization of the postsynaptic membrane 4. ACh is removed by AChE (acetylcholinesterase)

52 Figure 8-11 The Events at a Cholinergic Synapse. An action potential arrives and depolarizes the axon terminal Presynaptic neuron Synaptic vesicles Action potential EXTRACELLULAR FLUID Axon terminal AChE POSTSYNAPTIC NEURON Extracellular Ca 2+ enters the axon terminal, triggering the exocytosis of ACh ACh Ca 2+ Ca 2+ Synaptic cleft Chemically regulated sodium ion channels

53 Figure 8-11 The Events at a Cholinergic Synapse. ACh binds to receptors and depolarizes the postsynaptic membrane Initiation of action potential if threshold is reached ACh is removed by AChE Propagation of action potential (if generated)

54 Table 8-1 The Sequence of Events at a Typical Cholinergic Synapse

55 Other Important Neurotransmitters (8-4) Norepinephrine (NE) In the brain and part of the ANS, is found in adrenergic synapses Dopamine, GABA, and serotonin Are CNS neurotransmitters At least 50 less-understood neurotransmitters NO and CO Are gases that act as neurotransmitters

56 Excitatory vs. Inhibitory Synapses (8-4) Usually, ACh and NE trigger depolarization An excitatory response With the potential of reaching threshold Usually, dopamine, GABA, and serotonin trigger hyperpolarization An inhibitory response Making it farther from threshold

57 Neuronal Pools (8-4) Multiple presynaptic neurons can synapse with one postsynaptic neuron If they all release excitatory neurotransmitters: Then an action potential can be triggered If they all release an inhibitory neurotransmitter: Then no action potential can occur If half release excitatory and half inhibitory neurotransmitters: They cancel, resulting in no action

58 Neuronal Pools (8-4) A term that describes the complex grouping of neural pathways or circuits Divergence Is a pathway that spreads information from one neuron to multiple neurons Convergence Is when several neurons synapse with a single postsynaptic neuron

59 Figure 8-12 Two Common Types of Neuronal Pools. Divergence A mechanism for spreading stimulation to multiple neurons or neuronal pools in the CNS Convergence A mechanism for providing input to a single neuron from multiple sources

60 Checkpoint (8-4) 13. Describe the general structure of a synapse. 14. What effect would blocking calcium channels at a cholinergic synapse have on synapse function? 15. What type of neural circuit permits both conscious and subconscious control of the same motor neurons?

61 The Meninges (8-5) The neural tissue in the CNS is protected by three layers of specialized membranes 1. Dura mater 2. Arachnoid 3. Pia mater

62 The Dura Mater (8-5) Is the outer, very tough covering The dura mater has two layers, with the outer layer fused to the periosteum of the skull Dural folds contain large veins, the dural sinuses In the spinal cord the dura mater is separated from the bone by the epidural space

63 The Arachnoid Is separated from the dura mater by the subdural space That contains a little lymphatic fluid Below the epithelial layer is arachnoid space Created by a web of collagen fibers Contains cerebrospinal fluid

64 The Pia Mater Is the innermost layer Firmly bound to the neural tissue underneath Highly vascularized Providing needed oxygen and nutrients

65 Checkpoint (8-5) 16. Identify the three meninges surrounding the CNS.

66 Spinal Cord Structure (8-6) The major neural pathway between the brain and the PNS Can also act as an integrator in the spinal reflexes Involving the 31 pairs of spinal nerves Consistent in diameter except for the cervical enlargement and lumbar enlargement Where numerous nerves supply upper and lower limbs

67 Spinal Cord Structure (8-6) Central canal A narrow passage containing cerebrospinal fluid Surface of the spinal cord is indented by the: Posterior median sulcus Deeper anterior median fissure

68 31 Spinal Segments (8-6) Identified by a letter and number relating to the nearby vertebrae Each has a pair of dorsal root ganglia Containing the cell bodies of sensory neurons with axons in dorsal root Ventral roots contain motor neuron axons Roots are contained in one spinal nerve

69 Figure 8-14a Gross Anatomy of the Spinal Cord. Cervical spinal nerves Thoracic spinal nerves Lumbar spinal nerves C 1 C 2 C 3 C 4 C 5 C 6 C 7 C 8 T 1 T 2 T 3 T 4 T 5 T 6 T 7 T 8 T 9 T 10 T 11 T 12 L 1 L 2 L 3 L 4 L 5 Cervical enlargement Posterior median sulcus Lumbar enlargement Inferior tip of spinal cord Cauda equina Sacral spinal nerves Coccygeal nerve (Co 1 ) S 1 S 2 S 3 S 4 S 5 In this superficial view of the adult spinal cord, the designations to the left identify the spiral nerves.

