Viscerosensory System Flashcards
(32 cards)
Characteristics of the ANS
- What neural elements is is composed of?
- what kind of info is transmitted?
- What does it mediate and how?
- What are its divisions?
- Neural elements associated with internal organs/viscera including cardiac muscles, smooth muscle, and glandular epithelium
- Transmits afferent (viscerosensory) and efferent (visceromotor) information
- Mediates visceral reflexes through local circuits in the brainstem and spinal cord
- Divisions: Parasympathetic, Sympathetic, Enteric
What neurons transmit viscerosensory info?
Dorsal root ganglion neurons
CN 9 and 10
Receptors:
What are the two types?
Nociceptors
Physiologic receptors
Receptors: Nociceptors
What signals do they respond to?
Stimuli that have the potential to damage tissues or stimuli that result from the presence of damaged tissue
Receptors: Nociceptors
What signals do they respond to?
Stimuli that have the potential to damage tissues or stimuli that result from the presence of damaged tissue
Receptors: Nociceptors
Why is visceral pain often described as diffuse?
Visceral pain is diffuse/ difficult to localize because receptor density is low, and therefore the receptive fields are very large.
Hard to gauge where exactly pain is coming from.
Sensation of pain is also different
Receptors: Physiologic
What signals do they respond to?
Respond to innocuous stimuli that monitor the functions of the visceral structures on a regular basis.
These are the ones that help us maintain homeostasis.
Receptors: Fibers
What type of fibers are the viscersensory fibers?
They are General visceral afferent
Receptors: Fibers
How are these fibers classified
They are type 3 and 4 (slow transmission)
Receptors: Fibers
Where do these fibers travel?
Through sympathetic nerves:
sympathetic trunk
Through Parasympathetic nerves:
CN 9 and 10
Splanchnic nerves
Pathways: Sympathetic
What info does this pathway convey
Almost exclusively conveys info from nociceptors
Pathways: Sympathetic
What other pathway is this similar to? What are the similarities?
Similar to the somatosensory pathways
Similarities:
First order neurons have their cell bodies in dorsal root ganglion cells.
Uses the somatosensory pathways: dorsal column medial lemniscal system and anterolateral system
Pathways: Sympathetic
What is the clinical implication of having various pathways for viscerosensory info to travel up the chain?
We don’t have to worry about crossing: some of pathways cross in the spinal cord, other cross higher up in the brain stem.
There will be a different clinical presentation in viscerosensory and somatosensory impairment because the viscerosensory info can travel in so many pathways
Pathways: Sympathetic
What are the ultimate targets of the sympathetic viscerosensory pathways?
VPL of the thalamus
Post central gyrus and insular cortex
Reticular Formation
Pathways: Parasympathetic
What info does this pathway convey?
Almost exclusively conveys info originating from physiologic receptors
Pathways: Parasympathetic
What info does this pathway convey?
Almost exclusively conveys info originating from physiologic receptors
Pathways: Parasympathetic
Where are the cell bodies of the 1sr, 2nd, and 3rd order neurons?
1st: there are 2 parts, cranial and sacral
Cranial: CN 9 and 10; synapse in the brainstem, mostly in the nucleus of the solitary tract
Sacral: cell bodies int he dorsal root ganglia
Follow viscerosensory sympathetic pathways
2nd: cell bodies in the nucleus of the solitary tract; follow viscerosensory sympathetic pathways
3rd: same as viscerosensory sympathetic
Pathway Organization
Where do viscerosensory fibers that enter the SC at a particular level originate?
They originate from structures that receive GVE input form the same level
Pathway Organization
What visceral activity reaches the level of consciousness and what doesn’t?
Most of the visceral sensory info that enters the spinal cord and brainstem does not reach the level of consciousness.
Only the information that is related to pain reaches the level of consciousness. Therefore, we are not sensing physiologic sensation directly.
Info from the sympathetic pathway (carries nociceptive info) has to reach the cortex for us to perceive it.
Target Areas: reticular formation
What makes up the reticular fomation? Where is it located?
It is a diffuse and ill defined collection of nuclei interspersed among all of the more compact and named structures of the brainstem.
Target Areas: reticular formation
What kind of information does it receive?
Receives both sympathetic (pain) and parasympathetic (physiologic) viscerosensory info
Target Areas: reticular formation
Where does it project to?
Projects to the hypothalamus and the thalamus, which ultimately project to broad areas of the cerebral cortex, with the largest number terminating in the frontal lobe.
Fibers going to the thalamus and then from the thalamus to the cortex are what activate the cortex as a whole.
Target Areas: reticular formation
Which fibers from the reticular formation allow perception?
Fibers going to the thalamus and then from the thalamus to the cortex are what activate the cortex as a whole.
The brainstem has to activate the cortex in order for us to perceive a painful stimulus
Target Areas: reticular formation
Where does it project to?
Projects to the hypothalamus and the thalamus, which ultimately project to broad areas of the cerebral cortex, with the largest number terminating in the frontal lobe.
