CHAPTER 30 The Nervous System 30-2 Learning Outcomes (cont.) 30.1 Describe the general functions of...

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30The Nervous

System

30-2


Learning Outcomes (cont.)

30.1 Describe the general functions of the nervous system.

30.2 Summarize the structure of a neuron.

30.3 Explain the function of nerve impulses and the role of synapses in their transmission.

30.4 Describe the structures and functions of the central nervous system.

30-3


Learning Outcomes (cont.)

30.5 Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system.

30.6 Recognize common tests that are performed to determine neurologic disorders.

30.7 Describe the causes, signs and symptoms, and treatments of various diseases and

disorders of the nervous system.

30-4


Introduction

• Highly complex system

• Controls and helps to maintain balance in all other organ systems

Disorders are numerous and often difficult to diagnose and treat

30-5


General Functions of the Nervous System

• Central Nervous System (CNS)– Brain– Spinal cord

• Peripheral Nervous System (PNS)

– Peripheral nerves

– Somatic nervous system (SNS)

– Autonomic nervous system (ANS)

30-6


General Functions of the Nervous System (cont.)

• Afferent nerves ~ sensory information

• Efferent nerves ~ impulses that allow for movement or action

• Interneurons – interpreters between afferent and efferent nerves

30-7


Apply Your Knowledge

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

B

ANSWER:

30-8


Neuron Structure

• Functional cells of NS

• Transmit nerve impulses to – Other neurons – Effectors

• Cannot divide

• Neuroglia

– Support cells for neurons

– Astrocytes

– Microglia

– Oligodendrocytes

30-9


Neuron Structure (cont.)

• Neurons – Cell body

• Nucleus and organelles• Generates proteins and

energy

– Nerve fibers ~ extend from cell body

30-10



• Axons– One per neuron– Send nerve impulses away

from the cell body

• Dendrites – One or more per neuron– Receive nerve impulses

for the neuron

30-11



• Schwann cells

– Wrap around axons

– Membranes contain myelin

• White matter – myelin sheath

• Gray matter – no myelin sheath

30-12



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.

F

T

T

F

T

F

ANSWER:

They are the muscles or glands.

Neurons cannot reproduce.

They take part in myelin production.

GOOD JOB!GOOD JOB!

30-13


Nerve Impulse and Synapse

• Cell membrane potential - polarized

• Depolarized – sodium ions move into the cell

• Action potential is created

• Repolarization

– Positive ions move out

– Returns to polarized state

30-14


Nerve Impulse (cont.)

• Synaptic knob contains vesicles

• Neurotransmitters – Produced in vesicles

– Released to allow impulse transmission to post-synaptic structures

– Functions

30-15



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!

30-16


Central Nervous System

• Brain and spinal cord

• Blood-brain barrier– Protects layers of the

membranes of the CNS

– Formed by tight capillaries

30-17


Central Nervous System (cont.)

• Meninges – Dura mater

• Epidural space

• Subdural space

– Arachnoid mater

– Pia mater

– Subarachnoid space ~ cerebrospinal fluid (CSF)

30-18


Spinal Cord

• Descends through vertebral canal

• 31 spinal segments: – 8 cervical – 12 thoracic– 5 lumbar– 5 sacral – 1 coccygeal

• Cervical enlargement

• Lumbar enlargement

30-19


Spinal Cord (cont.)

• Gray matter – Neuron cell bodies

and their dendrites– Horns

• White matter – Myelinated axons – Funiculi

• Central canal – Center of the gray

matter – Contains CSF

30-20


Spinal Cord (cont.)

• Ascending tracts – sensory

• Descending tracts – motor

• Reflexes – predictable automatic responses

Receptor Sensory Neurons

Interneurons

Motor NeuronsEffectors

Stimulus

Stimulus

ResponseResponse

30-21


Brain

• Four sections

– Cerebrum

– Diencephalon

– Brain stem

– Cerebellum

• Cerebrum– Two hemispheres– Corpus callosum– Sulci– Gyri– Longtidtudinal

fissure

Brain

30-22


Brain (cont.)

30-23


Brain (cont.)

• Cerebral Cortex– Gray matter– Functions

• Sensory information• Body movement• Memories• Emotions

• Ventricles– Interconnected

cavities within the brain

– CSF

• Diencephalon– Thalamus– Hypothalamus

30-24


Brain (cont.)

• Brain Stem

– Midbrain

– Pons

– Medulla oblongata

• Cerebellum

– Complex body movements

– Fine muscle movements

Brain

30-26




___ 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

B

F

C

G

E

D

A

H

SUPER!

30-27


Peripheral Nervous System

• Nerves that branch off the CNS

– Cranial nerves

– Spinal nerves

30-28


Cranial Nerves

I. Olfactory nerves

II. Optic nerves

III. Oculomotor nerves

IV. Trochlear nerves

V. Trigeminal nerves

VI. Abducens nerves

Diagram

30-29


Cranial Nerves (cont.)

VII. Facial nerves

VIII. Vestibulocochlear nerves

IX. Glossopharyngealnerves

X. Vagus nerves

XI. Accessory nerves

XII. Hypoglossal nerves

Diagram

30-31


Spinal Nerves

• 31 pairs of spinal nerves– 8 pairs of cervical nerves

– 12 pairs of thoracic nerves

– 5 pairs of lumbar nerves

– 5 pairs of sacral nerves

– 1 pair of coccygeal nervesSpinal Nerves

30-32


Spinal Nerves (cont.)

