Chapter 14: The Autonomic Nervous System (ANS)
abdominal aortic plexus
-Autonomic plexus -Consists of the celiac plexus, superior mesenteric plexus, and inferior mesenteric plexus. -composed of postganglionic axons projecting from the prevertebral ganglia and preganglionic axons from the vagus nerve that enter the abdominopelvic cavity with the esophagus.
inferior hypogastric (pelvic) plexus
-Main autonomic plexus of pelvis -Provides motor and sensory innervation to pelvic organs
preganglionic and postganglionic sympathetic neurons can synapse at a higher or lower level:
-preganglionic axon ascends or descends the sympathetic trunk to another trunk ganglion -smooth muscle of blood vessels
preganglionic and postganglionic sympathetic neurons can synapse in a distant collateral ganglion:
-preganglionic axon passes through the trunk ganglion and emerges from the sympathetic trunk without synapsing -these fibers help form several splanchnic nerves and synapse in collateral, or prevertebral, ganglia located anterior to the vertebral column (collateral ganglia are neither paired nor segmentally arranged) -smooth muscle and glands of abdominal organs
preganglionic parasympathetic fibers in the vagus nerve (X)
-provide fibers to the neck and to nerve plexuses (interweaving networks of nerves) that serve virtually every organ in the thoracic and abdominal cavities -arise mostly from the dorsal motor nuclei of the medulla and synapse in terminal ganglia usually located in the walls of the target organ -most of the terminal ganglia are collectively called intramural ganglia
each sympathetic trunk has how many coccygeal ganglia?
1
as the vagus nerves pass into the thorax, they send branches through the:
1. cardiac plexus: supplies fibers to the heart that slow heart rate 2. pulmonary plexus: serves the airways of lungs 3. esophageal plexus: serves the esophagus and part of the stomach
like the parasympathetic nervous system, the sympathetic nervous system supplies the smooth muscles, cardiac muscle, and glands in internal body cavities. in addition, it supplies all smooth muscles and glands in the superficial (somatic) part of the body. these superficial structures are innervated only by the sympathetic nervous system. These structures include:
1. sweat glands (eccrine and apocrine) 2. hair-rising arrector pili muscles of the skin 3. smooth muscle in the walls of all arteries and veins, both deep and superficial
once a preganglionic axon reaches a trunk ganglion, one of three things can happen. The preganglionic neurons can
1. synapse in trunk ganglion at the same level 2. synapse in trunk ganglion at a higher or lower level 3. pass through sympathetic trunk to synapse in a collateral ganglion anterior to the vertebral column
each sympathetic trunk typically has how many thoracic ganglia?
11
Each sympathetic trunk typically has how many cervical sympathetic ganglia?
3
each sympathetic trunk has how many sacral ganglia?
4
each sympathetic trunk typically has how many lumbar ganglia?
4
all somatic motor neurons release _________ at their synapses with skeletal muscle fibers. The effect is always excitatory
Acetylcholine (ACh)
where are the motor neuron cell bodies in the SNS?
