Chapter 16: The Autonomic Nervous System

Autonomic Nervous System (ANS)

Visceral (Organ) motor system that controls involuntary effectors: glands, cardiac muscle, and smooth muscle.

Visceral Reflexes

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

Example of Visceral Reflex

A rise in blood pressure triggers a reflexive decrease in heart rate.

Sympathetic Division

Part of the ANS responsible for 'fight-or-flight' responses for increased physical activity.

Parasympathetic Division

Part of the ANS responsible for 'rest and digest' responses with calming effects.

Autonomic Tone

Balance between activity of sympathetic and parasympathetic nervous systems.

Preganglionic Fiber

Neurosoma in brainstem or spinal cord, axon terminals in ganglion

Postganglionic Fiber

Neurosoma in ganglion, axon extends to target

Somatic Nervous System

Nervous system that controls skeletal muscle and is usually voluntary.

Effectors of the Autonomic Nervous System

Glands, smooth muscle, and cardiac muscle.

Control of the Somatic Nervous System

Usually voluntary.

Control of the Autonomic Nervous System

Usually involuntary.

Efferent Pathways of Somatic Nervous System

One nerve fiber from CNS to effector; no ganglia.

Efferent Pathways of Autonomic Nervous System

Two nerve fibers from CNS to effector; synapse at a ganglion.

Effect on Target Cells in Somatic Nervous System

Always excitatory.

Effect on Target Cells in Autonomic Nervous System

Excitatory or inhibitory.

Thoracolumbar Division

Includes Sympathetic division where preganglionic neurosomas are in lateral horns of spinal cord.

Craniosacral Division

includes Parasympathetic division with long preganglionic fibers and short postganglionic fibers.

Enteric Nervous System

Nervous system of the digestive tract that innervates smooth muscle and glands.

Regulation by Enteric Nervous System

Regulates motility of the esophagus, stomach, and intestines, and secretion of digestive enzymes and acid.

Origin in CNS of Sympathetic Division

Thoracolumbar.

Origin in CNS of Parasympathetic Division

Craniosacral.

Location of Ganglia in Sympathetic Division

Paravertebral ganglia adjacent to spinal column and prevertebral ganglia anterior to it.

Location of Ganglia in Parasympathetic Division

Terminal ganglia near or within target organs.

Effects of Sympathetic Division

Often widespread and general.

Effects of Parasympathetic Division

More local and specific.

Horner Syndrome

Unilateral pupillary constriction, sagging of eyelid, and flushing of skin due to lesions in sympathetic division.

Raynaud Disease

Paleness, cyanosis, and pain in digits when cold or stressed due to excessive vasoconstriction.

In sympathetic, is pre ganglion longer or shorter than pre-ganglion

pre-ganglion is is shorter than post-ganglion

In parasympthatetic, is pre-ganglia shorter or longer than post-ganglion

Pre-ganglia is longer than post-ganglion, closer to target organ