G nervous system
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  • What are the two principal divisions of the nervous system? The central nervous system and the peripheral nervous system
  • What are the two types of cells found in the nervous system? Neurons, or nerve cells, and glia, specialized connective tissue cellsWhat is the direction of neural transmission from sensory neurons and motor neurons? Sensory neurons transmit impulses TO the spinal cord and brain; motor neurons transmit impulses AWAY from the brain and spinal cord.What are interneurons? Interneurons conduct impulses from sensory neurons to motor neurons. Also called central or connecting neurons.
  • What is the function of glia cells? Glia cells (Greek for glue) hold the functioning neurons together, protect them, and regulate neuron function.How are the three types of glia different? (1)Astrocytes are relatively large, star-shaped cells that attach to neurons and small blood vessels to hold these structures close to each other. (2) Microglia usually remain stationary but in inflammation or degeneration of the brain, they enlarge, move about, and act as microbe-eating scavengers. (3) Oligodendrocytes help hold nerve fibers together and also produce the fatty myelin sheath.What is myelin? Myelin is a white, fatty substance.
  • Where is myelin produced in the central nervous system? In oligodendrocytes.Where is myelin produced in the peripheral nervous system? In Schwann cells.How might symptoms differ according to where myelin production is being impaired? Symptoms will depend on the nerve affected as well as the area of the nerve affected.
  • What is white matter composed of ? Nerve fibers usually have a myelin sheath and myelin is white.What is gray matter composed of ? Tissue composed of cell bodies and unmyelinated axons and dendrites is called gray matter because of its characteristic gray appearance.
  • Ask students to describe the coverings that surround an axon.
  • What is the difference between a neuron pathway and a reflex arc? A reflex arc is the simplest type of neuron pathway.What is a two-neuron arc? The simplest type of reflex arc consisting of only two types of neurons: sensory neurons and motor neurons.What is a three-neuron arc? It consists of three different types of neurons: sensory neurons, motor neurons, and interneurons.What is an effector, and how does it relate to the reflex arc?
  • Where does impulse conduction originate? It normally starts in receptors, the beginnings of dendrites of sensory neurons.The end of the sensory neuron’s axon synapses first with an interneuron before chemical signals are sent across a second synapse, resulting in conduction through the motor neuron. For example, application of an irritating stimulus to the skin of the thigh initiates a three-neuron reflex response that causes contraction of muscles to pull the leg away from the irritant.What are some types of stimuli that initiate nerve impulses? Pressure, temperature, chemical changes
  • What are the three structures that make up a synapse? A synaptic knob, a neurotransmitter, and a synaptic cleftHow does a nerve impulse travel from one neuron to another? Through a synapse via a neurotransmitterAsk students to draw a schematic diagram correctly charting the following structures and chemicals: axon terminal, synaptic knob, presynaptic neuron, postsynaptic neuron, neurotransmitter, synaptic cleft, plasma membrane, receptor molecules.
  • What is a neurotransmitter and how many are there? Neurotransmitters are chemicals by which neurons communicate. At least 30 different compounds have been identified as neurotransmitters.Name some of the neurotransmitters. Acetylcholine, norepinephrine, dopamine, serotonin, catecholaminesAcetylcholine is released at some of the synapses in the spinal cord and at neuromuscular junctions.Norepinephrine, dopamine, and serotonin belong to a group of compounds called catecholamines, which may play a role in sleep, motor function, mood, and pleasure recognition.Two morphine-like neurotransmitters called endorphins and enkephalins are natural painkillers.
  • What are the three main parts of the brainstem? The medulla oblongata, pons, and midbrainStructure—white matter with bits of gray matter scattered through it.What is the function of the brainstem? It functions as a two-way conduction pathway. Many important reflex centers (cardiac, respiratory, and vasomotor centers – “vital centers”) are located in the brainstem.
  • What is the structure of the hypothalamus? One of the most important brain structures. Lies below thalamus.What is the function of the hypothalamus? Manufactures hormones, part of the mechanism for maintaining body temperature, involved in regulation of water balance, involved in sleep cycle, involved in control of appetite and many emotions of pleasure, fear, anger, sexual arousal, and pain.
  • What is the structure of the thalamus? Dumbbell-shaped section of gray matter above the hypothalamus. What is the function of the thalamus? (1) Helps produce sensations – relays impulses to the cerebral cortex from sense organs; (2) associates sensations with emotions; (3) plays a part in the arousal or alerting mechanism
  • What is the lay term for CVA? StrokeHow would you describe hemiplegia, paraplegia, triplegia, quadriplegia, and spastic paralysis? Hemiplegia – spastic paralysis of one side of the body; paraplegia – paralysis of both legs; triplegia – paralysis of both legs and one arm; quadriplegia – paralysis of all four extremities; paralysis – inability to initiate voluntary contractions, may be accompanied by involuntary contractions of affected muscles.What is an EEG? An electroencephalogram is a graphic representation of brain activity.
