Ascending Sensory Systems Flashcards
what are the 3 mechanisms that keep cerebral blood flow constant under regional changes
1 - autoregulation (vasodilation/vasoconstriction)
2 - collaboration and response to brain activity
3 - cerebral vascular autonomics
what do somatosensory receptors detect ?
mechanical, chemical, and thermal changes
somatosensory neurons are composed of what type of neurons
pseudounipolar
what type of receptors would you find in hairy skin ?
- Merkel nerve ending cells
what type of receptors would you find in glabrous (hairless) skin ?
- Meissner corpuscles
- Merkel cells
- Pacinian corpuscles
- ruffini ending
what do meissner corpuscles sense ? where ?
discriminative touch (2 point touch) -fingertips
what do merkel nerve ending cells sense ?
discrimintative (2 point) touch, fine touch
what is spacial resolution, and what part of arm has the best ?
the number of cutaneous receptors, fingers have the best cuz more Merkel nerve endings and meissner corpuscles in fingers than palm
what do pacinian corpuscles detect ? where ?
vibration, fingers and palm
what do free nerve endings sense/detect ?
pain, crude touch, temperature
what role does myelination have on free nerve endings
Myelinated - elicits sharp prick phase of pain
Unmyelinated - elicits slow/aching pain
where at anatomically are ascending tract pathways generally found in the brian
Anterior funiculi, lateral funiculi, posterior funiculi
whare at anatomically are descending tract pathways located in the brain
anterior funiculi, lateral funiculi
what is another name synonymous with posterior column
medial lemniscus system
what does the medial lemniscus system convey to the brain
conveys touch, pressure, vibration, and where limbs are positioned in space
as the spinal afferent fibers enter their ipsilateral dorsal root ganglion, then continue as rootlets to enter the spinal cord the fibers divide into 2 divisions, what are they ?
Medial - large, heavily myelinated fibers
Lateral - small/finely myelinated or unmyelinated fibers
T/F once fibers are ascending the spinal cord w/sensory input, there can be NO additional input into the posterior collumn laterally ?
False, fibers continue to add to the existing ones laterally untill reach the brainstem
once ascending fibers reach the brainstem, where do they synapse
synapse in the nucleus gracilis and nucleus cuneatus (posterior collumn nuclei)
what order of fibers cross the midline ? where do the cross at in the medial lemniscus system
second order fibers cross in the caudal medulla
where is the primary somatosensory cortex ?
postcentral gyrus of parietal lobe
what do the third order fibers in the medial lemniscus system do ?
originate in thalamus and synapse in primary somatosensory cortex (postcentral gyrus)
what is ataxia
uncoordinated movements as brain cant direct motor activity w/o sensory feed back, result of posterior collumn injury
what would happen if there was an injury to the posterior collumn
loss of proprioception and tactile discrimination
what is another name for the anterolateral pathway
spinothalamic tract
what does the spinothalamic tract detect/convey
pain and temperature
where does the spinothalamic tract ultimately convey the sensory information of pain and temperature in the brain
ventral posterolateral nucleus of the thalamus
what does in mean saying that the spinothalamic tract crosses the midline with rostral inclination ?
it means that the input can climb 1 or 2 spinal levels before it crosses and synapses forming the anterolateral pathway. So pain from T12 would be felt in T10 or T11
damage to the anterolateral pathway would cause ?
loss of pain and temperature sensations
-also loss of itch and tickle sensations
what Brodmann Areas comprise the primary somatosensory cortex
3,1,2
what Brodmann Ares comprise the primary motor cortex,l pre motor cortex ?
primary motor - 4
premotor - 6
what is a cordotomy, and how is it used today
it is the destruction/cutting of the spinothalamic tract (anterolateral pathway) in order to alleviate patients with never ending pain
-not used today much cuz pain comes back eventually
what are the 3 direct tracts that relay spinal cord information to the cerebellum
1 - posterior spinocerebellar tract
2 - cunocerebellar tract
3 - anterior spinocerebellar tract
what is the indirect way to relay spinal cord information to the cerebellum
brainstem relay nuclei
T/F humans have absolutely NO conscious awareness that there are tracts relaying information from spinal cord to cerebellum ot coordinate movement ?
True
what type of information does the posterior spinocerebellar tract convey ?
conveys ipsilateral leg proprioception
the posterior spinocerebellar tract is made of axon from cell bodies found where ? this is also where information synapses
Clarke’s nucleus
how far caudal does Clarke’s nucleus extend ?
L2 , does not exist caudal to L2 so all leg info will come and synapse at L2 in Clarke’s nucleus
what does the cuneocerebellar tract convey ?
ipsilateral arm proprioception
what does the anterior spinocerebellar tract convey ?
more complex ipsilateral leg information
which of the 3 tracts relaying information from the spinal cord to the cerebellum to coordinate moovement conveys information ipsilaterally because it crosses teh midline twice ?
anterior spinocerebellar tract
