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29-1 The Nervous System PowerPoint® presentation to accompany: Medical Assisting Third Edition Booth, Whicker, Wyman, Pugh, Thompson © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-2 Learning Outcomes 29.1 Explain the difference between the central nervous system and the peripheral nervous system. 29.2 Describe the functions of the nervous system. 29.3 Describe the structure of a neuron. 29.4 Describe the function of a nerve impulse and how a nerve impulse is created. © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-3 Learning Outcomes (cont.) 29.5 Describe the structure and function of a synapse. 29.6 Describe the function of the blood-brain barrier. 29.7 Describe the structure and functions of meninges. 29.8 Describe the structure and functions of the spinal cord. © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-4 Learning Outcomes (cont.) 29.9 Describe the location and function of cerebrospinal fluid. 29.10 Define reflex and list the parts of a reflex arc. 29.11 List the major divisions of the brain and give the general functions of each. 29.12 Explain the functions of the cranial and spinal nerves. © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-5 Learning Outcomes (cont.) 29.13 Describe the differences between the somatic nervous system and autonomic nervous system. 29.14 Explain the two divisions of the autonomic nervous system. 29.15 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-6 Introduction Highly complex system of two parts Central nervous system (CNS) Peripheral nervous system (PNS) Controls all other organ systems and is important for maintaining balance within those systems Disorders are numerous and often difficult to diagnose and treat © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-7 General Functions of the NS CNS Brain Spinal cord PNS Peripheral nerves Two sections Somatic nervous system (SNS) Skeletal or voluntary muscles Autonomic nervous system (ANS) Automatic functions © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-8 General Functions (cont.) Three types of neurons Afferent or sensory nerves Efferent or motor nerves Sensory information from environment or inside body to CNS for interpretation Impulses from CNS to PNS to allow for movement or action Interneruons Interpretive neurons between afferent and efferent nerves in the CNS © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-9 Apply Your Knowledge Match the following: ANSWER: ___ B Somatic nervous system A. Motor nerves ___ C Autonomic nervous system B. Governs skeletal or voluntary muscles ___ E Afferent nerves C. Governs respiratory and GI systems ___ A Efferent nerves D. Go-betweens or interpreters ___ D Interneurons E. Sensory nerves © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-10 Neuron Structure Functional cells of NS Transmit electrochemical messages called nerve impulses to Other neurons Effectors (muscles or glands) © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-11 Neuron Structure (cont.) Neurons lose their ability to divide If destroyed, not replaced Neuralgia Support cells for neurons that can divide Astrocytes – anchor blood vessels to nerves Microglia – act as phagocytes Oligodendrocytes – assist with production of myelin sheath © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-12 Neuron Structure (cont.) Neurons have cell body processes called nerve fibers that extend from the cell body. Dendrites – short Receive nerve impulses for the neuron Axons – long Send nerve impulses away from the cell body © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-13 Neuron Structure (cont.) White matter – axons with myelin sheath Dendrites Schwann cells – neurological cells Schwann cells Axon Wrap around some axons Cell membranes contain myelin Myelin insulates axons and enables axons to send nerve impulses more quickly Gray matter – axons without myelin sheath © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-14 Apply Your Knowledge True or False: ANSWER: ___ F Effectors are neurons. F Neurons can reproduce. ___ They are the muscles or glands. Neurons cannot reproduce. T Astrocytes anchor blood vessels to nerve cells. ___ T Microglia act as phagocytes. ___ They take part in myelin production. T Repolarization is the return to the resting state. ___ F Oligodendrocytes are reproductive cells. ___ GOOD JOB! © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-15 Nerve Impulse Membrane potential Neuron cell membrane at rest is in a polarized state As Na+ and K+ move into the cell, the membrane becomes depolarized Inside of cell membrane is negative Outside of cell membrane is positive due to more Na+ and K+ Inside becomes more positive Action potential (nerve impulse) is created Repolarization occurs when K+ and later Na+ move to the outside of the cell membrane Return of the cell to polarized (resting) state © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-16 Nerve action © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-17 Nerve Impulse (cont.) Impulse travels down axon to synaptic knob Vesicles or small sacs in synaptic knob Produce chemicals called neurotransmitters Neurotransmitters are released by synaptic knob Allow impulse transmission