Ascending Sensory Systems

Question 1

what are the 3 mechanisms that keep cerebral blood flow constant under regional changes

Answer 1

1 - autoregulation (vasodilation/vasoconstriction)
2 - collaboration and response to brain activity
3 - cerebral vascular autonomics

Question 2

what do somatosensory receptors detect ?

Answer 2

mechanical, chemical, and thermal changes

Question 3

somatosensory neurons are composed of what type of neurons

Answer 3

pseudounipolar

Question 4

what type of receptors would you find in hairy skin ?

Answer 4

• Merkel nerve ending cells

Question 5

what type of receptors would you find in glabrous (hairless) skin ?

Answer 5

• Meissner corpuscles
• Merkel cells
• Pacinian corpuscles
• ruffini ending

Question 6

what do meissner corpuscles sense ? where ?

Answer 6

discriminative touch (2 point touch) 
-fingertips

Question 7

what do merkel nerve ending cells sense ?

Answer 7

discrimintative (2 point) touch, fine touch

Question 8

what is spacial resolution, and what part of arm has the best ?

Answer 8

the number of cutaneous receptors, fingers have the best cuz more Merkel nerve endings and meissner corpuscles in fingers than palm

Question 9

what do pacinian corpuscles detect ? where ?

Answer 9

vibration, fingers and palm

Question 10

what do free nerve endings sense/detect ?

Answer 10

pain, crude touch, temperature

Question 11

what role does myelination have on free nerve endings

Answer 11

Myelinated - elicits sharp prick phase of pain

Unmyelinated - elicits slow/aching pain

Question 12

where at anatomically are ascending tract pathways generally found in the brian

Answer 12

Anterior funiculi, lateral funiculi, posterior funiculi

Question 13

whare at anatomically are descending tract pathways located in the brain

Answer 13

anterior funiculi, lateral funiculi

Question 14

what is another name synonymous with posterior column

Answer 14

medial lemniscus system

Question 15

what does the medial lemniscus system convey to the brain

Answer 15

conveys touch, pressure, vibration, and where limbs are positioned in space

Question 16

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 ?

Answer 16

Medial - large, heavily myelinated fibers

Lateral - small/finely myelinated or unmyelinated fibers

Question 17

T/F once fibers are ascending the spinal cord w/sensory input, there can be NO additional input into the posterior collumn laterally ?

Answer 17

False, fibers continue to add to the existing ones laterally untill reach the brainstem

Question 18

once ascending fibers reach the brainstem, where do they synapse

Answer 18

synapse in the nucleus gracilis and nucleus cuneatus (posterior collumn nuclei)

Question 19

what order of fibers cross the midline ? where do the cross at in the medial lemniscus system

Answer 19

second order fibers cross in the caudal medulla

Question 20

where is the primary somatosensory cortex ?

Answer 20

postcentral gyrus of parietal lobe

Question 21

what do the third order fibers in the medial lemniscus system do ?

Answer 21

originate in thalamus and synapse in primary somatosensory cortex (postcentral gyrus)

Question 22

what is ataxia

Answer 22

uncoordinated movements as brain cant direct motor activity w/o sensory feed back, result of posterior collumn injury

Question 23

what would happen if there was an injury to the posterior collumn

Answer 23

loss of proprioception and tactile discrimination

Question 24

what is another name for the anterolateral pathway

Answer 24

spinothalamic tract

Question 25

what does the spinothalamic tract detect/convey

Answer 25

pain and temperature

Question 26

where does the spinothalamic tract ultimately convey the sensory information of pain and temperature in the brain

Answer 26

ventral posterolateral nucleus of the thalamus

Question 27

what does in mean saying that the spinothalamic tract crosses the midline with rostral inclination ?

Answer 27

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

Question 28

damage to the anterolateral pathway would cause ?

Answer 28

loss of pain and temperature sensations

-also loss of itch and tickle sensations

Question 29

what Brodmann Areas comprise the primary somatosensory cortex

Answer 29

3,1,2

Question 30

what Brodmann Ares comprise the primary motor cortex,l pre motor cortex ?

Answer 30

primary motor - 4

premotor - 6

Question 31

what is a cordotomy, and how is it used today

Answer 31

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

Question 32

what are the 3 direct tracts that relay spinal cord information to the cerebellum

Answer 32

1 - posterior spinocerebellar tract
2 - cunocerebellar tract
3 - anterior spinocerebellar tract

Question 33

what is the indirect way to relay spinal cord information to the cerebellum

Answer 33

brainstem relay nuclei

Question 34

T/F humans have absolutely NO conscious awareness that there are tracts relaying information from spinal cord to cerebellum ot coordinate movement ?

Answer 34

True

Question 35

what type of information does the posterior spinocerebellar tract convey ?

Answer 35

conveys ipsilateral leg proprioception

Question 36

the posterior spinocerebellar tract is made of axon from cell bodies found where ? this is also where information synapses

Answer 36

Clarke’s nucleus

Question 37

how far caudal does Clarke’s nucleus extend ?

Answer 37

L2 , does not exist caudal to L2 so all leg info will come and synapse at L2 in Clarke’s nucleus

Question 38

what does the cuneocerebellar tract convey ?

Answer 38

ipsilateral arm proprioception

Question 39

what does the anterior spinocerebellar tract convey ?

Answer 39

more complex ipsilateral leg information

Question 40

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 ?

Answer 40

anterior spinocerebellar tract