PSL300 Final Exam Questions and Correct
Answers
What are the 4 somatic senses?
touch, temperature, proprioception, nociception
What is proprioception?
perception is awareness of the position of body parts relatiive to each other
ex. even w/ eyes close your know why your elbow is flexed
What does nociception detect?
Nociception detects tissue damage or threat of it. It is perceived as pain or itch
For somatic sensations below the chin, where do you expect he somatosesory receptors
to have their cell bodies?
receptors for somatic sensation below the chin have their cell bodies in the dorsal root ganglia
For sensations from the head, where do you expect to find the cell bodies?
For sensations from the head, the cell bodies of these sensory neurons are located within the
brain itself.
What do free nerve endings detect?
free nerve endings detect mechanical stimuli, temp., chemicals
What are Merkel receptors?
Merkel receptors or Merkel disks are mechanoreceptors nerve endings in contact w/
specialized epithelial cells called Merkel cells
,What are 2 kinds of encapsulated receptors and what does this mean?
- eg. : Meissner and Pacinian corpuscles are mechanoreceptors that are sheathed in
connective tissue
At the bottom of the epidermis you find.....
At the bottom of the epidermis you find. saucer shaped Merkel disks that are very sensitive to
deformation of the skin and are more tonic than phasic. These send a sustained message as
long as deformation persits so it essentially signals contact
Most mechanoreceptors are phasic. What dies this mean and what is a an exception to
this?
This means that when given a sustained/constant stimulus, the nerve ending's membrane will
depolarize and then return back to baseline potential in about 3ms. So it registers changes and
not steady levels (unless stimulation is changing you don't percieve much)
What receptor do you find at the top of the dermis and what are these responsible for?
- egg shaped Meissner corposcles
- mainly in tongue and hairless skin - erogenous zones, palms and fingertips
What receptor do you find deep in the dermis and what are these responsible for?
Are receptors uniformily distributed over the body surface?
NO.
how are the palms, fingertips and lips similar to the foeves
palms, fingertips and lips are like the foveas of the somatosensory system: they have more
densly packed receptors and therefore higher acquity than other areas
test of acuity / 2 pt. discrimination
,if your skin is touched at 2 places simultaneouslu, can you tell whether there are 1 or 2
contact points
how far apart do contact points need to be on lips and fingertips to distinguish them vs.
on your calves?
- on your lips and fingertips you can distinguish pts. 2 -4 mm apart but in your calves you
need 40 mm apart
2 types of thermoreceptors
cold and warm
* remember thermoreceptors are free nerve endings
At what temperature do cold and warm receptors respond maximally?
cold receptors respond maximally at 30 degrees celsius (well below body temp)
warm receptors respond maximally at about 45 degrees celsius
what does it mean that both cold and warm thermorecptors are phasic-tonic?
the fact that their response is phasic tonic means that the response is for a bit and then the
response fades away, which is why we get used to cold lakes or hot baths
What happens at above 45 degrees celsius?
Above 45 degrees celsius, pain receptors are activated. Cold fibres also respond briefly to
temp. greater than 45 degrees celsius, causing paradoxical cold: a hot object. touched briefly,
may feel cold
Are there more warm receptors or cold receptors?
, - there are more cold receptors than warm and few thermoreceptors in total (few as 1000
fibers may carry temp info. up the spinal cord to the brain - maybe b/c we dont need precise
localization in our temp. sensing
Nocireceptors are ......
Nociceptors are free nerve endings that respond to noxious stimuli/harmful stimuli
What damage do nocireceptors respond to?
- some respond to damaging mechanical stimuli, or others to damaging hesat or chemicals.
* some respond to chemicals released from damaged cells ( K+, histamine, prostaglandins) or
to serontonin released by platelets in response to injury
what are 2 categories for somatosensory afferents ?
small and large
What are small fibers?
C and A-delta: they come mainly from free nerve endings
* C fibers are unmyelinated and conduct spikes at speeds of 2 m/s
* A delta fibers are thicker than C's and are myelinated and conduct up to 30m/s
* diff. small fibers respond differently to adequate stimuli, like mechanical stimuli, chemicals
or temp.
What are large fibers?
- A-beta: they come from Merkel disks or encapsulated mechanoreceptors such as Meissner
or Pacinian corpuscles. They are myelinated and conduct at 70 m/s ( very fast)
How do large fibers project compared to small fibers?
