ANS Flashcards
Autonomic Nervous System other names
visceral nervous system” or “visceral motor system”
Autonomic Nervous System consist of what type of fibers
Motor (efferent fibers) and Afferent fibers
Motor (efferent fibers)
which travel to an end organ
Smooth muscle (viscera, blood vessels)
Modified cardiac muscle
Glandular cells
Glandular cells
A type of cell that makes mucus and is found in tissue that lines the inner part of the cervix.
when is the ANS active in the viscera
ANS is ALWAYS active in the viscera, to provide a “basal tone”
getting to the target in the Somatic system
primary neuron leaves CNS and directly innervates the effector organ
getting to the target in the autonomic system
At least 1 peripheral synapse
2 divisions of the efferent ANS
Sympathetic division
Parasympathetic division
Most organs are innervated by both (dual innervation)
Sympathetic division is found in what area of the spine
thoracolumbar
Parasympathetic division is found in what divsion of the back
craniosacral
how many neurons are involved in passing impluses from the CNS to the efferent organ
2 neurons
Presynaptic (aka preganglionic)
Postsynaptic (aka postganglionic)
Presynaptic cell body location
in the CNS grey matter
Postsynaptic cell body location - general
outside the CNS, in autonomic ganglia of thorax, abdomen, or pelvis
how can you tell if a neuron is part of the para or sym system
Location of presynaptic cell bodies
Which nerves conduct the presynaptic fibers from the CNS
how are the postsynaptic neurons of sym and para differ
postsynaptic neurons liberate different neurotransmitters
what NT do sym postsynaptic neurons give off
generally norepinephrine
what NT do para postsynapatic neurons give off
generally acetylcholine
what is the role of the sym NS
catabolic system
“Fight-or-flight” response – enables the body to deal with stress
what is the function of the sym NS
Primary function = regulate blood vessels
Generally, ↑ sympathetic signals = vasoconstriction
Exceptions: coronary vessels, skeletal muscle, and external genitalia
what is role of the para sysmtem
Homeostatic or anabolic system
“Rest and digest
how far does the sympathetic systems reach
goes to all parts of the body
Exceptions: avascular tissues (cartilage, nails)
length of pre and postsynaptic fibers in the sym system
Presynaptic fibers are short
Sympathetic ganglia are close to the midline of the body
Postsynaptic fibers are long
Need to travel all over the body
in the sym NS Cell bodies of presynaptic neurons are located where
ALL in the intermediolateral cell columns (IMLs) or nuclei of the spinal cord
where do we find IMLs
The R and L IMLs are part of gray matter in the thoracic and lumbar regions of the spinal cord
IMLs are organized
SOMATOTOPICALLY
SOMATOTOPICALLY
when a specific part of the body is associated with a distinct location in the central nervous system.
Cell bodies of postsynaptic neurons are in 2 locations
Paravertebral ganglia
Prevertebral ganglia
Prevertebral ganglia found in
In plexuses surrounding the abdominal aorta
Paravertebral ganglia
Linked; form R and L sympathetic trunks on each side of the vertebral column, from the base of the skull to the coccyx
Presynaptic neurons in the sym NS exit where
exit spinal cord through VENTRAL roots
exit ventral rami and pass through WHITE RAMI COMMUNICANTES to enter SYMPATHETIC TRUNKS
Presynaptic neurons in the sym NS enter where
enter VENTRAL rami of spinal nerves T1 through L2-L3
After entering the sympathetic trunks, fibers will take 1 of 4 possible courses
Ascend and synapse with a postganglionic neuron
Descend and synapse with a postganglionic neuron
Enter and synapse immediately (at the same level)
Pass through the sympathetic trunk without synapsing – continue through an abdominopelvic splanchnic nerve to reach the prevertebral ganglia
what is the target for nerve that travels through the splanchnic nerve
Fibers that provide autonomic innervation to the abdominal viscera take the 4th course
Ratio of presynaptic:postsynaptic fibers in te sym NS
approximately 1:30 or more
General Functions of the postsynaptic fiber of the SNS
pilomotion
vasomotion
sudomotion
Vasomotion
contraction of BV
Pilomotion
contraction of muscle in control of the hair – goose bumps
Sudomotion
sweating
what do Splanchnic Nerves carry
Convey visceral afferent AND efferent fibers to/from the viscera of the body cavities
postsynaptic in Splanchnic Nerves carry
