Question

8. Which is/are true about the somatosensory (touch) system?

a. receptive fields are arranged systematically on the sensory surface.

b. the relative arrangement of receptive fields is preserved at each synaptic level up to the cortex.

c. the amount of cortex devoted to each area of the body corresponds to how many touch receptor cells are in that area.

d. A and B

e. A, B, and C

9. Which is/are true about muscle spindle fibers?

a. Muscle spindle fibers are a very bad model for studying mechanosensory receptors

b. Single channel recordings from muscle spindle fibers show that increases in stretch causes individual channels to open more often and for longer durations.

c. Muscle spindle fibers rely primarily on G-protein coupled receptors to transduce stretch.

d. Muscle spindle fibers depolarize to the same extent in response to different amounts and rates of stretch (when action potentials are blocked with TTX).

e. C and D

10. What does the second messenger cascade we discussed for taste receptors do?

a. greatly amplifies very small signals

b. indicates salty and bitter but not sweet

c. inactivates otherwise leaky potassium channels.

d. A and B

e. A and C

Answer 1

8) E. A, B and C
In somaticsensory system the receptive fields are arranged systematically on the sensory surface. The sensory pathway consist of chain of neurons from receptor organ to cerebral cortex that are responsible for the perception of sensation and these are preserved by peripheral axon at synaptic level within each somaticsensory pathway.

The amount of cortex devoted to every part corresponds to density of cutaneous motor receptors present on it body part. The density of these motor receptors on {body half|part|piece} is indicative of necessary degree of precision movement required at that part.

9) E. C and D

Muscle spindle fibers rely totally on G protein coupled receptors to transduce stretch. As G protein is heterotrimeric which suggests they need 3 totally different subunits alpha, beta and gamma. Alpha and gamma are referred to as lipid anchors as they're attached to cell membrane. each receptors binds to a particular molecule fitting like lock and key and protein goes through a confrontational change and signals the stretch. this is often a very advanced method that undergoes binding of signal molecule to specific ligand that triggers stretch.

And muscle spindle fibers depolarise to the same extent in response to totally different amount and rates of stretch. If the muscle is rapidly stretched the muscle stretch reflux can cause it to contract very quickly , presumably as a protective response to stop injury to a muscle from being stretched rapidly.

10) A. Greatly amplifies very small signals
The second messenger elicits the amplification of weaker signal to stronger signals for the brain to recognise weaker taste signals.