Nervous System/Heart/Lungs Flashcards
Is the autonomic nervous system motor or sensory?
Visceral motor system
Interoreceptors
Visceral afferent fibers
2 Functions of interoreceptors
24/7 monitoring of internal activity, conveying visceral pain
2 Divisions of the autonomic nervous system
sympathetic and parasympathetic
What types of neurons are involved in the ANS
preganglionic visceral motor neuron and postganglionic visceral motor neuron. Can also say pre and postganglionic sympathetic, and pre and postganglionic parasympathetic.
Where are the cell bodies of preganglionic sympathetic neurons (of ANS) located?
Within central nervous system, ie intermediolateral area of gray matter
Where do the axons of postganglionic parasympathetic neurons (ANS) terminate?
On or near the target cell/tissue/organ
How are autonomic fibers distributed to target organs or tissues?
1) independent travel/distribution, 2) my travel with other nerves, 3) may form part of a plexus, 4) may travel with blood vessels
Name some notable examples of a target tissue/organ of the ANS that does NOT receive both sympathetic and parasypathetic fibers.
Cutaneous blood vessels; sweat glands; hair shafts (sympathetic input only)
What kind of ANS innervation do cutaneous blood vessels, hair shafts and sweat glands have?
Sympathetic input only.
Give another name for the sympathetic ANS.
Thoracolumbar component
What is the thoracolumbar component?
Another name for the sympathetic ANS, given because the preganglionic sympathetic cell bodies reside in the intermediolateral cell column of the gray matter in the spinal cord from T1 to L2.
Where does ALL sympathetic outflow originate and why?
T1 to L2, only location in the entire nervous system where preganglionic sympathetic neurons are found.
How do axons of preganglionic sympathetic neurons exit the spinal cord?
Ventral roots of spinal nerves (motor fibers only)
What is another name for a sympathetic chain ganglion?
Paravertebral chain ganglion.
Explain the structure of the sympathetic chain ganglia in the cervical spinal region.
Three large ganglia: superior, middle and inferior, serve as synaptic points for sympathetic fibers supplying the head, neck, heart and upper extremities.
What is the connection between the ventral root and the sympathetic chain ganglion and what travels through it?
WRC, white ramus communicans, traveled by the preganglionic sympathetic neuron.
What are the targets of postganglionic sympathetic neurons that travel to the skin?
1) smooth musculature of blood vessels (vasocontriction) - regulates the lumen of the blood vessels
2) smooth musculature of hair shafts of skin (make hair stand on end)
3) sweat glands - to stimulate them to secrete
If postganglionic sympathetic neurons do not exit the spinal nerve area via either the dorsal or ventral rami, what are their other “travel options”?
They can join other postganglionic fibers traveling directly to viscera/organs.
If an axon of a preganglionic sympathetic neuron does not synapse immediately, what are its “travel options”?
It can enter the sympathetic chain and travel either superiorly or inferiorly and exit in a different area of the body.
What is another name for the parasympathetic component of the ANS?
Craniosacral component
What is the craniosacral component?
Another name for the parasympathetic component of the ANS, so named because its preganglionic visceral motor neurons are located within specific nuclei of the brain OR in the gray matter of the intermediolateral cell column of the spinal cord at S2-S4.
What is the vagus nerve?
Made up of preganglionic parasympathetic fibers, aka the 10th cranial nerve
Where does the vagus nerve synapse?
The preganglionic fibers synapse in microscopic ganglia close to or within the organ that they innervate. The postganglionic fibers are very short.
Why is the parasympathetic fiber of the vagus nerve unique?
The parasympathetic fibers associated with other cranial nerves synapse in specific, named, macroscopic ganglia, while the vagus nerve (Cr. X) synapses in microscopic ganglia.
What other nerve collection behaves in the same way as the vagus nerve, in that it synapses on microscopic ganglia close to or within the area of innervation?
Pelvic splanchnic nerves - a collection of preganglionic parasympathetic fibers whose cell bodies are located at S2-S4.
Name the 2 types of sensory fibers serving the viscera.
1) Those that provide 24/7 internal monitoring for homeostasis, “monitoring and integration,” (parasympathetic fiber distribution), 2) Those that transmit what we perceive as pain (sympathetic fiber distribution).
Where are the cell bodies of interoreceptors that provide monitoring and integration of visceral activities?
The cell bodies of these sensory fibers are located in special nuclei and ganglia within the brain.
How do the processes of the “monitoring” interoreceptors travel?
Peripherally directed processes travel:
1) with cranial nerves
2) within specific tracts within the spinal cord
Give 2 examples of what activate the interoreceptors which detect visceral “pain.”
1) stretching of the GI tract wall, 2) lack of oxygen or nutrients to cardiac muscle
Where are the cell bodies of “visceral pain” interoreceptors located?
