encoding of thermosensory info - whitmire

Question 1

What is the labelled line theory?

Answer 1

In the somatosensory system, various different sensory receptors capture different stimuli and convey them to the sensory cortex. Each type of receptor is specialised, that is, receives the stimulus to which it is predetermined to receive. Immediately as it is stimulated, the receptor sends a signal to the somatosensory cortex, via nerve fibres, and the area of the cortex that receives the signal determines the mode of the consequent perception. This mechanism is called principle of the “labelled” lines.

Question 2

Name 6 thermal sensitive TRP channels and their temperature sensitivity

Answer 2

TRPV1, >42°C
TRPV2, >52°C
TRPV3, >33°C
TRPV4, 27-42°C°C
TRPM8, <25°C
TRPA1, <17°C

Question 3

What experimental approaches can be used to study TRP channels? What questions can be answered?

Answer 3

knock-out mice:
–> is a specific channel required for a thermal sensation?

recording from genetically identified sub-populations of sensory afferent neurons expressing a specific channel:
–> What features of a thermal stimulus are encoded?

Stimulation of genetically identified sub-populations of sensory afferent neurons expressing a specific channel
–> Does activation of a population of neurons expressing a single channel mimic the perception of temperature?

Question 4

Perception of cooling sensation is mediated by:

a. TRPM8
b. TRPV1
c. both of them
d. neither of them

Answer 4

a. TRPM8

Question 5

T/F

Encoding of warming sensation is the same as encoding of painful heat

Answer 5

False

Warming is related to, but different from, painful heat

Question 6

Explain the concept of paradoxical heat, how can it be studied

Answer 6

Paradoxical heat can be studied with the thermal grill.
A sensation of intense heat that is experienced in the absence of a hot stimulus if an area of the skin containing both cold spots and warm spots is stimulated with a heat grill of closely packed alternating warm and cold bars.

Question 7

What is paradoxical cold?

Answer 7

A sensation of coldness that is experienced when a warm stimulus touches a cold spot on the skin

Question 8

Choose the brain regions that are involved in processing cutaneous temperature?

a. Spinal cord
b. hypothalamus
c. S1, S2
d. amygdala
e. Insular Cortex
f. thalamus

Answer 8

a. Spinal cord
c. S1, S2
e. Insular Cortex
f. thalamus

Question 9

What is the trajectory of thermally responsive neurons?

Answer 9

Classical anatomical tracing techniques have shown that thermally responsive neurons project from LI/II and travel, via the spino-thalamic tract, to the contralateral somatosensory nuclei of the thalamus.

Question 10

T/F

Thermal thalamic input to S1 is provided by ventral posterolateral (VPL) and posterior medial (POm), to S2 by POm and the posterior triangular nucleus (PoT), and IC by PoT.

Answer 10

True

Thermal thalamic input to S1 is provided by ventral posterolateral (VPL) and posterior medial (POm), to S2 by POm and the posterior triangular nucleus (PoT), and IC by PoT.

Question 11

Choose the correct answer.

a. In the rat, superficial dorsal laminar spinal cord neurons project to restricted areas of the contralateral central, entire medial and most other thalamic nuclei.
b. In the rat, superficial dorsal laminar spinal cord neurons project to restricted areas of the contralateral ventral posterolateral (VPL), posterior medial (POm), and the caudally positioned triangular posterior thalamic (PoT) nuclei.
b. In the rat, superficial ventral laminar spinal cord neurons project to restricted areas of the contralateral posterior, medial, and central nuclei.

Answer 11

b. In the rat, superficial dorsal laminar spinal cord neurons project to restricted areas of the contralateral ventral posterolateral (VPL), posterior medial (POm), and the caudally positioned triangular posterior thalamic (PoT) nuclei.

Question 12

Which statement(s) is/are true?

a. heat-responding neurons encode absolute skin temperature without adaptation and receive input from TRPV1 neurons
b. heat-responding neurons adapt to ambient temperature, encode temperature changes and receive input from TRMP8 neurons
c. cold-responding neurons adapt to ambient temperature, encode temperature changes and receive input from TRMP8 neurons
d. cold-responding neurons encode absolute skin temperature without adaptation and receive input from TRPV1 neurons

Answer 12

a. heat-responding neurons encode absolute skin temperature without adaptation and receive input from TRPV1 neurons
c. cold-responding neurons adapt to ambient temperature, encode temperature changes and receive input from TRMP8 neurons

Question 13

Which channels have been implicated in warming sensation?

a. TRPV3
b. TRPM8
c. TRPV4
d. TRPM2
e. TRP10
f. TRPV1

Answer 13

a. TRPV3
c. TRPV4
d. TRPM2
f. TRPV1