central nervous system and peripheral nervous system anatomy and physiology assessment diagnostic...

Central Nervous System andPeripheral Nervous System

Anatomy and PhysiologyAssessment

Diagnostic Tests.

Objectives• Name the two structural divisions of the nervous

system and give the functions of each

• List the parts of the neuron and describe the function of each part

• Explain the anatomic location and functions of the cerebrum, brainstem, cerebellum, spinal cord, peripheral nerves, and cerebrospinal fluid

Objectives

• Discuss the parts of the peripheral nervous system and how the system works with the central nervous system

• List the 12 cranial nerves and the areas they serve

Objectives• Identify the significant subjective and objective data

related to the nervous system that should be obtained from a patient during assessment

• Differentiate between normal and common abnormal findings

• List the physiologic changes that occur in the nervous system with aging

• List common laboratory and diagnostic examinations for evaluation of neurologic disorders

General Overview

• The nervous system is responsible for communication and control within the body

• It interprets or processes information received and sends it to the appropriate area of the brain or spinal cord where the response is generated

• It works in conjunction with the endocrine system to maintain homeostasis

Overview of Anatomy and Physiology

• Structural divisions– Central nervous system (CNS)• Brain and spinal cord – interpret incoming sensory

information, and issues instructions based on past experience

– Peripheral nervous system• Somatic nervous system (conscious control) – sends

messages from the CNS to skeletal muscles (voluntary muscles)


• Autonomic nervous system (“involuntary NS – without conscious control). It transmits messages from CNS to the smooth muscle, cardiac muscle, and some glands.– Divided into:» Sympathetic » Parasympathetic» Enteric


• Cells of the nervous system– Neuron – 2 categories:• Neuron – transmitter cells; carry messages from the

brain and spinal cord• Glial or neuroglial cells- supports and protects neurons

while producing CSF

– Neuron = the basic unit of the nervous system• Composed of 3 parts:– Cell body– Axon– dendrites

Axons and Dendrites

• Branch off the main cell body

• Axons conduct impulses away from the cell body

• Dendrites convey impulses toward the cell body


– Neuromuscular junction• The area of contact between the ends of a large

myelinated nerve fiber and a fiber of skeletal muscle

• SYNAPSE: the “gap” or space between each neuron. Nerve impulses are transmitted across this “gap” or synapse by the action of “neurotransmitters”. – Neurotransmitters• chemicals• Act to make sure that the neurological impulse passess

from the nerve to the muscle

Neurotransmitters

• Functions– Acetylcholine: impulse transmission

– Norepinephrine: Maintaining arousal (from deep sleep), dreaming, mood regulation

– Dopamine: motor function; emotional responses

– Serotonin: induces sleep; controls temp.; mood control; affects sensory perception

Overview of Anatomy and Physiology• Neuron coverings• Many neurons have a white, waxy, fatty material called

“myelin”

• Myelin increases the rate of transmission of impulses and protects and insulates the fibers

• Axons leaving the CNS are wrapped in layers of myelin with indentations called the nodes of Ranvier

• These nodes further increase the rate of transmission because the impulse can jump from node to node


• In the peripheral nervous system, the myelin is protected by Schwann cells– Outer layer of Schwann cells protected by another

layer called “neurilemma” which helps to regenerate injured axonsRegeneration can only happen in the PNS

Cerebrospinal Fluid (CSF)

• Bathes the structures of the CNS

• Composed of water, glucose, sodium chloride, and protein

• Acts as a shock absorber for the brain and spinal cord

CENTRAL NERVOUS SYSTEM

Central Nervous System

• One of two divisions of the nervous system• Composed of the brain and spinal cord• Functions somewhat like a computer but more

complex• Cranium protects the brain• Vertebrae protect the spinal cord


• Central nervous system– Brain• Cerebrum• Diencephalon• Cerebellum• Brain stem

– Midbrain; pons; medulla oblongata; coverings of the brain and spinal cord; ventricles

