Cns Ho1. Anaphysio.assess

NEURO HO1: ANATOMY & PHYSIOLOGY I. Anatomy of the Nervous System * nervous system consists of 2 divisions: 1. CNS a. brain b. spinal cord 2. PNS a. somatic, or voluntary nervous system b. autonomic, or involuntary nervous sytem

* 3 parts of a neuron: a. cell body or soma - neuron’s main cellular space; houses the nucleus; where the neuron’s main genetic information can be found * ganglia / nuclei - nerve cell bodies occuring in clusters * center - cluster of cell bodies with the same function b. dendrite - receives messages from other neurons c. axons - sends messages to other neurons

4 morphologic regions of a neuron: a. cell body or soma b. dendrite c. axons d. presynaptic terminal: near the ends, the axon divides into fine branches that have specialized swelling called presynaptic terminals; through these terminals one neuron transmits information to other neurons * 2 types of neurons: 1. sensory - carry impulses to the brain 2. motor - carry impulses away from the brain > neurons are insulated by Schwann cells

living Schwann cells rendered in color through computer enhancement

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Gener C. Sibal, RN,MD,FPOA

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*Schwann cells are the supporting cells of the PNS. Like oligodendrocytes schwann cells wrap themselves around nerve axons, but the difference is that a single schwann cell makes up a single segment of an axon's myelin sheath. Oligodendrocytes on the other hand, wrap themselves around numerous axons at once.

The principle function of oligodendrocytes is to provide support to axons and to produce the Myelin sheath, which insulates axons.

* neurotransmitters: > communicate messages from one neuron to another; or from a neuron to a specific target tissue > action - to potentiate, terminate, or modulate a specific action and can either excite or inhibit the target cell’s activity > ex. of neurotransmitters - acetylcholine - serotonin - norepinephrine - amino acids - dopamine - polypeptides (not long enough to become a full-fledged amino acid) II. CNS - Anatomy of the Brain

* 3 major areas of the brain: 1. cerebrum - composed of: > 2 cerebral hemispheres - joined together by the corpus callosum (responsible for transmission of information from one side of the brain to the other) * gyri - convolutions on the outside surface each cerebrum - serve to increase the surface area of the brain * grey matter - makes up the external or outer portion (about 2 to 5 mm in depth) - made up of billions of nerve cell bodies hence the gray appearance * white matter - makes up the inner layer - composed of nerve fibers and neuroglia (support tissue)

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Gener C. Sibal, RN,MD,FPOA

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* dominant hemisphere - for verbal, linguistic, arithmetical, calculating, and analytical functions * non-dominant hemisphere - for geometric, spatial, visual, pattern, and musical functions *** right-handed person - has dominant left cerebral hemisphere > thalamus - acts as a relay station for all sensations except smell > hypothalamus - regulate appetite, sleep-wake cycle, blood pressure, aggressive and sexual behavior, emotional responses; also regulate and control the autonomic nervous system > basal ganglia - for controlling movement and establishing postures

> connections for CN I and CN III 2. brain stem - the stemlike part of the brain that is connected to the spinal cord; or conversely, the extension of the spinal cord up into the brain

* composed of: > midbrain > pons > medulla > connections for CN II, IV to XII

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Gener C. Sibal, RN,MD,FPOA

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3. cerebellum - located under the cerebrum and behind the brainstem - responsible for coordination of movement; for balance and position sense (awareness of where a body part is in relation to space)

5 lobes of the cerebral hemispheres:

a. frontal lobe - largest lobe - involved in motor function, problem solving, spontaneity, memory, language, initiation, judgement, impulse control, and social and sexual behavior - contains Broca’s area (motor control of speech); in the left cerebral hemisphere > responsible for producing coherent speech > damage to this area will result in people having trouble producing grammatical language

b. temporal lobe - organizes and interprets auditory sensory inputs - contains the Wernicke’s area; in the left cerebral hemisphere > responsible for analyzing spoken language > damage to this area results in a condition where people can hear spoken language but cannot understand it c. parietal lobe - responsible for sensory perception d. occipital lobe - responsible for visual interpretation

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Gener C. Sibal, RN,MD,FPOA

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** e. 5th lobe - limbic lobe - for feelings and emotions Meninges of the Brain:

a. dura mater - outermost layer - tough, fibrous connective tissue - between the dura and the arachnoid is the subdural space b. arachnoid - middle membrane - has no blood supply - contains the choroid plexus (responsible for the production of CSF) - between the arachnoid and the pia is the subarachnoid space which contains the CSF c. pia mater - innermost membrane; vascular membrane - transparent layer that hugs the brain closely Cerebrospinal Fluid