to postsynaptic structures Dendrites Cell bodies Axons of other neurons © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-18 Synapse © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-19 Nerve Impulse (cont.) Functions of neurotransmitters Cause muscles to contract or relax Cause glands to secrete products Activate or inhibit neurons © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-20 Apply Your Knowledge What is the function of neurotransmitters? ANSWER: Neurotransmitters cause muscles to contract or relax, cause glands to secret products, activate neurons to send nerve impulses, or inhibit neurons from sending them. Right! © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-21 Central Nervous System Includes the spinal cord and brain Blood-brain barrier Protects layers of the membranes of the CNS Formed by tight capillaries Prevents unwanted substances from entering the CNS tissues Inflammation can make more permeable © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-22 CNS (cont.) Meninges –protect brain and spinal cord Dura mater Arachnoid mater Tough outer layer Middle layer (web-like) Pia mater Innermost and most delicate Directly on top of brain and spinal cord Holds blood vessels on the surface of these structures © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-23 CNS (cont.) Epidural space Subdural space Above dura mater Below dura mater Subarachnoid space Between arachnoid mater and pia mater Contains cerebrospinal fluid (CSF) Cushions CNS © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-24 CNS: Spinal Cord Slender structure continuous with the brain Descends into the vertebral canal and ends around the level of the first or second lumbar vertebra 31 spinal segments: 8 cervical segments 12 thoracic segments 5 lumbar segments 5 sacral segments 1 coccygeal segment © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-25 CNS: Spinal Cord (cont.) Cervical enlargement Motor neurons that control muscles of the arms Lumbar enlargement Motor neurons that control muscles of the legs © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-26 CNS: Spinal Cord (cont.) Gray matter Inner tissue with darker color Contains neuron cell bodies and their dendrites Divisions are called horns Central canal runs down the entire length of the spinal cord through the center of the gray Spinal matter Cord/Nerve © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-27 CNS: Spinal Cord (cont.) White matter Outer tissue Contains myelinated axons Divisions are called columns (funiculi) Columns contain groups of axons called nerve tracts Spinal Cord/Nerve © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-29 CNS: Spinal Cord (cont.) One function of the spinal cord is to carry sensory information to and from the brain Ascending tracts Carry sensory information up to the brain Descending tracts Carry motor information down from the brain to muscles and glands © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-30 CNS: Spinal Cord (cont.) Reflexes Another function of the spinal cord is to participate in reflexes Reflex – a predictable, automatic response to stimuli Receptor Sensory Neurons Interneurons Effectors Motor Neurons © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-31 CNS: Brain Four sections Cerebrum Diencephalons Brain stem Cerebellum © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-32 CNS: Brain – Cerebrum Largest section Two cerebral hemispheres Connected by a thick bundle of nerve fibers called the corpus callosum Longitudinal fissure between hemispheres Sulci – grooves on surface Gyri or convolutions – bumps of brain matter between sulci Brain © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-33 CNS: Brain – Cerebrum (cont.) Lobes Frontal Motor areas for voluntary body movements Somatosensory – interprets sensations Temporal Parietal Parietal Frontal Auditory – interprets sounds Occipital Temporal Occipital Interprets what a person sees © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-34 CNS: Brain – Cerebrum (cont.) Cortex Outer layer – gray matter Interconnected cavities within the brain Filled with CSF Contains about 75% of all neurons Inner layer – white matter Functions Ventricles Interpret sensory information Initiate body movements Stores memories and creates emotions © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-35 CNS: Brain – Diencephalon Between the cerebral hemispheres superior to the brain stem Thalamus Relay station for sensory information going to the cerebral cortex for interpretation Hypothalamus Maintains homeostasis by regulating vital activities Brain © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-36 CNS: Brain – Brain Stem Connects the cerebrum to the spinal cord Midbrain Just beneath diencephalon Controls both visual and auditory reflexes Pons Rounded bulge on underside of brain stem Between midbrain and medulla oblongata Regulates respiration Medulla oblongata Inferior portion of brain stem Directly connected to spinal cord Controls many vital activities, such as heart rate, blood pressure, and breathing Brain © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-37 CNS: Brain – Cerebellum Location Inferior to the occipital lobes of the cerebrum Posterior to the