– Spinal cord

Central Nervous System

• Brain – Specialized cells (in the brain’s mass of convoluted

soft, gray or white tissue) coordinate and regulate the functions of the CNS

– One of the largest organs in the body• Approx 3 lbs

– 4 parts: cerebrum, diencephalon, cerebellum, brainstem

Cerebrum• Largest part of the brain• Divided into: left and right hemispheres

Each hemisphere controls the opposite side of the body: the right hemisphere controls the left side of the body, and the left hemisphere controls the right side of the body

• Outer portion = cerebral cortex (“gray” matter)– Arranged in folds called gyri (convolutions)– Grooves called sulci (fissures)

Cerebrum

• Largest part of the brain

• Divides the two hemispheres into 4 lobes named for the bones over them: frontal, parietal, temporal, and occipital lobes

• Corpus Callosum = the connecting bridge between the two hemispheres

Cerebrum

• Function: controls initiation of movement on the opposite side of the body– Specific areas of the cerebral cortex are associated

with specific functions

*NOTE: see box 14-1 p. 654

Sagittal section of the brain (note position of midbrain).

(From Thibodeau, G.A., Patton, K.T. [1987]. Anatomy and physiology. St. Louis: Mosby.)

Youtube.com Animation

Figure 28-1

Diencephalon

• The “interbrain”: lies beneath the cerebrum• Contains the thalamus and the hypothalamus.• Thalamus: serves as a relay station for some

sensory impulses while interpreting other sensory messages such as pain, light touch, and pressure

Diencephalon

• Hypothalamus: • Vital role in temperature, fluid balance, appetite,

and emotions such as fear, pleasure, and pain.

• Sympathetic and parasympathetic nervous systems are under the control of the hypothalamus

• Pituitary gland also under control of hypothalamus

Cerebellum (“little brain”)

• Lies posterior and inferior to the cerebrum• The 2nd largest portion of the brain• Also contains 2 hemispheres

• Uses information received from the cerebrum, muscles, joints, and inner ear to coordinate movement, balance, and posture

Cerebellum (“little brain”)

• Unlike the cerebrum, the right side of the cerebellum controls the right side of the body, and the left side of the cerebellum controls the left side of the body

Brainstem

• Located at the base of the brain • Contains the midbrain, pons, and medulla

oblongata• These structures connect the spinal cord and

the cerebrum• Carries all nerve fibers between the spinal

cord and cerebrum

Sagittal section of the brain (note position of midbrain).

(From Thibodeau, G.A., Patton, K.T. [1987]. Anatomy and physiology. St. Louis: Mosby.)

Brainstem

• Midbrain: responsible for motor movement, relay of impulses, auditory and visual reflexes– The origin of cranial nerves III and IV

• Pons (“bridge”): responsible for sending impulses to the structures superior and inferior to it– Contains a respiratory center– The origin of cranial nerves V through VIII

Brainstem

• Medulla Oblongata: controls heartbeat, rhythm of breathing, swallowing, coughing, sneezing, vomiting , hiccups

Protective Structure of the Brain

• Meninges- three layers that surround both the brain and spinal cord1. Dura mater – outermost membrane2. Arachnoid membrane – 2nd layer3. Pia mater – innermost membrane; provides

oxygen and nourishment to the nervous tissue• These layers bathe the spinal cord and brain in

CSF fluid

Ventricles• 4 spaces or cavities located in the brain• CSF flows into the subarachnoid spaces around the

brain and spinal cord and cushions them

• CSF contains protein, glucose, urea, salts

• Also contains substances that form a protective barrier (the blood-brain barrier) that prevents harmful substances from entering the brain or spinal cord

Spinal Cord

• 17-18 inches• Extends from the brainstem to the 2nd lumbar

vertebra• 31 pair of spinal nerve roots exit the spinal cord• 2 main functions:– Conducting impulses to and from the brain– Center for reflex actions