CNS
submandibular ganglia
Innervate submandibular and sublingual glands
lumbar splanchnic nerve
L1-L2 Inferior mesenteric ganglion
pterygopalatine ganglia
Postganglionic fibers innervate glands (lacrimal, nasal cavity, and pharynx) -preganglionic neurons come from facial nerve (VII)
the white rami, which carry preganglionic axons to the sympathetic trunks, are found only in the _______ cord segments, regions of sympathetic outflow
T1-L2
sympathetic preganglionic fibers innervating the thoracic organs originate at
T1-T6
sympathetic preganglionic fibers from _________ innervate the abdomen. they travel in the thoracic splanchnic nerves to synapse mainly at the celiac and superior mesenteric ganglia. postganglionic fibers issuing from these ganglia serve the stomach, small intestines, proximal large intestine, liver, spleen, and kidneys
T5 to L2
greater splanchnic nerve
T5-T9 nerve that contains fibers of the central sympathetic neurons that do not synapse in the chain ganglia but project onto the celiac ganglion
sympathetic division
The part of the autonomic nervous system that arouses the body to deal with perceived threats -"fight or flight" -constricts visceral blood vessels, shunting blood to active skeletal muscles and the vigorously working heart -dilates the bronchioles in the lungs, increasing air flow -stimulates liver to release more glucose into the blood to accommodate the increased energy needs of body cells
lesser splanchnic nerve (T10-T11)
Turns into Superior Mesenteric Ganglion (Upper Digestive Tract)
sympathetic preganglionic fibers from T5 to L2 innervate the __________. they travel in the thoracic splanchnic nerves to synapse mainly at the celiac and superior mesenteric ganglia. postganglionic fibers issuing from these ganglia serve the stomach, small intestines, proximal large intestine, liver, spleen, and kidneys
abdomen
the splanchnic nerves contribute to a number of interweaving nerve plexuses known collectively as the _______________, which clings to the surface of the abdominal aorta
abdominal aortic plexus
the preganglionic axons found in the oculomotor nerves issue from the ________________ in the midbrain
accessory oculomotor (Edinger-Westphal) nuclei
most parasympathetic fibers release
acetylcholine
when the main trunks of the vagus nerves reach the esophagus, their fibers intermingle, forming the
anterior and posterior vagal trunks
white rami communicantes
autonomic nerve fibers that attach to ventral rami
example of parasympathetic activity
blood pressure and heart rate are regulated at low normal levels, and the GI tract is actively digesting food -pupils are constricted and the lenses are accommodated for close vision to improve the clarity of the close-up image
Where do parasympathetic fibers originate?
brain and sacral spinal cord (craniosacral)
parasympathetic division
branch of the ANS, called the "rest and digest" -keeps body energy use as low as possible
what type of muscle(s) does the ANS stimulate?
cardiac and smooth
the cell bodies of the postganglionic axons found in the oculomotor nerves are in the ______________ within the eye orbits
ciliary ganglia
where are sympathetic ganglia located?
close to the spinal cord
splanchnic nerves
consist of axons that synapse in collateral ganglia -nerves that convey information about the nutrient contents of the stomach to the brain -includes greater, lesser, and least splanchnic nerves
lateral horns
contains somatic motor neurons
sympathetic trunk ganglia
distributes fibers through the ramus communicans for sympathetic influence into spinal nerves
what are the differences between the somatic and autonomic systems?
effectors, efferent pathways and ganglia, and target organ responses to their neurotransmitters
preganglionic axons
extend from the CNS nearly all the way to the structures to be innervated, where they synapse with ganglionic neurons in the terminal ganglia -thin and lightly myelinated
the parasympathetic fibers in the glossopharyngeal nerves (IX) originate in the inferior salivatory nuclei of the medulla and synapse in the otic ganglia, located just inferior to the _________ of the skull
foramen ovale
the postganglionic fibers in the _______________ course to and activate the parotid salivary glands anterior to the ears
glossopharyngeal fibers (IX)
the parasympathetic fibers in the _____________ originate in the inferior salivatory nuclei of the medulla and synapse in the otic ganglia, located just inferior to the foramen ovale of the skull
glossopharyngeal nerves (IX)
_______ carrying postganglionic fibers headed for the periphery issue from every trunk ganglion from the cervical to the sacral region, allowing sympathetic output to reach all parts of the body
gray rami
when synapses are made in sympathetic trunk ganglia, the postganglionic axons enter the ventral (or dorsal) ramus of the adjoining spinal nerves by way of communicating branches called
gray rami communicantes
the parasympathetic fibers of the facial (VII) nerves stimulate many large gland in the
head
where are parasympathetic ganglia located?
