CH 16 - Autonomic Nervous System

Visceral (Organ) motor system

involuntary control of effectors; glands, cardiac muscle, and smooth muscle

Visceral reflexes

• Unconscious, automatic, stereotypes responses of visceral effectors to stimuli

• Example: a rise in blood pressure triggers a reflexive decrease in heart rate

Division of ANS

• Sympathetic Division

• Parasympathetic Division

Sympathetic Division

• “Fight or Flight”

  • responses for increased physical activity

• Increases heart rate and blood glucose

• reduces blood flow to skin and GI tract

Parasympathetic Division

• “Rest and Digest”

  • responses with calming effects

• decreases heart rate

• stimulates digestion and waste elimination

Autonomic Tone

balance between activity of sympathetic and parasympathetic nervous system

Neural Pathways

• Pre ganglionic fiber

• Post ganglionic fiber

Pre ganglionic fiber

• neurosoma in the brainstem or spinal cord

• axon terminates in ganglion

Post ganglionic fiber

• neurosoma in ganglion

• axon extends to target

Thoracolumbar Division

pre ganglionic neurosomas are in lateral horns of spinal cords

The Enteric Nervous System

• Nervous system of the digestive tract

• innervates smooth muscle and glands

• Regulates:

  • motility of esophagus, stomach, and intestines

  • secretion of digestive enzymes and acid

Disorders of ANS

• Horner syndrome

• Raynaud disease

Raynaud disease

• paleness, cyanosis, and pain in digits when cold or stressed due to excessive vasoconstriction

• most common in young women

Horner Syndrome

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

Autonomic Nervous System

• Effectors:

  • glands, smooth muscle, cardiac muscle

• Control

  • usually involuntary

• Efferent Pathways

  • two nerve fibers from CNA to effector, synapse at a ganglion

• Effect on target cells

  • excitatory or inhibitory

Somatic Nervous System

• Effectors:

  • skeletal muscle

• Control

  • usually voluntary

• Efferent Pathways

  • one nerve fiber from CNA to effector; no ganglia

• Effect on target cells

  • always excitatory

Parasympathetic Division

• Origins in CNS

  • Craniosacral

• Location of Ganglia

  • terminal ganglia near or within target organs

• Fiber lengths

  • long pre ganglionic and short post ganglionic

• Effects of the system

  • more local and specific

Sympathetic Division

• Origins in CNS

  • Thoracolumbar

• Location of Ganglia

  • Paravertebral ganglia adjacent to the spinal column and prevertebral ganglia anterior to it

• Fiber lengths

  • short pre ganglionic and long post ganglionic

• Effects of the system

  • often widespread and general