pons and medulla oblongata Coordinates Complex skeletal muscle contractions that are needed for body movements Fine movements Brain © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-39 Preventing Brain and Spinal Cord Injuries Wear appropriate protective gear for sports Avoid diving into unknown waters Always wear seat belts Follow safety rules on playgrounds Children should be in car seats appropriate for age and weight Know how to get help quickly in emergencies Follow traffic rules and signs while walking, biking, or driving © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-40 Apply Your Knowledge SUPER! Match the following: ___ H Meninges A. Carry motor information from brain ___ D Ascending tracts B. Stores memories and creates emotions ___ A Descending tracts C. Grooves on the surface of the cerebrum ___ B Cerebral cortex D. Carry sensory information to the brain ___ F Hypothalamus E. Predictable, automatic response to stimuli ___ C Sulci F. Maintains homeostasis ___ G Cerebellum G. Coordinates skeletal muscle contractions ___ E Reflexes H. Protects the brain and spinal cord © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-41 Peripheral Nervous System Nerves that branch off the CNS Peripheral nerves Two types: Cranial nerves Spinal nerves © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-42 PNS: Cranial Nerves I. Olfactory nerves Carry smell information to the brain for interpretation II. Optic nerves Carry visual information to the brain for interpretation III. Oculomotor nerves Found within the muscles that move the eyeball, eyelid, and iris IV. Trochlear nerves Act in the muscles that move the eyeball. © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-43 PNS: Cranial Nerves (cont.) V. Trigeminal nerves Carry sensory information from the surface of the eye, the scalp, facial skin, the lining of the gums, and the palate to the brain for interpretation Also found within the muscles needed for chewing VI. Abducens nerves Act in the muscles that move the eyeball © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-44 PNS: Cranial Nerves (cont.) VII. Facial nerves Found in the muscles of facial expression as well as in the salivary and tear glands Also carry sensory information from the tongue VIII. Vestibulocochlear nerves Carry hearing and equilibrium information from the inner ear to the brain for interpretation © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-45 PNS: Cranial Nerves (cont.) IX. Glossopharyngeal nerves Carry sensory information from the throat and tongue to the brain for interpretation Also act in the muscles of the throat X. Vagus nerves Carry sensory information from the thoracic and abdominal organs to the brain for interpretation Also found within the muscles in the throat, stomach, intestines, and heart © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-46 PNS: Cranial Nerves (cont.) XI. Accessory nerves Found within the muscles of the throat, neck, back, and voice box XII. Hypoglossal nerves Found within the muscles of the tongue © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-47 PNS: Spinal Nerves Peripheral nerves originating from the spinal cord 31 pairs of spinal nerves 8 pairs of cervical nerves (C1 through C8) 12 pairs of thoracic nerves (T1 through T12) 5 pairs of lumbar nerves (L1 through L5) 5 pairs of sacral nerves (S1 through S5) Spinal 1 pair of coccygeal nerves (C0) Nerves © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-48 PNS: Spinal Nerves (cont.) Dermatome Ventral root Skin segment innervated by spinal nerve C1 is not associated with a dermatome Axons of motor neurons only Dorsal root Axons of sensory neurons only Dorsal root ganglion Contains cell bodies of sensory neurons © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-49 PNS: Spinal Nerves (cont.) Main portions of spinal nerves fuse to form nerve plexuses Cervical – supply skin and muscles of neck Phrenic nerve originates from this plexus Controls diaphragm Brachial – control muscles in the arms Lumbosacral – lower abdomen, external genitalia, buttocks, thighs, legs, and feet Sciatic nerve originates from this plexus Controls muscles of legs Spinal Nerves © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-51 PNS: Somatic Nervous System Nerves that connect the CNS to skin and skeletal muscle “Voluntary” nervous system Controls skeletal muscles, which are under voluntary control © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-52 PNS: Autonomic Nervous System Nerves that connect the CNS to organs and other structures “Involuntary” nervous system Motor neurons located in ganglia Neuron cell bodies outside the CNS © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-53 PNS: Autonomic Nervous System (cont.) Sympathetic division “Fight or flight” – Prepares body for stressful or emergency situations Neurons release neurotransmitter norepinephrine Increases heart and breathing rates Slows down muscles of the stomach and intestines Dilates pupils Constricts blood vessels – increases blood pressure © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-54 PNS: Autonomic Nervous System (cont.) Parasympathetic division Prepares body for rest and digesting Controls most of the body’s organs Releases acetylcholine