in or near the visceral effector organs
postganglionic neuron
in the autonomic division of the PNS, a neuron that has its cell body located in an autonomic ganglion (where a pre-ganglionic neuron synapses with it) and whose axon synapses with the effector organ
preganglionic neuron
in the autonomic nervous system of the PNS, a neuron that has its cell body located in the CNS and whose axon extends into the PNS to synapse with a second neuron at an autonomic ganglion (the second neuron's axon synapses with the target organ)
the parasympathetic fibers in the glossopharyngeal nerves (IX) originate in the ____________ and synapse in the otic ganglia, located just inferior to the foramen ovale of the skull
inferior salivatory nuclei of the medulla
pelvic splanchnic nerves
innervate part of large intestine, urinary bladder, ureters, reproductive organs
parasympathetic fibers of the oculomotor (III) nerves
innervates smooth muscle in the eyes that causes pupils to constrict and the lenses to bulge (actions needed to focus on close objects)
fibers that activate the nasal glands and the lacrimal glands of the eyes originate in the
lacrimal nuclei of the pons
the numerous cell bodies of preganglionic sympathetic neurons in the gray matter of the spinal cord form the
lateral horns
postganglionic axons
link visceral motor neurons in autonomic ganglia to their targets -thin and nonmyelinated
vagal trunks
located at the lower end of the esophagus -cardiac, pulmonary, and esophageal plexuses give off anterior and posterior vagal trunks, each of which contains fibers from both the right and left vagus nerves. NOTE: These trunks penetrate the diaphragm, enter the abdominal cavity (send fibers through the large abdominal aortic plexus), and contribute to the extensive abdominal aortic plexus.
terminal ganglia
located near organ innervated or embedded in wall of organ
dual innervation
most viscera receive nerve fibers from both parasympathetic and sympathetic divisions
autonomic ganglia
motor, visceral
most sympathetic fibers release
norepinephrine
autonomic postganglionic fibers release two neurotransmitters:
norepinephrine and acetylcholine
which cranial nerves supply the entire parasympathetic innervation of the head?
oculomotor (III), facial (VII), and glossopharyngeal (IX)
sacral part of parasympathetic division
originates from neurons in S2-S4 and -serves pelvic organs and distal half of large intestine -axons runs in the ventral roots of the spinal nerves to the ventral rami and then branch off to form the pelvic splanchnic nerves, which pass through the inferior hypogastric (pelvic) plexus in the pelvic floor
the parasympathetic fibers in the glossopharyngeal nerves (IX) originate in the inferior salivatory nuclei of the medulla and synapse in the __________, located just inferior to the foramen ovale of the skull
otic ganglia
where are sympathetic trunk ganglia located?
paired, beside spinal cord
what division of the autonomic nervous system innervates terminal ganglia?
parasympathetic
which division of the ANS has long preganglionic and short postganglionic fibers?
parasympathetic
the postganglionic fibers in the glossopharyngeal fibers (IX) course to and activate the _____________ anterior to the ears
parotid salivary glands
sympathetic preganglionic fibers from T5 to L2 innervate the abdomen. they travel in the thoracic splanchnic nerves to synapse mainly at the celiac and superior mesenteric ganglia. _____________ fibers issuing from these ganglia serve the stomach, small intestines, proximal large intestine, liver, spleen, and kidneys
postganglionic
the _________ fibers in the glossopharyngeal fibers (IX) course to and activate the parotid salivary glands anterior to the ears
postganglionic
gray rami communicantes
postganglionic sympathetic axons from sympathetic trunk to spinal nerve NONMYELINATED
what cranial nerves are involved in the parasympathetic division?
preganglionic fibers run in the oculomotor (III), facial (VII), glossopharyngeal (IX), and vagus (X) cranial nerves
Two-neuron chain of ANS
preganglionic neuron and postganglionic neuron
in parasympathetic fibers of the facial nerves, preganglionic fibers synapse with postganglionic neurons in the _____________ just posterior to the maxilla
pterygopalatine ganglia
which part of the parasympathetic division serves the pelvic organs and the distal half of the large intestine?
