Chapter 14 Lecture Outline See separate PowerPoint slides for all figures and tables preinserted into PowerPoint without notes. Copyright 2016 McGraw-Hill Education. Permission required for reproduction or display. 1
Nervous System 2
Points to ponder What are the three types of neurons? What are neuroglia? What is the structure of a neuron? What is the myelin sheath? Saltatory conduction? Schwann cell? Node of Ranvier? Explain the resting and action potential as they relate to a nerve impulse. How does the nerve impulse traverse the synapse? What are the two parts of the nervous system? What three things protect the CNS? What are the four parts of the brain and their functions? What is the reticular activating system and the limbic system? What are some higher mental functions of the brain? What are the two parts of the peripheral nervous system? How do abused drugs work? 3
14.1 Overview of the Nervous System The nervous divisions Two divisions Central nervous system (CNS): Brain and spinal cord Peripheral nervous system (PNS): Nerves and ganglia (collections of cell bodies) 4
14.1 Overview of the Nervous System The nervous divisions Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. brain Central Nervous System (CNS) cranial nerves brain spinal cord spinal cord spinal nerves Peripheral Nervous System (PNS) sensory (afferent) nerves carry sensory information into brain and spinal cord motor (efferent) nerves carry motor information from CNS to effectors somatic sensory nerves: signals from skin, muscles, joints, special senses visceral sensory nerves: signals from body organs somatic motor nerves: signals to skeletal muscles, voluntary autonomic motor nerves: signals to smooth muscle, cardiac muscle, glands, involuntary sympathetic division fight or flight parasympathetic division rest and digest a. b. Figure 14.1 The two divisions of the nervous system. 5
14.1 Overview of the Nervous System The nervous system The nervous system allows for communication between cells through sensory input, integration of data, and motor output. Two cell types: neurons and neuroglia 6
14.1 Overview of the Nervous System Expanding on neurons Three types of neurons Sensory takes impulses from sensory receptor to CNS Interneuron receives information in the CNS and sends it to a motor neuron Motor takes impulses from the CNS to an effector (i.e., gland or muscle fiber) 7
14.1 Overview of the Nervous System Expanding on neurons Neuron structure (Ch. 4 review) Cell body main cell where nucleus and most organelles reside Dendrites many short extensions that carry impulses to a cell body Axon (nerve fiber) single, long extension that carries impulses away from the cell body 8
14.1 Overview of the Nervous System Types of neurons Figure 14.2 The structure of sensory neurons, interneurons, and motor neurons. 9
14.1 Overview of the Nervous System The myelin sheath A lipid covering on long axons that acts to increase the speed of nerve impulse conduction, insulation, and regeneration in the PNS Schwann cells neuroglia that make up the myelin sheath in the PNS Nodes of Ranvier gaps between myelination on the axons Saltatory conduction conduction of the nerve impulse from node to node 10
14.1 Overview of the Nervous System Neuron structure Figure 14.2 The structure of sensory neurons, interneurons, and motor neurons. 11
14.1 Overview of the Nervous System The nerve impulse: Resting potential (RP) Resting potential when the axon is not conducting a nerve impulse More positive ions outside than inside the membrane Negative charge of -70 mv inside the axon More Na + outside than inside More K + inside than outside 12
14.1 Overview of the Nervous System The nerve impulse: Resting potential (RP) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. axonal membrane recording electrode inside axon reference electrode outside axon + + + + + + + + + + + + + + + + + + + + inside axon K + Na + gated K + channel outside axon gated Na + channel a. Resting potential: Na + outside the axon, K + and large anions inside the axon. Separation of charges polarizes the cell and causes the resting potential. Figure 14.3a Generation of an action potential. 13
14.1 Overview of the Nervous System The nerve impulse: Action potential Action potential rapid change in the axon membrane that allows a nerve impulse to occur Sodium gates open, letting Na + in. Depolarization occurs. Interior of axon loses negative charge (-55 mv, then +35 mv). 14