Answers
What are the 4 somatic senses?
touch, temperature, proprioception, nociception
What is proprioception?
perception is awareness of the position of body parts relatiive to each other
ex. even w/ eyes close your know why your elbow is flexed
What does nociception detect?
Nociception detects tissue damage or threat of it. It is perceived as pain or itch
For somatic sensations below the chin, where do you expect he somatosesory receptors
to have their cell bodies?
receptors for somatic sensation below the chin have their cell bodies in the dorsal root ganglia
For sensations from the head, where do you expect to find the cell bodies?
For sensations from the head, the cell bodies of these sensory neurons are located within the
brain itself.
What do free nerve endings detect?
free nerve endings detect mechanical stimuli, temp., chemicals
What are Merkel receptors?
Merkel receptors or Merkel disks are mechanoreceptors nerve endings in contact w/
specialized epithelial cells called Merkel cells
,What are 2 kinds of encapsulated receptors and what does this mean?
- eg. : Meissner and Pacinian corpuscles are mechanoreceptors that are sheathed in
connective tissue
At the bottom of the epidermis you find.....
At the bottom of the epidermis you find. saucer shaped Merkel disks that are very sensitive to
deformation of the skin and are more tonic than phasic. These send a sustained message as
long as deformation persits so it essentially signals contact
Most mechanoreceptors are phasic. What dies this mean and what is a an exception to
this?
This means that when given a sustained/constant stimulus, the nerve ending's membrane will
depolarize and then return back to baseline potential in about 3ms. So it registers changes and
not steady levels (unless stimulation is changing you don't percieve much)
What receptor do you find at the top of the dermis and what are these responsible for?
- egg shaped Meissner corposcles
- mainly in tongue and hairless skin - erogenous zones, palms and fingertips
What receptor do you find deep in the dermis and what are these responsible for?
Are receptors uniformily distributed over the body surface?
NO.
how are the palms, fingertips and lips similar to the foeves
palms, fingertips and lips are like the foveas of the somatosensory system: they have more
densly packed receptors and therefore higher acquity than other areas
test of acuity / 2 pt. discrimination
,if your skin is touched at 2 places simultaneouslu, can you tell whether there are 1 or 2
contact points
how far apart do contact points need to be on lips and fingertips to distinguish them vs.
on your calves?
- on your lips and fingertips you can distinguish pts. 2 -4 mm apart but in your calves you
need 40 mm apart
2 types of thermoreceptors
cold and warm
* remember thermoreceptors are free nerve endings
At what temperature do cold and warm receptors respond maximally?
cold receptors respond maximally at 30 degrees celsius (well below body temp)
warm receptors respond maximally at about 45 degrees celsius
what does it mean that both cold and warm thermorecptors are phasic-tonic?
the fact that their response is phasic tonic means that the response is for a bit and then the
response fades away, which is why we get used to cold lakes or hot baths
What happens at above 45 degrees celsius?
Above 45 degrees celsius, pain receptors are activated. Cold fibres also respond briefly to
temp. greater than 45 degrees celsius, causing paradoxical cold: a hot object. touched briefly,
may feel cold
Are there more warm receptors or cold receptors?
, - there are more cold receptors than warm and few thermoreceptors in total (few as 1000
fibers may carry temp info. up the spinal cord to the brain - maybe b/c we dont need precise
localization in our temp. sensing
Nocireceptors are ......
Nociceptors are free nerve endings that respond to noxious stimuli/harmful stimuli
What damage do nocireceptors respond to?
- some respond to damaging mechanical stimuli, or others to damaging hesat or chemicals.
* some respond to chemicals released from damaged cells ( K+, histamine, prostaglandins) or
to serontonin released by platelets in response to injury
what are 2 categories for somatosensory afferents ?
small and large
What are small fibers?
C and A-delta: they come mainly from free nerve endings
* C fibers are unmyelinated and conduct spikes at speeds of 2 m/s
* A delta fibers are thicker than C's and are myelinated and conduct up to 30m/s
* diff. small fibers respond differently to adequate stimuli, like mechanical stimuli, chemicals
or temp.
What are large fibers?
- A-beta: they come from Merkel disks or encapsulated mechanoreceptors such as Meissner
or Pacinian corpuscles. They are myelinated and conduct at 70 m/s ( very fast)
How do large fibers project compared to small fibers?
