Nervous System — Structure & Function

CNS (Central Nervous System) — brain and spinal cord

PNS (Peripheral Nervous System) — all other nerves

PNS → Somatic (voluntary) and Autonomic (involuntary)

Autonomic → Sympathetic (fight-or-flight) and Parasympathetic (rest-and-digest)

Neuron anatomy:

Dendrites receive signals → Cell body integrates → Axon transmits → Synaptic terminal releases neurotransmitters

Action potential:

Resting potential: −70 mV

Depolarization: Na⁺ rushes in through voltage-gated channels → membrane reaches +30 mV

Repolarization: K⁺ rushes out → returns toward resting potential

Hyperpolarization: briefly more negative than resting

Refractory period: cannot fire again immediately

Synaptic transmission:

Action potential → Ca²⁺ influx → vesicle fusion → neurotransmitter release → binds postsynaptic receptor → excitatory (EPSP) or inhibitory (IPSP)

Key neurotransmitters: Acetylcholine, Dopamine, Serotonin, GABA (inhibitory), Glutamate (excitatory), Norepinephrine

Reference:

Wikipedia: Nervous System

https://en.wikipedia.org/wiki/Nervous_system