• Dermatome – Skin segment innervated by spinal nerve– C1 is not associated with a dermatome

• Ventral root – axons of motor neurons

• Dorsal root– Axons of sensory neurons – Dorsal root ganglion ~ cell bodies of sensory

neurons

30-33


Spinal Nerves (cont.)

• Nerve plexuses– Cervical ~ skin and neck

– Brachial ~ arms

– Lumbosacral ~ lower abdomen, external genitalia, buttocks, thighs, legs, and feet

– Coccygeal ~ anus and back of thighs

Spinal Nerves

30-35


Somatic and Autonomic Nervous System

• Somatic Nervous System– Nerves that connect the CNS to skin and

skeletal muscle

– “Voluntary” nervous system

– Controls skeletal muscles

30-36


Somatic and Autonomic Nervous System (cont.)

• Autonomic Nervous System– Connect the CNS to organs and other structures

– “Involuntary” nervous system

– Ganglia

Motor neurons from

brain and spinal cord

Motor neurons in

ganglia

Organs and

blood vessels

Organs and

blood vessels

30-37



• Sympathetic division– “Fight or flight”

– Prepares body for stressful or emergency situations

– Releases norepinephrine

– Controls constriction of blood vessels

30-38



• Parasympathetic division

– Prepares body for rest and digesting

– Controls most of the body’s organs

– Releases acetylcholine

• Sympathetic and parasympathetic divisions are antagonistic

30-39


Apply Your KnowledgeWhat 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.

30-40


Neurologic Testing

• Typical neurologic examination– State of consciousness

– Reflex activity

– Speech patterns

– Motor patterns

30-41


Diagnostic Procedures

• Lumbar puncture

• Magnetic resonance imaging (MRI)

• Positron emission tomography (PET) scan

• Cerebral angiography

• Computerized tomography (CT) scan

• Electroencephalogram (EEG)

• X-ray

30-42


Cranial Nerve Tests

• Olfactory nerve (I) –have patient smell various substances

• Cranial nerves III, IV, and VI – have patient visually track movement of finger

30-43


Cranial Nerve Tests (cont.)

• Cranial nerve V – have patient clench teeth, feel jaw muscles

• Cranial nerve VII – check patient’s facial expression

• Cranial nerve XII – have patient extend and move tongue

30-44


Reflex Testing

• Terms– Areflexia

– Hyporeflexia

– Hyperreflexia

• Tests– Biceps reflex

– Knee reflex

– Abdominal reflexes

30-45




___ 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

A

D

B

C

ANSWER:

30-46


Common Diseases and Disorders of the Nervous System

• Brain and spinal cord injuries– Causes

• Motor vehicle accidents• Sports and recreational accidents• Violence

– Children and teens at highest risk

– Most are preventable

30-47


Common Diseases and Disorders of the Nervous System (cont.)

Disease/Disorder Description

Alzheimer’s disease

Progressive, degenerative disease of the brain

Amyotrophic lateral sclerosis (ALS)

Degeneration of neurons in the spinal cord and brain; Lou Gehrig’s disease; fatal

30-48




Bell’s palsy Weak or paralyzed facial muscles

Brain tumors and cancers

Abnormal growths

Can be primary or secondary tumors; most common – gliomas

30-49




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; sudden and unexpected onset

30-50




Headaches

Tension

Migraines

Cluster

Episodic or chronic

Most severe form of headache

Severe form of migraines; attacks occur in groups

30-51




Meningitis Inflammation of meninges

Multiple sclerosis (MS)

Chronic disease of CNS; myelin is destroyed

Neuralgias Disorders causing nerve pain

30-52




Parkinson’s diseaseProgressive and degenerative motor system disorder

Sciatica Damage to sciatic nerve

Stroke Brain cells die because of an inadequate blood flow; “brain attack”

30-53



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

F

T

Due to a burst of electrical signals that disrupt brain function.

They are group of disorders referred to as nerve pain.

T

ANSWER: Bravo!

30-54


In Summary

30.1 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.

Three types of neurons carry out the functions of the nervous system: the afferent (sensory) nerves detect sensation or other stimuli from the body or

environment and bring it to the CNS for interpretation, the efferent (motor) nerves produce movement or other functions at the direction of the CNS, and the interpretive interneurons act as “interpreters” between the afferent and efferent nerves.

30-55


In Summary (cont.)

30.2 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 function to bring impulses from the cell body to the dendrite of the next neuron.

30-56


In Summary (cont.)

30.3 Nerve impulses send information either from the CNS to the PNS or vice versa.

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.

30-57


In Summary (cont.)

30.4 The brain consists of the cerebrum, diencephalon, brain stem, and cerebellum. Other structures include the blood-brain barrier and the meninges.

The spinal cord consists of 31 spinal segments. The basic function of the spinal cord is to carry sensory information to the brain and motor information to the muscles and glands of the body.

Cerebrospinal fluid (CSF) is located within the subarachnoid space and the central canal of the spinal cord. It cushions the brain and spinal cord.

30-58


In Summary (cont.)

30.5 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.

30-59


In Summary (cont.)

30.6 Tests commonly used to determine neurologic disorders include tests of the reflexes and cranial nerves, as well as diagnostic procedures such as lumbar puncture, MRI, PET, cerebral angiography, CT scan, EEG, and X-ray.

30.7 Many types of diseases and disorders are 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.

30-60


Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.”

~ Dr. Ralph Gerard

End of Chapter 30

CHAPTER 30 The Nervous System 30-2 Learning Outcomes (cont.) 30.1 Describe the general functions of...

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