A needle is inserted into the right somatosensory nucleus of

A needle is inserted into the right somatosensory nucleus of the thalamus in the central nervous system and the area is injected with GABA.

A. Define the term “nucleus” as it relates to the statement above.

B. What is GABA and what effect would GABA have on the membrane potentials of neurons in this area? Explain

C. Describe how/why GABA released from axon terminals in the following neural arrangements would alter impulse transmission:

i) an axoaxonal synapse

ii) an axodendritic synapse

D. If information relayed to this area carries precise touch, what specific somatosensensory pathway would be affected by this injection?

E. Which side of the body would be affected? Why?

F. What fiber type is associated with neurons in this pathway and what does this mean?

G. Through what structure does a primary sensory neuron from the hand enter the central nervous system?

H. Where does the first synapse for this somatosensory pathway occur?

I. Describe the type(s) of sensory information carried by this pathway.

J. Name and describe two different classes of primary sensory receptors that are associated with this pathway.

K. Discuss the common features that all primary sensory receptors possess.

L. If an adrenergic substance had been injected instead of GABA, how would this have altered neural transmission? Explain.

Solution

Thanks for the query

A.  Nucleus is a collection of cell bodies of neurons in the central nervous system. They are located deep within the cerebral hemispheres and brainstem. Nuclei (which are multiple nuclei) are connected to other nuclei by tracts, which are nothing but the collectional of axonal part of neurons.

B. GABA is Gamma amino butyric acid which is an amino acid, which acts a neorotransmitter in the brain. They are inhibitory in nature, meaning they reduce or stop conduction of impulses in the brain. Hence they are used in situations where there is excessive neoronal activity.

C.

axodendritic: influences a dendrite, hence influences the graded potential of the neuron

axoaxonic: influences the axon only.

The axodendritic synapse influence the graded potential of the neuron, where the axoaxonic connection only influences whether the axon fires. Therefroe the effect of GABA will also be on the graded potential in the former and only on the axon in the latter.

D. Posterior colum medial lemniscus pathway would be effected as this is the one which carries fine touch.

Regards