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