ANS - Composition Flashcards
The autonomic nervous system is a system of visceral sensory (____) and visceral motor (____) neurons that regulates the activity of smooth muscle, cardiac muscle, and many glands
afferent
efferent
Like the somatic nervous system, the autonomic nervous system operates via ___
reflex arcs
A continual flow of nerve impulses from autonomic sensory neurons in visceral organs and blood vessels propagate into integrating centers in the central nervous system, and impulses in autonomic ___ propagate to various effector tissues (smooth muscle, cardiac muscle, many glands)
motor neurons
The ___ part of the autonomic nervous system consists of two branches: sympathetic division and parasympathetic division
motor
Most input to the autonomic nervous system comes from autonomic sensory neurons, which are mostly ___
interoceptors, such as . . .
Chemoreceptors that monitor blood CO2 levels
Mechanoreceptors that detect the degree of stretch in walls of organs (stomach, urinary bladder, intestines, uterus) or blood vessels
The signals are not consciously perceived most of the time, but intense activation of interoceptors may produce conscious sensation
such as angina pectoris from inadequate blood flow to the heart
Autonomic neurons regulate visceral activities by increasing (____) or decreasing (___) activities in their effector tissues (cardiac muscle, smooth muscle, glands)
exciting
inhibiting
Unlike skeletal muscle, tissues innervated by the ANS often have an intrinsic function that enables them to continue to operate even if their ___ is damaged (heart beat, gastrointestinal tract contractions)
nerve supply
Whereas a single myelinated somatic motor neuron extends from the CNS to the skeletal muscle fibers in its motor unit, autonomic motor pathways consist of __ motor neurons in series
two
slide 7
The first neuron has its cell body in the ___, and its myelinated axon extends from the CNS to an autonomic ganglion. This is the pre-ganglionic neuron
CNS
All pre-synaptic in the ANS are?
myelinated
The second neuron has its cell body in the ganglion, and its unmyelinated axon extends from the ganglion to the ___. This is the post-ganglionic neuron
effector
autonomic motor neurons release either ____ or ___
acetylcholine or norepinephrine.
An additional difference between somatic and autonomic motor neurons is that somatic motor neurons release only acetylcholine (Ach) as their neurotransmitter
motor part of the autonomic nervous system has two main components:
Sympathetic division
Parasympathetic division
Most organs have dual innervation, meaning they receive impulses from both sympathetic and parasympathetic neurons
As a general principle, nerve impulses from one division of the ANS stimulate increased activity in an organ (excitation), and impulses from the other division decrease activity (inhibition),
The heart rate is increased by an increased rate of nerve impulses from sympathetic division, and decreased by an increased rate of nerve impulses from the parasympathetic division
Muscular movements of the GI tract are slowed by sympathetic stimulation, and increased by parasympathetic stimulation
Autonomic motor pathways consist of two neurons:
Preganglionic neuron
Postganglionic neuron
Cell body is in the brain or spinal cord
Axon exits the CNS as part of a cranial nerve or spinal nerve
Conveys nerve impulses from the CNS to autonomic ganglia
Preganglionic neuron
The first of the two motor neurons in any autonomic motor pathway
Cell body and dendrites are in an autonomic ganglion
Relays nerve impulses from autonomic ganglia to visceral effectors
Postganglionic neuron
The second of the two motor neurons in any autonomic motor pathway
Preganglionic neurons of the ____ have their cell bodies in the lateral gray horns of the 12 thoracic segments and the first 2 lumbar segments of the spinal cord
sympathetic division
