Physiology 2: Sensory Receptors and Sensory Neurons Flashcards
name the 3 divisions of the somatosensory system and what they do
exteroceptive (cutaneous senses),
proprioceptive (posture and movement),
enteroceptive (autonomic function)
the 1st order neuron can also be called…
the primary sensory afferent
where are the 1st, 2nd and 3rd order neurons of the somatosensory pathway SPECIFICALLY located?
- PNS (dorsal root or cranial ganglia)
- CNS (dorsal horn of SC or brainstem nuclei)
- CNS (thalamus)
where does proprioceptive input go to?
cerebellum
where in the neuron is a sensory afferent received? what does it cause?
stimulus opens a cation selective ion channel in the PERIPHERAL terminal of a primary sensory afferent -> AP generated
what process starts the graded release of neurotransmitter?
when an AP arrives at the central terminal ready to go to the 2nd order neurons
the higher the ___ the higher the frequency of AP discharge in the primary sensory afferent neuron
stimulus
sensory units for touch, pressure and vibration?
skin mechanoreceptors
sensory units for proprioception?
joint and muscle mechanoreceptors
define threshold in terms of sensory function
intensity of a stimulus required to excite a sensory unit
low threshold receptors respond to what sensations?
fine discriminatory touch
mild/moderate temperatures
high threshold units respond to what sensations?
high temp (>45 degrees) high mechanical stimuli
a sensory unit with very fast adaptation will have what kind of firing rate?
responds only to fast movement
a sensory unit with fast adaptation will have what kind of firing rate
impulses will be proportional to rate of change of the stimulus
stretch receptors are an example of a __ adapting response
slow
a pacnian corpuscle has a __ adapting response
VERY fast
what kind of sensory axons have no myelination?
temp, pain and itch receptors
which kind of sensory axons have thick myelination?
proprioceptiors of skeletal muscle
what is a receptive field of a neuron?
the site of termination
a receptive field can branch into what?
free nerve endings or other specialised structures
2 point discrimination is a test for what?
spacial acuity for somatosensory function
if a mechanoreceptor is classified as FA2, what does this mean?
fast adapting (FA) type 2 unit (aka wide field)
if a mechanoreceptor is classified as SA1 what does this mean?
slow adapting type 1 (small field) unit
where are merkel cell neurite complexes located?
basal epithelium in ridges eg in hands
meissner corpuscles are present in hairy areas T or F
F, hairless areas
what sensory skin receptor could be described as onion-like in structure?
pacinian corpuscle
where are pacinian corpuscles located?
subcutaneously close to periosteum
what sensory receptors of hairless skin are the MOST sensitive to vibration?
pacinian corpuscles