14.1 Overview of the Nervous System The nerve impulse: Action potential Potassium gates open, letting K + out. Repolarization occurs. Interior of axon regains negative charge (-70 mv). Wave of depolarization/repolarization travels down the axon. Resting potential is restored by moving potassium inside and sodium outside. 15
14.1 Overview of the Nervous System The nerve impulse: Stimulus causes the axon to reach its threshold Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. + + + + + + + + + + + + direction of signal + + + + + + + + open Na + channel Figure 14.3b Generation of an action potential. b. Stimulus causes the axon to reach its threshold; the axon potential increases from 70 to 55. The action potential has begun. 16
14.1 Overview of the Nervous System The nerve impulse: Action potential Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. + + + + + + + + + + direction of signal + + + + + + + + + + open Na + channel c. Depolarization continues as Na + gates open and Na + moves inside the axon. Figure 14.3c Generation of an action potential. 17
14.1 Overview of the Nervous System The synapse The synapse is a small gap between the sending neuron (presynaptic membrane) and the receiving neuron (postsynaptic membrane). Transmission is accomplished across this gap by a neurotransmitter (e.g., ACh, dopamine, or serotonin). Neurotransmitters are stored in synaptic vesicles in the axon terminals. 18
14.1 Overview of the Nervous System How does transmission across the synapse occur? Nerve impulse reaches the axon terminal. Calcium ions enter the axon terminal and stimulate the synaptic vesicles to fuse with the presynaptic membrane. Neurotransmitters are released and diffuse across the synapse, where they bind with the postsynaptic membrane to inhibit or excite the neuron. 19
14.1 Overview of the Nervous System A synapse and how it functions Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. receiving neuron axon of sending neuron Sending neuron axon terminal Ca 2+ arriving action potential 1. After an action potential arrives at an axon terminal (arrow), Ca 2+ enters, and synaptic vesicles fuse with the plasma membrane of the sending neuron. Synaptic vesicles enclose neurotransmitter. Synapse Receiving neuron Synaptic cleft 2. Neurotransmitter molecules are released and bind to receptors on the membrane of the receiving neuron. neurotransmitter Receiving neuron Figure 14.4 Signal transmission at the synapse. neurotransmitter receptor Na + Receiving neuron ion channel 3. When an excitatory neurotransmitter binds to a receptor, Na + diffuses into the receiving neuron, and an action potential begins. 20
14.1 Overview of the Nervous System Synaptic integration Integration is the summation of the inhibitory and excitatory signals received by a postsynaptic neuron. This occurs because a neuron receives many signals. 21
14.1 Overview of the Nervous System Synaptic integration Figure 14.5 Integration of excitatory and inhibitory signals at the synapse. 22
14.2 The Central Nervous System The central nervous system The CNS consists of the brain and spinal cord. Both are protected by Bones skull and vertebral column Meninges 3 protective membranes that wrap around CNS Cerebral spinal fluid (CSF) space between meninges is filled with this fluid that cushions and protects the CNS 23
14.2 The Central Nervous System The central nervous system Both the brain and spinal cord are made up of two types of nervous tissue. Gray matter contains cell bodies and nonmyelinated fibers White matter contains myelinated axons 24
14.2 The Central Nervous System The CNS: Spinal cord It extends from the base of the brain and along the length of the vertebral canal formed by the vertebrae. The spinal cord functions to provide communication between the brain and most of the body. It is the center for reflex arcs. Gray matter in the center is a butterfly shape. White matter surrounds the gray matter. 25
14.2 The Central Nervous System What does the spinal cord look like? Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. white matter gray matter central canal a. spinal cord vertebra gray matter white matter dorsal root dorsal root ganglion Figure 14.7 The organization of white and gray matter in the spinal cord and the spinal nerves. spinal nerve ventral root vertebra b. central canal dorsal root dorsal gray matter white matter dorsal root branches dorsal root ganglion spinal nerve ventral root ventral dorsal root ganglion cut vertebrae meninges c. d. Dorsal view of spinal cord and dorsal roots of spinal nerves. a: Karl E. Deckart/Phototake; d: The McGraw-Hill Companies, Inc./Rebecca Gray, photographer and Don Kincaid, dissections 26
