Lecture 12: Autonomic Nervous System Flashcards
What actions are controlled by the autonomic nervous system?
Involuntary actions
Where is the autonomic nervous system located in the body
CNS (brain and spinal cord) and PNS
Is the autonomic nervous system afferent or efferent?
Efferent
2 subdivisions of the autonomic nervous system
Sympathetic and parasympathetic
What does the parasympathetic system regulate?
Body homeostasis (rest and digest)
What does the sympathetic system regulate?
Fight, Fright, or flight
What are the parasympathetic and the sympathetic systems anatogonistic of one another?
The sympathetic requires energy while the parasympathetic conserves energy.
Similarity between the parasympathetic and sympathetic systems: Embryonic origin of ganglia
Neural crest
What is another similarity between the sympathetic and parasympathetic systems
They both use a 2 neuron pathway with a preganglionic nerve fiber in the CNS and a postganglionic fiber in the PNS
What does the sympathetic system innervate
Sweat glands, arrector pili muscles, abd blood vessels
What does the parasympathetic system innervate
Visceral organs
The are the two afferent components of a spinal nerve
Somatic and Visceral afferent components
Role of Somatic afferent fibers?
Sense pain, temperature, propriocception, and touch (In other words senses stimuli outside the body)
Role of Visceral afferent fibers?
Senses pain and pressure from visceral organs (sense stimuli within the body)
Which localizes pain better, visceral or somatic afferent fibers?
somatic
What are the two efferent components of a spinal nerve?
Somatic and Visceral efferent components
Role of Somatic efferent fibers?
Innervate skeletal muscle
Role of Visceral efferent fibers
These are all autonomic fibers- target visceral organs, blood vessels, sweat glands, smooth muscle, and cardiac muscle
Describe the 2 neuron system in the autonomic nervous system
The preganglionic nerve fiber originates in the CNS and extends out to the PNS to synapse with the Postganglionic nerve fiber, which is always located in the PNS Which then propagates the synapse to the target organ
Where are the cell bodies of the preganglionic fibers ALWAYS located in the sympathetic nervous system
Lateral horn of the spinal cord
What spinal cord levels contain the lateral horn?
T1-L2(3)
What are the spinal cord levels for the preganglionic sympathetic nerve fibers
T1-L2(3)
Is the sympathetic trunk (or paravertebral ganglia) considered post or preganglionic fibers?
Postganglionic because it is not in the brain/spinal cord it is located in the periphery
Where does the sympathetic trunk extend
From the skull to coccyx
Location of the sympathetic trunk
Paravertebral in location (next to the vertebral column)
How many cervical, thoracic, lumbar, and sacral ganglia in the sympathetic chain?
3 cervical
11 thoracic
4 lumbar
4 sacral
Ganglion impar
When 2 sides of the trunks on the sympathetic chain unite as one final ganglia in the coccygeal region
Where are prevertebral ganglia located
Im front of the vertebral column and cemented on aorta
What do prevertebral fibers innervate?
Unpaired visceral arteries
What are the different ganglia associated with the prevertebral ganglia
Celical ganglia (pair), aorticorenal ganglia, superior mesenteric ganglia, and inferior mesenteric ganglia
Role of white rami communicantes
Brings fibers into the symapthetic trunk from spinal nerve
How many pairs of white rams communicantes are there?
14 (From T1-L2)
Are the white rams communicantes aggregates of preganglionic or postganglionic nerves?
Perganglionic
Why are the fibers in the white rams communicates white?
Because they are slightly myelinated
Role of the gray rams communicates
Brings fibers from the sympathetic trunk toothier target organ or gland
How many pairs of gray rams communicates are there
31 (there are 31 pairs of spinal nerves- gray rams communicates are distributed to each spinal nerve)
Why are the fibers in the gray rams communicates gray
Lack myelin
Are the gray rams communicates considered preganglionic or postganglionic fibers?
Postganglionic
Where do the greater, lesser, and least splanchnic nerves arise from?
Superior to or at the level of the diaphragm
Where does the lumbar splanchnic nerve arise?
Below the diaphragm
What is the common goal of the greater, lesser, least, and lumbar splanchnic nerves?
Provide sympathetic innervation to the organs of the abdomen and pelvis
What are the sympathetic neurotransmitters for preganglionic fibers?
Acetylcholine
What are the sympathetic neurotransmitters for postganglionic fibers?
Norepinephrine except for the postganglionic sympathetic fibers to sweat glands which is acetylcholine
Describe the sympathetic pathway to the periphery from levels T1-L2
Preganglionic cell body originates in the lateral horn of the spinal cord leaves via the ventral root and enters the sympathetic chain via the white rams communicates. In the sympathetic chain, the preganglionic cell synapses with the postganglionic cell, which leaves via the gray matter communicates to the peripheral organ (sweat gland, peripheral arteriole, or arrestor pili muscle).
Describe the sympathetic pathway to the periphery above or below levels T1-L2
The pre ganglionic fibers from the lateral horn enter the sympathetic chain via the white rams communicantes. The preganglionic fibers then either ascend or desend along the trunk until they reach the level they want to be at. Then the preganglionic fiber synapses with the postganglionic fiber in the trunk and levels via the gray matter communicantes.
