ANS Flashcards
The ANS consists of motor neurons that:
Innervate smooth and cardiac muscle and glands Make adjustments to ensure optimal support for body activities Operate via subconscious control
Somatic and Autonomic Nervous
Systems
The two systems differ in
- Effectors
- Efferent pathways (and their
neurotransmitters) - Target organ responses to
neurotransmitters
Somatic nervous system = Skeletal muscles ONLY ANS = a. Cardiac muscle b. Smooth muscle c. Glands
What are they?
Effectors
Somatic nervous system = one thick,
heavily myelinated somatic motor fiber
makes up each pathway from the CNS to
the muscle
Efferent Pathways
ANS pathway is a two-neuron chain 1.Preganglionic neuron (in CNS) has a thin, lightly myelinated preganglionic axon 2.Postganglionic neuron in autonomic ganglion has an unmyelinated
Efferent Pathways
Somatic nervous system = All somatic motor
neurons release acetylcholine (ACh)
Effects are always stimulatory!!
Neurotransmitter Effects
ANS Preganglionic fibers release ACh Postganglionic fibers release norepinephrine or ACh at effectors Effect is either stimulatory or inhibitory, depending on type of receptors
Neurotransmitter Effects
2
Preganglionic = Ach
Postganglionic =
Ach & NE
ANS (Motor neurons)
Somatic (Motor Neurons)
1
Ach only
ANS (Effectors smooth & cardiac muscle glands)
Smooth & Cardiac
muscle; Glands
Somatic (Effector)
Skeletal muscle
PARASYMPATHETIC
Nerves emerge from _____
region of brain or spinal cord
craniosacral
PARASYMPATHETIC
___preganglionic fibers (synapse
close to or within target organ)
__- postganglionic fibers
long
short
PARASYMPATHETIC
neurotransmitters =
ACh only
Parasympathetic
____ effect
localized
physiological effects = ______
____ = increases salivation,
lacrimation, urination, defecation and digestion
“rest and digest”;
“SLUDD”
3 things/structures it decreases = ___
rate, airways (constriction) and pupils (restriction)
heart
3 things/structures it decreases = ___
rate, airways (constriction) and pupils (restriction)
heart
Cranial Part of Parasympathetic
Division:
CN’s 3, 7, 9 & 10
Serves pelvic organs and distal half of large
intestine
From neurons in lateral gray matter / horns of
S2-S4
Axons travel in ventral root of spinal nerves
Synapse with
Ganglia in pelvic floor
Intramural ganglia in walls of distal half of large
intestine, urinary bladder, ureters, and reproductive
organs
Sacral Part of Parasympathetic
Division
Sympathetic
nerves emerge from _____ region
thoracolumbar
Sympathetic
______ preganglionic fibers (cell bodies in
lateral gray horns)
____postganglionic fibers (cell bodies in
paravertebral chain)
short
long
Sympathetic
neurotransmitters
preganglionic = ____________
postganglionic =__________
Ach (just like
Parasympathetic)
NE ** (except sweat
glands = ACh)
Some preganglionic fibers pass directly to
the adrenal medulla without synapsing
Upon stimulation, the adrenal medulla
secretes norepinephrine and epinephrine into
the blood
Pathways with Synapses in the Adrenal
Medulla
Parasympathetic (Origin)
Craniosacral
Sympathetic (Origin)
Thoracolumbar
Parasympathetic (Fibers)
LONG
Preganglionic
SHORT
Postganglionic
Sympathetic (fibers)
SHORT
Preganglionic
LONG
Postganglionic
Parasympathetic (Neurotransmitte
rs)
ACh
Sympathetic (Neurotransmitte
rs)
ACh NE
Parasympathetic (Distance)
Local Effects
Sympathetic (Distance)
Widespread Effects
Parasympathetic (Phycological effects)
“Rest and Digest”
“SLUDD”
Sympathetic (Physiological
Effects)
“Fight or Flight”
“E’s”
All postganglionic neurons (1st synapse area
of both sympathetic and parasympathetic)
Hormone-producing cells of the adrenal
medulla
Effect of ACh at nicotinic receptors is always
excitatory
Nicotinic Receptors
All postganglionic neurons (1st synapse area
of both sympathetic and parasympathetic)
Hormone-producing cells of the adrenal
medulla
Effect of ACh at nicotinic receptors is always
excitatory
Nicotinic Receptors
Found on
All effector cells (2nd synapse) stimulated
by parasympathetic fibers
The effect of ACh at muscarinic receptors
Can be either inhibitory or excitatory
Depends on the receptor type of the target
organ
Muscarinic Receptors
generally excitatory: located on
virtually all sympathetic organs and radial muscles
of the pupil to dilate the pupil, constrict blood
vessels to skin, digestive organs; excitatory to
constrict visceral organ sphincters
α1 receptors
generally inhibitory: inhibit insulin
release from the pancreas.
α2 receptors
generally excitatory predominately located in the heart to increase heart rate and the kidneys to release Renin (a vasoconstrictor).
β1 receptors
generally inhibitory: located in the lungs
inhibit smooth muscle of bronchioles and thus dilate
bronchioles; dilate blood vessels to skeletal muscles and
heart, liver to increase blood delivery; relax smooth muscle
of gastrointestinal tract and uterus to decrease movement
through that tube.
β2 receptors
found in the fat cells of the body (thus
thermogenesis) to stimulate lipolysis
β3 receptors
controls blood
pressure, even at rest
Sympathetic division
Keeps the blood vessels in a continual
state of partial constriction(similar to
muscle tone)
Sympathetic tone (vasomotor tone)
Sympathetic fibers fire more rapidly to constrict blood vessels and cause blood pressure to rise Sympathetic fibers fire less rapidly and thus to prompt vessels to dilate to decrease blood pressure
Sympathetic Tone
\_\_\_\_\_\_ division normally dominates the heart and smooth muscle of digestive and urinary tract organs Slows the heart Dictates normal activity levels of the digestive and urinary tracts
Parasympathetic Tone
The sympathetic division can override these effects during times of stress Drugs that block parasympathetic responses increase heart rate and block fecal and urinary retention
Parasympathetic Tone
The sympathetic division can override these effects during times of stress Drugs that block parasympathetic responses increase heart rate and block fecal and urinary retention
Parasympathetic Tone
short-
lived, highly localized control over
effectors
Parasympathetic division
long-lasting,
body wide effects
Sympathetic division
= main integrative
center of ANS activity
Hypothalamus
Subconscious cerebral input via limbic lobe connections influences hypothalamic function Other controls come from the cerebral cortex, the reticular formation, and the spinal cord
Control of ANS Functioning