14.2 The Central Nervous System The CNS: Brain Four major parts 1. Cerebrum 2. Diencephalon 3. Cerebellum 4. Brain stem 27
14.2 The Central Nervous System The CNS: Overview of the brain Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. lateral ventricle third ventricle pineal gland Cerebrum skull meninges corpus callosum Diencephalon thalamus (surrounds the third ventricle) hypothalamus pituitary gland Brain stem midbrain pons medulla oblongata fourth ventricle spinal cord Cerebellum a. Parts of brain b. Cerebral hemispheres Figure 14.8 The human brain. 28
14.2 The Central Nervous System The brain: Cerebrum Cerebral hemispheres Cerebral cortex Primary motor and sensory areas of the cortex Association areas Processing centers Central white matter 29
14.2 The Central Nervous System 1. The brain: Cerebrum The lobes Cerebrum largest portion of the brain Divided into four lobes 1. Frontal lobe: primary motor area and conscious thought 2. Temporal lobe: primary auditory, smell, and speech area 3. Parietal lobe: primary somatosensory and taste area 4. Occipital lobe : primary visual area 30
14.2 The Central Nervous System 1. The brain: Cerebrum The cerebral lobes Frontal lobe primary motor area premotor area motor speech (Broca s) area prefrontal area anterior ventral Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. face hand tongue trunk arm central sulcus leg Parietal lobe primary somatosensory area somatosensory association area primary taste area general interpretation area posterior dorsal primary olfactory area lateral sulcus Temporal lobe Occipital lobe primary visual area visual association area auditory association area primary auditory area sensory speech (Wernicke s) area Figure 14.9 The lobes of the cerebral hemispheres. 31
14.2 The Central Nervous System 1. The brain: Cerebrum The cerebral cortex Cerebral cortex thin, outer layer of gray matter Primary motor area voluntary control of skeletal muscle Primary somatosensory area for sensory information from skeletal muscle and skin Association areas integration occurs here Processing centers perform higher level analytical functions including Wernicke s and Broca s areas, both involved in speech 32
14.2 The Central Nervous System 1. The brain: Cerebrum The cerebral cortex Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. salivation vocalization mastication swallowing facial expression thumb, fingers, and hand forearm arm a. Primary motor area trunk pelvis thigh leg foot and toes longitudinal fissure lips teeth and gums tongue and pharynx upper face hand, fingers, and thumb arm neck trunk pelvis forearm thigh b. Primary somatosensory area leg foot and toes genitals longitudinal fissure Figure 14.10 The primary motor and primary somatosensory areas of the brain. 33
14.2 The Central Nervous System 2. The brain: Diencephalon Includes the Hypothalamus helps maintain homeostasis (hunger, sleep, thirst, body temperature, and water balance) and controls pituitary gland Thalamus Two masses of gray matter that receive all sensory input except smell; involved in memory and emotions Pineal gland secretes melatonin that controls our daily rhythms 34
14.2 The Central Nervous System 2. The brain: Diencephalon Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. lateral ventricle third ventricle pineal gland Cerebrum skull meninges corpus callosum Diencephalon thalamus (surrounds the third ventricle) hypothalamus pituitary gland Brain stem midbrain pons medulla oblongata fourth ventricle spinal cord Cerebellum a. Parts of brain b. Cerebral hemispheres Figure 14.8 The human brain. 35
14.2 The Central Nervous System 3. The brain: Cerebellum Receives and integrates sensory input from the eyes, ears, joints, and muscles about the current position of the body Functions Maintains posture Coordinates voluntary movement Allows learning of new motor skills (i.e., playing the piano or hitting a baseball) 36
14.2 The Central Nervous System 4. The brain: The brain stem Includes Midbrain relay station between the cerebrum and spinal cord or cerebellum; reflex center Pons a bridge between cerebellum and the CNS; regulates breathing rate; reflex center for head movements Medulla oblongata contains reflex centers for regulating breathing, heartbeat, and blood pressure Reticular formation major component of the reticular activating system (RAS) that regulates alertness 37