Preganglionic neurons of the parasympathetic division have their cell bodies in the nuclei of cranial nerves III, VII, IX, and X of the ____ , and in the lateral gray horns of the second through the ____ sacral segments of the spinal cord
brain stem
fourth
Sympathetic ganglia are of two major types
Sympathetic trunk ganglia
Prevertebral ganglia
Also called vertebral chain ganglia, or paravertebral ganglia
Ganglia lie in a vertical row on each side of the vertebral column
(sympathetic)
Sympathetic trunk ganglia
Preganglionic axons are usually short
Postganglionic axons are generally fairly long
Postganglionic axons mostly innervate organs above the diaphragm
(sympathetic)
Sympathetic trunk ganglia
The ganglia are anterior to the vertebral column, close to the large abdominal arteries
(sympathetic)
Prevertebral ganglia
Postganglionic axons mostly innervate organs below the ___
(Prevertebral ganglia)
(sympathetic)
diaphragm
As with paravertebral ganglia, preganglionic axons are usually short and postganglionic axons are generally fairly long
(sympathetic)
Prevertebral ganglia
part of sympathetic
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
Aorticorenal ganglion
Renal ganglion
(sympathetic)
five major prevertebral ganglia
five major prevertebral ganglia
sympathetic
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
Aorticorenal ganglion
Renal ganglion
Preganglionic axons of the parasympathetic division synapse with postganglionic neurons in terminal ganglia
Most terminal ganglia are located close to or within the wall of the visceral organ
Preganglionic axons are typically long
Postganglionic axons are short, or seemingly non-existent
Parasympathetic ganglia
“terminal ganglia”
Parasympathetic ganglia of the head have specific names:
Ciliary ganglion
Pterygopalatine ganglion
Submandibular ganglion
Otic ganglion
Ciliary ganglion
Pterygopalatine ganglion
Submandibular ganglion
Otic ganglion
Parasympathetic ganglia
Parasympathetic splanchnic nerves extend to ____
viscera
Axons of parasympathetic neurons extend to parasympathetic postganglionic neurons in terminal ganglia in the walls of the colon, ureters, urinary bladder, and reproductive organs by means of pelvic ___
splanchnic nerves
Sympathetic preganglionic neurons arriving at sympathetic trunk ganglia may connect with postganglionic neurons by . . .
(4 options)
Synapsing in the ganglion it first reaches, OR BY…
Ascending or descending before synapsing, OR BY…
Continuing, without synapsing, through the trunk ganglion to a prevertebral ganglion and synapsing there with postganglionic neurons, OR BY…
Continuing without synapsing through both the sympathetic trunk ganglion and a prevertebral ganglion to extend to chromaffin cells of the adrenal medullae
Sympathetic preganglionic fibers have many axon ___, and synapse with a number of postganglionic neurons (20 or more)
collaterals
This is a divergent projection pattern
Explains in part why sympathetic responses typically affect almost the entire body, and why they do so simultaneously
Postganglionic axons of the sympathetic division usually terminate in several ___ after leaving their ganglia
effectors
Parasympathetic preganglionic neurons have ___ collaterals, and synapse with a limited number of postganglionic neurons, all of which are in the same visceral effector
few axon
This is technically a divergent projection pattern (but not much divergence)
Explains in why parasympathetic responses can be localized to a single effector
Parasympathetic postganglionic axons terminate in the __ effector after leaving their ganglia (rather than branching out to different effectors)
same
tangled networks of neurons formed jointly by the sympathetic and parasympathetic nervous systems
Autonomic plexuses
They are present in the thorax, abdomen, and pelvis
Many of them lie along major arteries
Visceral afferent fibers are commonly also present?
