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Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892

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BuyFindarrow_forward

Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892
Textbook Problem

Transmission of a nerve impulse to its target cell requires:

a. endocytosis of neurotransmitters by excitatory presynapticvesicles.

b. the release of thousands of molecules of neurotransmitterstored in the postsynaptic cell into the synaptic cleft.

c. Ca2+ ions to diffuse through voltage-gated Ca2+ channels.

d. a fall in Ca2+ in the cytoplasm to trigger a protein that causes the presynaptic vesicle to fuse with the plasma membrane.

e. an action potential to open the Ca2+ gates so that Ca2+ ions, in higher concentration outside the axon, can flow back into the cytoplasm of the neuron.

Summary Introduction

Introduction:

The nerves of the human nervous system are not continuous. There is a small gap between two neurons, which is known as a synapse. The communication between two neurons takes place due to the release of a neurotransmitter into the synapse. The release of neurotransmitter is regulated by the calcium ion concentration inside the neuron.

Explanation

Justification/explanation for the correct answer:

Option (e) states that the transmission of nerve impulses requires action potential to open voltage-gated Ca2+ ion channels so that Ca2+ ions that are present in a higher concentration at the outside region of the axon, can flow back into the axon cytoplasm of the neuron. The Ca2+ ions are present in high concentration at the outside region of the neuron. The condition when voltage-gated Ca2+ ion channels open due to the generation of the action potential, Ca2+ ions enters into the axon from high concentration to low concentration due to diffusion. Hence, option (e) is correct.

Explanation for the incorrect answers:

Option (a) states that the endocytosis of neurotransmitters by excitatory presynaptic vesicles is required for transmission of nerve impulse. The neurotransmitters are located in the synaptic vesicles present in the terminal branch of the neuron. These chemical messengers are released into the synapse by a process called exocytosis (not endocytosis). The synaptic vesicles fuse with the plasma membrane of the neuron So, it is an incorrect option.

Option (b) states that the transmission of the nerve impulse to the target cell requires the release of thousands of molecules of neurotransmitter stored in the postsynaptic cell into the synaptic cleft

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