The cell bodies of “visceral pain” afferent fibers are located in the dorsal root ganglia (with the cell bodies of the somatic afferent fibers**).
What is referred pain?
Referred pain is a phenomenon whereby visceral stress from an area of the body that the brain is not accustomed to receiving pain signals from, causes “confusion” in the brain, and is interpreted as pain arising from whatever extremities whose somatic sensory nerve cell bodies share the DRG with the cell bodies of the actual source (visceral) of the pain.
If someone is having a heart attack, in what areas might that person experience pain?
Chest and down left arm, the extremities and skin served by T1-T5.
Walk me through a heart attack from the point of view of the nervous system
Deprivation of blood to myocardium –>
Visceral afferent fibers are stimulated –>
Centrally directed processes of visceral afferent fibers transmit the stimulus to the gray matter of the spinal cord in the areas at T1-T5 –>
The afferent somatic nerve cell bodies that share this DRG and gray matter area serve the skin of dermatomes T1-T5 –> Brain receives information and cannot discern the true source of the painful stimulus, so the pain is interpreted and felt to be coming from the skin and extremity areas, in this case the chest and radiating down the arm.
What parts of the body comprise the CNS?
Brain and spinal cord.
What parts of the body comprise the PNS?
Associated nerves, processes, and ganglia, including spinal nerves (originate in spinal cord) and cranial nerves (originate in the brain)
Name three places where you might find the cell body of a nerve fiber, generally speaking.
1) brain
2) spinal cord (gray matter)
3) peripheral ganglion
Define a nerve.
A collection of the processes of individual cells (neurons); the structural and functional unit of the nervous system.
What is an axon?
An axon is the process of a motor neuron that carries information from the cell body to the area of synapse with another neuron.
What is a dendrite?
A dendrite is the area of a motor neuron where information is first received from a synapse with another neuron.
How many processes are contained within a sensory neuron, generally speaking?
In general, sensory neurons have a single process.
How are cell bodies of sensory neurons involved in afferent communication?
They’re NOT, UNLESS they are part of the ANS afferent sensory fiber system (referred pain guys). Cell bodies of afferent sensory neurons are not involved in information transmission.
In dissection, you identify a peripheral nerve. Of what is this nerve typically comprised?
Peripheral nerves will generally be made up up groups of axons of motor neurons and processes of sensory neurons that run in parallel to their specific destination.
What are the 2 STRUCTURAL components of the PNS?
1) Bundles of axons and processes = “nerves”
2) Collections of nerve cell bodies called ganglia
Why are ganglia unique among nervous structures?
Ganglia are the ONLY structures that house cell bodies of nerves outside the CNS.
What are the 2 functional components of the PNS?
1) Efferent/motor fibers that produce an effect in their target organ/tissue
2) Afferent/sensory fibers, which take in information FROM the periphery and relay it to the CNS.
What are the 2 destinations for the nerves found in the PNS?
1) Somatic nerves control voluntary muscle movements, ie skeletal muscle and skin
2) Visceral nerves control involuntary muscle movements and viscera, ie smooth muscle and internal organs
How many pairs of spinal nerves are there? What sections are they divided into?
31 pairs of spinal nerves: 8 pairs of cervical 12 pairs of thoracic 5 pairs of lumbar 5 pairs of sacral 1 pair of coccygeal
What are the 2 destinations of spinal nerves?
Skeletal muscles and skin, therefore all spinal nerves are referred to as somatic nerves.
What are the 3 main structural components of a spinal nerve?
Ventral root, dorsal root, dorsal root (or spinal) ganglion
What does a ventral root consist of?
A ventral root is made up by axons of MOTOR neurons, whose cell bodies are in the gray matter of the spinal cord. The direction of transmission is outward to the target muscle/area.
What does a dorsal root consist of?
A dorsal root is made up by processes of SENSORY neurons, whose cell bodies are housed in the dorsal root ganglion.
Where are dorsal root ganglia typically found?
DRG’s are located just outisde the spinal cord in spaces between the vertebrae called intervertebral foraminae.
What is an intervertebral foramina and what can be found there?
The intervertebral foramina is a space between the vertebrae where dorsal root ganglia can be found (and in turn, the sensory neuron cell bodies they house)
Why are PREvertebral ganglia unique?
Prevertebral ganglia are locations of sympathetic preganglionic neuron cell bodies, but this is NOT part of the sympathetic (PARAverterbal) chain ganglia. PREvertebral ganglia are located in the abdominal cavity in association with the major branches of the abdominal aorta.
What basic components make up every spinal nerve?
Ventral root (for motor efferent), dorsal root (for sensory afferent), and the dorsal root ganglion (for cell bodies of sensory afferents)
Dorsal root me. What is there?
Groups of centrally directed sensory processes, exteroreceptors at the periphery, sending info to the CNS, specifically temperature, touch, pain and pressure sensations
The dorsal ramus is part of what kind of nerve, and what extremity areas does it supply?