sacral
superior cervical ganglion
serves skin and blood vessels of the head -stimulate the dilator muscles of the irises -inhibit the nasal and salivary glands -innervate the smooth muscle that lifts the upper eyelid
what type of muscle(s) does the somatic nervous system stimulate?
skeletal
sympathetic preganglionic fibers serving the head emerge from spinal cord segments T1-T4 and ascend the sympathetic trunk to synapse with postganglionic neurons in the ______________. this ganglion contributes sympathetic fibers that run in several cranial nerves and in the upper three or four cervical spinal nerves
superior cervical ganglion
the preganglionic neurons that stimulate the submandibular and sublingual salivary glands originate in the _________. They synapse with postganglionic neurons in the submandibular ganglia
superior nuclei of the pons
____________ preganglionic fibers from T5 to L2 innervate the abdomen. they travel in the thoracic splanchnic nerves to synapse mainly at the celiac and superior mesenteric ganglia. postganglionic fibers issuing from these ganglia serve the stomach, small intestines, proximal large intestine, liver, spleen, and kidneys
sympathetic
what division of the autonomic nervous system innervates collateral ganglia (prevertebral ganglia)?
sympathetic
what division of the autonomic nervous system innervates sympathetic trunk ganglia?
sympathetic
which division of the ANS has short preganglionic fibers and long postganglionic fibers?
sympathetic
rami communicantes are associated only with the ____________________
sympathetic division -they never carry parasympathetic fibers
after leaving the cord via the ventral root, preganglionic sympathetic fibers pass through a white ramus communicans (plural: rami communicantes) to enter an adjoining sympathetic trunk ganglion forming part of the ________________
sympathetic trunk (or sympathetic chain)
after leaving the cord via the ventral root, preganglionic sympathetic fibers pass through a white ramus communicans (plural: rami communicantes) to enter an adjoining ______________ forming part of the sympathetic trunk (or sympathetic chain)
sympathetic trunk ganglion
preganglionic and postganglionic sympathetic neurons can synapse at the same level:
synapse is in the same trunk ganglion -arrector pili muscles and sweat glands of skin
autonomic nervous system (ANS)
the part of the peripheral nervous system (under the motor (efferent) division) that controls the glands and the muscles of the internal organs (such as the heart) -has a sympathetic division that arouses and a parasympathetic division calms
Somatic Nervous System (SNS)
the part of the peripheral nervous system that controls voluntary movement of skeletal muscles
somatic motor fibers
thick, heavily myelinated, group A fibers that conduct nerve impulses rapidly
where do sympathetic fibers originate?
thoracic and lumbar regions of the spinal cord (thoracolumbar)
all preganglionic fibers of the sympathetic division arise from cell bodies of preganglionic neurons in spinal cord segments T1 through L2. For this reason, the sympathetic division is also referred to as the ______________
thoracolumbar division
where are collateral ganglia (prevertebral ganglia) located?
unpaired, anterior to spinal cord
how does the ANS reach its effectors?
using a two-neuron chain
which cranial nerve accounts for about 90% of all preganglionic parasympathetic fibers in the body?
vagus nerve (X)
after leaving the cord via the __________, preganglionic sympathetic fibers pass through a white ramus communicans (plural: rami communicantes) to enter an adjoining sympathetic trunk ganglion forming part of the sympathetic trunk (or sympathetic chain)
ventral root
the _________, which carry preganglionic axons to the sympathetic trunks, are found only in the T1-L2 cord segments, regions of sympathetic outflow
white rami
after leaving the cord via the ventral root, preganglionic sympathetic fibers pass through a ____________ to enter an adjoining sympathetic trunk ganglion forming part of the sympathetic trunk (or sympathetic chain)
white ramus communicans (plural: rami communicantes)
where are terminal ganglia located?
within wall of organ served (intramural ganglia) or close to organ