Autonomic plexuses
at the base of the heart, it surrounds the large blood vessels emerging from the heart. It is contributed to by both post-ganglionic sympathetic and pre-ganglionic parasympathetic nerves. Sympathetic neurons to this plexus increase heart rate and contractility. Parasympathetic innervation, provided by the vagus nerve, supplies fibers to the heart that slow heart rate
Cardiac plexus
posterior to each lung, sympathetic and parasympathetic branches of the autonomic nervous system serve the lungs, bronchi, and pulmonary blood vessels. Sympathetic innervation causes bronchodilation. Parasympathetic pathway causes bronchoconstriction and increased secretion from mucous glands of the bronchial tree
Pulmonary plexus
(AKA solar plexus): the largest autonomic plexus, it surrounds the celiac and superior mesenteric arteries, and is at the level of the last thoracic / first lumbar vertebrae
Celiac plexus
supplies the small and large intestine
Celiac plexus
Superior mesenteric plexus
innervates the large intestine
Celiac plexus
Inferior mesenteric plexus
Cell bodies are part of the ___ horns of all thoracic segments plus the first two or three lumbar segments of the spinal cord
Sympathetic Preganglionic Neurons
lateral
(The axons are myelinated)
Sympathetic Preganglionic Neurons
Preganglionic axons leave the spinal cord through the ___ root of a spinal nerve along with somatic motor neurons at the same level, and exit through the intervertebral foramina
Sympathetic Preganglionic Neurons
anterior
The myelinated axons pass through a white ___ to enter an adjoining paravertebral (chain) ganglion, thereby forming part of the sympathetic trunk, AKA sympathetic chain
Sympathetic Preganglionic Neurons
ramus communicans
White rami communicantes are present only in the _____, since those are the only regions with sympathetic outflow
thoracic and first two lumbar nerves (T1-L2)
Sympathetic trunk ganglia are paired, one on each side of the vertebral column, typically consisting of:
3 cervical ganglia 11 or 12 thoracic ganglia 4 or 5 lumbar ganglia 4 or 5 sacral ganglia 1 coccygeal ganglion (fused at midline)
Cervical ganglia (Sympathetic preganglionic ) fibers that serve the head and neck emerge from spinal cord segments T1 – T6, and ascend to synapse with postganglionic neurons within cervical ganglia in the neck, comprising
Superior cervical ganglion
Middle cervical ganglion
Inferior cervical ganglion
Superior cervical ganglion postganglionic sympathetic fibers supply the head and heart
Sweat glands Smooth muscle of the eye Blood vessels of the face Salivary glands Pineal gland Lacrimal glands Heart
Middle cervical ganglion and inferior cervical ganglion postganglionic sympathetic fibers supply the ___
heart
The thoracic region receives most of the sympathetic ___ axons
(sympathetic)
preganglionic
Postganglionic fibers from the thoracic sympathetic trunk innervate . . .
Heart Lungs Bronchi Sweat glands Blood vessels of the skin Arrectores pilorum muscles
Heart Lungs Bronchi Sweat glands Blood vessels of the skin Arrectores pilorum muscles
innervated by what of the sympathetic trunk?
Postganglionic fibers from the thoracic sympathetic trunk
Axons leave the sympathetic trunk in four possible ways
Enter spinal nerves
Form cephalic periarterial nerves
Form sympathetic nerves
Form splanchnic nerves
Sympathetic trunk pathways: enter a spinal nerve…
Some incoming sympathetic preganglionic neurons synapse with postganglionic neurons either in the ganglion at the level of entry, or farther up or down the sympathetic chain
Axons of those postganglionic neurons leave the trunk by means of a gray ramus (gray ramus communicans), then merge with the anterior ramus of a spinal nerve
Axon collaterals from preganglionic neurons may pass up or down the ___ for a variable distance, forming sympathetic chains, which are the fibers on which the ganglia are located
sympathetic trunk
Unmyelinated postganglionic axons pass through a ____ to connect the ganglia of the sympathetic trunk to spinal nerves
gray ramus communicans
gray ramus communicans are all the way up and down the spine
Since gray rami communicantes are associated with all spinal nerves, they outnumber white rami communicantes, which are associated with only the _____
thoracic nerves and two or three lumbar nerves
Some preganglionic neurons ascend in the sympathetic trunk to the superior _____, where they synapse with postganglionic neurons
cervical ganglion
Those postganglionic neurons (from the cervical ganglion) extend to the head by wrapping around and following certain arteries (such as the carotid artery) from the neck to the head, forming _____
(sympathetic)
cephalic periarterial nerves
Cephalic periarterial nerves supply sympathetic innervation to:
(sympathetic)
skin of the face (sweat glands, smooth muscle of blood vessels, arrectores pilorum muscles)
visceral effectors of the head (smooth muscles of the eye, lacrimal glands, pineal gland, nasal mucosa, salivary glands)
After synapsing with preganglionic neurons, some postganglionic neurons form sympathetic nerves that extend to visceral effectors in the thoracic cavity, providing:
(sympathetic)
Sympathetic nerves to the heart (the superior, middle, and inferior cervical ganglia, and first through fourth thoracic ganglia)
Sympathetic nerves to smooth muscle of bronchi and lungs
Some sympathetic preganglionic neurons pass through the trunk without terminating in it. They then form nerves called ____ that generally extend to prevertebral ganglia
splanchnic nerves
Splanchnic nerves are formed by preganglionic axons that pass through the ____ without terminating in it, then terminate in prevertebral ganglia
sympathetic trunk
generally innervate organs below the diaphragm
Postganglionic neurons of the greater splanchnic nerve supply . . .
