ch 16 - autonomic nervous system

visceral (organ) motor system

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

visceral reflexes

• unconscious, automatic stereotyped responses of visceral effectors to stimuli

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

effector

they cause an effect in response to directions from the nervous system

divisions of the ANS

• sympathetic “fight or flight”

• parasympathetic “rest and digest”

autonomic tone

balance btwn activity of sympathetic and parasympathetic nervous system

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

neural pathways

• preganglionic fiber

  • neurosoma in brainstem or spinal cord

  • axon terminates in ganglion

• postganglionic fiber

  • neurosoma in ganglion

  • axon extends to target

preganglionic fiber

• neurosoma in brainstem or spinal cord

• axon terminates in ganglion

postganglionic fiber

• neurosoma in ganglion

• axon extends to target

somatic

• effectors: skeletal muscle

• control: usually voluntary

• efferent pathways: one nerve fiber from CNS to effector; no ganglia

• effect on target cells: always excitatory

autonomic

• effectors: glands, smooth muscle, cardiac muscle

• control: usually involuntary

• efferent pathways: 2 nerve fibers from CNS to effector; synapse at a ganglion

• effect on target cells: excitatory or inhibitory

sympathetic division

• thoracolumbar division

  • preganglionic neurosomas are in lateral horns of spinal cord

• short preganglionic fibers and long postganglionic fibers

• sympathetic chain ganglia (paravertebral ganglia) from cervical to coccygeal levels

short

preganglionic fibers in the sympathetic division are ____?

long

postganglionic fibers in the sympathetic division are ____?

sympathetic chain ganglia

from cervical to coccygeal levels

parasympathetic division

• craniosacral division

• long preganglionic fibers and short postganglionic fibers

• terminal ganglia are in or near target organ

long

preganglionic fibers in the parasympathetic division are _____?

short

postganglionic fibers in the parasympathetic division are _____?

enteric nervous system

• nervous system of the digestive tract

• innervates smooth muscle and glands

• regulates

  • motility of the esophagus, stomach, and intestines

  • secretion of digestive enzymes and acid

sympathetic

• Origin in CNS: Thoracolumbar

• Location of ganglia: Paravertebral ganglia adjacent to spinal column and prevertebral ganglia anterior to it

• Fiber lengths: Short preganglionic Long postganglionic

• Effects of system: Often widespread and general

parasympathetic

• Origin in CNS: Craniosacral

• Location of ganglia: Terminal ganglia near or within target organs

• Fiber lengths: Long preganglionic Short postganglionic

• Effects of system: More local and specific

disorders of the ANS

• 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 (most common in young women)

myelinated fiber

preganglionic fiber

unmyelinated fiber

postganglionic fiber

thoracolumbar

where do the nerves of the sympathetic nervous system arise from

brainstem and sacral

where do the nerves of the parasympathetic nervous system arise from

enteric

1. Regulate motility through digestive tract

2. Regulate secretion of digestive enzymes