A&P 14: The Autonomic Nervous System Flashcards
Autonomic nervous system
although all body systems contribute, the stability of our internal environment depends largely on this system of motor neurons that innervates smooth and cardiac muscles and glands
Involuntary nervous system
another name for the autonomic nervous system; reflects its subconscious control
General Visceral Motor System
another name for the autonomic nervous system; indicates the location of most of its effectors
Preganglionic neuron
the cell body of the 1st neuron in the ANS; resides in the brain or spinal cord
Preganglionic axon
axon of the preganglionic neuron; synapses with the 2nd motor neuron; thin, lightly myelinated fibers
Postganglionic (ganglionic) neuron
2nd motor neuron
Autonomic ganglion
cell body of the 2nd motor neuron
Postganglionic axon
axon of the 2nd motor neuron; extends to the effector neuron; thinner than preganglionic axons, nonmyelinated
Acetylcholine (ACh)
all somatic neurons release this neurotransmitter at their synapses with skeletal muscle fibers; the effect is always excitatory; if stimulation reaches threshold, the muscle fibers contract; autonomic postganglionic fibers release this (secreted by parasympathetic fibers)
Norepinephrine (NE)
autonomic postganglionic fibers release this neurotransmitter, which is secreted by most sympathetic fibers
Dual innervation
while 1 division of the ANS stimulates certain smooth muscles to contract or a gland to secrete, the other division inhibits that action; the 2 divisions counterbalance each other to keep body systems running smoothly
Parasympathetic division
“rest and digest system;” keeps body energy use as low as possible, even as it directs vital “housekeeping” activities like digesting food and eliminating feces and urine; blood pressure & heart rate are regulated at low normal levels, GI tract is actively digesting; pupils constrict and the lenses are accommodated for close vision
Sympathetic division
“fight or flight” system; evident when we are excited or find ourselves in emergency or threatening situations; rapidly pounding heart, deep breathing, dry mouth, cold, sweaty skin, and dilated pupils
Craniosacral division
another name for the parasympathetic division because its preganglionic fibers spring from opposite ends of the CNS (brain stem and the sacral region of the spinal cord)
Terminal ganglia
the preganglionic axons extend from the CNS nearly all the way to the structures they innervate; there the axons synapse with postganglionic neurons located in ___ ___ that lie close to or within the target organs
Oculomotor nerves (III)
innervate smooth muscles in the eyes that cause the pupils to constrict and the lenses to bulge - actions needed to focus on close objects
Ciliary ganglia
the cell bodies of postganglionic neurons are in this within the eye orbits
Facial nerves (VII)
the parasympathetic fibers of these nerves stimulate many large glands in the head
Pterygopalatine ganglia
the preganglionic fibers synapse with postganglionic neurons in ___ ___ just posterior to the maxillae
Glossopharyngeal nerves (IX)
the parasympathetics in these nerves originate in the inferior salivatory nuclei of the medulla and synapse in the otic ganglia
Otic ganglia
where the glossopharyngeal nerves synapse; located just inferior to the foramen ovale of the skull
Vagus nerves (X)
the two of these account for about 90% of all preganglionic parasympathetic fibers in the body; provide fibers to the neck and to nerve plexuses that serve virtually every organ in the thoracic and abdominal cavities
Cardiac plexuses
supply fibers to the heart
Pulmonary plexuses
serve the lungs and bronchi
Esophageal plexuses
supply the esophagus
Anterior/posterior vagal trunks
when the main trunks of the vagus nerves reach the esophagus, their fibers intermingle, forming these, each containing fibers from both vagus nerves
Abdominal aortic plexus
formed by a number of smaller plexuses (celiac, superior mesenteric, and hypogastric) that run along the aorta
Pelvic splanchnic nerves
axons of S2-4 run in the ventral roots of the spinal nerves to the ventral rami and then branch off to form these nerves, which pass through the inferior hypogastric (pelvic) plexus in the pelvic floor
Inferior hypogastric (pelvic) plexus
Pelvic splanchnic nerves pass through this plexus in the pelvic floor
Thoracolumbar division
another name for the sympathetic division because all of its preganglionic fibers arise from cell bodies of preganglionic neurons in spinal cord segments T1 - L2
Lateral horns
the numerous preganglionic sympathetic neurons in the gray matter of the spinal cord form these structures that are just posterolateral to the ventral horns that house somatic motor neurons; there are none of these in the sacral region of the spinal cord
White ramus communicans (pl = rami communicantes)
after leaving the cord through the ventral root, preganglionic sympathetic fibers pass through this
