Nervous System

Anatomy and Physiology Review

Neurological Assessment

Anatomy and Physiology

The basic and functional unit

Neurons

The spinal cord and brain

The nerves and nerve ganglia

Sympathetic and parasympathetic

Central Nervous System

Peripheral Nervous System

Autonomic Nervous System

Neurons

TypesSensory (Afferent) neurons: transmit impulses to spinal cord or brain

Motoneurons (efferent) : transmit impulses away from brain or spinal cord to muscles or glands

Interneurons: transmit impulses from sensory neurons to motoneurons

StructureCell Body: contains a nucleus and other cytoplasmic matter

Axon: carries impulse away from cell body

Dendrites: carry impulses toward cell body

Myelin: multiple, dense layers of membrane around an axon or dendrite; myelinated nerve fibers transmit nerve impulses more rapidly than nonmyelinated fibers

SynapsePoint of contact between axon of one cell and dendrite of another

Neuroglia: support, defend, and nourish

Brain

Brain Stem

Medulla: conducts impulses between the cord and brainPons: conducts impulses between the cord and various parts of the brainMidbrainIntegrates and analyzes sensory input from ears, eyes and various regions of the cerebral cortex

Cerebellum: exerts synergic control over skeletal muscles

Diencephalon

Thalamus: crudely translates sensory impulses into sensations but does not localize them

Hypothalamus: makes ADH and oxytocin, which are secreted by the posterior pituitary

Optic chiasm: the point of crossing over (decussation) of optic nerve fibers

Cerebral Cortex

Frontal lobe: influences abstract thinking, sense of humor, and uniqueness of personality

Parietal lobe: Interpret sensations; provide appreciation of size, shape, texture, and weight

Temporal lobesTranslate nerve impulses into sensations of sound and interpret sounds (Wernicke’s area; usually in dominant hemisphere)

Occipital lobeTranslates nerve impulse into sights and interprets sights

Brain and Cord Fluid SpacesSubarachnoid space around the brain and cord, extending into the fourth and fifth lumbar vertebraeCentral canal inside the cordVentricles and cerebral aqueduct inside the brain; four cavities known as first, second, third, fourth ventriclesCerebrospinal fluid (CFS) formed by plasma filtering from network of capillaries (chronoid plexus) in each ventricleCFS circulates throughout ventricles, brain and subarachnoid space and returns to blood via venous sinuses of brain

Autonomic NervousSystem

Two Divisions

Sympathetic: adrenergic fibers secrete norepinephrine; influences smooth muscle of blood vessels, hairs, and sweat glands

Parasympathetic: cholinergic fibers secrete acetylcholine, influences digestive tract and smooth muscle to promote digestive gland secretion, peristalsis, and defecation; influences the heart to decrease rate and strengthen contractility

DIAGNOSTICPROCEDURES

NEUROLOGIC ASSESSMENT

Definition: systematic evaluation of the cranial nerves, motor and sensory functioning, and mental status to detect neurologic abnormalities

Cranial Nerves

Olfactory (I)ability to identify familiar odors such as mini or alcohol with eyes closed and one nostrils occluded at a time

Optic (II) visual acuity measured by use of Snellen chart or by gross estimation with reading material; gross comparison of visual fields with those of examiner; color perception

Oculomotor (III), Trochlear (IV) and Abducens (VI)ability of the pupils to react equally to light and to accommodate to varying distances

Trigeminal (V)sensation of the face evaluated by lightly stroking cotton across forehead, chin, and cheeks while the client’s eyes are closed; ability to clench the teeth (jaw closed)

Facial (VII)symmetry of the facial muscles as the client speaks or is asked to

make faces

Acoustic or Vestibulocochlear (VIII)hearing acuity determined by watch tick or whispered numbers; Weber’s test may be performed by holding the stem of a vibrating tuning fork at midline of the skull (should be heard equally in both ears)

Glossopharyngeal (IX) and Vagus (X)uvula should hang in midline; swallow and gag reflexes should be

intact

Spinal accessory (XI)symmetric ability to turn the head or shrug the shoulders against counterforce of the examiner’s hands

Hypoglossal (XII)ability to protrude the tongue without deviation, to left or right,

and without tremors

Motor function BalanceObservation of gaitRomberg Test: positive if the client fails to maintain an upright position with feet together when the eyes are closedCoordination: ability to touch the finger to the nose when arms are extended or to perform similar tasks smoothlyMuscle strength: evaluated by having the client move symmetrical muscle groups against opposition supplied by the examiner

Sensory function : bilateral testing of the response to light touch with cotton, sharp versus dull stimuli, vibration of a tuning forkMental Status (cerebral functioning)Level of consciousness: determined by the response to stimuli (verbal, tactile or painful)Orientation to person, place, and time: determined by general conversation and direct questioning>Judgment, memory, and ability to perform simple calculations>Appropriateness of behaviour and moodReflexesDeep tendon reflexes (biceps, triceps, patellar, Achilles) with a reflex hammer; classification from 0 (absent) to 4+ (hyperactive); 2+ is normalPlantar: plantar flexion of the foot when the sole is stroked firmly with a hard object such as tongue blade; abnormal adult response (dorsiflexion of the foot and fanning of the toes) is described as a positive Babinski and is indicative of corticospinal tract disease

GLASGOW COMA SCALE (GCS)Definition : technique of objectifying a client’s level of responses; client’s best response in each are is given a numeric value, and the three values are totalled for a score ranging from 3 (deep coma) to 15 (normal)Eye-opening ability: spontaneous (4); to speech (3); to pain (2); no response (1)Motor response: obeys commands (6); localizes pain (5); withdraws (4); abnormal flexing (3); extension (2); no response (1)Verbal response: oriented (5); confused (4); inappropriate words (3); incomprehensible soundes (2); no response (1)

COMPUTERIZED TOMOGRAPHY (CT)Definition>Cross-sectional visualization of the head or other body cavity determined by computer analysis of relative tissue density as an x-ray beam passes through>Provides three-dimensional information about location and extent of tumors, infracted areas, atrophy, and vascular lesions>May be done with intravenous injection of dye for contrast enhancement

MAGNETIC RESONANCE IMAGING (MRI)Definition>Uses magnetic fields and radio waves to produce cross-sectional images>Produces accurate images of blood vessels, bone marrow, gray and white brain matter, spinal cord, globe of the eye, heart, abdominal structures, and breast tissue, and can monitor blood velocity

LUMBAR PUNCTUREDefinition: involves the introduction of a needle into the subarachnoid space below the spinal cord, usually between L3 and L4 or L4 and L5Purposes>Withdrawal of cerebral spinal fluid for diagnostic purposes or to reduce spinal pressure (normal is 70 to 200 mm H2O)>Measurement of spinal pressure (Queckenstedt’s test involves compression of the jugular veins; normally pressure will rise; but it blockage exists, pressure will not change)>Injection of medication such as anesthetics

POSITRON EMISSION TOMOGRAPHY (PET)Definition>Client is given strong radioactive tracers that emit signals, computer analysis of the emitted gamma rays forms images>Determines blood flow, glucose metabolism, and oxygen extraction>Effective in diagnosis of brain attack, brain tumors, epilepsy; can evaluate progress of >Alzheimer’s disease, Parkinson’s disease, bipolar disorders, and head injuries

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