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Ch. 11 Introduction to the Nervous System and Nervous Tissue
Amerman- Human Anatomy & Physiology 3e
Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814Not the one you use?Change textbook
All textbooksAmerman 3rd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblem 10
Chapter 11, Problem 10

The trigger for exocytosis of synaptic vesicles from the presynaptic neuron is:
a. Arrival of an action potential at the axon terminal and influx of calcium ions.
b. Summation of IPSPs at the presynaptic neuron.
c. Binding of neurotransmitters to the axon hillock.
d. Influx of Na+ into the postsynaptic neuron.

Verified step by step guidance
1
Understand the process of synaptic transmission: Synaptic vesicles in the presynaptic neuron store neurotransmitters, which are released into the synaptic cleft to communicate with the postsynaptic neuron.
Recall the role of an action potential: An action potential travels down the axon of the presynaptic neuron and reaches the axon terminal, triggering a series of events.
Identify the role of calcium ions: The arrival of the action potential at the axon terminal causes voltage-gated calcium channels to open, allowing calcium ions (Ca²⁺) to flow into the presynaptic neuron.
Connect calcium influx to exocytosis: The influx of calcium ions triggers the synaptic vesicles to fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft through exocytosis.
Eliminate incorrect options: Summation of IPSPs (b) occurs at the postsynaptic neuron, binding of neurotransmitters (c) happens at the postsynaptic membrane, and Na⁺ influx (d) is part of postsynaptic depolarization, not exocytosis.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Exocytosis

Exocytosis is a cellular process where vesicles fuse with the plasma membrane to release their contents outside the cell. In the context of neurons, synaptic vesicles containing neurotransmitters undergo exocytosis when triggered, allowing communication between neurons. This process is essential for neurotransmission and is regulated by various factors, including calcium ion concentration.
Recommended video:
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Endocytosis and Exocytosis

Action Potential

An action potential is a rapid, temporary change in the membrane potential of a neuron, which occurs when a stimulus causes depolarization. This electrical signal travels along the axon to the axon terminal, where it triggers the opening of voltage-gated calcium channels. The influx of calcium ions is crucial for initiating the exocytosis of neurotransmitters from synaptic vesicles.
Recommended video:
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Action Potential

Calcium Ions (Ca<sup>2+</sup>) in Neurotransmission

Calcium ions play a pivotal role in neurotransmission by acting as a signaling molecule. When an action potential reaches the axon terminal, calcium channels open, allowing Ca<sup>2+</sup> to flow into the neuron. This increase in intracellular calcium concentration is the key trigger for the fusion of synaptic vesicles with the membrane, leading to the release of neurotransmitters into the synaptic cleft.
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Neurotransmitter Receptors
Related Practice
Textbook Question

Which of the following is not a method by which the effects of neurotransmitters are terminated?

a. Reuptake into the presynaptic neuron

b. Diffusion away from the synaptic cleft and uptake by glial cells

c. Movement back to the cell body by retrograde axonal transport

d. Degradation by enzymes in the synaptic cleft

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Textbook Question

Identify the following as properties of electrical synapses (ES), chemical synapses (CS), or both (B).           

a. ______ The plasma membranes of presynaptic and postsynaptic neurons are joined by gap junctions.          

b. ______ Transmission is unidirectional and delayed.          

c. ______ A presynaptic neuron and a postsynaptic neuron are involved.          

d. ______ The use of neurotransmitters packaged into synaptic vesicles is required.          

e. ______ Transmission is nearly instantaneous and bidirectional.

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Textbook Question

The ________ is the period of time during which it is impossible to stimulate a neuron to have an action potential, whereas the ________ is the period of time during which a larger-than-normal stimulus is required to elicit an action potential.

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

The Na+/K+ pumps and gated channels maintain the Na+ and K+ gradients necessary for action potentials to occur.

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Textbook Question

A ________ is characterized by multiple input neurons synapsing on one postsynaptic neuron.

a. Diverging circuit

b. Discharge zone

c. Facilitation zone

d. Converging circuit

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Textbook Question

Which of the following statements best describes saltatory conduction?

a. Every section of the axolemma must be depolarized and triggered to generate an action potential.

b. The internodes must generate action potentials.

c. The dendrites and cell bodies propagate EPSPs toward the trigger zone.

d. Only the nodes of Ranvier must generate action potentials.

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