Episode Details

1. Structure & Cellular Biology

• Organization: The CNS consists of the brain, spinal cord, and CN I-II. The PNS contains CN III-XII, spinal nerves, and the ANS.
• Cells & Myelin: Neurons conduct action potentials via saltatory conduction across nodes of Ranvier, accelerated by myelin. Astrocytes form the blood-brain barrier and create scar tissue (gliosis) upon injury. Oligodendrocytes myelinate CNS axons; Schwann cells myelinate PNS axons.
• Synapses: Neurotransmitters cross synapses to alter impulse transmission, using excitatory (glutamate) or inhibitory (GABA) pathways.

2. Pathways, Lobes & Perfusion

• Tracts: Ascending tracts carry sensory input (spinothalamic for pain/temp; dorsal columns for touch, vibration, position). Descending tracts (corticospinal) carry motor output.
• Motor Lesions: UMN lesions cause spasticity, hyperreflexia, and weakness. LMN lesions cause flaccidity, hyporeflexia, and muscle atrophy.
• Cerebral Lobes: Frontal lobe controls cognition and motor speech (Broca's). Parietal lobe senses sensory data. Temporal lobe handles hearing/language (Wernicke's); occipital processes vision.
• Perfusion: Anterior circulation stems from carotids; posterior from vertebral-basilar systems, joining at the circle of Willis.

3. Bedside Assessment

• Mental Status: Ongoing check of consciousness, orientation, cognition, and mood/affect.
• Cranial Nerves: CN III, IV, VI coordinate eye movements. Pupil non-constriction (CN III) is an early sign of brain herniation. Corneal reflex tests CN V/VII. Gag reflex tests CN IX/X; a weak gag risks aspiration. Midline tongue protrusion checks CN XII.
• Sensory & Proprioception: Test touch, pain, vibration, and digit position. A positive Romberg test indicates posterior column dysfunction.
• Reflexes: Deep tendon reflexes are graded 0–5. An extensor plantar response (toes up) signals an abnormal UMN lesion.

4. Diagnostics & Nursing Interventions

• CSF Analysis: Normal CSF is clear/colorless, with pressure of 60–150 mm H2O, protein of 15–45 mg/dL, and glucose of 40–70 mg/dL.
• Lumbar Puncture (LP) Care: LP is contraindicated in increased ICP due to risk of herniation. Pre-procedure, check coagulation and place the patient in a sitting/side-lying flexed position. Post-procedure, keep flat, monitor for headache, and push fluids.
• Aging: Aging causes cerebral atrophy, wider ventricles, reduced blood flow, and demyelination. This leads to orthostatic hypotension, poor thermoregulation, and high fall risks.