CH 15 Flashcards
autonomic
“self-governed” and fully independent.
Autonomic nervous system (ANS)
a motor nervous system that controls smooth, cardiac muscle, and glands.
-A.K.A visceral motor system.
Primary organs of the ANS
viscera of thoracic and abdominal cavities.
Some structures of the body wall.
- cutaneous blood vessels.
- sweat glands.
- piloerector muscles.
ANS (cont.)
carries out actions INVOLUNTARILY: without our conscious intent or awareness.
Denervation hypersensitivity
exaggerated response of cardiac and smooth muscle if autonomic nerves are severed.
-spinal cord injuries
Visceral reflexes
unconscious, automatic
example of homeostatic negative feedback loop
high blood pressure detected by arterial stretch receptors (1), afferent neuron (2) carries signal to CNS, efferent (3) signals travel to the heart, then (4) heart slows reducing blood pressure.
example of homeostatic negative feedback loop
high blood pressure detected by arterial stretch receptors (1), afferent neuron (2) carries signal to CNS, efferent (3) signals travel to the heart, then (4) heart slows reducing blood pressure.
Sympathetic divison
prepares body for physical activity: exercise, trauma, arousal, competition, anger or fear.
- increases heart rate, BP, airflow, blood glucose levels, etc.
- reduces blood flow to skin and digestive tract.
Parasympathetic division
clams many body functions reducing energy expenditure and assists in bodily maintenance (rest and digest)
Parasympathetic tone
- maintains smooth muscle tone in intestines.
- hold resting heart rate down to about 70 to 80 beats per minute.
Sympathetic tone
keeps most blood vessels partially constricted and maintains blood pressure.
(Autonomic output pathways) control nucleus in the ______ and other brainstem regions.
hypothalamus
Autonomic pathway
- signal must travel across 2 NEURONS to get to target organ.
- must cross a synapse where these two neurons meet in an autonomic ganglion.
Presynaptic neuron
the first neuron has a some in the brainstem or spinal cord. (type B)
____ with a _________ whose axone extends the rest of the way to the target cell. (type C)
Synapses ; postganglionic neuron
Sympathetic division
- also called thoracolumbar division.
- relatively short preganglionic and long postganglionic fibers.
Preganglionic neurosomas
in lateral horns and nearby regions of the grey matter of spinal cord.
- fibers exit spinal corby way of spinal nerves T1 to L2.
- lead to nearby sympathetic chain of ganglia (paravertebral ganglia)
each paravertebral ganglion is connected to a spinal nerve by two branches:
communicating rami
Preganglionic fibers
small myelinated fibers that travel from spinal nerve to the ganglion by way of the white communicating ramus. (myelinated)
Postganglionic fibers
leave the ganglion by way of the gray communicating ramus (unmyelinated).
-forms a bridge back to the spinal nerve.
extend the rest of the way to the target organ.
nerve fibers leave the sympathetic chain by___, ___, and _____.
spinal, sympathetic, splanchnic nerves.
spinal nerve route
- some postganglionic fibers exit a ganglion by way of the grey ramus.
- return to the spinal nerve and travel the rest of the way to the target organ.
- most sweat glands, piloerector muscles, and blood vessels of the skin and skeletal muscles.
sympathetic nerve route
- other nerves weaver by way of sympathetic nerves that extend to heart, lungs, esophagus, and thoracic.
- these nerves form carotid plexus around each carotid artsy of the neck.
- issue fibers from there to the effectors in the head. (sweat, salivary, nasal glands, piloerector muscles, blood vessels, dilator of iris) (superior cervical)
some fibers of superior and middle cervical ganglia form _____ to the heart. (sympathetic division)
cardiac nerves
Splanchnic nerve route
some fibers that arise from spinal nerves T5 to T12 pass through the sympathetic ganglia without synapsing.
- continue on as the splanchnic nerves.
- lead to second set of ganglia: collateral ganglia and synapse there.
Collateral ganglia contribute to a network called the ________
abdominal aortic plexus
abdominal aortic plexus
3 major collateral ganglia:
wraps around abdominal aorta
- celiac: heart, lungs, liver, gall bladder.
- superior mesenteric: small intestine, proximal colon.
- inferior mesenteric: kidneys, urinary bladder, reproductive organs, distal colon, rectum.
Solar plexus
collective name for the celiac and superior mesenteric ganglia.
-nerves radiate from ganglia like ray of the sun.
Adrenal glands
paired on superior poles of the kidneys.
-each is two glands with different functions:
adrenal cortex
adrenal medulla
Adrenal cortex
(outer layer)
secretes steroid hormones
Adrenal medulla
(inner core)
-essentially a sympathetic ganglion.
secretes a mixture of hormones into blood stream.
-catecholamines–85% epinephrine (adrenaline) and 15% norepinephrine (noradrenaline)
-also function as neurotransmitters
parasympathetic division
pathways of long preganglionic fibers
- fibers in cranial nerves III, VII, IX, and X.
- fibers arising from sacral spinal cord.
terminal ganglia
in or near target organs
-long preganglionic, short postganlionic fibers.
Neuronal divergence (PD)
less than sympathetic division.
Oculomotor nerve
(III) narrows pupil and focuses lens.
Facial nerve
(VII) tear, nasal, and salivary glands.
Glossopharyngeal nerve
(IX) parotid salivary gland
Vagus nerve
(X) (90%)
- viscera as far as proximal half of colon.
- cardiac, pulmonary, and esophageal plexus.
Enteric nervous system
the nervous system of the digestive tract.
- does not arise from the brainstem or spinal cord.
