Lecture 7: ANS Flashcards
ANS coordinates what functions?
Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions
What is another name for the ANS?
The visceral efferent motor system
ANS is concerned with what two things?
Internal organs and viscera
What is the function of the ANS?
regulate visceral activities to maintain homeostasis
Two types of neurons in the ANS
preganglionic and postganglionic
Where do preganglionic neurons originate?
in the CNS
Purpose of preganglionic neurons
Send axons to synapse on the ganglionic neurons in the autonomic ganglia outside the CNS
Where do postganglionic neurons originate?
from the autonomic ganglia
What is the purpose of postganglionic neurons?
Send axons to effector organs
Visceral efferents from the thoracic and lumbar segments of the vertebral spinal form the
Thoracolumbar division
or the Sympathetic division
What does the sympathetic division do?
Prepares body for heightened level of activity
Flight or fight
Visceral efferents from the brain and sacral segments of the vertebral spinal cord form
the craniosacral division or the parasympathetic division
Purpose of the parasympathetic division
Regulates activities that conserve and restore body energy during rest
Rest or repose
Innervation of most visceral organs
Most are dually innervated
By both sympathetic and parasympathetic fibers
Three types of dual innervation effects
- Antagonistic
- Complementary
- Cooperative
Antagonistic effects on the heart
Regulation of heart rate, conduction velocity and force of contraction
Antagonistic effects of the digestive tract
Sympathetic fibers inhibit
Parasympathetic stimulate intestinal movements and secretions
Antagonistic effects of the eyes
- Sympathetically innervated radial muscles of the iris dilate the pupil
- Parasympathetically innervated circular muscles of the iris constrict the pupil
Complementary effects of saliva secretion
- Secretion (digestion) by parasympathetic
- Sympathetic stimulates salivary secretory cells
Cooperative effects of reproduction system
- Erection of penis is due to vasodilation from parasympathetic
- Ejaculation is due to sympathetic
Three organs solely innervated by sympathetic
- Adrenal medulla
- Sweat glands
- Most blood vessels
Blood vessel stimulation
- Solely by sympathetic
- Constriction - increased activity
- Vasodilation - decreased activity
Two distinct results of stimulation of the sympathetic nervous system
- The release of norepinephrine at specific locations
- The secretion of epinephrine and norepinephrine into the general circulation
Two types of adrenergic receptors
Alpha
beta
Most postganglionic fibers are adrenergic and release _____
norepinephrine
Postganglionic fibers innervating sweat glands release _____ which binds to ______ receptors
acetylcholine
muscarinic
All preganglionic fibers are ____. They release ___ which binds to ____ receptors
cholinergic
ACh
Nicotinic
What are the sites of neurotransmitter storage and release in ANS post ganglionic neurons?
Beads or varicosities that line the branches
Some nerve fibers of post ganglionic neurons of ANS contain vesicles which contain _____ or _____
acetylcholine
norepinephrine
Neuroeffector junctions of the ANS
The junctions between postganglionic autonomic neurons and their effectors (target tissues)
The neuroeffector junctions in ANS are analogous to what in the SNS?
Neuromuscular junctions
Post ganglionic neuron in ANS vs motor neuron in SNS
- A skeletal muscle fiber is innervated by a single motor neuron
- Post-ganglionic neurons that innervate different target tissues form diffused branching networks