The dorsal ramus is a component of the spinal nerve, and supplies the muscles bones and skin of the posterior neck and truck. This explains why it’s kind of thinner than the ventral ramus.
The ventral ramus is part of what kind of nerve, and what extremity areas does it supply?
The ventral ramus is a component of the spinal nerve, and supplies the muscles, bones and skin of the anterior thoracic and abdominal walls and corresponding extremities.
What is another term for the ventral rami, when they are specifically located in the thoracic region of the spinal cord?
Intercostal nerves, run parallel to each rib.
What is the main DIFFERENCE between the ventral rami of the cervical, lumbar and sacral spinal nerves and the intercostal nerves of the thoracic region?
The intercostal nerves are regular and segmented, whereas the other ventral rami form large plexi that intermingle and network with one another.
Why are there 31 pairs of spinal nerves but only 30 dermatomes?
The spinal nerve serving the spinal cord at C1 has no corresponding skin neuron access (no cutaneous innervation.)
What is the cause of Herpes zoster?
Herpes virus lives in the DRG and is dormant in general, but can become active again if the patient becomes very stressed or immunosuppressed (or being old or having bad luck).
Are sensory ganglia associated with all spinal nerves?
No, because C1 has no cutaneous terminus, therefore it has no sensory information transmission taking place.
If a highway was the spinal cord, and the cars on the highway were neuronal pulses or stimuli traveling along it, what structures would be the on and off ramps at a particular exit?
Dorsal root would be the on ramp (bringing information TO the CNS/afferent/sensory) and the ventral root would be the off ramp (bringing information/responses AWAY from the CNS/efferent/motor).
Our friend, the phrenic nerve, innervates a few destinations. Give me a few, and which KINDS of innervation is taking place.
Motor fibers of the phrenic nerve innervate the diaphragm, whereas sensory fibers innervate the pericardium, mediastinal pleura and diaphragmatic peritoneum. Wikipedia also claims there is lung innervation…
Intercostal nerves are made up of what kind of fibers?
Somatic motor and somatic sensory. Dr. Stearns said, “Don’t you go telling me that they are autonomics!”…hopefully I heard this correctly.
All spinal nerves are composed of:
Somatic motor and somatic sensory nerve fibers
What characteristics make spinal nerves “short” in general?
They divide immediately into branches of unequal size, the dorsal and ventral rami. However both rami still have the same component fibers.
Which rami (dorsal or ventral) supply the intercostal nerves?
Ventral rami contain the axons of the intercostal neurons (motor).
A patient complains of pain in their cervical/neck region. Based on your knowledge of nerves, what could be the actual source of the pain?
A problem in the diaphragm is a good candidate for cervical pain because of innervation by the phrenic nerve, which begins at C5-C7 and contains somatic motor and somatic sensory fibers (and postganglionic sympathetic fibers that supply the vasculature).
What are two causes of Horner’s Syndrome?
1) A physical mass putting pressure on the sympathetic chain ganglia
2) Carotid artery dissection (widening, stretches the sympathetic chain ganglia that run with it, causing the same symptoms and sympathetic disfunction)
What is the brachial plexus?
The brachial plexus is a large, intricate group of ventral rami controlling movements of the upper extremity.
What are the symptoms of Horner’s syndrome?
The 3 “osises” – hemianhydrosis (no sweating), pitosis (droopy eyelid), myosis (pupil constriction)
As a general rule, all visceral plexi contain:
1) postG sympathetic fibers
2) preG parasympathetic fibers
3) visceral afferent fibers (monitoring and “pain”)
Why do visceral plexi generally NOT contain preganglionic sympathetic fibers?
Because the sympathetic fibers have typically already synapsed in the paravertebral ganglia before joining to form the plexus.
What is the main example of a preganglionic parasympathetic fiber in the thoracic region?
The vagus nerve.
Explain the five types of innervations of the lung.
1) Sympathetic, postG fibers go directly to lungs
2) PreG parasympathetic, part of the vagus nerve, synapse in microscopic ganglia in or near the lung
3) Visceral afferent monitoring
4) Visceral afferent pain, follow with sympathetics of the region (dermatomes at T1-T5)
5) Somatic afferent, from parietal pleura, transmitted by phrenic and intercostal nerves
What are the two functions of the parasympathetic fibers innervating the lung (Cr. X)?
1) Bronchoconstrict
2) Initiate secretary activity from glands
Neonates lack what visual cortex structure?
Ocular dominance columns
What was used to study the development of ocular dominance columns in neonates?
tritiated proline
Where is the source of the problem causing amblyopia?
Brain (not eye itself)
In monoclear deprivation experiments, what happened to the non-deprived eye?
The non-deprived eye columns became overly large, taking over cortical territory normally used by the other eye