70 Figure 8-14b Gross Anatomy of the Spinal Cord. Dorsal root Dorsal root ganglion Posterior median sulcus Central canal Spinal nerve Ventral root White matter Gray matter Anterior median fissure C 3 This cross section through the cervical region of the spinal cord shows some prominent features and the arrangement of gray matter and

71 Sectional Anatomy of the Spinal Cord (8-6) The central gray matter is made up of glial cells and nerve cell bodies Projections of gray matter are called horns Which extend out into the white matter White matter is myelinated and unmyelinated axons The location of cell bodies in specific nuclei of the gray matter relate to their function

72 Sectional Anatomy of the Spinal Cord (8-6) Posterior gray horns are somatic and visceral sensory nuclei Lateral gray horns are visceral (ANS) motor nuclei The anterior gray horns are somatic motor nuclei White matter can be organized into three columns Which contain either ascending tracts to the brain, or descending tracts from the brain to the PNS

73 Figure 8-15 Sectional Anatomy of the Spinal Cord. Dorsal root ganglion Lateral white column Posterior gray horn Lateral gray horn Anterior gray horn Posterior white column Posterior median sulcus Posterior gray commissure Somatic Visceral Visceral Somatic Functional Organization of Gray Matter The cell bodies of neurons in the gray matter of the spinal cord are organized into functional groups called nuclei. Sensory nuclei Motor nuclei Ventral root Anterior gray commissure Anterior white column Anterior white commissure Anterior median fissure The left half of this sectional view shows important anatomical landmarks, including the three columns of white matter. The right half indicates the functional organization of the nuclei in the anterior, lateral, and posterior gray horns. Posterior gray commissure Dura mater Arachnoid mater (broken) Central canal Anterior gray commissure Anterior median fissure Pia mater POSTERIOR ANTERIOR Posterior median sulcus Dorsal root Structural Organization of Gray Matter The projections of gray matter toward the outer surface of the spinal cord are called horns. Posterior gray horn Lateral gray horn Anterior gray horn Dorsal root ganglion Ventral root A micrograph of a section through the spinal cord, showing major landmarks in and surrounding the cord.

74 Figure 8-15a Sectional Anatomy of the Spinal Cord. Dorsal root ganglion Lateral white column Posterior gray horn Lateral gray horn Anterior gray horn Posterior white column Posterior median sulcus Posterior gray commissure Somatic Visceral Visceral Somatic Functional Organization of Gray Matter The cell bodies of neurons in the gray matter of the spinal cord are organized into functional groups called nuclei. Sensory nuclei Motor nuclei Ventral root Anterior gray commissure Anterior white column Anterior white commissure Anterior median fissure The left half of this sectional view shows important anatomical landmarks, including the three columns of white matter. The right half indicates the functional organization of the nuclei in the anterior, lateral, and posterior gray horns.

75 Figure 8-15b Sectional Anatomy of the Spinal Cord. Posterior gray commissure Dura mater Arachnoid mater (broken) Central canal Anterior gray commissure Anterior median fissure Pia mater POSTERIOR ANTERIOR Posterior median sulcus Dorsal root Structural Organization of Gray Matter The projections of gray matter toward the outer surface of the spinal cord are called horns. Posterior gray horn Lateral gray horn Anterior gray horn Dorsal root ganglion Ventral root A micrograph of a section through the spinal cord, showing major landmarks in and surrounding the cord.

76 Checkpoint (8-6) 17. Damage to which root of a spinal nerve would interfere with motor function? 18. A person with polio has lost the use of his leg muscles. In which areas of his spinal cord could you locate virus-infected neurons? 19. Why are spinal nerves also called mixed nerves?

77 Six Major Regions of the Brain (8-7) 1. The cerebrum 2. The diencephalon 3. The midbrain 4. The pons 5. The medulla oblongata 6. The cerebellum

78 Major Structures of the Brain (8-7) The cerebrum Is divided into paired cerebral hemispheres Deep to the cerebrum is the diencephalon Which is divided into the thalamus, the hypothalamus, and the epithalamus The brain stem Contains the midbrain, pons, and medulla oblongata The cerebellum Is the most inferior/posterior part

79 Figure 8-16a The Brain. Longitudinal fissure A N T E R I O R Cerebral veins and arteries below arachnoid mater Superior view Right cerebral hemisphere Left cerebral hemisphere CEREBELLUM P O S T E R I O R CEREBRUM

80 Figure 8-16b The Brain. Central sulcus Precentral gyrus Frontal lobe of left cerebral hemisphere Postcentral gyrus Parietal lobe Lateral sulcus Occipital lobe Temporal lobe PONS Lateral view CEREBELLUM MEDULLA OBLONGATA