  • Typically, how long is the spinal cord? About 17 to 18 inches long.Distinguish between the spinal cord and the spinal column. The spinal cord lies inside the spinal column in the spinal cavity.Tracts are functional organizations: all axons composing one tract serve a general function.Other ascending tracts transmit sensations of touch and pressure to the brain.
  • Nerve tissue needs to be protected, so the brain and spinal cord are surrounded by a tough, fluid-containing membrane called the meninges.The meninges are surrounded by bone. The spinal meninges form a tubelike covering around the spinal cord and line the bony vertebral foramen of the vertebrae that surround the cord.What are the three layers of the spinal meninges? Dura mater – tough outer layer that lines the vertebral canal; arachnoid mater – membrane between the dura and pia mater; pia mater – innermost membrane covering the spinal cord.
  • What are some of the structures included in the peripheral nervous system? Includes cranial and spinal nerves that connect the brain and spinal cord, respectively, to peripheral structures such as the skin surface and the skeletal muscles.Other structures in the autonomic nervous system are considered part of the peripheral nervous system; they connect the brain and spinal cord to various glands in the body and to the cardiac and smooth muscles in the thorax and abdomen.
  • What is the causative agent for herpes zoster? Varicella zosterWhat childhood disease has a patient contracted to be susceptible to herpes zoster? ChickenpoxWhat is a dermatome? Skin surface areas supplied by a single spinal nerve.
  • Motor nerves that control the voluntary actions of skeletal muscles are sometimes called the somatic nervous system.What are the two divisions of the autonomic nervous system (ANS)? Sympathetic nervous system, parasympathetic nervous systemSpinal nerves conduct impulses between the spinal cord and parts of the body not supplied by cranial nerves.Spinal nerves function to make possible sensations and movements.
  • What are autonomic effectors? Tissues to which autonomic neurons conduct impulses—cardiac and smooth muscle and glandular epithelial tissue.Autonomic paths to visceral effectors consist of two-neuron relays. Impulses travel over preganglionic neurons from the spinal cord or brainstem to autonomic ganglia. There they are relayed across synapses to postganglionic neurons, which then conduct the impulses from the ganglia to visceral effectors.In contrast, somatic motor neurons conduct all the way from the spinal cord or brainstem to somatic effectors with no intervening synapses.
  • What are the two divisions of the autonomic nervous system (ANS)? Sympathetic and parasympathetic; see Figure 9-26.What is the structure of the sympathetic nervous system? Also referred to as the “thoracolumbar system,” it leaves the spinal cord in the anterior (ventral) root of a spinal nerve, enters the spinal nerve, but soon leaves it to extend to and through a sympathetic ganglion and terminate in a collateral ganglion where it synapses with several postganglionic neurons whose axons extend to terminate in visceral effectors.
  • What are the functions of the sympathetic nervous system? It functions as an emergency system. It takes control of many internal organs when we exercise strenuously and when strong emotions are elicited. It other words, it functions during stress. See Table 9-3.What physiological changes are associated with the fight-or-flight response? Heart beats faster, blood vessels constrict causing blood pressure to increase, blood vessels in muscle dilate delivering more blood to the muscles, sweat glands and adrenal glands secrete more abundantly, salivary and other digestive glands secrete more sparingly, peristalsis becomes sluggish, and we are ready for “flight or flight.”The sympathetic nervous system controls visceral effectors during strenuous exercise and strong emotions (such as anger, fear, hate, or anxiety).
  • Where are the dendrite and cell bodies of the sympathetic preganglionic neurons located? In the parasympathetic nervous system in the spinal cord and brainstem.
  • What are the functions of the parasympathetic nervous system, and how do they differ from the functions of the sympathetic nervous system? It dominates control of many visceral effectors during normal, everyday conditions. Impulses tend to slow heartbeat, increase peristalsis, and increase secretion of digestive juices and insulin. See Table 9-3.
