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The Nervous System Chapter 29 Medical Assisting
PowerPoint® presentation to accompany: Medical Assisting Third Edition Booth, Whicker, Wyman, Pugh, Thompson
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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.
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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.
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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.
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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.
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Disorders are numerous and often difficult to diagnose and treat
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
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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
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General Functions (cont.)
Three types of neurons Afferent or sensory nerves Sensory information from environment or inside body to CNS for interpretation Efferent or motor nerves Impulses from CNS to PNS to allow for movement or action Interneruons Interpretive neurons between afferent and efferent nerves in the CNS
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Apply Your Knowledge Correct! ANSWER: Match the following:
B ANSWER: Match the following: ___ Somatic nervous system A. Motor nerves ___ Autonomic nervous system B. Governs skeletal or voluntary muscles ___ Afferent nerves C. Governs respiratory and GI systems ___ Efferent nerves D. Go-betweens or interpreters ___ Interneurons E. Sensory nerves C A E D Correct!
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Neuron Structure Functional cells of NS
Transmit electrochemical messages called nerve impulses to Other neurons Effectors (muscles or glands)
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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
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Neuron Structure (cont.)
Dendrites – short Receive nerve impulses for the neuron Axons – long Send nerve impulses away from the cell body Neurons have cell body processes called nerve fibers that extend from the cell body.
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Neuron Structure (cont.)
White matter – axons with myelin sheath Schwann cells – neurological cells 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 Schwann cells Axon Dendrites
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GOOD JOB! Apply Your Knowledge ANSWER: True or False:
___ Effectors are neurons. ___ Neurons can reproduce. ___ Astrocytes anchor blood vessels to nerve cells. ___ Microglia act as phagocytes. ___ Oligodendrocytes are reproductive cells. ___ Repolarization is the return to the resting state. They are the muscles or glands. F Neurons cannot reproduce. T T They take part in myelin production. F T GOOD JOB!
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Nerve Impulse Membrane potential
Neuron cell membrane at rest is in a polarized state Inside of cell membrane is negative Outside of cell membrane is positive due to more Na+ and K+ As Na+ and K+ move into the cell, the membrane becomes depolarized 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
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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
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Nerve Impulse (cont.) Functions of neurotransmitters
Cause muscles to contract or relax Cause glands to secrete products Activate or inhibit neurons
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Right! 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!
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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
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CNS (cont.) Meninges –protect brain and spinal cord Dura mater
Tough outer layer Arachnoid mater 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
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CNS (cont.) Epidural space Subdural space Subarachnoid space
Above dura mater Subdural space Below dura mater Subarachnoid space Between arachnoid mater and pia mater Contains cerebrospinal fluid (CSF) Cushions CNS
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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
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CNS: Spinal Cord (cont.)
Cervical enlargement Motor neurons that control muscles of the arms Lumbar enlargement Motor neurons that control muscles of the legs
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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 matter Spinal Cord/Nerve
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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 Spinal Cord/Nerve
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CNS: Spinal Cord (cont.)
Previous Slide
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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
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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
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CNS: Brain Four sections Cerebrum Diencephalons Brain stem Cerebellum
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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
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CNS: Brain – Cerebrum (cont.)
Lobes Frontal Motor areas for voluntary body movements Parietal Somatosensory – interprets sensations Temporal Auditory – interprets sounds Occipital Interprets what a person sees Parietal Frontal Temporal Occipital
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CNS: Brain – Cerebrum (cont.)
Cortex Outer layer – gray matter Contains about 75% of all neurons Inner layer – white matter Functions Interpret sensory information Initiate body movements Stores memories and creates emotions Ventricles Interconnected cavities within the brain Filled with CSF
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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
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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
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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
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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
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Apply Your Knowledge SUPER! Answer: Match the following:
___ Meninges A. Carry motor information from brain ___ Ascending tracts B. Stores memories and creates emotions ___ Descending tracts C. Grooves on the surface of the cerebrum ___ Cerebral cortex D. Carry sensory information to the brain ___ Hypothalamus E. Predictable, automatic response to stimuli ___ Sulci F. Maintains homeostasis ___ Cerebellum G. Coordinates skeletal muscle contractions ___ Reflexes H. Protects the brain and spinal cord D A B F C G E
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Peripheral Nervous System
Nerves that branch off the CNS Peripheral nerves Two types: Cranial nerves Spinal nerves
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PNS: Cranial Nerves I. Olfactory nerves II. Optic 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.
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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
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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
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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
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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
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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) 1 pair of coccygeal nerves (C0) Spinal Nerves
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PNS: Spinal Nerves (cont.)
Dermatome Skin segment innervated by spinal nerve C1 is not associated with a dermatome Ventral root Axons of motor neurons only Dorsal root Axons of sensory neurons only Dorsal root ganglion Contains cell bodies of sensory neurons
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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
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Previous slide
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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
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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
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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
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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
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Apply Your Knowledge Impressive!
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. Impressive!
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Neurologic Testing Typical neurologic examination
State of consciousness Reflex activity Speech patterns Motor patterns
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Neurologic Testing: Diagnostic Procedures
Lumbar puncture Magnetic resonance imaging (MRI) Positron emission tomography (PET) scan Cerebral angiography Computerized tomography (CT) scan Electroencephalogram (EEG) X-ray
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Neurologic Testing – Cranial Nerve Tests
Olfactory nerves (Cranial nerve I) Have patient smell various substances Cranial nerves III, IV, and VI Have patient track movement of finger Cranial nerve V Have patient clench teeth, feel jaw muscles
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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
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Neurologic Testing: Reflex Testing
Areflexia Absence of a reflex Hyporeflexia Decreased reflex Hyperreflexia Stronger-than-normal reflex
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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
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Apply Your Knowledge Excellent! ANSWER: Match the following:
___ State of consciousness A. Determines the health of peripheral nerves ___ Reflex activity B. Loss of balance, abnormal posture ___ Speech patterns C. Stupor, delirium, vegetative ___ Motor patterns D. Loss of ability to form words Excellent! C ANSWER: A D B
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Common Diseases and Disorders
Disease/Disorder Description Alzheimer’s disease Progressive, degenerative disease of the brain Amyotrophic lateral sclerosis (ALS) Lou Gehrig’s disease Degeneration of neurons in the spinal cord and brain Bell’s palsy Weak or paralyzed facial muscles
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Common Diseases and Disorders (cont.)
Disease/Disorder Description Brain tumors and cancers Abnormal growths Can be primary or secondary tumors Most common – gliomas Epilepsy and seizures Occurs as a result of bursts of electrical signals that disrupt normal brain functioning Guillain-Barré Syndrome Body’s immune system attacks the PNS
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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
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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”
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Bravo! Apply Your Knowledge ANSWER: True or false:
___ Alzheimer’s disease is a progressive degenerative disease of the brain. ___ Epilepsy is due to degenerative neurons in the spinal cord and brain. ___ Neuralgias are motor system disorders. ___ Stroke occurs when brain cells die because of inadequate blood flow. F Due to a burst of electrical signals that disrupt brain function. F They are group of disorders referred to as nerve pain. T
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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
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End of Chapter End of Chapter 29 Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.” ~ Dr. Ralph Gerard
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