14.2 The Central Nervous System The reticular formation Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. RAS radiates to cerebral cortex. thalamus reticular formation ascending sensory tracts (touch, pain, temperature) Figure 14.11 The reticular formation of the brain. 38
14.3 The Limbic System and Higher Mental Functions The limbic system It joins primitive emotions (i.e., fear, pleasure) with higher functions such as reasoning. The limbic system can cause strong emotional reactions to situations but conscious thought can override and direct our behavior. Includes Amygdala imparts emotional overtones Hippocampus important to learning and memory 39
14.3 The Limbic System and Higher Mental Functions The limbic system Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. thalamus corpus callosum hypothalamus olfactory bulb olfactory tract Figure 14.12 The regions of the brain associated with the limbic system. amygdala hippocampus 40
14.3 The Limbic System and Higher Mental Functions Higher mental functions Learning what happens when we recall and use past memories Memory ability to hold a thought or to recall past events Short-term memory retention of information for only a few minutes 41
14.3 The Limbic System and Higher Mental Functions Higher mental functions Long-term memory retention of information for more than a few minutes and includes the following Episodic memory people and events Semantic memory numbers and words Skill memory performing skilled motor activities (i.e., riding a bike) Language depends on semantic memory 42
14.3 The Limbic System and Higher Mental Functions What parts of the brain are active in reading and speaking? Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. primary auditory cortex primary motor cortex visual cortex 1. The word is seen in the visual cortex. Wernicke s area 2. Information concerning the word is interpreted in Wernicke s area. Broca s area 3. Information from Wernicke s area is transferred to Broca s area. 4. Information is transferred from Broca s area to the primary motor area. (all): Marcus Raichle Figure 14.13 The areas of the brain involved in reading. 43
14.4 The Peripheral Nervous System The peripheral nervous system (PNS) It includes cranial nerves (12 pairs), spinal nerves (31 pairs), and ganglia outside the CNS. - Spinal nerves conduct impulses to and from the spinal cord. - Cranial nerves conduct impulses to and from the brain. The PNS is divided into two systems. - Somatic division - Autonomic division 44
14.4 The Peripheral Nervous System The peripheral nervous system Figure 14.14 The structure of a nerve. 45
14.4 The Peripheral Nervous System The peripheral nervous system Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cranial Nerves I II III IV V VI from olfactory receptors from retina of eyes to eye muscles to eye muscles from mouth and to jaw muscles to eye muscles VII from taste buds and to facial muscles and glands VIII from inner ear IX XII X XI from pharynx and to pharyngeal muscles to tongue muscles from and to internal organs to neck and back muscles Figure 14.15 The cranial nerves. 46
14.4 The Peripheral Nervous System The PNS: Somatic division The somatic system serves the skin, skeletal muscles and tendons. Automatic responses are called reflexes. 47
14.4 The Peripheral Nervous System The PNS: Somatic division Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pin dorsal root ganglion central canal white matter sensory receptor (in skin) dendrites Dorsal gray matter dorsal horn dendrite of sensory neuron cell body of sensory neuron interneuron dendrites axon of motor neuron cell body of motor neuron effector (muscle) ventral root ventral horn Ventral Figure 14.16 The events in a spinal reflex. 48
14.4 The Peripheral Nervous System The PNS: Autonomic division The autonomic system regulates the activity of involuntary muscles (cardiac and smooth) and glands. 49
14.4 The Peripheral Nervous System The PNS: Autonomic division Two divisions 1. Sympathetic division: coordinates the body for the fight or flight response by speeding up metabolism, heart rate, and breathing while slowing down and regulating other functions. 2. Parasympathetic division: counters the sympathetic system by bringing up a relaxed state by slowing down metabolism, heart rate, and breathing, and returning other functions to normal. 50
