25 The Nervous System.

25 The Nervous System

Learning Outcomes 25.1 Explain the difference between the central nervous system and the peripheral nervous system. 25.2 Describe the functions of the nervous system. 25.3 Describe the structure of a neuron. 25.4 Describe the function of a nerve impulse and how a nerve impulse is created.

Learning Outcomes (cont.)
25.5 Describe the structure and function of a synapse. 25.6 Describe the function of the blood-brain barrier. 25.7 Describe the structure and functions of meninges. 25.8 Describe the structure and functions of the spinal cord.

25.9 Describe the location and function of cerebrospinal fluid. 25.10 Define reflex and list the parts of a reflex arc. 25.11 List the major divisions of the brain and give the general functions of each. 25.12 Explain the functions of the cranial and spinal nerves.

25.13 Describe the differences between the somatic nervous system and autonomic nervous system. 25.14 Explain the two divisions of the autonomic nervous system. 25.15 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system.

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 Learning Outcomes: 25.1 Explain the difference between the central nervous system and the peripheral nervous system. 25.2 Describe the functions of the nervous system. Disorders are numerous and often difficult to diagnose and treat

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 Learning Outcomes: 25.1 Explain the difference between the central nervous system and the peripheral nervous system. 25.2 Describe the functions of the nervous system.

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 Interneurons Interpretive neurons between afferent and efferent nerves in the CNS Learning Outcome: 25.2 Describe the functions of the nervous system.

Apply Your Knowledge Correct! 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 B C A E D Correct!

Neuron Structure Functional cells of NS
Transmit electrochemical messages called nerve impulses to Other neurons Effectors (muscles or glands) Learning Outcome: 25.3 Describe the structure of a neuron.

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 Learning Outcome: 25.3 Describe the structure of a neuron.

Dendrites – short Receive nerve impulses for the neuron Axons – long Send nerve impulses away from the cell body Neurons have a cell body and processes called nerve fibers that extend from the cell body. Learning Outcome: 25.3 Describe the structure of a neuron. Cell body Contains nucleus and typical organelles Generates large amount of proteins and energy Nerve fibers Axon: Typically one per neuron Dendrites: One or more per neuron; branch profusely near cell body

White matter – axons with myelin sheath Schwann 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 Learning Outcome: 25.3 Describe the structure of a neuron.

GOOD JOB! Apply Your Knowledge 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. ANSWER: F They are the muscles or glands. F Neurons cannot reproduce. T T They take part in myelin production. F T GOOD JOB!

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 Learning Outcome: 25.4 Describe the function of a nerve impulse and how a nerve impulse is created. Unmyelinated axons do not conduct nerve impulses as quickly as myelinated axons do. Speed of nerve impulse is related to diameter of axon. The larger the axon diameter, the faster the nerve impulse travels to the end of the axon.

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 Learning Outcome: 25.4 Describe the function of a nerve impulse and how a nerve impulse is created. 25.5 Describe the structure and function of a synapse. Synaptic space: The space between the axon of one neuron and the dendrite of the next. There are about 50 different neurotransmitters, but most neurons release only one type.

Nerve Impulse (cont.) Functions of neurotransmitters
Cause muscles to contract or relax Cause glands to secrete products Activate or inhibit neurons Learning Outcome: 25.4 Describe the function of a nerve impulse and how a nerve impulse is created.

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!

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 Learning Outcome: 25.6 Describe the function of the blood-brain barrier.

Central Nervous System (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 Learning Outcome: 25.7 Describe the structure and functions of meninges.

Central Nervous System (cont.)
Epidural space Above dura mater Subdural space Below dura mater Subarachnoid space Between arachnoid mater and pia mater Contains cerebrospinal fluid (CSF) Cushions CNS Learning Outcome: 25.7 Describe the structure and functions of meninges. 25.9 Describe the location and function of cerebrospinal fluid. Cerebrospinal fluid: Fluid that cushions and protects the central nervous system.

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 Learning Outcome: 25.8 Describe the structure and functions of the spinal cord.

Spinal Cord (cont.) Cervical enlargement Lumbar enlargement
Motor neurons that control muscles of the arms Lumbar enlargement Motor neurons that control muscles of the legs Learning Outcome: 25.8 Describe the structure and functions of the spinal cord.

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 Learning Outcome: 25.8 Describe the structure and functions of the spinal cord. Central canal contains CSF. Spinal Cord/Nerve

Spinal Cord (cont.) White matter Outer tissue
Contains myelinated axons Divisions are called columns (funiculi) Columns contain groups of axons called nerve tracts Learning Outcome: 25.8 Describe the structure and functions of the spinal cord. Spinal Cord/Nerve Spinal Cord/Nerve

Spinal Cord (cont.) Learning Outcome:
25.8 Describe the structure and functions of the spinal cord. Previous Slide

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 Learning Outcome: 25.8 Describe the structure and functions of the spinal cord.

