CH 7: PNS Vocab List

Nerve

A bundle of neuron fibers (axons) found outside the central nervous system (CNS).

Endoneurium

A delicate connective tissue sheath that surrounds each individual neuron fiber (axon) within a nerve.

Perineurium

A coarse connective tissue wrapping that binds groups of neuron fibers into bundles called fascicles.

Fascicles

Bundles of neuron fibers bound together by the perineurium.

Epineurium

A tough fibrous sheath that binds all the fascicles together to form the cordlike nerve.

Mixed nerves

Nerves that carry both sensory and motor fibers; all spinal nerves are mixed nerves.

Sensory (Afferent) nerves

Nerves that carry impulses toward the central nervous system (CNS).

Motor (Efferent) nerves

Nerves that carry only motor fibers, transmitting impulses away from the CNS to effector organs.

Cranial nerves

12 pairs of nerves that primarily serve the head and neck; only one pair (vagus nerves) extends to the thoracic and abdominal cavities.

Dorsal rami

Branches of the spinal nerves that serve the skin and muscles of the posterior body trunk.

Ventral rami

Branches of spinal nerves T{1} through T{12} that form the intercostal nerves; other ventral rami form complex networks called plexuses.

Plexuses

Complex networks of nerves formed by the ventral rami of spinal nerves that serve the motor and sensory needs of the limbs.

Autonomic nervous system (ANS)

The motor subdivision of the peripheral nervous system (PNS) that controls body activities automatically; it regulates cardiac muscle, smooth muscle, and glands.

Involuntary nervous system

Another name for the autonomic nervous system, reflecting its role in regulating activities not under conscious control.

Preganglionic axon

The axon of the first motor neuron in the autonomic nervous system, which is located in the brain or spinal cord.

Postganglionic axon

The axon of the second motor neuron in the autonomic nervous system, which extends from a ganglion to the organ it serves.

Sympathetic division

The "fight or flight" division of the ANS that mobilizes the body during extreme situations such as fear, exercise, or rage.

Parasympathetic division

The "rest and digest" division of the ANS that allows the body to unwind and conserve energy during non-stressful situations.

Terminal ganglion

A ganglion in the parasympathetic division where the preganglionic axon synapses with the second motor neuron, located very close to the target organ.

Splanchnic nerves

Nerves of the sympathetic division that pass through the trunk ganglion and travel to the viscera to synapse in collateral ganglia.

Cerebral palsy

A neuromuscular disability in which voluntary muscles are poorly controlled or paralyzed due to brain damage, often caused by temporary lack of oxygen during delivery.

Anencephaly

A birth defect in which the cerebrum fails to develop, resulting in a child who cannot hear, see, or process sensory information.

Spina bifida

A developmental defect in which the vertebrae form incompletely; in severe cases, parts of the spinal cord or meninges protrude from the spine.

Arteriosclerosis

The hardening and narrowing of the arteries, which can lead to decreased oxygen delivery to brain neurons as people age.

Senility

A condition characterized by forgetfulness, irritability, and confusion, often resulting from a gradual decrease in oxygen supply to brain tissue.