14.4 The Peripheral Nervous System The PNS: Autonomic division Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. inhibits tears dilates pupils stimulates tears constricts pupils ganglion Sympathetic Division inhibits salivation Parasympathetic Division stimulates salivation cranial nerves speeds heart slows heart dilates air passages constricts bronchioles vagus nerve cervical nerves stimulates liver to release glucose stimulates adrenal secretion stimulates gallbladder to release bile increases activity of stomach and pancreas thoracic nerves inhibits activity of kidneys, stomach, and pancreas increases intestinal activity decreases intestinal activity Figure 14.17 The two divisions of the autonomic nervous system. lumbar nerves sympathetic ganglia ganglion causes orgasmic contractions inhibits urination stimulates urination causes erection of genitals sacral nerves Acetylcholine is neurotransmitter. Norepinephrine is neurotransmitter. 51
14.5 Drug Therapy and Drug Abuse Drugs and drug abuse Both legal pharmaceuticals and illegal drugs of abuse have certain basic modes of action. They: promote the action of a neurotransmitter. interfere with or decrease the action of a neurotransmitter. replace or mimic a neurotransmitter or neuromodulator. 52
14.5 Drug Therapy and Drug Abuse Drugs and drug abuse Most drug abusers take drugs that affect dopamine and thus artificially affect this reward circuit to the point that they ignore basic physical needs in favor of the drug. Drug abusers tend to show a physiological and psychological effect. Once a person is physically dependent, they usually need more of the drug for the same effect because their body has become tolerant. 53
14.5 Drug Therapy and Drug Abuse Drug abuse: Alcohol Alcohol a depressant directly absorbed from the stomach and small intestine Alcohol is the most socially accepted form of drug use. About 80% of college-aged people drink. Alcohol denatures proteins and causes damage to tissues such as the brain and liver; chronic consumption can damage the frontal lobe. High blood alcohol levels can lead to poor judgment, loss of coordination, or even coma and death. 54
14.5 Drug Therapy and Drug Abuse Drug abuse: Nicotine Nicotine stimulant derived from tobacco plant Nicotine stimulates neurons to release dopamine that reinforces dependence on the drug. It adversely affects a developing embryo or fetus. Smoking increases heart rate and blood pressure. Nicotine causes psychological and physiological dependency. 55
14.5 Drug Therapy and Drug Abuse Drug abuse: Cocaine Cocaine stimulant derived from a shrub Cocaine causes a rush sensation that lasts from 5-30 minutes. A cocaine binge occurs when a user takes the drug at ever-higher doses, resulting in hyperactivity, little desire for food and sleep, and an increased sex drive. There is extreme physical dependence with this drug. Crack is the street name for cocaine that is processed to a free-base form for smoking. 56
14.5 Drug Therapy and Drug Abuse Drug abuse: Methamphetamine Powder form is called speed and crystal form is called meth or ice. It is a stimulant that reverses the effects of fatigue and is a mood elevator. High agitation is common after the rush and can lead to violent behavior. Methamphetamine causes psychological dependency and hallucinations. Ecstasy is the street name for a drug that has the same effects as meth without the hallucinations. 57
14.5 Drug Therapy and Drug Abuse Drug abuse: Heroin Heroin depressant from the sap of the opium poppy plant It leads to a feeling of euphoria and no pain because it is delivered to the brain and converted into morphine. Side effects are nausea, vomiting, and depression of the respiratory and circulatory systems. Heroin use can lead to HIV, hepatitis, and other infections due to shared needles. Extreme dependency is common. 58
14.5 Drug Therapy and Drug Abuse Drug abuse: Marijuana Marijuana psychoactive drug derived from a hemp plant called Cannabis It is most often smoked as a joint. Occasional users experience mild euphoria, alterations to vision and judgment, as well as impaired motor coordination with slurred speech. Heavy users may experience depression, anxiety, hallucinations, paranoia, and psychotic symptoms. Long term use may lead to brain damage. K2 ( Spice ) is a synthetic drug with higher potency than the active chemical in marijuana. 59