> CSF is produced mainly by a structure called the choroid plexus in the right and left lateral, third and fourth ventricles > CSF flows from the 2 lateral ventricles to the third ventricle through the interventricular foramen (also called the foramen of Monro) > CSF flows from the third ventricle to the fourth ventricle through the cerebral aqueduct (also called the Aqueduct of Sylvius) > from the fourth ventricle CSF then flows into the cisterna magna through the lateral foraminae of Luschka (there are two of these) and the median foramen of Magendie (only one) * cisterna magna - opening in the subarachnoid space created by the separation of the arachnoid and pia mater

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Gener C. Sibal, RN,MD,FPOA

5

> CSF flows down the dorsal surface of the spinal cord and is then returned to the brain where it is absorbed back into the blood stream through the arachnoid villi * when the CSF pressure is greater than the venous pressure, CSF will flow into the blood stream; however, if the CSF pressure is less than the venous pressure, the arachnoid villi will not let blood pass into the ventricular system * normal adult - approximately 500 ml of CSF is produced / day - approximately 125 to 150 ml is left unabsorbed and circulating at any given time CSF functions: 1. protection - CSF acts to cushion a blow to the head and lessen the impact 2. bouyancy - because the brain is immersed in fluid, the net weight of the brain is reduced from about 1,400 grams to about 50 grams; therefore, pressure at the base of the brain is reduced 3. excretion of waste products - the one-way flow from the CSF to the blood takes potentially harmful metabolites, drugs and other substances away from the brain 4. endocrine medium - CSF serves to transport hormones to other areas of the brain; hormones released into the CSF can be carried to remote sites of the brain where they may act III. CNS - Anatomy of the Spinal Cord * spinal cord > extends from the foramen magnum at the base of the skull to the level of L1-L2 or L2-L3 where it tapers to a fibrous band called the conus medullaris > below the conus medullaris extend the nerve roots called cauda equina because they resemble horse’s tail > unlike in the brain where the gray matter is external and white matter is internal, in the spinal cord grey matter is in the center and is sorrounded on all sides by white matter

brain spinal cord > contained in the grey matter: - anterior horn - motor / efferent; for voluntary and reflex activity of muscles - posterior horn - sensory / afferent; serve as a relay station in the sensory/reflex pathway > contained in the white matter: - ascending tracts (sensory) - descending tracts (motor) IV. Peripheral Nervous System > includes: a. cranial nerves CN NERVE I Olfactory II

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Optic

TYPE EXAMINATION Se - with eyes closed, test for ability to recognize objects through sense of smell using one nostril at a time Se

- for vision: a) Snellen’s chart - test for visual acuity VA = 20/50 → means this patient can read at 20 ft.

Gener C. Sibal, RN,MD,FPOA

6

III

Oculomotor

Mo

IV V

Trochlear Trigeminal

Mo Mi

VI VII

Abducens Facial

Mo Mi

VIII Auditory

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Se

what a normal eye can read from 50 ft. * for patients using corrective lenses - test using the corrective lenses * legally blind: VA ≤ 20/200 or VA of < 20˚ of the visual field in the better eye b) confrontation test - test for visual field / peripheral vision c) check color vision Ishihara test - for red-green color blindness - pupillary constriction; upper eyelid elevation (should be non-ptotic; most eye movements - downward and inward eye movement - S: sensation to cornea, nasal/oral mucosa, facial skin test for corneal reflex M: try to separate a clenched jaw - lateral eye movement - S: taste perception on anterior 2/3 of the tongue M: ask client to puff out cheeks / and to close eyelids against resistance - cochlear portion: test for ability to hear 1. voice test - block 1 ear; examiner stands 1-2ft away and whispers; ask what the examiner said; repeat for other ear 2. watch test - test for high-frequency sounds; ticking watch is held 5 inches away from each ear 3. tuning fork tests: a. Weber - vibrating tuning fork is held in contact with the midpoint of the vertex; sound must be heard equally in both ears - if not: ex. if lateralized to the right ear (heard louder at the right ear) - either means: > conductive (due to physical obstruction to transmission of sound waves) hearing loss of the right side… or > sensorineural (due to defect in any of the ff: ear / CN8 / brain) hearing loss of the left side b. Rinne - compares air and bone conduction - tuning fork is placed in contact with the mastoid process until the client no longer hears it then quickly transfers it in front of the pinna (w/o touching the client) (+) Normal: sound is heard 2x longer in front of the pinna (-) if patient can no longer hear the sound in front of the pinna > this means patient has conductive hearing loss on that side (BC>AC) - Rinne test has no value in determining sensorineural hearing loss 4. Audiometry a. pure tone audiometry - to identify problems with hearing sounds in the environment b. speech audiometry - measures the ability to hear spoken words - vestibular portion: test for sense of equilibrium