81 Figure 8-16c The Brain. Corpus callosum Precentral gyrus Fornix Frontal lobe Central sulcus Optic chiasm Mamillary body Temporal lobe MIDBRAIN Brain stem PONS MEDULLA OBLONGATA Postcentral gyrus Sagittal section Thalamus Hypothalamus Pineal gland (part of epithalamus) Parieto-occipital sulcus CEREBELLUM DIENCEPHALON

82 The Ventricles of the Brain (8-7) Filled with cerebrospinal fluid and lined with ependymal cells The two lateral ventricles within each cerebral hemisphere drain through the: Interventricular foramen into the: Third ventricle in the diencephalon, which drains through the cerebral aqueduct into the: Fourth ventricle, which drains into the central canal

83 Figure 8-17 The Ventricles of the Brain. Cerebral hemispheres Ventricles of the Brain Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Cerebral hemispheres Pons Medulla oblongata Spinal cord Central canal A lateral view of the ventricles Fourth ventricle Central canal Cerebellum An anterior view of the ventricles

84 Cerebrospinal Fluid (8-7) CSF Surrounds and bathes the exposed surfaces of the CNS Floats the brain Transports nutrients, chemicals, and wastes Is produced by the choroid plexus Continually secreted and replaced three times per day Circulation from the fourth ventricle into the subarachnoid space into the dural sinuses

85 Figure 8-18a The Formation and Circulation of Cerebrospinal Fluid. Extension of choroid plexus into lateral ventricle Arachnoid granulations Choroid plexus of third ventricle Cerebral aqueduct Lateral aperture Choroid plexus of fourth ventricle Median aperture Arachnoid mater Subarachnoid space Dura mater Superior sagittal sinus Central canal Spinal cord A sagittal section of the CNS. Cerebrospinal fluid, formed in the choroid plexus, circulates along the routes indicated by the red arrows.

86 Figure 8-18b The Formation and Circulation of Cerebrospinal Fluid. Superior sagittal sinus Cranium Dura mater (outer layer) Arachnoid granulation Fluid movement Cerebral cortex The relationship of the arachnoid granulations and dura mater. Pia mater Dura mater (inner layer) Subdural space Arachnoid mater Subarachnoid space

87 The Cerebrum (8-7) Contains an outer gray matter called the cerebral cortex Deep gray matter in the cerebral nuclei and white matter of myelinated axons beneath the cortex and around the nuclei The surface of the cerebrum Folds into gyri Separated by depressions called sulci or deeper grooves called fissures

88 The Cerebral Hemispheres (8-7) Are separated by the longitudinal fissure The central sulcus Extends laterally from the longitudinal fissure The frontal lobe Is anterior to the central sulcus Is bordered inferiorly by the lateral sulcus

89 The Cerebral Hemispheres (8-7) The temporal lobe Inferior to the lateral sulcus Overlaps the insula The parietal lobe Extends between the central sulcus and the parietooccipital sulcus

90 The Cerebral Hemispheres (8-7) The occipital lobe Located most posteriorly The lobes are named for the cranial bone above it Each lobe has sensory regions and motor regions Each hemisphere sends and receives information from the opposite side of the body

91 Motor and Sensory Areas of the Cortex (8-7) Are divided by the central sulcus The precentral gyrus of the frontal lobe Contains the primary motor cortex The postcentral gyrus of the parietal lobe Contains the primary sensory cortex

92 Motor and Sensory Areas of Cortex (8-7) The visual cortex is in the occipital lobe The gustatory, auditory, and olfactory cortexes are in the temporal lobe

93 Association Areas (8-7) Interpret incoming information Coordinate a motor response, integrating the sensory and motor cortexes The somatic sensory association area Helps to recognize touch The somatic motor association area Is responsible for coordinating movement

94 Figure 8-19 The Surface of the Cerebral Hemispheres. Primary motor cortex (precentral gyrus) Somatic motor association area (premotor cortex) FRONTAL LOBE Prefrontal cortex Gustatory cortex Insula Lateral sulcus Olfactory cortex Central sulcus TEMPORAL LOBE Primary sensory cortex (postcentral gyrus) PARIETAL LOBE Somatic sensory association area Visual association area OCCIPITAL LOBE Visual cortex Auditory association area Auditory cortex

95 Cortical Connections (8-7) Regions of the cortex are linked by the deeper white matter The left and right hemispheres are linked across the corpus callosum Other axons link the cortex with: The diencephalon, brain stem, cerebellum, and spinal cord

96 Higher-Order Centers (8-7) Integrative areas, usually only in the left hemisphere The general interpretive area or Wernicke's area Integrates sensory information to form visual and auditory memory The speech center or Broca's area Regulates breathing and vocalization, the motor skills needed for speaking

97 The Prefrontal Cortex (8-7) In the frontal lobe Coordinates information from the entire cortex Skills such as: Predicting time lines Making judgments Feelings such as: Frustration, tension, and anxiety

