Neural Control and Coordination — Master Overview — Notes

Human Brain Anatomy Figure: Sagittal section of the human brain showing major subdivisions.

Cue Column | Notes Column

What is the CNS? | Brain + Spinal cord. Integration and command centre.

What is the PNS? | 12 pairs cranial nerves + 31 pairs spinal nerves. Connects CNS to body.

What is a neuron? | Cell body (cyton/soma with Nissl granules = rough ER), dendrites (receive), axon (transmit). Myelinated by Schwann cells (PNS) or oligodendrocytes (CNS).

Resting potential value? | -70 mV. Inside NEGATIVE. Maintained by Na+/K+ pump (3 Na+ OUT, 2 K+ IN) + K+ leak channels.

What causes depolarization? | Na+ influx via voltage-gated Na+ channels. Reaches +30 mV.

What causes repolarization? | K+ efflux via voltage-gated K+ channels. Restores negative potential.

All-or-none principle? | AP fires full strength at threshold or not at all.

Saltatory conduction? | AP jumps node to node in myelinated neurons (faster, more efficient).

Synapse mechanism? | AP → Ca2+ influx → NT exocytosis into 20 nm cleft → receptor binding → new AP.

Brain divisions? | Forebrain: Cerebrum+Thalamus+Hypothalamus. Midbrain: visual/auditory reflexes. Hindbrain: Cerebellum+Pons+Medulla.

KEY DISTINCTION: | Cerebrum INITIATES voluntary movement. Cerebellum COORDINATES (does NOT initiate).

Medulla functions? | Vital: cardiovascular centre, respiratory rhythmicity, vomiting, swallowing.

Hypothalamus? | Thermoregulation, hunger, thirst, circadian, controls pituitary. Nervous+Endocrine link.

ANS divisions? | Sympathetic ("fight/flight": ↑HR, dilates pupils). Parasympathetic ("rest/digest": ↓HR, constricts pupils).

Eye photoreceptors? | Rods: 120M, rhodopsin, dim light (scotopic). Cones: 6-7M, iodopsin, colour (photopic), fovea.

Ear ossicles? | MIS: Malleus → Incus → Stapes (smallest bone in body) → oval window. Amplify 20x.

Summary

Neural control operates via specialized neurons organized into CNS (brain + spinal cord) and PNS (cranial + spinal nerves). The nervous impulse depends on ion gradients: -70 mV rest (Na+/K+ pump), depolarization (Na+ in, +30 mV), repolarization (K+ out). Transmission between neurons uses chemical synapses (Ca2+ triggers NT release). Brain regions have distinct functions: cerebrum (cognition, initiates voluntary movement), cerebellum (coordinates movement, balance), medulla (vital autonomic functions), hypothalamus (homeostasis). The ANS (sympathetic vs parasympathetic) controls involuntary visceral functions. Sense organs (eye, ear) transduce physical stimuli to nerve impulses.