Specific sensory stimuli evoke characteristics motor responses very rapidly because few synapses are involved.
Specific simple reflex
occurs at a specific spinal chord segment and involves particular nerves
What determines the speed of motor response?
The number of synapses to be crossed between the afferent flow of impulses and the activation of efferent nerves
(knee-jerk reflex) the simplest reflex requires only one synapse between sensory and motor neurons.
Patellar Reflex (procedure and tests for)
procedure:plantar flexion should happen
Biceps Tendon Reflex
Procedure: extension of the elbow
tests: radial nerve
cutaneous reflex, the plantar reflex and Babinski's sign
Procedure: planter flexion and toe flexion
If you are unable to elicit a response from your patient you can have them try several things. What are they
1) Have them grip their hands together and try to pull apart
2) Have them count backwards from 100 by
7's out loud
3) Have them clench their teeth together really hard
4) Have them say the alphabet backwards out loud
4 cutaneous sensations
warmth, cold, touch, pain
(also pressure, itch and tickle)
1) free nerve endings
2) Merkel's Discs
3) Ruffini Corpuscles
4) Meissner's Corpuscles
5) Pacinian Corpuscles
Free nerve endings
sensation: light, touch, cold, hot, pain
Location: around hair follicles
sensation: sustained touch, pressure
Location: stratum Basale
sensation: sustained pressure
location: deep in dermis, hypodermis
sensation: changes in texture, slow vibrations
location: papillary dermis
sensation: deep pressure, fast vibrations
location: deep in dermis
where is touch receptor density dense?
hands, lips, and face
How is the density of touch receptors tested?
By using the test-point threshold test.
A calipers w/2 points is applied w/equal pressure to the skin. Subject is asked if 2 distinct points can be felt. The caliper points are moved closer together and the subject retested until only 1 point can be felt
ability of our sensory receptors to respond strongly to acute changes and then stop responding when these stimuli become constant
what is susceptible to sensory adaptation
temperature and smell
what sensation rarely adapts at all
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