98 Hemispheric Lateralization (8-7) The concept that different brain functions can and do occur on one side of the brain The left hemisphere tends to be involved in language skills, analytical tasks, and logic The right hemisphere tends to be involved in analyzing sensory input and relating it to the body, as well as analyzing emotional content

99 Figure 8-20 Hemispheric Lateralization. LEFT HAND RIGHT HAND Prefrontal cortex Prefrontal cortex Speech center C O RP Anterior commissure Writing Auditory cortex (right ear) General interpretive center (language and mathematical calculation) U S C AL L O SU M Analysis by touch Auditory cortex (left ear) Spatial visualization and analysis Visual cortex (right visual field) LEFT HEMISPHERE RIGHT HEMISPHERE Visual cortex (left visual field)

100 The Electroencephalogram (8-7) EEG A printed record of brain wave activity Can be interpreted to diagnose brain disorders More modern techniques Brain imaging, using the PET scan and MRIs, has allowed extensive "mapping" of the brain's functional areas

101 Figure 8-21 Brain Waves. Patient being wired for EEG monitoring Alpha waves are characteristic of normal resting adults Beta waves typically accompany intense concentration Theta waves are seen in children and in frustrated adults Delta waves occur in deep sleep and in certain pathological conditions Seconds

102 Memory (8-7) Fact memory The recall of bits of information Skill memory Learned motor skill that can become incorporated into unconscious memory Short-term memory Doesn't last long unless rehearsed Converting into long-term memory through memory consolidation Long-term memory Remains for long periods, sometimes an entire lifetime Amnesia Memory loss as a result of disease or trauma

103 The Basal Nuclei (8-7) Masses of gray matter Caudate nucleus Lies anterior to the lentiform nucleus Which contains the medial globus pallidus and the lateral putamen Inferior to the caudate and lentiform nuclei is the amygdaloid body or amygdala Basal nuclei Subconscious control of skeletal muscle tone

104 Figure 8-22 The Basal Nuclei. Head of caudate nucleus Amygdaloid body Lentiform nucleus Thalamus Tail of caudate nucleus Head of caudate nucleus Lateral view of a transparent brain, showing the relative positions of the basal nuclei Corpus callosum Lateral ventricle Insula Lentiform nucleus Putamen Amygdaloid Globus pallidus body Frontal section Tip of lateral ventricle

105 The Limbic System (8-7) Includes the olfactory cortex, basal nuclei, gyri, and tracts between the cerebrum and diencephalon A functional grouping, rather than an anatomical one Establishes the emotional states Links the conscious with the unconscious Aids in long-term memory with help of the hippocampus

106 Figure 8-23 The Limbic System. Cingulate gyrus Corpus callosum Thalamic nuclei Hypothalamic nuclei Olfactory tract Amygdaloid body Hippocampus Fornix Mamillary body

107 The Diencephalon (8-7) Contains switching and relay centers Centers integrate conscious and unconscious sensory information and motor commands Surround third ventricle Three components 1. Epithalamus 2. Thalamus 3. Hypothalamus

108 The Epithalamus (8-7) Lies superior to the third ventricle and forms the roof of the diencephalon The anterior part contains choroid plexus The posterior part contains the pineal gland that is endocrine and secretes melatonin

109 The Thalamus (8-7) The left and right thalamus are separated by the third ventricle The final relay point for sensory information Only a small part of this input is sent on to the primary sensory cortex

110 The Hypothalamus (8-7) Lies inferior to the third ventricle The subconscious control of skeletal muscle contractions is associated with strong emotion Adjusts the pons and medulla functions Coordinates the nervous and endocrine systems

111 The Hypothalamus (8-7) Secretes hormones Produces sensations of thirst and hunger Coordinates voluntary and ANS function Regulates body temperature Coordinates daily cycles

112 The Midbrain (8-7) Contains various nuclei Two pairs involved in visual and auditory processing, the colliculi Contains motor nuclei for cranial nerves III and IV Cerebral peduncles contain descending fibers Reticular formation is a network of nuclei related to the state of wakefulness The substantia nigra influence muscle tone

113 The Pons (8-7) Links the cerebellum with the midbrain, diencephalon, cerebrum, and spinal cord Contains sensory and motor nuclei for cranial nerves V, VI, VII, and VIII Other nuclei influence rate and depth of respiration

114 The Cerebellum (8-7) An automatic processing center Which adjusts postural muscles to maintain balance Programs and fine-tunes movements The cerebellar peduncles Are tracts that link the cerebral cortex, basal nuclei, and brain stem Ataxia Is disturbance of coordination Can be caused by damage to the cerebellum

