nero part 1

nervous system parts

CNS (brain and spinal cord) and PNS (nerve roots/plexuses and peripheral nerves)

PNS is divided into

autonomic and somatic nervous system

broad functions of the nervous system

Perception (sensory input and recognition), action (motor output) and cognition

main nervous system pathways

afferent pathway (info from periphery to CNS) and efferent pathway (info from CNS to periphery for action)

upper motor neurons

fibers from the cortex through the spinal cord that synapse on anterior horn cells in the anterior spinal cord. pain signals from the body to spinal cord

lower motor neurons

Anterior horn cells/axonal projections in peripheral nerves. signals from spinal cord to muscles

Decussation

corticospinal tract crosses at the cervicomedullary junction (bottom of brainstem)

Lesions above decussation

opposite sided or contralateral weakness

Lesions below decussation

same sided or ipsilateral weakness

UMN lesions can occur in

cerebral hemispheres, cerebellum, brainstem and spinal cord

LMN lesions can occur in

anterior horns, nerve roots, peripheral nerves, neuromuscular junctions or muscles

muscle weakness in UMN

all types of plegia (paralysis)

muscle weakness in LMN

proximal (myopathy) or distal (neuropathy)

muscle tone in UMN

spasticity and rigidity

muscle tone in LMN

hypotonia

fasiculations in UMN

absent

fasiculations in LMN

present (especially on the tongue)

tendon reflexes in UMN

hyperreflexia

tendon reflexes in LMN

hypo/areflexia

Lesions in UMN can cause

paralysis, muscle spasticity (state of tonic contraction), CLONUS, hyperactive reflexes and babinski reflex

in paralysis from lesions in UMN

LMN still work but dont receive signals from the brain

spinal cord injury

Bilateral weakness with bowel/bladder signs

peripheral nerve injury

Bilateral distal weakness with lower neuron signs

neuromuscular junction injury

Bilateral fatigable weakness

muscle disease

Bilateral proximal weakness

Somatosensory input

periphery to CNS using peripheral nerves (connect to the spinal cord by posterior dorsal roots)

somatosensory pathways

Posterior (dorsal) columns and Spinothalamic (anterolateral) tracts. both tracts transmit some light

Posterior (dorsal) columns

Transmit vibration and proprioception (position in space). CROSS IN THE LOWER MEDULLA

Spinothalamic (anterolateral) tracts

Transmit pain and temp. cross right after entering the spinal cord

in the Spinothalamic tract

lesions in the brain/brainstem and spinal cord cause contralateral pain/temp loss

Dermatomes

areas of skin that connect to a single dorsal nerve root (8 cervical, 12 thoracic and 5 lumbar/sacral)

Wernicke’s area

L temporo-parietal region and responsible for speech comprehension. lesions can cause receptive aphasia-a (difficulty understanding others) and senseless speech

Broca’s area

L inferior frontal gyrus and responsible for speech production. lesions cause expressive aphasia and difficulty speaking (NORMAL COMPREHENSION)

motor homunculus

body parts along the PREcentral gyrus

sensory homunculus

body parts along the POSTcentral gyrus

Cerebrovascular Accident

stroke

stroke in the Anterior cerebral artery causes

abulia (lack of motivation/willpower) from ischemia/infarction in the frontal lobe

stroke in the middle cerebral artery

L side causes aphasia and R side causes neglect (cant recognize contralateral side of body)

stroke in Posterior cerebral artery causes

visual field deficits

stroke in Lacunar infarcts cause

isolated motor/sensory deficits

stroke in Watershed infarcts causes

person in barrel syndrome (proximal weakness in arms)

Watershed infarcts at MCA/PCA territories

Higher order visual deficits

Nerve I Olfactory

smell. lesions are caused by nasal obstruction from viral/sinus infections, Kallmans syndrome or tumor (unilateral loss of smell)

Nerve V Trigeminal

facial SENSATION and chewing. 3 branches ophthalmic (V1) maxillary (V2) and mandibular (V3)

Nerve VI Abducens

eye Abducens

Nerve VII Facial

inner ear, facial MUSCLES and Taste

unilateral UMN lesion (hemispheric stroke)

contralateral lower face weakness but normal forehead movement

Nerve VIII Vestibulocochlear

sound/info about the heads movement/position. lesions can cause hearing loss or vestibular deficits

Vestibulo-ocular reflex

turn head to one side and eyes turn in the opposite direction. shows whether brainstem is intact

Nerve IX Glossopharyngeal

gag reflex and sensory input from the external ear

Nerve X Vagus

parasympathetic. lesions cause palate deviation, hoarseness, difficulty swallowing and no gag reflex

Nerve XI Accessory

sternocleidomastoid and trapezius muscles. lesions cause difficulty shrugging and turning head to one side

Nerve XII Hypoglossal

tongue muscles