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 Learning Outcome: 25.10 Define reflex and list the parts of a reflex arc. It is possible to consciously inhibit a reflex because the information also goes to the cerebral cortex, where a person makes conscious decisions. Interneurons Effectors Motor Neurons

Brain Four sections Cerebrum Diencephalon Brain stem Cerebellum
Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each.

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 Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each. Brain

Cerebrum (cont.) Lobes Frontal Parietal Temporal Occipital
Motor areas for voluntary body movements Parietal Somatosensory – interprets sensations Temporal Auditory – interprets sounds Occipital Interprets what a person sees Parietal Frontal Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each. Temporal Occipital

Cerebrum (cont.) Cortex Ventricles 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 Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each.

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 Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each. Sensory information that does not pass through the thalamus before reaching the cerebral cortex cannot be interpreted correctly. Hypothalamus regulates Heart rate Blood pressure Breathing rate Brain

Brain Stem Connects the cerebrum to the spinal cord Midbrain Pons
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 Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each. Medulla oblongata also controls reflexes associated with Coughing Sneezing Vomiting Brain

Cerebellum Location Coordinates
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 Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each. Brain

Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each. Previous slide

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 Learning Outcome: 25.11 List the major divisions of the brain and give the general functions of each. Additional tips: Do not drive or do any recreational activity while under the influence of alcohol or drugs. Avoid surfing headfirst. Store firearms and ammunition in separate and locked places. Teach children the safety rules to follow if they find a gun.

Apply Your Knowledge Answer: Match the following:
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 H D A B F C G E

Peripheral Nervous System
Nerves that branch off the CNS Peripheral nerves Two types: Cranial nerves Spinal nerves Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves.

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. Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves.

Cranial Nerves (cont.) V. Trigeminal nerves VI. Abducens 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 Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves. Trigeminal nerves are also found in the muscles needed for chewing.

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 Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves.

Cranial Nerves (cont.) IX. Glossopharyngeal nerves X. Vagus 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 Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves.

Cranial Nerves (cont.) XI. Accessory nerves XII. Hypoglossal nerves
Found within the muscles of the throat, neck, back, and voice box XII. Hypoglossal nerves Found within the muscles of the tongue Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves.

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) Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves. Spinal Nerves

Spinal Nerves (cont.) Dermatome Ventral root Dorsal root
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 Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves.

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 and controls the diaphragm Brachial – control muscles in the arms Lumbosacral – lower abdomen, external genitalia, buttocks, thighs, legs, and feet Sciatic nerve originates from this plexus and controls muscles of legs Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves. Spinal Nerves

Learning Outcome: 25.12 Explain the functions of the cranial and spinal nerves. Previous slide

Somatic Nervous System
Nerves that connect the CNS to skin and skeletal muscle “Voluntary” nervous system Controls skeletal muscles, which are under voluntary control Learning Outcome: 25.13 Describe the differences between the somatic nervous system and autonomic nervous system.

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

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 Learning Outcome: 25.14 Explain the two divisions of the autonomic nervous system. Sympathetic division is also called the thoracolumbar division because many of its neurons are located in the thoracic and lumbar regions of the spinal cord.

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 Learning Outcome: 25.14 Explain the two divisions of the autonomic nervous system. Parasympathetic division is also called the craniosacral division because many of its neurons are located in brain stem and sacral regions of the spinal cord.

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 rates, constricts pupils, and stimulates the GI system. It has no effect on most blood vessels. Impressive!

Neurologic Testing Typical neurologic examination
State of consciousness Reflex activity Speech patterns Motor patterns Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases. Common signs and symptoms of nervous system disorders Headache Muscle weakness Paresthesias Paresthesias: Loss of feeling. States of consciousness Normal Asleep Stupor Delirium Vegetative Coma

Diagnostic Procedures
Lumbar puncture Magnetic resonance imaging (MRI) Positron emission tomography (PET) scan Cerebral angiography Computerized tomography (CT) scan Electroencephalogram (EEG) X-ray Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases. Lumbar puncture: Extraction of CSF from spinal column for analysis. MRI: Uses powerful magnets to generate images of the brain and spinal cord from many angles. PET: Uses radioactive chemicals that collect in specific areas of the brain, allowing images of those areas to be generated. Cerebral angiography: Uses contrast material that can be visualized in the blood vessels of the brain. CT scan: Produces images that provide more information than a standard x-ray. EEG: Detects electrical activity in the brain. X-ray: Used to detect skull or vertebral fractures.

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 Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases.

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 Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases.