  • What are neurotransmitters? Chemicals that continue a nervous impulse through a synapse.Ask students to offer examples of neurotransmitters associated with the ANS, including the division of the ANS associated with each neurotransmitter.Three axons—the sympathetic preganglionic axon, the parasympathetic preganglionic axon, and the parasympathetic postganglionic axon—release acetylcholine. These axons are classified as cholinergic fibers.Only one type of autonomic axon releases the neurotransmitter norepinephrine; this is the axon of a sympathetic postganglionic neuron, and such neurons are classified as adrenergic fibers.What determines the nature of an organ’s response to stimulation by the autonomic nervous system? Cholinergic and adrenergic fibers
  • What are examples of stress-induced diseases? Heart disease, ulcers, colitis, autoimmune disorders, and a depressed immune system resulting in infections, colds, etc.Stress can oversecrete gastric hydrochloric acid.

Transcript

  • 1. The Nervous SystemMosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 2. Objectives• List the organs and divisions of the nervous system and describe the generalized functions of the system as a whole• Identify the major types of cells in the nervous system and discuss the function of each• Identify the anatomical and functional components of a three-neuron reflex arc. Compare and contrast the propagation of a nerve impulse along a nerve fiber and across a synaptic cleft. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 3. Objectives• Identify the major anatomical components of the brain and spinal cord and briefly comment on the function of each• Identify and discuss the coverings and fluid spaces of the brain and spinal cord• Compare and contrast spinal and cranial nerves• Discuss the structure and function of the two divisions of the autonomic nervous system• Describe major nervous system disorders Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 4. Organs and Divisions of the Nervous System• Central nervous system (CNS)—brain and spinal cord• Peripheral nervous system (PNS)—all nerves• Autonomic nervous system (ANS) Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 5. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 6. Cells of the Nervous System• Neurons – Consist of three parts • Cell body of neuron—main part • Dendrites—branching projections that conduct impulses to cell body of neuron • Axon—elongated projection that conducts impulses away from cell body of neuron Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 7. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 8. Cells of the Nervous System• Neurons – Neurons classified according to function or direction of impulse • Sensory neurons: conduct impulses to the spinal cord and brain; also called afferent neurons • Motor neurons: conduct impulses away from brain and spinal cord to muscles and glands; also called efferent neurons • Interneurons: conduct impulses from sensory neurons to motor neurons; also called central or connecting neurons Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 9. Cells of the Nervous System• Glia (neuroglia) – Support cells, bringing the cells of nervous tissue together structurally and functionally – Three main types of connective tissue cells of the CNS • Astrocytes—star-shaped cells that anchor small blood vessels to neurons • Microglia—small cells that move in inflamed brain tissue carrying on phagocytosis • Oligodendrocytes—form myelin sheaths on axons in the CNS (Schwann cells form myelin sheaths in PNS only) Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 10. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 11. Cells of the Nervous System• Disorders of nervous tissue – Multiple sclerosis—characterized by myelin loss in central nerve fibers and resulting conduction impairments – Tumors • General name for nervous system tumors is neuroma • Most neuromas are gliomas, glial tumors • Multiple neurofibromatosis—characterized by numerous benign tumors Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 12. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 13. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 14. Nerves• Nerve—bundle of peripheral axons – Tract—bundle of central axons – White matter—brain or cord tissue composed primarily of myelinated axons (tracts) – Gray matter—brain or cord tissue composed primarily of cell bodies and unmyelinated fibers Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 15. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 16. Nerves• Nerve coverings—fibrous connective tissue – Endoneurium—surrounds individual fibers within a nerve – Perineurium—surrounds a group (fascicle) of nerve fibers – Epineurium—surrounds the entire nerve Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 17. Reflex Arcs• Nerve impulses are conducted from receptors to effectors over neuron pathways or reflex arcs; conduction by a reflex arc results in a reflex (i.e., contraction by a muscle or secretion by a gland)• The simplest reflex arcs are two-neuron arcs— consisting of sensory neurons synapsing in the spinal cord with motor neurons; three-neuron arcs consist of sensory neurons synapsing in the spinal cord with interneurons that synapse with motor neurons Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 18. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 19. Nerve Impulses• Definition—self-propagating wave of electrical disturbance that travels along the surface of a neuron membrane; sometimes called action potentials Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 20. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 21. Nerve Impulses• Mechanism – At rest, the neuron’s membrane is slightly positive on the outside—polarized—from a slight excess of Na+ on the outside – A stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 22. Nerve Impulses• Mechanism – Inward movement of Na+ depolarizes the membrane by making the inside more positive than the outside at the stimulated point; this depolarization is a nerve impulse (action potential) – The stimulated section of membrane immediately repolarizes, but by that time the depolarization has already triggered the next section of membrane to depolarize, thus propagating a wave of electrical disturbances (depolarizations) all the way down the membrane Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 23. The Synapse• Definition—the place where impulses are transmitted from one neuron to another (the postsynaptic neuron)• Synapse made of three structures—synaptic knob, synaptic cleft, and plasma membrane• Neurotransmitters bind to specific receptor molecules in the membrane of a postsynaptic neuron, opening ion channels and thereby stimulating impulse conduction by the membrane Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 24. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 25. The Synapse• Names of neurotransmitters—acetylcholine, catecholamines (norepinephrine, dopamine, and serotonin), endorphins, enkephalins, nitric oxide (NO), and other compounds• Parkinson disease (PD)—characterized by abnormally low levels of dopamine in motor control areas of the brain; patients usually exhibit involuntary trembling and muscle rigidity Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 26. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 27. Central Nervous System• Divisions of the brain – Brainstem • Consists of three parts, named in ascending order: medulla oblongata, pons, and midbrain • Structure—white matter with bits of gray matter scattered through it Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 28. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 29. Central Nervous System• Divisions of the brain – Brainstem • Functions – All three parts of brainstem are two-way conduction paths – Sensory tracts in the brainstem conduct impulses to the higher parts of the brain – Motor tracts conduct from the higher parts of the brain to the spinal cord – Many important reflex centers lie in the brainstem Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 30. Central Nervous System– Diencephalon • Structure and function of the hypothalamus – Consists mainly of the posterior pituitary gland, pituitary stalk, and gray matter – Acts as the major center for controlling the ANS; therefore, helps control the functioning of most internal organs – Controls hormone secretion by anterior and posterior pituitary glands; therefore, it indirectly helps control hormone secretion by most other endocrine glands – Contains centers for controlling appetite, wakefulness, pleasure, etc. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 31. Central Nervous System• Structure and function of the thalamus – Dumbbell-shaped mass of gray matter extending into each cerebral hemisphere – Relays sensory impulses to cerebral cortex sensory areas – In some way produces the emotions of pleasantness or unpleasantness associated with sensationsMosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 32. Central Nervous System– Cerebellum • Second largest part of the human brain • Helps control muscle contractions to produce coordinated movements so that we can maintain balance, move smoothly, and sustain normal postures • Recent evidence shows the coordinating effects of the cerebellum may be more extensive, also assisting the cerebrum and other regions of the brain Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 33. Central Nervous System– Cerebrum • Largest part of the human brain • Outer layer of gray matter is the cerebral cortex; made up of lobes; composed mainly of dendrites and cell bodies of neurons • Interior of the cerebrum composed mainly of white matter (i.e., nerve fibers arranged in bundles called tracts) • Functions of the cerebrum—mental processes of all types, including sensations, consciousness, memory, and voluntary control of movements Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 34. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 35. Central Nervous System• Brain disorders – Destruction of brain tissue • Cerebrovascular accident (CVA)—hemorrhage from or cessation of blood flow through cerebral blood vessels; a ―stroke‖ • Cerebral palsy (CP)—condition in which damage to motor control areas of the brain before, during, or shortly after birth causes paralysis (usually spastic) of one or more limbs Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 36. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 37. Central Nervous System• Brain disorders – Dementia—progressive loss of memory, shortened attention span, personality changes, reduced intellectual capacity, motor control deficit • Alzheimer disease (AD)—brain disorder of the middle and late adult years characterized by dementia • Huntington disease (HD)—inherited disorder characterized by chorea (purposeless movement) progressing to severe dementia • HIV (also causes AIDS) can infect neurons and thus cause dementia Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 38. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 39. Central Nervous System• Brain disorders – Seizure disorders • Seizure—sudden burst of abnormal neuron activity that results in temporary changes in brain function • Epilepsy—many forms, all characterized by recurring seizures • Electroencephalogram—graphic representation of voltage changes in the brain used to evaluate brain activity Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 40. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 41. Central Nervous System• Spinal cord – Columns of white matter, composed of bundles of myelinated nerve fibers, form the outer portion of the H-shaped core of the spinal cord; bundles of axons called tracts – Interior composed of gray matter made up mainly of neuron dendrites and cell bodies (Figure 9-18) – Spinal cord tracts provide two-way conduction paths— ascending and descending – Spinal cord functions as the primary center for all spinal cord reflexes; sensory tracts conduct impulses to the brain, and motor tracts conduct impulses from the brain Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 42. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 43. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 44. Central Nervous System• Coverings and fluid spaces of the brain and spinal cord – Coverings • Cranial bones and vertebrae • Cerebral and spinal meninges—the dura mater, arachnoid mater, and the pia mater – Fluid spaces • Subarachnoid spaces of meninges • Central canal inside cord • Ventricles in brain Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 45. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 46. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 47. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 48. Peripheral Nervous System• Cranial nerves – 12 pairs—attached to undersurface of the brain – Connect brain with the neck and structures in the thorax and abdomen• Spinal nerves – 31 pairs—contain dendrites of sensory neurons and axons of motor neurons – Conduct impulses necessary for sensations and voluntary movements – Skin surface area supplied by a single nerve is called a dermatome Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 49. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 50. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 51. Peripheral Nervous System• Peripheral nerve disorders – Neuritis—general term referring to nerve inflammation • Sciatica is inflammation of the sciatic nerve that innervates the legs • Neuralgia, or muscle pain, often accompanies neuritis Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 52. Peripheral Nervous System• Peripheral nerve disorders – Trigeminal neuralgia—recurring episodes of stabbing pain along one or more branches of the trigeminal (fifth cranial) nerve in the head – Bell palsy—paralysis of facial features resulting from damage to the facial (seventh cranial) nerve Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 53. Peripheral Nervous System• Peripheral nerve disorders – Herpes zoster or shingles • Viral infection caused by chickenpox virus that has invaded the dorsal root ganglion and remained dormant until an episode of shingles • Usually affects a single dermatome, producing characteristic painful plaques or vesicles Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 54. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 55. Autonomic Nervous System• Autonomic nervous system—motor neurons that conduct impulses from the central nervous system to cardiac muscle, smooth muscle, and glandular epithelial tissue; regulates body’s automatic or involuntary functions• Autonomic neurons—preganglionic autonomic neurons conduct from spinal cord or brainstem to an autonomic ganglion; postganglionic neurons conduct from autonomic ganglia to cardiac muscle, smooth muscle, and glandular epithelial tissue Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 56. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 57. Autonomic Nervous System• Autonomic or visceral effectors—tissues to which autonomic neurons conduct impulses (i.e., cardiac and smooth muscle and glandular epithelial tissue) Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 58. Autonomic Nervous System• Composed of two divisions: the sympathetic system and the parasympathetic system• Autonomic conduction paths – Consist of two-neuron relays (i.e., preganglionic neurons from the CNS to autonomic ganglia, synapses, postganglionic neurons from ganglia to visceral effectors) – In contrast, somatic motor neurons conduct all the way from the CNS to somatic effectors with no intervening synapses Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 59. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 60. Autonomic Nervous System• Sympathetic nervous system – Dendrites and cell bodies of sympathetic preganglionic neurons located in gray matter of thoracic and upper lumbar segments of spinal cord – Axons leave spinal cord in the anterior roots of spinal nerves, extend to sympathetic or collateral ganglia, and synapse with several postganglionic neurons whose axons extend to spinal or autonomic nerves to terminate in visceral effectors – A chain of sympathetic ganglia is in front of and at each side of the spinal column Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 61. Autonomic Nervous System– Functions of the sympathetic nervous system • Serves as the emergency or stress system, controlling visceral effectors during strenuous exercise and when strong emotions (anger, fear, hate, or anxiety) are elicited • Group of changes induced by sympathetic control is called the fight-or-flight response Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 62. Autonomic Nervous System• Parasympathetic nervous system – Structure • Parasympathetic preganglionic neurons have dendrites and cell bodies in the gray matter of the brainstem and the sacral segments of spinal cord • Parasympathetic preganglionic neurons terminate in parasympathetic ganglia located in the head and the thoracic and abdominal cavities close to visceral effectors • Each parasympathetic preganglionic neuron synapses with postganglionic neurons to only one effector Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 63. Autonomic Nervous System• Parasympathetic nervous system – Function—dominates control of many visceral effectors under normal, everyday conditions Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 64. Autonomic Nervous System• Autonomic neurotransmitters – Cholinergic fibers—preganglionic axons of parasympathetic and sympathetic systems and parasympathetic postganglionic axons release acetylcholine – Adrenergic fibers—axons of sympathetic postganglionic neurons release norepinephrine (noradrenaline) Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 65. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 66. Autonomic Nervous System• Autonomic nervous system as a whole – Regulates the body’s automatic functions in ways that maintain or quickly restore homeostasis – Many visceral effectors are doubly innervated (i.e., they receive fibers from parasympathetic and sympathetic divisions and are influenced in opposite ways by the two divisions) Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 67. Autonomic Nervous System• Disorders of the autonomic nervous system – Stress-induced disease • Prolonged or excessive response to stress can disrupt normal functioning throughout the body • Examples of stress-induced conditions include heart disease, digestive problems, and reduced resistance to disease Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 68. Autonomic Nervous System• Disorders of the autonomic nervous system – Neuroblastoma—highly malignant tumor of the sympathetic nervous system, primarily affecting young children Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.