Bio 168 Chapter 11 Application Questions

1. A neuron at rest maintains a membrane potential of -70 mV. This is primarily due to:

Greater leakage of potassium than sodium

3 multiple choice options

During depolarization, which event occurs?

Sodium channels open and Na+ enters the cell

3 multiple choice options

If the threshold potential of a neuron is -55 mV and the cell reaches only -60 mV, what happens?

An action potential will not be produced

3 multiple choice options

A drug that blocks voltage-gated potassium channels would affect which phase of the action potential?

Repolarization

3 multiple choice options

Saltatory conduction occurs only in:

Myelinated fibers

3 multiple choice options

In a clinical setting, local anesthetics block sodium channels. This results in:

Inability to generate action potentials

3 multiple choice options

The refractory period ensures that:

Each action potential is separate

3 multiple choice options

A neuron receives excitatory and inhibitory postsynaptic potentials simultaneously. The outcome depends on:

The summation of all graded potentials

3 multiple choice options

A patient is given a drug that inhibits acetylcholinesterase. What effect will this have at a cholinergic synapse?

Acetylcholine accumulates and stimulates the postsynaptic neuron

3 multiple choice options

Which statement best describes temporal summation?

One presynaptic neuron releases neurotransmitters in rapid succession

3 multiple choice options

Which statement best describes spatial summation?

Several presynaptic neurons release neurotransmitters at once

3 multiple choice options

A presynaptic neuron releases a neurotransmitter that opens chloride channels in the postsynaptic membrane. The effect will be:

Hyperpolarization

3 multiple choice options

Calcium's role in synaptic transmission is to:

Trigger synaptic vesicle fusion and neurotransmitter release

3 multiple choice options

In myasthenia gravis, the immune system destroys acetylcholine receptors. This causes:

Muscle weakness due to reduced signal transmission

3 multiple choice options

An inhibitory neurotransmitter typically causes:

Hyperpolarization of the postsynaptic membrane

3 multiple choice options

A patient taking an SSRI (selective serotonin reuptake inhibitor) experiences mood improvement. This drug works by:

Preventing serotonin reuptake

3 multiple choice options

Which mechanism ensures unidirectional propagation of an action potential?

· Absolute refractory period

3 multiple choice options

Multiple sclerosis slows down nerve transmission because it:

Removes myelin from CNS axons

3 multiple choice options

In an unmyelinated axon, the action potential moves by:

Continuous conduction

3 multiple choice options

Which event directly triggers neurotransmitter release from the axon terminal?

Calcium influx

3 multiple choice options

A patient sustains a spinal cord injury that disrupts sensory pathways but leaves motor function intact. Which division of the nervous system is primarily affected?

Sensory (afferent) division

3 multiple choice options

A boxer receives a blow to the head and temporarily loses consciousness. Which major function of the nervous system is directly disrupted?

Integration

3 multiple choice options

When a student hears an unexpected loud noise and turns her head, which functional division of the peripheral nervous system is primarily responsible for this response?

Somatic motor

3 multiple choice options

The myelin sheath around neurons in the peripheral nervous system is produced by:

Schwann cells

3 multiple choice options

Which of the following best explains why demyelinating diseases such as multiple sclerosis cause slower nerve conduction?

Loss of ions inside the axon that would maintain the action potential.

3 multiple choice options

A neuron that carries impulses from the skin to the spinal cord would be classified functionally as a:

Sensory neuron

3 multiple choice options

A lesion that destroys oligodendrocytes would primarily affect which part of the nervous system?

Central nervous system

3 multiple choice options

The term 'integration' in the nervous system refers to:

Processing and interpretation of sensory input

3 multiple choice options

Damage to the ependymal cells would most likely affect:

Circulation of cerebrospinal fluid

3 multiple choice options

A patient with Guillain-Barré syndrome has difficulty moving the limbs due to demyelination in the PNS. Which cells are directly damaged?

Schwann cells

3 multiple choice options

The ability of the neuron’s membrane to maintain a resting potential depends on:

Sodium-potassium pump activity

3 multiple choice options

The part of a neuron that conducts impulses away from the cell body is the:

Axon

3 multiple choice options

Which neuroglial cell acts as a phagocyte in the CNS?

Microglia

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A child's brain tumor is found to originate from glial cells. Which of the following explains this finding?

Glial cells retain mitotic ability

3 multiple choice options

A neuron that connects sensory and motor neurons is a(n):

Interneuron

3 multiple choice options

When a neurotransmitter causes the opening of chemically gated sodium channels on a postsynaptic membrane, what type of potential is most likely to occur?

Excitatory postsynaptic potential (EPSP)

3 multiple choice options

Graded potentials differ from action potentials primarily in that graded potentials:

Can summate over time and space

3 multiple choice options

1. A neurotransmitter opens potassium channels on a postsynaptic neuron. What is the immediate electrical effect?

Hyperpolarization

3 multiple choice options

The strength of a graded potential is determined by:

The number and duration of neurotransmitters released

3 multiple choice options

Why can an excitatory postsynaptic potential (EPSP) not trigger an action potential by itself?

It is a localized, small depolarization that must summate to reach threshold

3 multiple choice options

In spatial summation, action potential generation depends on:

Multiple presynaptic neurons releasing neurotransmitter at the same time

3 multiple choice options

Temporal summation occurs when:

A single presynaptic neuron fires multiple times in quick succession

3 multiple choice options

What is the key difference between a graded potential and an action potential in terms of signal propagation?

Graded potentials decay with distance; action potentials propagate without decreasing

3 multiple choice options

If a postsynaptic membrane becomes more permeable to chloride ions immediately after neurotransmitter binding, which best describes the resulting electrical event?

IPSP leading to hyperpolarization and reduced excitability

3 multiple choice options

How does an inhibitory postsynaptic potential (IPSP) affect the postsynaptic neuron?

Decreases the likelihood of an action potential by hyperpolarizing the membrane

3 multiple choice options

When multiple EPSPs and IPSPs occur simultaneously, what determines whether an action potential will be generated?

The net effect of depolarizing and hyperpolarizing influences at the axon hillock

3 multiple choice options

Why do graded potentials decay over distance while action potentials do not?

The membrane of the soma and dendrites lack voltage-gated channels to regenerate the signal

3 multiple choice options

Which event would most likely generate an action potential?

Multiple EPSPs summating to threshold

3 multiple choice options

Why would the axon hillock be known as the "trigger zone"?

It determines whether threshold is reached and an action potential will occur

3 multiple choice options

Why does transmission across the synaptic cleft ensure one-way communication between neurons?

Neurotransmitters are only released from axon terminals and bind to receptors on the next neuron

3 multiple choice options

1. A postsynaptic neuron receives simultaneous inputs from three presynaptic neurons. Two release excitatory neurotransmitters, and one releases an inhibitory neurotransmitter. The neuron reaches threshold and fires an action potential. What best explains this outcome?

Spatial summation of excitatory inputs outweighed the inhibitory input

3 multiple choice options

A toxin blocks voltage-gated calcium channels in presynaptic axon terminals. What would be the most immediate effect on graded and action potentials?

Graded potentials would still form, but neurotransmitter release would fail, preventing postsynaptic potentials

3 multiple choice options

A neuron's membrane potential moves from -70 mV to -55 mV after receiving several EPSPs. What event will occur next if voltage-gated sodium channels open?

Sodium enters the cell, triggering an action potential

3 multiple choice options