Chapter 16 - The Autonomic Nervous System_Student

Autonomic Nervous System (ANS)

The visceral (organ) motor system responsible for involuntary control of effectors such as glands, cardiac muscle, and smooth muscle.

Visceral Reflexes

Unconscious, automatic, stereotyped responses of visceral effectors to stimuli.

Sympathetic Division

'fight-or-flight' responses, increasing heart rate and blood glucose while reducing blood flow to the skin and gastrointestinal tract.

Parasympathetic Division

'rest and digest' responses, decreasing heart rate and stimulating digestion and waste elimination.

Autonomic Tone

The balance between activity of the sympathetic and parasympathetic nervous systems.

Preganglionic Fiber

A nerve fiber originating in the brainstem or spinal cord that terminates in a ganglion.

Postganglionic Fiber

A nerve fiber that extends from a ganglion to the target organ.

Somatic Nervous System

The part of the nervous system that controls skeletal muscle and is usually under voluntary control. Uses one nerve fiber from CNS to effector using no ganglia

Comparison of Somatic and Autonomic Systems

Somatic system has one nerve fiber and is usually voluntary, while autonomic system has two nerve fibers, often involuntary.

Thoracolumbar Division

The origin of the sympathetic division, with preganglionic neurosomas located in the lateral horns of the spinal cord.

Craniosacral Division

The origin of the parasympathetic division, where long preganglionic fibers exit from the brain and sacral region.

Enteric Nervous System

The nervous system of the digestive tract that regulates motility and secretion of digestive enzymes and acid.

Horner Syndrome

A disorder of the ANS characterized by unilateral pupillary constriction, sagging of the eyelid, and flushing of the skin, due to lesions in the sympathetic division.

Raynaud Disease

A disorder characterized by paleness, cyanosis, and pain in digits when cold or stressed, due to excessive vasoconstriction.

Parasympathetic Nervous System

It is a part of the ANS that affects glands, smooth muscle, and cardiac muscle. It is usually involuntary and uses two nerve fibers from the CNS to the effector; it synapses at a ganglion.

Sympathetic Division

Has Short preganglionic fibers and long postganglionic fibers.

Short Preganglionic Fibers

Fibers that originate in the central nervous system and project to nearby ganglia, characteristic of the sympathetic division.

Long Preganglionic Fibers

Fibers that originate in the central nervous system and extend to distant ganglia, characteristic of the parasympathetic division.

Short Postganglionic Fibers

Fibers that extend from ganglia to effector organs and are typical in the sympathetic division.

short postganglionic fiber

Fibers that extend from ganglia to effector organs and are typical in the parasympathetic division.