Crash Course : The Peripheral Nervous System (PNS)

Peripheral Nervous System (PNS)

All neural structures outside the brain and spinal cord; connects the central nervous system to the rest of the body.

Sensory Division (Afferent Division)

Carries sensory information FROM receptors in the body TOWARD the central nervous system.

Motor Division (Efferent Division)

Carries motor commands FROM the central nervous system TO muscles and glands.

Somatic Nervous System

Division of the PNS that controls voluntary movements of skeletal muscles.

Autonomic Nervous System (ANS)

Division of the PNS that controls involuntary functions of glands, smooth muscle, and cardiac muscle.

Sympathetic Division

:"Fight or flight" division of the ANS; activates during stress, danger, or activity.

Parasympathetic Division

"Rest and digest" division of the ANS; conserves energy and maintains body functions at rest.

Nerves

Bundles of axons in the peripheral nervous system.

Ganglia

Clusters of neuron cell bodies located outside the central nervous system.

Cranial Nerves

12 pairs of nerves that emerge directly from the brain.

Spinal Nerves

31 pairs of nerves that emerge from the spinal cord.

Afferent Nerves

Nerves that carry sensory information toward the CNS (sensory nerves).

Efferent Nerves

Nerves that carry motor commands away from the CNS (motor nerves).

Acetylcholine

Primary neurotransmitter used in the somatic nervous system and parasympathetic division.

Norepinephrine

Primary neurotransmitter used by the sympathetic division.

Two-Neuron Chain

Characteristic of autonomic pathways: preganglionic neuron → postganglionic neuron → effector.

Preganglionic Neuron

The first neuron in an autonomic pathway; cell body in CNS, axon extends to ganglion.

Postganglionic Neuron

The second neuron in an autonomic pathway; cell body in ganglion, axon extends to effector.

Effectors

The muscles or glands that respond to motor commands from the nervous system.

Voluntary Control

Characteristic of the somatic nervous system; conscious control of skeletal muscles.

Involuntary Control

Characteristic of the autonomic nervous system; automatic control of internal organs.

Fight or Flight" Response

Sympathetic activation that prepares the body for emergency action.

Rest and Digest" Response

Parasympathetic activation that promotes digestion and energy conservation.