W19/L7: Periph. Somatosensation Flashcards
What type of skin are the palms & soles of feet covered in?
Glabrous skin
What are the two distinguishing features of glabrous skin?
No hair
Skin ridges
Name 2 purposes of skin ridges
Provides grip
Tells us if the surface is moving
What are the 4 types of mechanoreceptors in glabrous skin?
Meissner corpuscles
Merkel complexes
Ruffini organs
Pacinian corpuscles
Which mechanoreceptors are found close to the surface?
Meissner corpuscles
Merkel complexes
Which mechanoreceptors are found deeper in the skin?
Ruffini organs
Pacinian corpuscles
Where are the cell bodies of the mechanoreceptors found?
In the dorsal root ganglie
Where are Meissner corpuscles usually found?
which part of the skin layers
At the crest of the dermal ridges
Where are Merkel complexes usually found?
which part of the skin layers
At the valleys of the neural ridges
In which layer of skin are the Ruffini corpuscles normally found?
The dermis
In which layer of skin are the Pacinian corpuscles normally found?
In the dermis & subcutaneous
In what ways can we measure the sensitivity of the mechanoreceptors?
Minimum distortion that can be detected
Minimum weight that can be detected
Minimum frequency that can be detected as separate events
How does activation of a Pacinian corpuscle lead to transduction of a nerve signal?
Stretch of the connective tissue pulls on the membrane of the nerve ending, which opens the Na+ channels
(simplified)
What signal does a sub-threshold stimulus produce in the nerve cell?
None
What sort of signals does a rapidly adapting mechanoreceptor send?
What sort of signals does a slowly adapting mechanoreceptor send?
Which of the glabours skin mechanoreceptors are slowly adapting?
Merkel complexes
Ruffini organs
Which of the glabrous skin mechanoreceptors are rapidly adapting?
Meissner copuscles
Pacinian corpuscles
What do Merkel complexes respond to?
Indentation
What do Ruffini organs respond to?
Skin movement (sustained response)
What do Meissner corpuscles respond to?
Skin movement (transient response)
What do Pacinian corpuscles respond to?
Vibration
How does the firing rate/threshold differ between tactile receptors and nociceptors?
The threshold of tactile receptors is easily reached, but the firing rate won’t increase when pain/damage increases
Nociceptors require a higher threshold, but can increase their firing rate to indicate severity of pain or damage.
What’s the weird place (other than the skin) that we find Pacinian corpuscles?
In the peritoneal cavity
How can Ruffini organs tell us about the position of our hands?
They detect skin stretching - which can also indicate finger potision
What is the receptor field?
The territory that a single receptor is “responsible for”
What arrangement of receptor fields would give us the most specific information about the location of a stimuli?
Small but densely packed
What is the problem with dermatome pictures in textbook?
Dermatomes have significant overlap & can’t be distinguished like that.
Mechanoreceptor signals travel on which side of the spinal cord?
Ipsilateral
Nociceptor signals travel on which side of the spinal cord?
Contralateral
Where are the cell bodies of nociceptory nerves found?
Dorsal root gangleon