Gener C. Sibal, RN,MD,FPOA

7

IX

Glossopharyngeal

Mi

X

Vagus

Mi

XI

Accessory spinal

Mo

XII

Hypoglossal

Mo

1. Romberg’s test - test for falling; stand with feet together, arms at the sides, eyes closed > (-) normal if with no or little swaying > (+) if with significant sway 2. caloric testing - patient supine with HOB elevated to 30˚ - instill cold or warm water: normal (normal CN3,6,8) response is conjugate eye movements toward the side being irrigated followed by rapid nystagmus to opposite side 3. test for past-pointing 4. gaze nystagmus evaluation - client’s eyes are examined as client looks ahead, 30˚ to each side, upward, downward > if abn. - will have nystagmus 5. Hallpike’s maneuver - to assess for positional vertigo or induced dizziness - client supine, head rotated to 1 side for 1 minute > (+) if with nystagmus after 5 to 10 secs. 6. Electronystagmography - distinguishes between normal and drug-induced & pathologic nystagmus - S: test for sensation to pharyngeal soft palate and tonsillar mucosa; taste perception on posterior 1/3 of the tongue M: test for ability to swallow - S: elicit gag reflex M: observe soft palate and note for symmetrical elevation when the patient says “AHHH” - S: test for sensation behind the ear M: test for swallowing and phonation - S: elicit gag reflex M: observe soft palate and note for symmetrical elevation when the patient says “AHHH” - shrug shoulders against resistance - resist neck rotation - push chin against the examiner’s hand - tongue should be symmetrical

b. spinal nerves > 31 pairs of spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal > dorsal roots - sensory ventral roots - motor c. autonomic nervous system > regulates the activities of internal organs (heart, lungs, blood vessels, digestive organs, glands) > responsible for maintenance and restoration of internal homeostasis > 2 major divisions: - thoracolumbar division: sympathetic nervous system - mediated by norepinephrine > predominate during stressful conditions; fight or flight response - craniosacral division: parasympathetic nervous system - mediated by acetylcholine > predominate during non-stressful conditions; “wine and dine” - calms the nerves

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Gener C. Sibal, RN,MD,FPOA

8

> pulse / BP > pupils > peristalsis > salivation > blood vessels > bladder > skin > activity

Autonomic Nervous System Sympathetic Parasympathetic (adrenergic) (cholinergic) ↑ ↓ dilated constricted ↓ ↑ ↓ ↑ constricted dilatation relaxed constricted dry diaphoresis hyperactive weakness

V. Upper Motor Neuron vs. Lower Motor Neuron Lesions * Upper Motor Neuron - located entirely within the CNS UMN lesions - occur above the anterior horn or the motor nuclei of cranial nerves * Lower Motor Neuron - located both in the CNS and PNS LMN lesions - occur if a motor nerve between the muscle and the spinal cord is damaged; result in paralysis * Comparison: UMN Lesion > loss of voluntary control > increased muscle tone > muscle spasticity > no muscle atrophy > hyperactive and abnormal reflexes

LMN Lesion > loss of voluntary control > decreased muscle tone > flaccid muscle paralysis > muscle atrophy > absent or decreased reflexes

VI. Abnormal Motor Posturing - characterized by generalized extension of the trunk and lower limbs with increased muscular tone * Decorticate Posturing - definiton above plus: rigidity, flexion of the arms, clenched fists; the person holds the arms bent and inward toward the body with the wrists and fingers bent and held on the chest - indicates damage to the cerebral hemispheres - better prognosis than decerebrate * Decerebrate Posturing - involves rigid extension of the arms and legs, downward pointing of the toes, and backward arching of the head - indicates damage to the midbrain VII. Muscle Strength Grading: * Grading: 0 - absolutely no visible contraction 1 - there is visible contraction but no movement 2 - some movement but insufficient to counteract gravity 3 - barely against gravity (with inability to resist any additional force) 4 - less than normal (but more than enough to resist gravity) 5 - normal

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Gener C. Sibal, RN,MD,FPOA

9

* Myotome: refers to a muscle and the nerve supplying it C5 – Shoulder abduction / Elbow flexion C6 – Elbow flexion / Wrist extension C7 – Elbow flexion / Wrist extension / Finger extension C8 – Finger flexion / Thumb abduction T1 – Finger abduction / Finger adduction L1 - Hip flexion L2 – Hip flexion L3 – Knee extension L4 – Foot dorsiflexion with inversion L5 – Great toe extension S1 – Ankle plantar flexion