115 The Medulla Oblongata (8-7) Connects the brain with the spinal cord Contains sensory and motor nuclei for cranial nerves VIII, IX, X, XI, and XII Contains reflex centers Cardiovascular centers Adjust heart rate and arteriolar diameter Respiratory rhythmicity centers Regulate respiratory rate

116 Figure 8-24a The Diencephalon and Brain Stem. Cerebral peduncle Optic tract Cranial nerves N II N III N IV N V N VI N VII N VIII N IX N X N XI N XII Pons Spinal nerve C 1 Spinal nerve C 2 Thalamus Diencephalon Thalamic nuclei Midbrain Superior colliculus Inferior colliculus Cerebellar peduncles Medulla oblongata Spinal cord Lateral view

117 Figure 8-24b The Diencephalon and Brain Stem. N IV Choroid plexus Thalamus Third ventricle Pineal gland Corpora quadrigemina Superior colliculi Inferior colliculi Cerebral peduncle Cerebellar peduncles Choroid plexus in roof of fourth ventricle Dorsal roots of spinal nerves C 1 and C 2 Posterior view

118 Checkpoint (8-7) 20. Describe one major function of each of the six regions of the brain. 21. The pituitary gland links the nervous and endocrine systems. To which portion of the diencephalon is it attached? 22. How would decreased diffusion across the arachnoid granulations affect the volume of cerebrospinal fluid in the ventricles? 23. Mary suffers a head injury that damages her primary motor cortex. Where is this area located?

119 Checkpoint (8-7) 24. What senses would be affected by damage to the temporal lobes of the cerebrum? 25. The thalamus acts as a relay point for all but what type of sensory information? 26. Changes in body temperature stimulate which area of the diencephalon? 27. The medulla oblongata is one of the smallest sections of the brain. Why can damage to it cause death, whereas similar damage in the cerebrum might go unnoticed?

120 Peripheral Nervous System (8-8) Links the CNS to the rest of the body through peripheral nerves They include the cranial nerves and the spinal nerves The cell bodies of sensory and motor neurons are contained in the ganglia

121 The Cranial Nerves (8-8) 12 pairs, noted as Roman numerals I through XII Some are: Only motor pathways Only sensory pathways Mixed having both sensory and motor neurons Often remembered with a mnemonic "Oh, Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly"

122 The Cranial Nerves (8-8) The olfactory nerves (N I) Are connected to the cerebrum Carry information concerning the sense of smell The optic nerves (N II) Carry visual information from the eyes, through the optic foramina of the orbits to the optic chiasm Continue as the optic tracts to the nuclei of the thalamus

123 The Cranial Nerves (8-8) The oculomotor nerves (N III) Motor only, arising in the midbrain Innervate four of six extrinsic eye muscles and the intrinsic eye muscles that control the size of the pupil The trochlear nerves (N IV) Smallest, also arise in the midbrain Innervate the superior oblique extrinsic muscles of the eyes

124 The Cranial Nerves (8-8) The trigeminal nerves (N V) Have nuclei in the pons, are the largest cranial nerves Have three branches 1. The ophthalmic From the orbit, sinuses, nasal cavity, skin of forehead, nose, and eyes 2. The maxillary From the lower eyelid, upper lip, cheek, nose, upper gums, and teeth 3. The mandibular From salivary glands and tongue

125 The Cranial Nerves (8-8) The abducens nerves (N VI) Innervate only the lateral rectus extrinsic eye muscle, with the nucleus in the pons The facial nerves (N VII) Mixed, and emerge from the pons Sensory fibers monitor proprioception in the face Motor fibers provide facial expressions; control tear and salivary glands

126 The Cranial Nerves (8-8) The vestibulocochlear nerves (N VIII) Respond to sensory receptors in the inner ear There are two components 1. The vestibular nerve Conveys information about balance and position 2. The cochlear nerve Responds to sound waves for the sense of hearing Their nuclei are in the pons and medulla oblongata

127 The Cranial Nerves (8-8) The glossopharyngeal nerves (N IX) Mixed nerves innervating the tongue and pharynx Their nuclei are in the medulla oblongata The sensory portion monitors taste on the posterior third of the tongue and monitors BP and blood gases The motor portion controls pharyngeal muscles used in swallowing, and fibers to salivary glands

128 The Cranial Nerves (8-8) The vagus nerves (N X) Have sensory input vital to autonomic control of the viscera Motor control includes the soft palate, pharynx, and esophagus Are a major pathway for ANS output to cardiac muscle, smooth muscle, and digestive glands

129 The Cranial Nerves (8-8) The accessory nerves (N XI) Have fibers that originate in the medulla oblongata Also in the lateral gray horns of the first five cervical segments of the spinal cord The hypoglossal nerves (N XII) Provide voluntary motor control over the tongue

