Ch.9 Quiz 2

Trace the direction of flow of electrical activity through a neuron, starting with the arrival of a signal at a dendrite.

1. Arrival of incoming signal... 2. Dendrite 3. Cell body 4. Axon hillock 5. Axon 6. Axon terminal 7. Synaptic knob 8. Signal transmitted across synapse

Put the steps of synaptic transmission in the correct order using the image as a guide.

1. Nerve impulse arrives at axon terminal 2. Calcium ions enter 3. Exocytosis of neurotransmitter 4. Diffusion through synaptic cleft 5. Binding to receptor on postsynaptic membrane

2

Acetylcholine binds to receptors

1

Acetylcholine released

Which is true of drugs that decrease membrane permeability to sodium ions?

All of these are true.

1

Calcium entry via voltage-gated channels

Membrane Potential Becomes More Negative (closer to -90 mV)

Decreased sodium concentration outside the cell.

A nerve is a single neuron.

False

Membrane Potential Becomes More Negative (closer to -90 mV)

Increased membrane permeability to potassium

Membrane Potential Becomes More Negative (closer to -90 mV)

Increased potassium concentration inside the cell.

Membrane Potential Becomes More Positive (closer to 0 mV)

Increased sodium concentration inside the cell.

Membrane Potential Becomes More Positive (closer to 0 mV)

Membrane becomes equally permeable to sodium and potassium.

Membrane Potential Becomes More Positive (closer to 0 mV)

No sodium-potassium pumps

2

Postsynaptic neuron

2

Presence of acetylcholine receptors

1

Presence of synaptic vesicles

1

Presynaptic neuron

2

Sodium entry via chemically-gated channel

Which describes the ion concentrations inside and outside of a neuron?

The sodium ion concentration is higher on the outside of the cell and potassium ion concentration is higher on the inside of the cell.

A synapse is the functional connection between two neurons.

True

When the membrane potential reaches threshold in the neighboring membrane, voltage-gated channels open, triggering a(n) __________ at the location.

action potential

This local current alters the membrane potential nearby, and stimulates the _____________ to reach its threshold.

adjacent membrane

(4) The cytoplasm contains many ____________ such as phosphate, sulfate, and proteins. These contribute to the negative charge within the cell.

anions

An infant's responses to stimuli are coarse and undifferentiated because its nerve fibers

are not completely myelinated.

This is called ________________ and makes it possible for impulses to have an additive effect or to collect a variety of sensory information.

convergence

As these ions enter the cell, the cell membrane undergoes _______________, with the membrane potential increasing to a peak of approximately +30mV.

depolarization

This is an example of _____________, which allows an impulse originating from a single neuron to be sent to several regions within the CNS.

divergence

A neurotransmitter which brings the postsynaptic membrane closer to threshold is ___________.

excitatory

When a neuron becomes more excitable as a result of incoming subthreshold stimulation, it is said to be

facilitated

Finally, a neuron may receive a subthreshold signal from one neuron and make it easier for other neurons in the pool to cause excitation. This process is called _____________.

facilitation

The membrane potential actually dips lower than -70mV because the potassium channels do not close quickly enough. This phase is called _________________.

hyperpolarization

With a longer duration of activation than sodium channels, the potassium channels allow for a greater movement of potassium to the extracellular fluid causing a short period of _______________.

hyperpolarization

This cycle continues, resulting in action potentials traveling down the axon. This propagation of action potentials is also called _______________ conduction.

impulse

A neurotransmitter that causes the membrane potential to move away from threshold is considered ____________.

inhibitory

In a resting neuron, the inside of the membrane has a more ____________ charge than the outside of the membrane.

negative

Neurons are organized into ___________ which can make multiple synaptic connections to receive and transmit information in the brain.

neuronal pools

Neurons communicate chemically with each other by using ____________ at a synapse.

neurotransmitters

The binding of the neurotransmitter to the ___________ causes electrical changes in the membrane.

postsynaptic neuron

An impulse from a single neuron that is transmitted to several ____________ can amplify or spread an impulse.

postsynaptic neurons

Through the activated channels, _____ now flows outwards causing the membrane to repolarize back towards RMP.

potassium

With membrane potentials approaching +35 mV, the voltage-regulated __________ channels become fully activated.

potassium

During an action potential, repolarization occurs as a result of

potassium ions diffusing to the outside of the cell membrane.

(2) Membrane permeability differs for sodium and potassium. The membrane has more channels for ___________ than it has for ______________.

potassium; sodium

For example, any single neuron in the group may receive information from more than one _____________.

presynaptic neuron

The release of neurotransmitters by the ______________ is triggered by nerve impulses.

presynaptic neuron

As cations leave the cell, the membrane potential at that part of the membrane is reestablishing resting membrane potential. This phase of the action potential is called ______________.

repolarization

As the membrane potential __________, the voltage-regulated ___________ channels begin closing which in turn reduces the ___________ movement to the cell.

rises toward zero; sodium; sodium

An action potential begins with the opening of ____________.

sodium channels

During an action potential, depolarization occurs as a result of

sodium ions diffusing to the inside of the cell membrane.

(1) There is a higher concentration of ____________ ions outside the cell, while ___________ ions are more abundant inside the cell.

sodium; potassium

As a result, _________ ions want to diffuse from outside into the cell and ____________ ions want to diffuse from inside to outside of the cell

sodium; potassium

(3) The sodium-potassium pump actively transports ___________ sodium ions out of the cell for every ____________ potassium ions transported into the cell.

three; two

These channels open when the membrane potential reaches a level called_____________.

threshold

An action potential will not occur unless the membrane potential at the _______________ (the initial segment of the axon) reaches a level called ____________.

trigger zone; threshold

As the peak of the action potential is reached, the sodium channels close and the ______________ open, allowing these ions to diffuse out of the cell.

voltage-gated potassium channels

When threshold is reached, ____________ of the initial segment open briefly, allowing to _____________ diffuse into the cell.

voltage-gated sodium channels; sodium