Question

Neurons can “talk” to other cells, including other neurons and muscle fibers. Discuss how this is accomplished. Include details about pumps, channels, carriers, various solutes, membrane potentials, timing, and locations. Details should include how the cell returns to “ready state”. How does a motor neuron . . . . . .

· decide to trigger an axon action potential? The role of stimulatory and inhibitory neuron to neuron communication, and the summation role of the axon hillock should be clearly explained.

· Discuss how an action potential travels along a neuron once it has left the axon hillock.

· What occurs at the end of the axon that triggers neurotransmitter release?

· What happens when the NT binds to its receptor on the receiving cell?

Answer 1

Once an action potential has been initiated,it does not remain localised at a particular site but it is propagated down the length of a cell as a nerve impulse.Action potentials are normally initiated at one end of the nerve cell and move from there to opposite ends .In certain experimental cases ,the action potential has been triggered somewhere in the middle of the neuron and it moves out from that site in both directions.

Nerve impulses are propagated along the membrane because an action potential at one site has an effect on adjacent site.The large depolarization that accompanies an action potential draws positive ions towards that site on the outer surface of the membrane and forces then away from that site on the inner surface.This flows of current causes the membrane in the region just ahead of the action potential to become depolarized itself.Because the depolarisation accompanying the action potential is readily depolarized to a level greater than threshold value,and sodium gates swing open in this adjacent region ,generating another action potential.Thus,once triggered a wave of action potential passes down the entire length of the neuron without any loss of intensity arriving its target cell with the same strength it had at its point of origin.

Neurotransmitters such as acetylcholine act on the outer surface of certain cationic channels such as cAMP act on the inner surface of certain calcium ion channels.

Genes that encode a variety of K+ channels have been isolated and Molecular anatomy of their anatomy have been scrutinized.These channels can exist in either an open or closed confirmation depending on the voltage across the membrane.