Nervous System Overview: CNS, PNS, Neurons, and Autonomic Functions

Nervous system

The body's communication network, consisting of all nerve cells.

Central nervous system (CNS)

The brain and spinal cord; the body's decision-making system.

Peripheral nervous system (PNS)

The network of sensory and motor neurons connecting the CNS to the body.

Nerves

Bundles of axons that carry signals in the PNS.

Sensory neurons (afferent)

Neurons that carry incoming information from sense receptors to the CNS.

Motor neurons (efferent)

Neurons that carry outgoing information from the CNS to muscles and glands.

Interneurons

Neurons within the CNS that connect sensory and motor neurons.

Somatic nervous system

Controls voluntary muscle movements.

Autonomic nervous system

Controls involuntary body functions (e.g., heartbeat, digestion).

Sympathetic nervous system

Arouses the body for action (fight-or-flight).

Parasympathetic nervous system

Calms the body and conserves energy (rest-and-digest).

Reflexes (reflex arc)

Automatic, simple responses to sensory stimuli, bypassing the brain.