130 Figure 8-25 The Cranial Nerves. Olfactory bulb, termination of olfactory nerve (I) Mamillary body Basilar artery Pons Vertebral artery Cerebellum Medulla oblongata Inferior view of the brain Spinal cord Olfactory tract Optic chiasm Optic nerve (II) Infundibulum Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Hypoglossal nerve (XII) Accessory nerve (XI) Diagrammatic view showing the attachment of the 12 pairs of cranial nerves

131 Table 8-2 The Cranial Nerves

132 The Spinal Nerves (8-8) Found in 31 pairs grouped according to the region of the vertebral column 8 pairs of cervical nerves, C 1 C 8 12 pairs of thoracic nerves, T 1 T 12 5 pairs of lumbar nerves, L 1 L 5 5 pairs of sacral nerves, S 1 S 5 1 pair of coccygeal nerves, Co 1

133 Nerve Plexuses (8-8) The origin of major nerve trunks of the PNS The cervical plexus Innervates the muscles of the head and neck and the diaphragm The brachial plexus Innervates the shoulder girdle and upper limb The lumbar plexus and the sacral plexus Innervate the pelvic girdle and lower limb

134 Figure 8-26 Peripheral Nerves and Nerve Plexuses. Cervical plexus Brachial plexus Lumbar plexus Sacral plexus C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T 11 T 12 L1 L2 L3 L4 L5 S1 S2 S3 S4 S5 Co 1 Phrenic nerve (extends to the diaphragm) Femoral nerve Obturator nerve Gluteal nerves Axillary nerve Musculocutaneous nerve Radial nerve Ulnar nerve Median nerve Saphenous nerve Sciatic nerve

135 Dermatome (8-8) A clinically important area monitored by a specific spinal nerve

136 Figure 8-27 Dermatomes. C 2 C 3 N V C 2 C 3 C 3 C 3 C 4 T 2 C 6 L 1 T 2 C C 4 5 T T 3 1 T T 4 2 T T 5 3 T T 6 4 T 7 T 5 T 8 T 6 T 9 T 2 T T 7 10 T T 11 8 T T 12 9 L 1 T 10 L 2 T 11 L L 3 4L5 T 12 C 5 C 6 C 7 T 1 C 8 L 2 S 2 S 4 S 3 C 7 T 1 L 3 L 4 L 1 L 2 S 2 S 1 L 5 S 5 C 8 L 5 L 3 S 1 L 4 ANTERIOR POSTERIOR

137 Table 8-3 Nerve Plexuses and Major Nerves

138 Checkpoint (8-8) 28. What signs would you associate with damage to the abducens nerve (N VI)? 29. John is having trouble moving his tongue. His physician tells him it is due to pressure on a cranial nerve. Which cranial nerve is involved? 30. Injury to which nerve plexus would interfere with the ability to breathe?

139 Reflexes (8-9) Rapid, automatic, unlearned motor response to a stimulus Usually removes or opposes the original stimulus Monosynaptic reflexes For example, the stretch reflex Which responds to muscle spindles, is the simplest with only one synapse The best known stretch reflex is probably the knee jerk reflex

140 Simple Reflexes (8-9) Are wired in a reflex arc A stimulus activates a sensory receptor An action potential travels down an afferent neuron Information processing occurs with the interneuron An action potential travels down an efferent neuron The effector organ responds

141 Figure 8-28 The Components of a Reflex Arc. Arrival of stimulus and activation of receptor Activation of a sensory neuron Dorsal root Sensation relayed to the brain by axon collaterals Stimulus Response by effector Effector Receptor REFLEX ARC Ventral root Activation of a motor neuron Information processing in the CNS KEY Sensory neuron (stimulated) Excitatory interneuron Motor neuron (stimulated)

142 Figure 8-29 A Stretch Reflex. Stretching of muscle tendon stimulates muscle spindles Stretch Muscle spindle (stretch receptor) REFLEX ARC Spinal Cord Contraction Activation of motor neuron produces reflex muscle contraction

143 Complex Reflexes (8-9) Polysynaptic reflexes With at least one interneuron Are slower than monosynaptic reflexes, but can activate more than one effector Withdrawal reflexes Like the flexor reflex, move a body part away from the stimulation Like touching a hot stove Reciprocal inhibition Blocks the flexor's antagonist To ensure that flexion is in no way interfered with

144 Figure 8-30 The Flexor Reflex, a Type of Withdrawal Reflex. Distribution within gray horns to other segments of the spinal cord Painful stimulus Flexors stimulated Extensors inhibited KEY Sensory neuron (stimulated) Excitatory interneuron Motor neuron (stimulated) Motor neuron (inhibited) Inhibitory interneuron

145 Input to Modify Reflexes (8-9) Reflexes are automatic, but higher brain centers can influence or modify them The Babinski sign Triggered by stroking an infant's sole, resulting in a fanning of the toes As descending inhibitory synapses develop, an adult will respond by curling the toes instead, called the plantar reflex

146 Checkpoint (8-9) 31. Define reflex. 32. Which common reflex do physicians use to test the general condition of the spinal cord, peripheral nerves, and muscles? 33. Why can polysynaptic reflexes produce more involved responses than can monosynaptic reflexes? 34. After injuring his back lifting a sofa, Tom exhibits a positive Babinski reflex. What does this imply about Tom's injury?

