Chapter 43. Neural Communication

Learning Objectives

action potential

a brief electrical charge (neural impulse) that travels down an axon

axon

part of a neuron specialized to send impulses to other neurons (or to muscles and glands)

axon terminals

branching fibers at the end of an axon that contain the neurotransmitters; also called synaptic terminals or terminal buttons

cell body

part of a neuron that contains the genetic material (in the nucleus) and generates energy; also called the soma

dendrites

parts of a neuron specialized to receive messages from other neurons and conduct them toward the cell body

excitatory signals

synaptic connections which, when stimulated, increase the likelihood that the receiving neuron will fire

inhibitory signals

synaptic connections which, when stimulated, decrease the likelihood that the receiving neuron will fire

nervous system

the body's fast communication system, consisting of billions of neurons; divided into the peripheral and central nervous systems

neural impulse

an electrical signal that carries a message along an axon

neuron

a single nerve cell, forming the basic unit of the nervous system

neurotransmitters

chemical messengers released by the axon terminal into the synaptic gap between neurons

synapse

the junction of the axon terminal of the sending neuron with the dendrite or cell body of the receiving neuron

synaptic gap

the tiny space between the sending neuron and the receiving neuron; also called synaptic cleft

synaptic vesicles

sacs in the axon terminals that contain the neurotransmitters

Neural Communication

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Learning Objectives:

Describe the processes through which neurons communicate with each other.

Contrast the effects of excitatory synapses and inhibitory synapses.

Review

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1. Neurons are the building blocks of the nervous system. Each neuron consists of a cell body and its branching fibers.

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2. The bushy dendrite fibers receive information as electrical signals and conduct those signals toward the cell body. Based on those signals, the axon generates a new electrical message and passes it along to the axon terminals. When the message reaches a synapse, chemical signals pass the message across the synaptic gap to other neurons or to muscles or glands.

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3. The process of neural communication begins when a neuron is stimulated by chemical messages from neighboring neurons. Most of these messages are excitatory signals that increase the neuron's ability to fire (generate a neural impulse), but some are inhibitory signals that block the excitation.

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4. The neural impulse, called the action potential, is a brief electrical surge that travels down the axon from the cell body toward the axon terminals.

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5. When the action potential reaches the knoblike terminals at the axon's end, it causes the synaptic vesicles to release chemical messengers called neurotransmitters into the synaptic gap.

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6. Within a fraction of a second, the neurotransmitter molecules cross the synaptic gap and stimulate a dendrite or the cell body of the next neuron.

Practice 1: Generating a Message

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Practice 1: Generating a Message

Play the animation for an overview of the neural communication process.

Practice 2: Excitatory and Inhibitory Signals

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Practice 2: Excitatory and Inhibitory Signals

Play the animation to view the interplay between excitation and inhibition of the neuron.

Quiz 1

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Quiz 1

Select buttons A, B, and C to play segments of an animation about neural communication. Then match each segment with its description. When matches have been made for all the segments, select the CHECK ANSWER button.

Provides an overview of neural communication.

Segment

A B C

Shows release of neurotransmitter molecules.

Segment

A B C

Shows synaptic vesicles migrating toward the axon membrane.

Segment

A B C

Note: this video has no audio.

Quiz 2

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Quiz 2

For each statement, select one of the buttons to indicate whether the statement is True or False. When you have responded to all the statements, select the CHECK ANSWER button

Select the NEXT button and move to the Conclusion.

Try to respond to the statements again.

True	False
		The neural communication process usually begins when the axon receives signals from other nearby neurons.
		Excitatory signals make it more likely that a neuron will generate its own electrical impulse.
		When the message reaches the axon terminal, an electrical impulse travels across the synaptic gap and stimulates the next neuron.
		Inhibitory signals can block the effect of excitatory signals, reducing the likelihood that the neuron will fire.

Conclusion

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Congratulations!

You have completed
Neural Communication