Disks• Vertebrae separated by disks which serve as shock

absorbers for the vertebral column

• Composed of– Anulus fibrosus: ring of tissue; encircles nucleus pulposus – Nucleus pulposus: saclike structure with a gelatinous

filling that has a high water content

• As we age, nucleus pulposus loses much of its water; less effective as a shock absorber

Pyramids and Pyramidal Tracts

• Pyramidal Tracts carry motor information from the CNS neurons to the PNS neurons

• In the medulla of the brainstem, information from one side of the brain “crosses over” and goes down the pyramidal tracts to affect the other side of the body.

• The area where the “crossing over” occurs is the Pyramids

Spinal Cord

• Reflexive Action• Sensory neuron sends information to the cord• A central neuron (located within the cord) interprets

the impulse• Motor neuron sends the message back to the organ or

muscle involvedA message is sent, interpreted and acted upon without

having traveled to the brain– E.g. knee jerk

Ganglia and Nuclei

• Ganglia are information “hubs” of the PNS– Eg. Dorsal root ganglia contain the cell bodies of

sensory neurons• Nuclei are information “hubs” of the CNS– Eg. Basal Ganglia in the brain contains neurons

connecting the cerebral cortex, thalamus, and brainstem. (incorrectly named; should be “Basal Nuclei)

Peripheral Nervous System


• Peripheral nervous system– Spinal nerves (31 pairs)• Mixed nerves: transmit sensory information to the

spinal cord through afferent neurons and • motor information sent to the CNS to the various areas

of the body through efferent neurons

• Named according to the corresponding vertebra– E.g. C1, C2, T12, L3


• Cranial Nerves (12 pairs)• Attach to the posterior surface of the brain, mainly the

brainstem• Conduct impulses between the head, neck, and brain

except the vagus nerve (X) which also serves the organs in the thoracic and abdominal cavities

• More detail: p. 657 Table14-1 Cranial Nerves


– Autonomic nervous system: Controls the involuntary activities of the viscera, including smooth muscle, cardiac muscle, and glands• Primary function : maintain internal homeostasis– E.g. nml heartbeat, constant body temp, nml

respirations• To maintain homeostasis, autonomic nervous system

has 2 divisions:• Sympathetic nervous system: “Fight or Flight”• Parasympathetic nervous system: Conserves, restores,

and maintains vital body functions

Sympathetic vs Parasympathetic

• These 2 divisions are antagonistic to each other: one slows action; one accelerates action

• These systems function simultaneously but have the ability to dominate when the need arises


• Effects of Normal Aging on the Nervous System– Loss of brain weight– Loss of neurons– Reduction in cerebral blood flow– Decrease in brain metabolism and oxygen

utilization– Decreased blood supply to spinal cord causes

decreased reflexes

Prevention of Neurological Problems

• Modifying lifestyle factors– Reducing risk for cardiac disease– Stop smoking– Avoid drug/alcohol– Safe use of motor vehicles: seat belts, appropriate

speed, helmets for motorcycle riding

Prevention of Neurological Problems

• Modifying Lifestyle factors (cont.)

– Safe swimming practices– Safe handling and storage of firearms– Prompt treatment of infections: sinus, ear– Sexually safe practices

Laboratory and Diagnostic Examinations

Laboratory and Diagnostic Examinations• For the neurologically impaired person:• Urine:– Culture: to rule out infection– Drug screens: to rule out drug use– Glucosuria

• Blood:– Arterial blood gases: monitor the oxygen content

of the blood– Routine lab work


• Cerebrospinal fluid: – Checked and cultured if indicated for: infection, protein

(elevated with degenerative diseases and brain tumor)

• Radiographs: – Skull and vertebra: can detect fractures– Used less frequently than CT