147 Sensory Pathways (8-10) Are ascending pathways Posterior column pathway Spinothalamic pathway Spinocerebellar pathway A sensory homunculus A mapping of the area of the cortex dedicated to the number of sensory receptors, not the size of the body area

148 Figure 8-31 The Posterior Column Pathway. Sensory homunculus of left cerebral hemisphere KEY Axon of firstorder neuron Second-order neuron Third-order neuron Nucleus in medulla oblongata Nuclei in thalamus MIDBRAIN MEDULLA OBLONGATA SPINAL CORD Dorsal root ganglion Fine-touch, pressure, vibration, and proprioception sensations from right side of body

149 Motor Pathways (8-10) Are descending pathways Corticospinal pathway Also called pyramidal system Medial and lateral pathways Also called extrapyramidal system A motor homunculus Represents the distribution of somatic and ANS motor innervation

150 Figure 8-32 The Corticospinal Pathway. KEY Axon of upper motor neuron Lower motor neuron Motor homunculus on primary motor cortex of left cerebral hemisphere To skeletal muscles To skeletal muscles Motor nuclei of cranial nerves Motor nuclei of cranial nerves MIDBRAIN MEDULLA OBLONGATA Lateral corticospinal tract To skeletal muscles Anterior corticospinal tract SPINAL CORD Motor neuron in anterior gray horn

151 Table 8-4 Sensory and Motor Pathways

152 Checkpoint (8-10) 35. As a result of pressure on her spinal cord, Jill cannot feel touch or pressure on her legs. What sensory pathway is being compressed? 36. The primary motor cortex of the right cerebral hemisphere controls motor function on which side of the body? 37. An injury to the superior portion of the motor cortex would affect the ability to control muscles of which parts of the body?

153 The Autonomic Nervous System (8-11) Unconscious adjustment of homeostatically essential visceral responses Sympathetic division Parasympathetic division The somatic NS and ANS are anatomically different SNS: one neuron to skeletal muscle ANS: two neurons to cardiac and smooth muscle, glands, and fat cells

154 Two Neuron Pathways of the ANS (8-11) Preganglionic neuron Has cell body in spinal cord, synapses at the ganglion with the postganglionic neuron In sympathetic division Preganglionic fibers are short Postganglionic fibers are long In parasympathetic division Preganglionic fibers are long Postganglionic fibers are "short"

155 Figure 8-33 The Organization of the Somatic and Autonomic Nervous Systems. Upper motor neurons in Primary motor cortex Visceral motor nuclei in hypothalamus Somatic motor nuclei of brain stem Skeletal muscle Lower motor neurons BRAIN SPINAL CORD Preganglionic neuron Smooth muscle Glands Cardiac muscle Visceral Effectors Autonomic ganglia Ganglionic neurons BRAIN Autonomic nuclei in brain stem SPINAL CORD Skeletal muscle Somatic motor nuclei of spinal cord Adipocytes Preganglionic neuron Autonomic nuclei in spinal cord Somatic nervous system Autonomic nervous system

156 Neurotransmitters at Specific Synapses (8-11) All synapses between pre- and postganglionic fibers: Are cholinergic (ACh) and excitatory Postganglionic parasympathetic synapses Are cholinergic Some are excitatory, some inhibitory, depending on the receptor Most postganglionic sympathetic synapses: Are adrenergic (NE) and usually excitatory

157 The Sympathetic Division (8-11) Sympathetic chain Arises from spinal segments T 1 L 2 The preganglionic fibers enter the sympathetic chain ganglia just outside the spinal column Collateral ganglia are unpaired ganglia that receive splanchnic nerves from the lower thoracic and upper lumbar segments Postganglionic neurons innervate abdominopelvic cavity

158 The Sympathetic Division (8-11) The adrenal medullae Are innervated by preganglionic fibers Are modified neural tissue that secrete E and NE into capillaries, functioning like an endocrine gland The effect is nearly identical to that of the sympathetic postganglionic stimulation of adrenergic synapses