- does not innervate smooth muscle and glands.
- 100 million neurons found in digestive tract.
- no components in CNS
- has its own reflex arcs (stretch receptors)
- regulates motility of esophagus, stomach, and intestines and secretion.
- normal digestive func. requires sympathetic and parasympathetic systems.
Hirschsprung disease
hereditary defect causing absence of enteric nervous system.
- no innervation in sigmoid colon and rectum.
- constricts permanently and will now passage of feces.
- feces becomes impacted.
Megacolon
massive dilation of bowel accompanied by abdominal dissension and chronic constipation.
- may be colonic gangrene, perforation of bowel, and peritonitis.
- usually evident in newborns who fail to have their first bowel movement.
How can different autonomic neurons have different effects constricting some vessels but dilating others?
- Sympathetic and parasympathetic fibers secrete different neurotransmitters.
- Target cells respond to the same neurotransmitter differently depending upon the type of receptor they have for it.
All autonomic fibers secrete either _____ or ________.
acetylcholine
norepinephrine
acetylcholine (ACh) is secreted by all preganglionic neurons both divisions and the postganglionic parasympathetic neurons called ________.
Cholinergic fibers
NEis secreted by nearly __________.
called__________.
receptors for it called _________.
all sympathetic postganglionic neurons.
adrenergic fibers
adrenergic receptors
alpha-adrenergic receptors
two subclasses use different second messengers (a1 & a2)
Beta-adrenergic receptors
two subclasses with different effects, but both act through cAMP as a second messenger (B1 & B2)
A1
smooth muscle contraction (blood vessels to skin, GI tract, kidneys) contraction of uterus, arrector pili, internal urethral sphincter.
A2
beta cells of pancreas, GI sphincters.
B1
increase HR, increase renin in kidneys.
B2
vasodilation to heart, skeletal muscle, liver, bronchodilation.
B3
adipose tissue
Autonomic effects are often an _____ result other effect on blood vessels.
indirect
Vasodilation
increased blood flow; increased secretion.
Vasoconstriction
decreased blood flow; decreased secretion.
Sympathetic effects tend to last ____ than parasympathetic effects.
longer
- ACh released by parasympathetics is broken down quickly at synapse.
- NE by sympathetics is reabsorbed by nerve, diffuses to adjacent tissues, and much passes into blood stream.
Sympathetic fibers
also secrete endothelial cells, substance P, neuropeptide Y, somatostatin, Neurotensin.
Parasympathetic fibers
stimulate endothelial cells to release gas, nitric oxide, which cause vasodilation by inhibiting smooth muscle tone
-function is crucial to penile erection— means of action of viagra.
Dual innervation
most viscera receive nerve fibers from both parasympathetic and sympathetic division.
2 types:
antagonistic effect
cooperative effect
-both do not normally innervate an organ equally (digestion, heart rate)
Antagonistic effect
oppose each other
- exerted through dual innervation of same effector cells
- heart rate decreases (parasympathetic )
- heart rate increases (sympathetic)
- Exerted because each division innervates different cells.
- pupillary dilator muscle (sympathetic) dilates pupil.
- constrictor pupillae (parasympathetic) constrict pupil.
Cooperative effects
two division act on different effectors to produce a unified overall effect.
- parasympathetics increases salivary serous cell secretion.
- sympathetics increase salivary mucous cell secretion.
some effectors receive only sympathetic fibers.
examples:
adrenal medulla, arrector pili muscles, sweat glands and many blood vessels.
ex’s: regulation of blood pressure and routes of blood flow.
vasomotor tone
a baseline firing frequency of sympathetics.
- keeps vessels in state of partial constriction.
- can shift blood flow from one organ to another as needed.
sympathetic divisions acting alone can exert opposite effects on the target organ through control of blood
- during stress
- blood vessels to muscles and heart dilate.
- blood vessels to skin constrict.
vasoconstriction
increase in firing frequency
vasodilation
decrease in firing frequency
blood vessels to skin _____ to minimize bleeding if injury occurs during stress or exercise.
vasoconstrict
Cerebral cortex (in ANS)
has an influence: anger, fear, anxiety
- powerful emotional influence the ANS because of the connections between out limbic system, and the hypothalamus.
- phobia
- biofeedback
Hypothalamus (in ANS)
major visceral motor control center
-nuclei for primitive functions: hunger, thirst, sex.
Midbrain, pons, and medulla oblongata contain:
in ANS
nuclei for cardiac and vasomotor control, salivation, swallowing, sweating, bladder control, and pupillary changes.
Spinal cord reflexes
- defecation and micturition reflexes are integrated in spinal cord.
- we control these functions because of our control over skeletal muscle sphincters; if the spinal cord is damaged, the smooth muscle of bowel and bladder is controlled by autonomic reflexes built into the spinal cord (baroreceptors)
Neuropharmacology
study the effects of drugs on the nervous system
Sympathomimetics
enhance sympathetic activity
- stimulate receptors or increase norepinephrine release.
- cold medicines that dilate the bronchioles or constrict nasal blood vessels (sudafed, a1, b2 blocker)
Sympatholytics
suppress sympathetic activity
- block receptors or inhibit norepinephrine release.
- Beta blockers reduce high BP interfering with effects of epinephrine/norepinephrine on heart and blood vessels.
Parasympathomimetics
enhance activity
parasympatholytics
suppress activity
Many drugs also act on neurotransmitters in ____
ex:
CNS
prozac blocks reuptake of serotonin to prolong its mood-elevating effect
Caffeine competes with ______ (the presence of which causes sleepiness) by binding to its receptors.
adenosine
