Physiology of Sensory Receptors

Question 1

Generator potential

Answer 1

Depolarization of the peripheral, receptive portion of the sensory axon
Caused by the sensory stimulus
Exception is in rods and cones, where the GP is a hyperpolarization

Question 2

In myelinated sensory axons, where is the AP initiated?

Answer 2

At the 1st node of Ranvier

Question 3

Properties of the GP (3)

Answer 3

Can be graded in amplitude (bigger stimulus = bigger GP)
Does not cause the membrane to be refractory
Is not actively propagated

Question 4

2 coding strategies

Answer 4

Frequency coding

Population coding

Question 5

Frequency coding

Answer 5

Greater the intensity, greater the frequency of APs in individual axons

Question 6

Population coding

Answer 6

With increased intensity, more individual receptors are recruited

Question 7

Tonic receptors

Answer 7

Slowly adapting
Monitor static unchanging stimuli
Will give you absolute info the entire time the stimulus is there

Question 8

Phasic receptors

Answer 8

Rapidly adapting
Detect the onset (and offset) of the stimulus
Tells you about the rate of change

Question 9

How does a Pacinian corpuscle detect texture and vibration?

Answer 9

Depress the skin and force is transmitted through the CT structure surrounding the axon
Causes the opening of the VG channels
As you hold pressure, the maintained force will cause the gel to move out of the way and this reorganization of the fluid causes the fluid to dispense and the channels can close, resulting in adaptation

Question 10

3 examples of phasic receptors

Answer 10

Meissner’s corpuscles
Pacinian corpuscles
Endings surrounding hair follicles

Question 11

2 examples of tonic receptors

Answer 11

Merkel’s endings

Ruffini endings

Question 12

Pain and temperature are sensed by what kinds of receptors?

Answer 12

Free nerve endings

Question 13

Touch and proprioception are carried in what 2 groups?

Answer 13

Groups 1 and 2 (myelinated and fast)

Question 14

Path of touch and proprioception

Answer 14

Ascend the spinal cord ipsilaterally without synapsing via the dorsal columns
In the caudal medulla, they synapse with the 2nd order neuron in the dorsal column nuclei
2nd order neuron crosses immediately and ascends through medulla in the medial lemniscus

Question 15

Pain and temperature are carried in what 2 groups?

Answer 15

Groups 3 and 4 (slow fibers - 3 is myelinated but 4 is not)

Question 16

Path of pain and temperature

Answer 16

In the cord, the 1st order neurons synapse in the dorsal horn with the 2nd order neurons
2nd order neurons cross in the cord at the same level and ascend in the spinothalamic tract

Question 17

Fibers from the
1. Body
2. Head
terminate in what part of the thalamus?

Answer 17

1. Ventroposteriolateral nuclei (VPL)

2. Ventroposteriormedial nuclei (VPM)

Question 18

What part of the parietal lobe does touch, pain, proprioception, and temperature all go to?

Answer 18

The signal terminates in the postcentral gyrus of the parietal lobes

Question 19

The intermediolateral horn is found at what spinal levels? What does it carry?

Answer 19

T1-L2 and S2-4

Contains cell bodies of preganglionic autonomic neurons

Question 20

Where is the ventral horn largest?

Answer 20

Cervical (upper limbs) and lumbar (lower limbs) regions