Slows heart and breathing rates Constricts pupils Activates muscles of stomach and intestine No communication with blood vessels Sympathetic and parasympathetic divisions are antagonistic © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-55 Apply Your Knowledge What is the difference between the sympathetic and parasympathetic nervous systems? ANSWER: The sympathetic nervous system prepares the body for stress. It releases norepinephrine, causing an increase in heart and respiratory rate, slows down the GI system, and dilates pupils. The sympathetic system also controls constriction of blood vessels. The parasympathetic system prepares the body for resting and digesting. It releases acetylcholine, which slows heart and respiratory rate, constricts pupils and stimulates the GI system. It has no effect on most blood vessels. © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-56 Neurologic Testing Typical neurologic examination State of consciousness Reflex activity Speech patterns Motor patterns © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-57 Neurologic Testing: Diagnostic Procedures Lumbar puncture Computerized tomography (CT) scan Magnetic resonance imaging (MRI) Electroencephalogram (EEG) Positron emission tomography (PET) scan X-ray Cerebral angiography © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-58 Neurologic Testing – Cranial Nerve Tests Olfactory nerves (Cranial nerve I) Cranial nerves III, IV, and VI Have patient smell various substances Have patient track movement of finger Cranial nerve V Have patient clench teeth, feel jaw muscles © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-59 Neurologic Testing – Cranial Nerve Tests (cont.) Cranial nerve VII Check patient’s facial expression Cranial nerve XII Have patient extend his tongue and move it from side to side © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-60 Neurologic Testing: Reflex Testing Areflexia Hyporeflexia Absence of a reflex Decreased reflex Hyperreflexia Stronger-than-normal reflex © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-61 Neurologic Testing: Reflex Testing Biceps reflex Absence indicates spinal cord damage in the cervical region Knee reflex Absence may indicate damage to lumbar or femoral nerves Abdominal reflexes Used to evaluate damage to thoracic spinal nerves © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-62 Apply Your Knowledge Match the following: ANSWER: C State of consciousness ___ A Reflex activity ___ D Speech patterns ___ B Motor patterns ___ A. Determines the health of peripheral nerves B. Loss of balance, abnormal posture C. Stupor, delirium, vegetative D. Loss of ability to form words © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-63 Common Diseases and Disorders Disease/Disorder Description Alzheimer’s disease Amyotrophic lateral sclerosis (ALS) Bell’s palsy Progressive, degenerative disease of the brain Lou Gehrig’s disease Degeneration of neurons in the spinal cord and brain Weak or paralyzed facial muscles © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-64 Common Diseases and Disorders (cont.) Disease/Disorder Description Brain tumors and Abnormal growths cancers Can be primary or secondary tumors Most common – gliomas Epilepsy and Occurs as a result of bursts of seizures electrical signals that disrupt normal brain functioning Guillain-Barré Syndrome Body’s immune system attacks the PNS © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-65 Common Diseases and Disorders (cont.) Disease/Disorder Description Headaches Tension Migraines Cluster Episodic or chronic With aura/without aura Form of migraines; occurs in groups Meningitis Inflammation of meninges Multiple sclerosis (MS) Chronic disease of CNS Myelin is destroyed © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-66 Common Diseases and Disorders (cont.) Disease/Disorder Description Neuralgias Disorders causing nerve pain Parkinson’s disease Progressive and degenerative motor system disorder Sciatica Damage to sciatic nerve Stroke Brain cells die because of an inadequate blood flow; “brain attack” © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-67 Apply Your Knowledge True or false: Bravo! ANSWER: T Alzheimer’s disease is a progressive degenerative disease of ___ the brain. F Epilepsy is due to degenerative neurons in the spinal cord ___ and brain. Due to a burst of electrical signals that disrupt brain function. F Neuralgias are motor system disorders. ___ They are group of disorders referred to as nerve pain. T Stroke occurs when brain cells die because of inadequate ___ blood flow. © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-68 In Summary Functions of the nervous system Detecting and interpreting sensory information Making decision about that information Responding to and carrying out motor functions Neurons are responsible for functions Divisions CNS – brain and spinal cord PNS – cranial and spinal nerves Knowledge of this system is essential when assisting the physician during a neurologic exam © 2009 The McGraw-Hill Companies, Inc. All rights reserved 29-69 End of Chapter Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.” ~ Dr. Ralph Gerard © 2009 The McGraw-Hill Companies, Inc. All rights reserved