Why is this pathway described in the previous card important
Allows the entire body to receive sympathetic innervation even though the lateral horn only extends from T1-L2,3 (example: sweaty feet during a run)
What are the similarities between the first 2 sympathetic pathways I have already described
They have the same target organs (sweat glands, arrestor pili muscles, peripheral blood vessels
Describe the pathway for sympathetic innervation to visceral organs of the thorax
Prevertebral ganglion begin in the lateral horn, travel out of the ventral orotund into the sympathetic chain via the white matter communicates, the signal can then either ascend, descend, or stay at the same level along the sympathetic chain. The preganglionic fibers synapse with the postganglionic fibers in the sympathetic chain BUT do NOT leave via the gray matter communicates. Instead the postganglionic fibers leave medially to form splanchnic nerves that course internally to supply visceral organs
What does the pathway previously described provide innervation to?
The heart
Describe the sympathetic pathway to the visceral organs of the abdomen/pelvis
The preganglionic fibers begin in the lateral horn, enter the ventral root, enter the sympathetic chain via the white rams communicates. The preganglionic fiber can ascend, descend or stay at the same spinal cord level along the sympathetic chain. The preganglionic fiber DOES NOT synapse in the sympathetic chain and DOES NOT exit via the gray matter communicates. Instead it exits via the splanchnic nerve and synapses on four major groups of ganglia with the postganglionic fiber, which then targets the organ of interest
What are the four major groups of splanchnic nerves in the sympathetic pathway for the visceral organs of the abdomen/pelvis along with their spinal cord levers
Greater- T(5)6-9 splanchnic nerve
Lesser- T(9)10-11 splanchnic nerve
Least- T12 splanchnic nerve
Lumbar splanchnic nerve
Where does the greater splanchnic nerve synapse
celiac ganglia
What does the celiac ganglia innervate
forgut organs
Where do the lesser and least splanchnic nerves synapse
aorticorenal ganglia
What does the aorticorenal ganglia innervate?
The kidneys
What synapses at the superior mesenteric ganglion
collaterals from the celiac ganglion No splanchnic nerve goes directly into the superior mesenteric ganglion
What does the superior mesenteric ganglion innervate
midgut
What synapses at the inferior mesenteric ganglion
The lumbar splanchnic nerves from L1-3
What does the inferior mesenteric ganglion innervate?
Hindgut
Compare the location of the sympathetic verses the parasympathetic nervous systems
Parasympathetic= craniosacral Sympathetic= thoracolumbar
In the parasympathetic system compare the length of the preganglionic fibers and the postganglionic fibers
The preganglionic fibers are long and the postganglionic fibers are short (the opposite is true in the sympathetic system)
CN X (vagus nerve) innervation
Travels all the way through various organs (Heart, bronchi, stomach, small intestine: biggest supply is forgut and midgut. Supplies everything up until the distinction between mid and hind gut/ Starts in brain
Major influences of the parasympathetic nervous system
Salivary glands, GI secretion, mobility, control over pupillary sphincter, and peristalisis
Where is the parasympathetic nervous system distributed to
Trunk regions such as thorax, abdomen, and pelvis
What does the cranial portion of the parasympathetic nervous system consist of
Preganglionic fibers that originate in the brain stem and travel through the cranial nerves
Sacral portion of parasympathetic nervous system: Spinal cord levels
S2-4
What organs are targeted by the sacral portion of the parasympathetic nervous system?
Reproductive and rectum
What is the neurotransmitter for parasympathetic preganglionic and postganglionic nerve fibers
Acetylcholine
Does the parasympathetic nervous system go to the periphery
No
Does the sympathetic nervous system go to the periphery?
Yes
Actions of the parasympathetic and sympathetic nervous system in the gut?
Parasympathetic- Increase peristalsis Sympathetic: Decrease peristalsis
Actions of the parasympathetic and sympathetic nervous system in the heart
parasympathetic: decrease heart rate and sympathetic: increase heart rate
Actions of the parasympathetic and sympathetic nervous system in sweat glands
SYMPATHETIC ONLY (only one that goes to periphery): Promotes secretion
Actions of the parasympathetic and sympathetic nervous system on bronchi/bronchioles
Parasympathetic: Constrict
Sympathetic: Dialates
Actions of the parasympathetic and sympathetic nervous system on pupils
Parasympathetic: Light response (pupil constricted)
Sympathetic: Dark response (pupil dilated)
Actions of the parasympathetic and sympathetic nervous system on Peripheral blood vessels
SYMPATHETIC ONLY (only one that goes to periphery)- vasoconstriction
Actions of the parasympathetic and sympathetic nervous system on blood vessels to skeletal muscle
SYMPATHETIC ONLY- Vasodialation
Actions of the parasympathetic and sympathetic nervous system on the adrenal gland
SYMPATHETIC ONLY- The exception organ that receives preganglionic sympathetic fibers to enhance the secretion of adrenaline
Actions of the parasympathetic and sympathetic nervous system on salivary glands
Parasympathetic- increase salivation
Sympathetic- Decrease salivation
Actions of the parasympathetic and sympathetic nervous system on genitals
Parasympathetic- Erection (S2,3,4 get penis off the floor)
Sympathetic- Ejaculation
Mechanism of referred pain
Pain from visceral organs can be “referred” to somatic afferents that enter the same level of the spinal cord and have their cell bodies in the same dorsal root ganglia as the visceral afferents.
Examples of referred pain
- Pain in tooth that turned out to be a sinus infection
- Appendicitis which results in pain around umbilicus
- Heart attack can give nagging pain on medial side of the arm resulting from the fact that the same spinal cord segments that feed into the heart are the spinal segments from the arm
