Question 1

The membrane of an axon acts as a resistor and a __________ because it resists the flow of current and can store an electrical charge.

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Question 2

__________,or afferent neurons,are capable of sending information about the environment (internal and external)to the central nervous system.

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Question 3

Synapses where pre- and postsynaptic cells are directly connected so that current can pass from one cell to another are called __________.

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Question 4

Briefly state the importance of voltage-gated Na⁺ channels.Explain why the tetrodotoxin (TTX)found in California newts (Taricha torosa)does not kill the newts.Would you expect garter snakes (Thamnopis sirtalis),which are predators of newts,to die once they consume the toxic newts?

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Question 5

__________ receptors bind both epinephrine and norepinephrine.

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Question 6

Neurotransmitter is packaged in vesicles that are released in response to an action potential.This leads to a "steplike" increase in the amount of neurotransmitter being released (one step for each vesicle),termed __________.

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Question 7

The distance a membrane potential can travel before reaching 37% of its original value is termed the __________.

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Question 8

A decrease in neurotransmitter release with repeated action potentials is termed _________.

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Question 9

A high speed of conduction along axons is very important for the survival of organisms,particularly when quicker response times allow escape from a predator.Many factors affect speed of conduction,including temperature,myelination,and the diameter of the axon.Discuss how myelination and diameter affect the cable properties of a neuron and affect conduction speeds.

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Question 10

Neurotransmitters are synthesized in the cell body,then transported in vesicles to the axon terminals using __________.

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Question 11

Neurons have four functional zones,and each performs a task required for communication.What are these four zones and what structural features found in each allow it to perform its function?

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Question 12

Most neurons show __________,such that one end of the neuron receives a signal and the other sends a signal.The cnidarians are an exception to this principle.

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Question 13

Glial cells were originally thought to play a very minor role in the nervous system.In fact,their name is derived from the Greek word for glue.However,recent findings have demonstrated a number of functions for these cells.Discuss these functions and their importance in allowing neurons to function.

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Question 14

Neurons use both graded and action potentials to carry electrical signals from one point to another.Describe the similarities and differences between these two types of signals that could be seen within an individual neuron.

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Question 15

Describe the differences between electrical and chemical synapses in terms of mechanisms and functional characteristics of transmission.

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Question 16

Inhibitory neurotransmitters generally cause ________________,and the changes in membrane potential are referred to as inhibitory postsynaptic potential.

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Question 17

Muscarinic ACh receptors are an example of a __________ receptor,which eventually lead to the opening of an ion channel.

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Question 18

The absolute and relative refractory periods of an action potential determine other parameters of action potentials such as causing unidirectional conduction and limiting their frequency.Describe what is happening during each of the refractory periods.Then use this information to describe how the different periods affect conduction and frequency.

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Question 19

You have isolated two neurons,joined by a synapse,in a Petri dish.You have stimulated the first neuron at the axon hillock and successfully generated an action potential.However,there is no response by the postsynaptic neuron.Describe possible malfunctions in synaptic transmission that would prevent the postsynaptic neuron from responding as it should.

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Question 20

When membrane potential changes,we use the terms depolarization,hyperpolarization,and repolarization.Explain what is happening to the membrane potential in relation to the extracellular fluid during depolarization and hyperpolarization and how each phase could be achieved by negatively charged ions.Next,explain how it is possible for the membrane to be in both hyperpolarization and repolarization at the same time.

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Quiz 5: Neuron Structure and Function