Postsynaptic sympathetic fibers to the heart, lungs, and esophagus travel through cardiopulmonary splanchnic nerves
presynaptic in Splanchnic Nerves carry
Presynaptic sympathetic fibers to the abdominal organs (stomach, intestines) travel through abdominopelvic splanchnic nerves
Adrenal Gland other name
AKA suprarenal gland
how do cell travel to adrenal glands
Some presynaptic sympathetic fibers pass through prevertebral ganglia without synapsing, and terminate directly on cells of the adrenal glands
Only expectation to the 2-neuron chain
what do adrenal gland do
Adrenal gland medullary cells directly release neurotransmitters into the bloodstream widespread sympathetic response in the body
what does the adrenal gland release
adreniline
Parasympathetic Division of ANS is located in what part of the SC
Craniosacral Division
Parasympathetic Division of ANS main role
Works to conserve body energy
Presynaptic parasympathetic cell bodies are located
2 sites
Gray matter of the brainstem, exiting via CN III, VII, IX, and X
Gray matter of S2-S4 segments of spinal cord, exiting via VENTRAL RAMI of S2-S4 spinal nerves and PELVIC SPLANCHNIC nerves
Cranial outflow provides parasympathetic innervation where
to the head
Sacral outflow provides parasympathetic innervation to where
to the pelvic viscera And the distal GI tract (descending and sigmoid colon, and rectum)
4 peripheral ganglia, near the head:
Ciliary
Pterygopalatine
Submandibular
Otic
Ciliary peripheral ganglia
associated with CN III, goes to pupil and ciliary muscle
Pterygopalatine peripheral ganglia
associated with CN VII, goes to lacrimal gland
Submandibular peripheral ganglia
associated with CN VII, goes to submandibular and sublingual glands
Otic peripheral ganglia
Associated with CN IX, goes to parotid gland
Vagus nerve (CN X) also has a lot of autonomic fibers
Lungs (bronchoconstriction) – do not need as much air in the lung
Heart (slows heart rate)– do not need as much blood flow
Esophagus (motility)
Stomach (secretions and motility)
Intestines (motility of small intestine and most of lg intestine)
Parasympathetic vs. Sympathetic
PNS has less “reach” than SNS
Fewer ganglia
In parasympathetic, presynaptic fibers are very long and postsynaptic fibers are very short
PNS has less “reach” than SNS
Does not reach the body wall or limbs (at all)
Except for S2-S4, parasympathetic fibers do not form components of spinal nerves or their branches
SNS presynaptic:postsynaptic neurons 1:30 ratio; PNS 1:1 or 1:few
what is the Enteric Nervous System
disgestive tract NS
May be considered a 3rd component of the visceral motor system
Sometimes called a “second brain”
Very complex
Functions autonomously
Enteric Nervous System plexuses
2 interconnected plexuses within the GI tract walls
Myenteric plexus
Submusocal plexus
Myenteric plexus
In the walls of the smooth muscle of the GI tract
Submusocal plexus
Deep to the gut lining
parts of the plexus - in the entric NS
Motor neurons are greatly interconnected
Plexuses also have sensory (afferent) neurons that receive local input and stimulate the motor neurons that help with gut motility and immune function
ANS function is mostly carried out by what kind of fibers
efferent fibers
Afferent fibers important role too in the ANS
Provide information about the condition of the body’s internal environment
Afferent fibers relay this information to the CNS
CNS responds by triggering visceral and/or somatic reflexes
Efferent fibers carry out these responses on the effector organ (gland, smooth muscle)
Visceral Sensation conscious
Typically unconscious
When it reaches a conscious level, typically felt as cramps or as poorly localized pain (a vague pain)
Horner’s Syndrome caused by
occurs with spinal cord lesion at approximately T1 level
Horner’s Syndrome presentations
Pupillary constriction
Anhidrosis – decrease sweating
Ptosis – droopy eyeline
Enophthalmos – posterior displacement of eyeball, further in the eyeball then normal
Absence of sweating in face & neck – normally on the side of the lesion
Baroreceptors
afferent fibers in carotid sinus that detect change in BP
Increased BP pathway
Afferent fibers activate pathways in brainstem that will inhibit sympathetic system, causing decreased peripheral vascular resistance
Afferent fibers also activate interneurons in the brainstem to increase vagus output, resulting in decreased HR and cardiac output
Blood pressure meds often act upon what system
SNS