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Gener C. Sibal, RN,MD,FPOA 10

* Dermatome: - a skin area innervated by the sensory fibers of a single nerve root

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Gener C. Sibal, RN,MD,FPOA 11

VIII. Glasgow Coma Scale Motor

obeys commands localizes pain withdraws from pain decorticate (flex) decerebrate (ext) no response

M6 M5 M4 M3 M2 M1

Verbal

oriented confused inappropriate words incomprehensible sounds no response

V5 V4 V3 V2 V1

Eye Opening

spontaneous to sound to pain no response

E4 E3 E2 E1

note: GCS ≤ 7 = COMA most important indicator - eye opening IX. Levels of Consciousness Alert - normal awake and responsive state Lethargic - easily aroused with mild stimulation; can maintain arousal Somnolent - easily aroused by voice or touch; awakens and follows commands; requires stimulation to maintain arousal Obtunded/Stuporous - arousable only with repeated and painful stimulation; verbal output is unintelligible or nil; with some purposeful movement to noxious stimuli Comatose - no arousal despite vigorous stimulation, no purposeful movement - only posturing * Coma - a clinical state of unconsciousness in which the patient is unaware of self or the environment for prolonged periods * Akinetic mutism - a state of unresponsiveness to the environment in which the patient makes no movement or sound but sometimes opens the eyes * Persistent vegetative state - a condition in which the patient is described as wakeful but devoid of conscious content, without cognitive or affective mental function

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Gener C. Sibal, RN,MD,FPOA 12

X. Reflexes: Deep and Superficial / Pathologic * Deep reflexes: - are all stretch (myotatic) reflexes such as those elicited by a sharp tap in the appropriate tendon or muscle to induce stretching of the muscle that results in a reflexive shortening of the same muscle * myotatic reflex - tonic contraction of the muscles in response to a stretching force, due to stimulation of muscle proprioceptors

Biceps reflex - C5, C6 Brachioradialis reflex - C5, C6 Triceps reflex - C6, C7 Finger flexors - C6 to T1 Knee or Patellar reflex - L2, L3, L4 Ankle or Achilles Tendon reflex - S1, S2

Grade Description 0

absent

1+

hypoactive

2+

normal

3+

hyperactive without clonus

4+

hyperactive with clonus

> decreased reflexes should lead to suspicion that the reflex arc has been affected (LMN); lesions of the UMNs result in increased reflexes at the spinal cord by decreasing tonic inhibition of the spinal segment. > if the DTRs are hyperactive, test for ankle clonus (with the knee partially flexed, quickly dorsiflex the ankle * clonus - a repetitive, usually rhythmic, and variably sustained reflex response elicited by manually stretching the tendon; clonus may be sustained as long as the tendon is manually stretched or may stop after up to a few beats despite continued stretch of the tendon * Superficial reflexes: - are withdrawal reflexes induced by noxious or tactile stimuli - these reflexes are quite different from the muscle stretch reflexes in that the sensory signal has to not only reach the spinal cord, but also must ascend the cord to reach the brain; the motor limb then has to descend the spinal cord to reach the motor neurons (polysynaptic reflex) - these reflexes can be abolished by severe lower motor neuron damage or destruction of the sensory pathways from the skin that is stimulated; however, the utility of superficial reflexes is that they are decreased or abolished by conditions that interrupt the pathways between the brain and spinal cord (such as with spinal cord damage)

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Gener C. Sibal, RN,MD,FPOA 13

> Abdominal reflex - stroke the abdomen lightly on each side in an inward direction above and below the umbilicus - above umbilicus (T8, T9, T10) below umbilicus (T10, T11, T12) > ex. other superficial reflexes: corneal / gag / cremasteric / plantar * Pathologic reflexes: > Babinski reflex - stroke the lateral aspect of the sole of each foot and then come across the ball of the foot medially with a sharp object - positive: dorsiflexion of the great toe and fanning of the lesser toes - indicative of UMN lesion XI. Abnormal Respiratory Patterns and Localizations

Cheyne-Stokes - rhythmical with periods of apnea Neurogenic Hyperventilation - regular, rapid & deep sustained respirations Apneustic - irregular respiration with pauses at the end of inspiration and expiration Cluster - clusters of breath with irregularly spaced pauses Ataxic - totally irregular in rhythm and depth

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Gener C. Sibal, RN,MD,FPOA 14