159 Figure 8-34 The Sympathetic Division. PONS Eye Salivary glands Cervical sympathetic ganglia Spinal nerves Postganglionic fibers to spinal nerves (innervating skin, blood vessels, sweat glands, arrector pili muscles, adipose tissue) Sympathetic chain ganglia KEY Preganglionic neurons Ganglionic neurons T 1 T 1 L 2 L 2 Spinal cord Splanchnic nerve Collateral ganglion Uterus Splanchnic nerves Ovary Sympathetic nerves Cardiac and pulmonary plexuses Collateral ganglion Collateral ganglion Penis Scrotum Heart Lung Liver and gallbladder Stomach Spleen Pancreas Large intestine Small intestine Adrenal medulla Kidney Urinary bladder

160 The Sympathetic Division (8-11) Also called the "fight-or-flight" division Effects Increase in alertness, metabolic rate, sweating, heart rate, blood flow to skeletal muscle Dilates the respiratory bronchioles and the pupils Blood flow to the digestive organs is decreased E and NE from the adrenal medullae support and prolong the effect

161 The Parasympathetic Division (8-11) Preganglionic neurons arise from the brain stem and sacral spinal cord Include cranial nerves III, VII, IX, and X, the vagus, a major parasympathetic nerve Ganglia very close to or within the target organ Preganglionic fibers of the sacral areas form the pelvic nerves

162 The Parasympathetic Division (8-11) Less divergence than in the sympathetic division, so effects are more localized Also called "rest-and digest" division Effects Constriction of the pupils, increase in digestive secretions, increase in digestive tract smooth muscle activity Stimulates urination and defecation Constricts bronchioles, decreases heart rate

163 Figure 8-35 The Parasympathetic Division. PONS Terminal ganglion N III Terminal ganglion N VII Terminal ganglion N IX N X (Vagus) Terminal ganglion Lacrimal gland Eye Salivary glands Heart Cardiac and pulmonary plexuses Lungs Pelvic nerves Liver and gallbladder Stomach Spleen Pancreas Large intestine Small intestine Rectum Spinal cord S 2 S 3 Kidney S 4 KEY Preganglionic neurons Ganglionic neurons Uterus Ovary Penis Scrotum Urinary bladder

164 Dual Innervation (8-11) Refers to both divisions affecting the same organs Mostly have antagonistic effects Some organs are innervated by only one division

165 Table 8-5 The Effects of the Sympathetic and Parasympathetic Divisions of the ANS on Various Body Structures (1 of 2)

166 Table 8-5 The Effects of the Sympathetic and Parasympathetic Divisions of the ANS on Various Body Structures (2 of 2)

167 Checkpoint (8-11) 38. While out for a brisk walk, Megan is suddenly confronted by an angry dog. Which division of the ANS is responsible for the physiological changes that occur as she turns and runs from the animal? 39. Why is the parasympathetic division of the ANS sometimes referred to as the anabolic system? 40. What effect would loss of sympathetic stimulation have on the flow of air into the lungs? 41. What physiological changes would you expect in a patient who is about to undergo a root canal procedure and is quite anxious about it?

168 Aging and the Nervous System (8-12) Common changes Reduction in brain size and weight and reduction in number of neurons Reduction in blood flow to the brain Change in synaptic organization of the brain Increase in intracellular deposits and extracellular plaques Senility can be a result of all these changes

169 Checkpoint (8-12) 42. What is the major cause of age-related shrinkage of the brain?

170 Reproductive (Page 671) Urinary (Page 637) Digestive (Page 572) Respiratory (Page 532) Lymphatic (Page 500) Cardiovascular (Page 467) Endocrine (Page 376) Muscular Muscular (Page 241) Skeletal Skeletal (Page 188) Integumentary Integumentary (Page 138) Figure 8-36 SYSTEM INTEGRATOR Body System Nervous System Nervous System Body System Provides sensations of touch, pressure, pain, vibration, and temperature; hair provides some protection and insulation for skull and brain; protects peripheral nerves Controls contraction of arrector pili muscles and secretion of sweat glands Provides calcium for neural function; protects brain and spinal cord Controls skeletal muscle contractions that results in bone thickening and maintenance and determine bone position Facial muscles express emotional state; intrinsic laryngeal muscles permit communication; muscle spindles provide proprioceptive sensations Controls skeletal muscle contractions; coordinates respiratory and cardiovascular activities The NERVOUS System The nervous system is closely integrated with other body systems. Every moment of your life, billions of neurons in your nervous system are exchanging information across trillions of synapses and performing the most complex integrative functions in the body. As part of this process, the nervous system monitors all other systems and issues commands that adjust their activities. However, the impact of these commands varies greatly from one system to another. The normal functions of the muscular system, for example, simply cannot be performed without instructions from the nervous system. By contrast, the cardiovascular system is relatively independent the nervous system merely coordinates and adjusts cardiovascular activities to meet the circulatory demands of other systems. In the final analysis, the nervous system is like the conductor of an orchestra, directing the rhythm and balancing the performances of each section to produce a symphony, instead of simply a very loud noise.