Sympathetic trunk ganglion
after leaving the cord through the ventral root, preganglionic sympathetic fibers pass through white rami communicantes to enter this adjoining cluster
Sympathetic trunk/chain
looks like strands of glistening white beads; flanks each side of the vertebral column; consist of the sympathetic ganglia and fibers running from 1 ganglion to another
Collateral (prevertebral) ganglia
the preganglionic axon passes through the trunk ganglion and emerges from the sympathetic trunk without synapsing; these preganglionic fibers help form several splanchnic nerves and synapse in these clusters located anterior to the vertebral column; neither paired nor segmentally arranged, unlike sympathetic trunk ganglia; occur only in the abdomen and pelvis
Gray rami communicantes
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 these communicating branches; from there they travel via branches of the rami to their effectors, including sweat glands and arrector pili muscles of the skin
Superior cervical ganglion
sympathetic preganglionic fibers serving the head emerge from spinal cord segments T1-4 and ascend the sympathetic trunk to synapse with postganglionic neurons in this cluster; contributes sympathetic fibers that run in several cranial nerves and in the upper 3 or 4 cervical spinal nerves; serve the skin and blood vessels of the head, stimulate the dilatory muscles of the irises of the eyes, inhibit the nasal and salivary glands, and innervate smooth (tarsal) muscle that lifts the upper eyelid; also sends direct branches to the heart
Middle/inferior cervical ganglia
postganglionic fibers emerging from these clusters enter cervical nerves C4-8; some of these fibers innervate the heart via the cardiac plexus, some innervate the thyroid gland, most serve the skin
Splanchnic nerves
includes thoracic ___ nerves (greater, lesser, and least), & lumbar and sacral ___ nerves; contribute to a number of interweaving nerve plexuses known collectively as the abdominal aortic plexus, which clings to the surface of the abdominal aorta
Celiac ganglia
most superior of the ganglia serving the abdominopelvic viscera
Superior mesenteric
middle of the ganglia serving the abdominopelvic viscera
Inferior mesenteric
most inferior of the ganglia serving the abdominopelvic viscera
Visceral sensory neurons
send info concerning chemical changes, stretch, and irritation of the viscera; 1st link in autonomic reflexes
Visceral reflex arcs
have essentially the same components as somatic reflex arcs (receptor, sensory neuron, integration center, motor neuron, effector); however, a key difference is that a it has 2 neurons in its motor component
Cholinergic fibers
fibers that release ACh
Adrenergic fibers
most sympathetic postganglionic axons release NE and are called this (exception is sympathetic postganglionic fibers that secrete ACh onto sweat glands)
Nicotinic receptors
type of cholinergic (ACh-binding) receptors that respond to nicotine
Muscarinic receptors
type of cholinergic receptors that can be activated by the mushroom poison muscarine
Alpha & beta adrenergic receptors
2 major classes of adrenergic (NE-binding) receptors
Sympathetic (vasomotor) tone
with few exceptions, the vascular system is entirely innervated by sympathetic fibers that keep the blood vessels in this continual state of partial constriction
Vasomotor fibers
when blood pressure is too low to maintain blood flow, the sympathetic fibers fire more rapidly, causing blood vessels to constrict (and raising blood pressure); when blood pressure becomes to high, sympathetic fibers fire less rapidly and the vessels dilate; alpha-blockers (drugs that block the response in these fibers) are sometimes used to treat hypertension
Parasympathetic tone
the heart and the smooth muscle of digestive and urinary tract organs exhibit this
Autonomic neuropathy
damage to autonomic nerves; common complication of diabetes mellitus; early/troubling symptom = sexual dysfunction
Biofeedback
way of becoming aware of physiological conditions (such as heart rate and blood pressure) with the goal of being able to influence them consciously
Biofeedback training
during this training, subjects are connected to monitoring devices that detect and amplify changes in physiological processes; feedback comes in the form of flashing lights or audible tones
Neural crest
ANS structures in the PNS - postganglionic neurons, the adrenal medulla, and all autonomic ganglia - derive from this developmental structure
Nerve growth factor (NGF)
protein that promotes survival and development of neurons; secreted by their target cells and many other cell types
Orthostatic hypotension
fainting episodes when one stands up (low blood pressure following changes in position); occurs because aging pressure receptors become less responsive to changes in blood pressure, and aging cardiovascular centers fail to maintain healthy blood pressure
