The Nervous System
The nervous system is the master control system, comprising the CNS (brain and spinal cord) and PNS (peripheral nerves). It processes sensory information, coordinates motor responses, and enables higher cognitive functions. Neurology covers conditions from headaches and epilepsy to stroke and neurodegenerative diseases like Alzheimer's and Parkinson's.
Learning Objectives
- 1Distinguish central nervous system from peripheral nervous system
- 2Describe major brain regions and their functions
- 3Identify combining forms for nervous system structures
- 4Recognize neurological diseases and emergency conditions
- 5Interpret neurological diagnostic tests
1Central Nervous System
Brain (encephal/o): Protected by skull and meninges
Cerebrum: Largest part; divided into 4 lobes:
Cerebellum: Coordination, balance, fine motor
Brainstem: Midbrain, pons, medulla oblongata
Diencephalon: Thalamus (relay station), Hypothalamus (homeostasis, ANS, hormones)
Spinal Cord: Extends from foramen magnum to L1–L2; contains ascending (sensory) and descending (motor) tracts
2Peripheral Nervous System
Somatic NS: Voluntary; controls skeletal muscles; 31 pairs of spinal nerves + 12 cranial nerves
Autonomic NS: Involuntary; controls smooth muscle, cardiac muscle, glands
12 Cranial Nerves (mnemonics: "Oh, Oh, Oh, To Touch And Feel Very Good Velvet — Absolutely Heavenly"):
I Olfactory, II Optic, III Oculomotor, IV Trochlear, V Trigeminal, VI Abducens, VII Facial, VIII Vestibulocochlear, IX Glossopharyngeal, X Vagus, XI Accessory, XII Hypoglossal
3Neurological Diseases
Stroke (CVA — Cerebrovascular Accident):
Epilepsy/Seizures: Abnormal electrical discharges in brain
Multiple Sclerosis (MS): Autoimmune demyelination → muscle weakness, vision problems, fatigue
Parkinson's Disease: Degeneration of dopaminergic neurons in substantia nigra → tremor, rigidity, bradykinesia
Alzheimer's Disease: Progressive dementia; amyloid plaques and neurofibrillary tangles
Meningitis: Bacterial (Neisseria meningitidis) — emergency; viral (most common)
Guillain-Barré Syndrome: Ascending paralysis after infection; autoimmune attack on peripheral nerves
4Neurological Diagnostics
CT scan of head: First-line for stroke — rules out hemorrhage quickly
MRI brain/spine: Detailed soft tissue; shows MS plaques, tumors, strokes
EEG (Electroencephalogram): Records brain electrical activity; diagnoses epilepsy
Lumbar puncture (LP/spinal tap): CSF sample; diagnoses meningitis, MS, subarachnoid hemorrhage
EMG/Nerve conduction: Evaluate peripheral nerve and muscle function
Neurological exam: Level of consciousness (GCS), cranial nerves, motor/sensory, reflexes, coordination
Clinical Connections
- ►Stroke is the 5th leading cause of death and the #1 cause of long-term disability in the US
- ►The blood-brain barrier (BBB) protects the CNS from most pathogens but also limits drug delivery
- ►Neuroplasticity — the brain's ability to reorganize after injury — is the basis for rehabilitation therapy