Liver Stomach Spleen Small intestine Kidney
Postganglionic neurons of the lesser splanchnic nerve innervate . . .
Small intestine
Colon
Postganglionic neurons of the lumbar splanchnic nerve innervate . . .
Colon
Rectum
Genitals
Urinary bladder
Although there are no postganglionic neurons from the adrenal medullae, developmentally the adrenal medullae are derived from the same type of precursor cell, called ____, that gives rise to postganglionic neurons elsewhere in the body
chromaffin cell
In effect, then, the adrenal medullae themselves comprise a large complex of _____, the cells of which release hormones into the blood (mostly epinephrine, some norepinephrine, a trace of dopamine)
postganglionic neurons
Cell bodies are in nuclei in the brain stem and in the ___ horns of the second through fourth sacral segments of the spinal cord
(Parasympathetic Preganglionic Neurons)
lateral
Axons emerge as part of a cranial nerve, or as part of the anterior root of a spinal nerve:
(Parasympathetic Preganglionic Neurons)
cranial parasympathetic outflow consists of preganglionic axons, from the brain stem in four of the cranial nerves
sacral parasympathetic outflow, comprises preganglionic axons in anterior roots of the second through fourth sacral spinal nerves
cranial parasympathetic outflow consists of preganglionic axons, from the brain stem in four of the cranial nerves
sacral parasympathetic outflow, comprises preganglionic axons in anterior roots of the second through fourth sacral spinal nerves
(Parasympathetic Preganglionic Neurons)
The axons are myelinated, and end in terminal ganglia close to the organ they innervate
(Parasympathetic Preganglionic Neurons)
located near the posterior aspect of each eyeball; preganglionic axons from oculomotor nerves (CN III); postganglionic axons innervate smooth muscles in eyeball
Cranial parasympathetic ganglia
Ciliary ganglia
preganglionic axons from facial (VII) nerves; postganglionic axons to nasal mucosa, pharynx, and to lacrimal glands
Cranial parasympathetic ganglia
Pterygopalatine ganglia
located near submandibular salivary gland ducts; preganglionic axons from facial (VII) nerves; postganglionic axons to submandibular salivary glands and sublingual salivary glands
Cranial parasympathetic ganglia
Submandibular ganglia
inferior to each foramen ovale; pregangliionic axons from glossopharyngeal (IX) nerves; postganglionic axons to parotid salivary glands
Cranial parasympathetic ganglia
Otic ganglia
Most (80%) of the total craniosacral outflow is carried by preganglionic axons that leave the brain as part of the ____
vagus nerves (cranial nerve X)
The vagus nerve sends axons to the . . .
Heart Airways of the lungs Liver Gallbladder Stomach Pancreas Small intestine Large intestine
Heart Airways of the lungs Liver Gallbladder Stomach Pancreas Small intestine Large intestine
innervated by Vagus nerve
Preganglionic neurons of the sacral parasympathetic outflow form pelvic splanchnic nerves, the postganglionic neurons of which innervate smooth muscle and glands in . . .
(PARASYMPATHETIC)
Colon
Ureters
Reproductive organs
Urinary bladder
