Anatomy PNS

Nerve

A bundle of nerve fibers (axons) in the peripheral nervous system, enclosed by connective tissue. Nerves transmit electrical and chemical signals between the brain, spinal cord, and the rest of the body.

Endoneurium

A layer of delicate connective tissue that surrounds individual nerve fibers (axons) within a nerve.

Perineurium

A protective sheath of connective tissue that surrounds a bundle of nerve fibers (fascicle) within a nerve.

Fascicles

Bundles of nerve fibers (axons) within a nerve, surrounded by the perineurium.

Epineurium

The outermost layer of dense connective tissue that surrounds the entire nerve, enclosing all the fascicles and providing support and protection.

Mixed nerves

Nerves that contain both sensory (afferent) and motor (efferent) fibers, allowing them to transmit both incoming sensory information and outgoing motor commands.

Sensory/afferent nerves

Nerves that transmit sensory information from receptors in the body to the central nervous system (brain and spinal cord).

Motor/efferent nerves

Nerves that transmit motor commands from the central nervous system to muscles or glands, causing them to contract or secrete.

Cranial nerves

Twelve pairs of nerves that originate from the brain and exit through foramina in the skull, serving sensory and motor functions in the head and neck.

Dorsal rami

Branches of spinal nerves that supply the skin and muscles of the posterior trunk (back).

Ventral rami

Branches of spinal nerves that supply the skin and muscles of the anterior and lateral trunk, as well as the limbs.

Plexuses

Networks of intersecting nerves formed by the ventral rami of spinal nerves. Autonomic nervous system

Involuntary nervous system

Another name for the autonomic nervous system, which controls bodily functions that occur without conscious control.

Preganglionic axon

The axon of a neuron in the autonomic nervous system that extends from the central nervous system to a ganglion.

Postganglionic axon

The axon of a neuron in the autonomic nervous system that extends from a ganglion to the target organ (muscle or gland).

Sympathetic division

The division of the autonomic nervous system responsible for the "fight or flight" response, preparing the body for stressful or emergency situations.

Parasympathetic division

The division of the autonomic nervous system responsible for "rest and digest" functions, conserving energy and promoting normal body maintenance.

Terminal ganglion

A type of parasympathetic ganglion located near or within the wall of the target organ.

Splanchnic nerves

Nerves that carry sympathetic fibers to the abdominal and pelvic organs.

Cerebral palsy

A group of neurological disorders caused by damage to the brain during development or birth, resulting in motor impairments, muscle weakness, and coordination problems.

Anencephaly

A severe birth defect in which the brain and skull do not develop properly, resulting in a missing or incomplete brain.

Spina bifida

A birth defect in which the spinal cord does not close completely during pregnancy, resulting in neurological deficits and physical disabilities.

Arteriosclerosis

A chronic disease characterized by the thickening and hardening of the arterial walls, reducing blood flow and increasing the risk of heart attack and stroke.

Senility

A general term for the decline in mental abilities, such as memory, thinking, and judgment, that can occur with aging or as a result of neurological disorders.