Axonal transport directions

Anterograde (cell body→terminal) and retrograde (terminal→cell body)

Axonal transport function

Moves molecular materials, not electrical impulses

Axonal transport pathogen risk

Retrograde transport can carry viruses

Guillain–Barré demyelination

Leaves axon exposed; slowed conduction; axon dies without remyelination

GBS myelin fact

Myelin loss does not destroy Schwann cells

Multiple sclerosis effect

CNS demyelination causing slowed, disorganized impulses

MS tremors cause

Irregular signal arrival to muscles

R-on-T consequence

Can trigger ventricular tachycardia leading to unresponsiveness

Brain oxygen storage

Brain cannot store oxygen or perform anaerobic metabolism

Repolarization phase

Sodium channels close; potassium channels open; membrane resets

Chemical synapse

One-way communication via neurotransmitters across synaptic cleft

Electrical synapse

Gap junctions, not chemical

Neuron connectivity

Each neuron connects to thousands of others

GABA effect

Produces IPSPs; hyperpolarizes membrane; decreases excitability

Acetylcholine at NMJ

Excitatory

Acetylcholine at SA node

Inhibitory

SVA neurons

Taste, smell, gut receptors; control chewing, swallowing, salivation

Pharyngeal efferent neurons

Control mastication, facial expression, pharynx/larynx, head movement

White matter outer layer

Neolayer; controls fine motor movements

Withdrawal reflex

Spinal reflex removing body from painful stimulus; no brain required

Golgi tendon reflex

Excess tension causes muscle relaxation (inverse myotatic reflex)

Vagus nerve damage

Dysphagia, constipation, hypoactive bowel sounds, impaired GI motility

CN XI function

Head turning

CN VII damage

Facial droop, dry eyes

CN XII function

Tongue movement

Hypothalamus functions

Controls endocrine system, ANS, fluid/electrolyte balance

Hypothalamus damage

Endocrine and autonomic dysfunction

Thalamus function

Sensory relay; processes emotional auditory stimuli; allows hearing in coma

Frontal lobe motor cortex

Highest control of voluntary movement (arm/hand)

Cerebellum function

Coordination, balance, posture

CSF functions

Cushions CNS; diffusion medium for nutrients/electrolytes/waste

CSF does not transport

Proteins, oxygen, blood cells

Alcohol and BBB

Highly lipid-soluble; rapidly crosses BBB; can cause fatal toxicity

Erectile function

Controlled by sacral parasympathetic fibers

Stress response

Increased glucocorticoids → increased epinephrine → tachycardia, tremors, anxiety

Stroke first assessment

Check capillary blood glucose

Pulseless rhythm but awake

Check telemetry leads first

Withdrawal reflex

Triggered by painful stimulus

Vestibular nerve damage

Vertigo, nystagmus, instability; treat with motion sickness meds, fall precautions

Romberg test

Feet together, eyes closed; tests proprioception

UMN lesion

Spasticity and hyperreflexia

LMN lesion

Atrophy, hyporeflexia, distal weakness

Duchenne muscular dystrophy

Progressive weakness, pseudohypertrophy, cardiomyopathy, respiratory failure; dystrophin deficiency