• Computed tomography (CT) • Noninvasive examination of the specific levels of the

spinal cord to be visualized, bony vertebrae, and the spinal nerves


• Brain scan– Uses radioisotopes and a scanner• Concentrated areas of uptake detects pathological

conditions in the cerebrum• Used less frequently than CT or MRI

• Magnetic Resonance Imaging (MRI) • Produces precise, clear images of internal structures,

soft tissue• Pt. must remove anything metal in or on clothing, or

body.Internal devices may preclude the use of MRI


• Positron Emmission Tomography Scan (PET)• Injection of radioactive flourine shows glucose

metabolism in the area that is questioned. • Color composite picture is obtained • Level of glucose metabolism can be translated into

indications of a pathologic state


• Lumbar puncture: – To obtain CSF for examination, to relieve pressure, or to

introduce dye or medication

Contraindicated in pts. with increased intracranial pressure due to the risk of the medulla oblongata herniating into the foramen magnum during withdrawal of CSF fluid

Figure 14-5

Position and angle of the needle when lumbar puncture is performed.

(From Elkin, M.K., Perry, A.G., Potter, P.A. [2004]. Nursing interventions and clinical skills. [3rd ed.]. St. Louis: Mosby.)

Figure 27-8


• Electroencephalogram– EEG– Used to provide evidence of focal or generalized

disturbances of brain function by measuring the electrical activity of the brain

• Angiogram– A procedure used to visualize the cerebral arterial

system by using radiopaque material


• Carotid duplex study: – Combines ultrasound and pulsed Doppler technology– Graph measures velocity of blood flow in the carotid

arteries

• Electromyogram (EMG)– Measures the contraction of a muscle in response to an

electrical stimulus– Provides evidence of lower motor neuron disease

• Echoencephalogram– Uses ultrasound to depict intracranial structures

Miscellaneous Slides

NEUROLOGICAL ASSESSMENT

• Cerebral function• Cranial nerve function• Motor function• Sensory function• Reflexes

Assessment of the Neurological System

• History– Comprehensive– From patient; family members/significant other– Symptoms experienced– Pt. understanding and perception of what is

happening– Pp. 691, 692


• Mental status– Orientation, mood, behavior, general knowledge– Short and long-term memory– Attention span and ability to concentrate– Be specific in documentation


• Level of consciousness– The earliest and most sensitive indicator that

something is changing• E.g. A decreasing LOC is the earliest sign of increased

intracranial pressure

– 2 components: arousal (wakefulness); awareness– Observations are recorded in terms of behavior

and signs (not a general “disoriented”)


• Language and speech– Aphasia: language function is defective or absent• Due to injury to frontal lobe and part of temporal lobe• Includes speech, reading, writing, and understanding


– Dysarthria• Difficult, poorly articulated speech• Usually results from interference in the control over the

muscles of speech• Cause is usually damage to a central or peripheral

nerve


• Cranial nerve function– See handouts

• Motor function– Assess gait, stance, muscle tone, coordination,

involuntary movements, and muscle stretch reflexes

– Note bilateral responses


• Motor function cont.– Mobility: • Paralysis = loss of function• Paresis = lesser degree of movement deficit• Flaccid = weak, soft, flabby or lacking normal muscle

tone• Spastic = involuntary sudden movement or muscle

contraction


• Sensory and Perceptual Status– Pain, touch, temperature and proprioception– Proprioception: the sensation pertaining to

spatial-position and muscular-activity stiumuli• Gives one the ability to know the position of the body

without looking at it and to know objects by the sense of touch

– Unilateral neglect: perceptually unaware of and inattentive to one side of the body

– Hemianopia: blindness or defective vision in half of the visual field


• Glasgow coma scale• A quick, practical, standardized system for assessing the

degree of consciousness impairment in the critically ill patient, and

• For predicting the duration and ultimate outcome of coma, particularly with head injuries

• Consists of an assessment of 3 parts:– Eye opening– Best motor response– Best verbal response

central nervous system and peripheral nervous system anatomy and physiology assessment diagnostic...

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