Reflex Testing Areflexia Hyporeflexia Hyperreflexia
Absence of a reflex Hyporeflexia Decreased reflex Hyperreflexia Stronger-than-normal reflex Learning Outcomes: 25.10 Define reflex and list the parts of a reflex arc. 25.15 Describe the causes, signs and symptoms, and treatments of various diseases.

Reflex Testing (cont.) Biceps reflex Knee reflex Abdominal reflexes
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 Learning Outcomes: 25.10 Define reflex and list the parts of a reflex arc. 25.15 Describe the causes, signs and symptoms, and treatments of various diseases.

Apply Your Knowledge Excellent! 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 ANSWER: C A D B

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 Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases.

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 Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases. Brain tumors: Gliomas arise from neuroglial cells. Types of seizures Petit mal: Partial Grand mal: Generalized

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 Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases.

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” Learning Outcome: 25.15 Describe the causes, signs and symptoms, and treatments of various diseases. Transient ischemic attacks (TIAs): “Mini strokes” that may precede a stroke (CVA).

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. T F Due to a burst of electrical signals that disrupt brain function. F They are group of disorders referred to as nerve pain. T

In Summary 25.1 The central nervous system is composed of the brain and spinal cord. The peripheral nervous system consists of the peripheral nerves located throughout the body. The peripheral nervous system is further divided into two distinct systems: the somatic and autonomic nervous systems There are three separate types of neurons to carry out the functions of the nervous system. The afferent (sensory) nerves, the efferent (motor) nerves, and the interpretive interneurons that act as “interpreters” between the afferent and efferent nerves.

In Summary (cont.) 25.3 All neurons are composed of a cell body, the shorter and more numerous dendrites that receive information for the cell body, and the longer axons that bring an impulse from the cell body to the dendrite of the next neuron The function of a nerve impulse is the sending of information either from the CNS to the PNS or vice versa. At rest, a neuron is said to be in a polarized state, and when it responds to stimuli, depolarization takes place. Repolarization occurs after the electrical current (impulse) has passed.

In Summary (cont.) 25.5 A synapse is the space between the axon of one neuron and the dendrite of the next. At the end of each axon is the synaptic knob, which contains vesicles that produce neurotransmitters. These are released by the synaptic bulb to allow impulse transmission to continue to the next neuron. 25.6 The blood-brain barrier is a layer of tightly woven capillaries that protects the delicate tissues of the CNS. This barrier prevents certain substances, such as various waste products and drugs, from easily crossing this barrier and entering the brain tissues.

In Summary (cont.) 25.7 The meninges, a triple-layered membrane protecting the brain and spinal cord, are composed of the following layers: The tough outer layer is the dura mater. The space between the cranium and the dura mater is called the epidural space. Below the dura mater is the subdural space. The middle layer is the arachnoid, and below it is the subarachnoid space, which contains cerebrospinal fluid (CSF). The innermost layer is the pia mater.

In Summary (cont.) 25.8 The spinal cord is continuous with the brain and consists of 31 spinal segments: 8 cervical 5 sacral 12 thoracic 1 coccygeal 5 lumbar The basic function of the spinal cord is to carry sensory information from the body to the brain and motor information from the brain to the muscles and glands of the body.

In Summary (cont.) 25.9 Cerebrospinal fluid (CSF) is located within the subarachnoid space of the brain and within the central canal of the spinal cord. It cushions the brain and spinal cord A reflex is a predictable automatic response to a stimulus. A typical reflex flows as follows: Sensory receptors send information (impulse) to the interneurons, which in turn send the information on to the effectors of the motor neurons, producing a response.

In Summary (cont.) 25.11 The cerebrum is the largest part of the brain and is divided into two hemispheres subdivided into four lobes: frontal, parietal, temporal and occipital. The diencephalon contains the thalamus and hypothalamus. The brain stem consists of three parts: the midbrain, pons, and medulla oblongata. The cerebellum is the final area of the brain.

In Summary (cont.) 25.12 Twelve cranial nerves carry sensory information: Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vagus Vestibulocochlear Glossopharyngeal Accessory Hypoglossal There are 31 pairs of spinal nerves, each except C1 innervating a dermatome. Refer to Figure 25.8 for a map of the spinal nerves.

In Summary (cont.) 25.13 The somatic nervous system connects the CNS to the skin and skeletal muscle (voluntary functions). The autonomic nervous system connects the CNS to the internal organs (involuntary functions) The autonomic nervous system is divided into the sympathetic system, which prepares the body for “fight or flight” (stressful) situations, and the parasympathetic system, which is the body’s everyday “resting” system for normal situations.

In Summary (cont.) 25.15 There are many and varied diseases and disorders related to the nervous system. The signs, symptoms, and treatments of these diseases are as varied as the diseases themselves. Many of the more common diseases are included in the Pathophysiology section at the end of this chapter.

End of Chapter 25 Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.” ~ Dr. Ralph Gerard

25 The Nervous System.

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