The Nervous System. PowerPoint Lecture Slides C H A P T E R 7. Prepared by Patty Bostwick-Taylor, Florence-Darlington Technical College

PowerPoint Lecture Slides Prepared by Patty Bostwick-Taylor, Florence-Darlington Technical College C H A P T E R 7 The Nervous System

NERVOUS SYSTEM OVERVIEW Essential Question: What are the primary functions of the system and how do the microscopic structures help perform the functions?

Figure 7.2

Functions of the Nervous System 1. Sensory input gathering information To monitor changes occurring inside and outside the body Changes = stimuli

Functions of the Nervous System 2. Integration To process and interpret sensory input and decide if action is needed

Functions of the Nervous System 3. Motor output A response to integrated stimuli The response activates muscles or glands

Figure 7.1

Mitochondrion Dendrite Cell body Nissl substance Axon hillock Axon Nucleus Neurofibrils Collateral branch One Schwann cell Axon terminal Node of Ranvier Schwann cells, forming the myelin sheath on axon (a) Figure 7.4a

Neuron cell body Dendrite (b) Figure 7.4b

Nervous Tissue: Neurons Structures of a Typical Motor Neuron 1. Cell body nucleus and metabolic center of the cell 2. Processes fibers that extend from the cell body

Nervous Tissue: Neurons a. Dendrites conduct impulses toward the cell body. Neurons may have hundreds of dendrites b. Axons conduct impulses away from the cell body. Neurons have only one axon arising from the cell body. i. axon hillock connects the cell body with the axon

Nervous Tissue: Neurons ii. Collateral Branch small side branch located in some neurons iii. Axon Terminal the end of the axon, contain vesicles with neurotransmitters, separated from the next neuron by a gap. iv. Synaptic Cleft gap between adjacent neurons

Nervous Tissue: Neurons c. Myelin sheath whitish, fatty material covering axons i. Nodes of Ranvier gaps in myelin sheath along the axon

STRUCTURAL AND FUNCTIONAL CLASSIFICATION OF NEURONS Essential Question: How does the function of the nerve relate to its function?

Dendrites Cell body Axon (a) Multipolar neuron Figure 7.8a

Structural Classification of Neurons Multipolar neurons Structure: many extensions from the cell body Location: All motor and interneurons are multipolar. Most common structure

Cell body Dendrite Axon (b) Bipolar neuron Figure 7.8b

Structural Classification of Neurons Bipolar neurons Structure: one axon and one dendrite Location: special sense organs such as nose and eye, rare in adults

Dendrites Cell body Short single process Peripheral process (c) Unipolar neuron Axon Central process Figure 7.8c

Structural Classification of Neurons Unipolar neurons Structure: have a short single process leaving the cell body Location: Sensory neurons found in PNS ganglia

Functional Classification of Neurons Groups neurons according to the direction the nerve impulse is traveling relative to the CNS.

Dendrites Peripheral process (axon) Ganglion Cell body Central process (axon) Sensory neuron Spinal cord (central nervous system) Peripheral nervous system Afferent transmission Interneuron (association neuron) Receptors Efferent transmission Motor neuron To effectors (muscles and glands) Figure 7.6

Functional Classification of Neurons Sensory Also called afferent neurons Direction of Impulse Carry impulses from the sensory receptors to the CNS Cutaneous sense organs Proprioceptors detect stretch or tension

Functional Classification of Neurons Motor Also called efferent neurons Direction of impulse Carry impulses from the central nervous system to viscera, muscles, or glands

Functional Classification of Neurons Interneurons Also called association neurons Direction of Impulse Found in neural pathways in the central nervous system Connect sensory and motor neurons

Cutaneous Receptors Sensory receptors in the skin Meissner s corpuscle detects touch and is located closer to the surface of the skin Lamellar corpuscle detects deep pressure and is located deep in the skin Figure 7.7b

Proprioceptors Receptors found in muscle and tendon to detect strech Golgi tendon organ Muscle spindle Figure 7.7d

Pain Receptors Bare nerve endings Least specialized cutaneous receptors Most numerous because pain warns us that some type of body damage is occurring or about to occur Figure 7.7a

Figure 7.7e

SUPPORTING CELLS AND PROTECTION Essential Question: How does the structure of the cells or supporting structures contribute to the function?

Nervous Tissue: Support Cells Support cells in the CNS are grouped together as neuroglia General functions Support Insulate Protect neurons

Capillary Neuron Astrocyte (a) Astrocytes are the most abundant and versatile neuroglia. Figure 7.3a

Nervous Tissue: Support Cells Astrocytes Abundant, star-shaped cells Brace neurons Form barrier between capillaries and neurons Control the chemical environment of the brain

Neuron Microglial cell (b) Microglial cells are phagocytes that defend CNS cells. Figure 7.3b

Nervous Tissue: Support Cells Microglia Spiderlike phagocytes Dispose of debris

Fluid-filled cavity Ependymal cells (c) Ependymal cells line cerebrospinal fluid-filled cavities. Brain or spinal cord tissue Figure 7.3c

Nervous Tissue: Support Cells Ependymal cells Line cavities of the brain and spinal cord Cilia assist with circulation of cerebrospinal fluid

Myelin sheath Process of oligodendrocyte Ner ve fibers (d) Oligodendrocytes have processes that form myelin sheaths around CNS ner ve fibers. Figure 7.3d

Nervous Tissue: Support Cells Oligodendrocytes Wrap around nerve fibers in the central nervous system Produce myelin sheaths

Satellite cells Cell body of neuron Schwann cells (forming myelin sheath) Nerve fiber (e) Satellite cells and Schwann cells (which form myelin) surround neurons in the PNS. Figure 7.3e

Nervous Tissue: Support Cells Satellite cells Protect neuron cell bodies Schwann cells Form myelin sheath in the peripheral nervous system

Protection of the Central Nervous System Scalp and skin Skull and vertebral column Meninges Cerebrospinal fluid (CSF) Blood-brain barrier

Superior sagittal sinus Subdural space Subarachnoid space (a) Skin of scalp Periosteum Bone of skull Periosteal Meningeal Dura mater Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) Figure 7.17a

Meninges Dura mater Tough outermost layer Double-layered external covering Folds inward in several areas

Meninges Arachnoid layer Middle layer Web-like extensions span the subarachnoid space Arachnoid villi reabsorb cerebrospinal fluid

Meninges Pia mater Internal layer Clings to the surface of the brain

Occipital lobe Tentorium cerebelli Cerebellum Arachnoid mater over medulla oblongata (b) Skull Scalp Superior sagittal sinus Dura mater Transverse sinus Temporal bone Figure 7.17b

Cerebrospinal Fluid (CSF) Similar to blood plasma composition Formed by the choroid plexus Choroid plexuses capillaries in the ventricles of the brain Forms a watery cushion to protect the brain Circulated in arachnoid space, ventricles, and central canal of the spinal cord

Superior sagittal sinus 4 Arachnoid villus Choroid plexus Corpus callosum Interventricular foramen Third ventricle (c) CSF circulation 3 Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord 1 Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle 1 CSF is produced by the choroid plexus of each ventricle. 2 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. 3 CSF flows through the subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi. Figure 7.18c 2

Blood-Brain Barrier Includes the least permeable capillaries of the body Excludes many potentially harmful substances Useless as a barrier against some substances Fats and fat soluble molecules Respiratory gases Alcohol Nicotine Anesthesia