week 3 practice question and explanation

Question 10

1 / 1 pts

The refractory period of an action potential...

  

Has no effect on direction of action potential propagation

 

  

Is not a component of every action potential

 

  

Allows bidirectional flow of the action potential

 

  

Prevents flow of action potential toward cell body

 

 Question 5

Question 5                                                                                                                           1 / 1 pts

One type of channel involved in generating postsynaptic potentials at a chemical synapse is the:

  

mechanically gated ion channel.

 

  

ligand-gated ion channel.

 

  

light-gated ion channel.

 

  

voltage-gated ion channel.

 

Question 11

1 / 1 pts

The faster, more efficient way of propagating an action potential is:

  

continuous conduction.

 

  

unmyelinated conduction.

 

  

disruptive conduction.

 

  

saltatory conduction.

 

explanation and definition

Saltatory conduction is a fascinating process that allows nerve impulses to travel rapidly along myelinated axons.

Saltatory conduction refers to the propagation of action potentials (electrical signals) along myelinated axons from one node of Ranvier to the next. These nodes are uninsulated gaps in the myelin sheath that allow ions to exchange across the axon membrane, effectively “refreshing” the signal as it leaps from one node to another.

How It Works:

Myelinated Axons: Saltatory conduction occurs exclusively in myelinated axons. The myelin sheath insulates most of the axon, leaving only the nodes of Ranvier exposed.

Rapid Signal Transmission: When an action potential reaches a node, sodium ions rush into the cell, creating an electrical force. This force pushes on the ions already inside the axon, rapidly propagating the signal to the next node. The process repeats, allowing the signal to “jump” along the myelinated portion of the axon.

High Conduction Velocity: Compared to unmyelinated axons (which conduct at speeds of 0.5 to 10 meters per second), saltatory conduction achieves impressive conduction velocities of up to 150 meters per second!

Energy Efficiency: Besides speed, myelination also reduces energy expenditure. The myelin sheath minimizes the amount of sodium and potassium ions that need to be pumped to restore resting state concentrations after each action potential.

Distribution: Saltatory conduction is widespread in vertebrate myelinated nerve fibers. Interestingly, it has also been observed in shrimp and earthworms, emphasizing its importance across different species.

In summary, saltatory conduction allows nerve signals to travel long distances swiftly without signal degradation. It’s like a coordinated leapfrog game along the axon! 🚀

Is there anything else you’d like to explore or learn about? 😊

 

Question 12

1 / 1 pts

The threshold potential is best defined as the potential at which...

  

Chemically gated sodium channels open

 

  

Voltage-gated potassium channels close

 

  

Voltage-gated sodium channels open

 

  

Voltage-gated potassium channels open

 

 

Question 13

1 / 1 pts

Action potentials self-propagate because...

  

Neurotransmitter is released constantly

 

  

ATP is always available to drive the action potential

 

  

Each action potential triggers another in the next section of axon

 

  

They are a form of negative feedback

 

 Question 7

1 / 1 pts

Which of the following does NOT happen to neurotransmitters during synaptic transmission termination?

  

Degradation by enzymes

 

  

Diffusion away from synaptic cleft

 

  

Uptake into postsynaptic neuron

 

  

Reuptake into presynaptic neuron

 

Question 9

1 / 1 pts

During the absolute refractory period, the axon membrane:

  

is at –90 mV.

 

  

is more responsive to depolarization.

 

  

contains open voltage-gated Na+ channels.

  

is unable to generate an action potential.

 

 Incorrect

Question 6

0 / 1 pts

Selective serotonin reuptake inhibitors (or SSRIs), such as Prozac, Celexa, Lexapro, Paxil, and Zoloft, are a class of drugs used to treat mood disorders such as depression and anxiety. They inhibit the transporter responsible for serotonin reuptake into the presynaptic neuron. What is the effect of the SSRIs on the serotonin concentration in the synaptic cleft?

  

The serotonin concentration in the synaptic cleft will decrease. (incorrect) 

Incorrect. If the reuptake transporters are not working, there will be less serotonin reuptake. Therefore, more serotonin will remain in the cleft and will be available to stimulate postsynaptic neurons.

  

The serotonin concentration in the synaptic cleft will increase.

IncorrectQuestion 7

0 / 1 pts

Which of the following does NOT happen to neurotransmitters during synaptic transmission termination?

  

Diffusion away from synaptic cleft

 

  

Uptake into postsynaptic neuron

  (CORRECT) 

  

Degradation by enzymes

  (INCORRECT ) 

  

Reuptake into presynaptic neuron

 

Question 4

1 / 1 pts

Identify the ion that would move through the channel to produce an IPSP.

Ions 1-3 are in the extracellular fluid (blue background),  ions 4-6 are in the cytosol (yellow background). Figure out which ion and which direction it would flow based on what you know about concentration gradients for each ion.

  

Ca2+

 

  

K+

 

  

Na+

 

Question 2

1 / 1 pts

Some neurotransmitter receptors are ion channels that open when the neurotransmitter binds to them. Those receptors are called:

  

light-gated ion channels.

 

  

voltage-gated ion channels.

 

  

ligand-gated ion channels.

 

  

mechanically gated ion channels.

 

UnansweredQuestion 9

Use what you learned during the Lecture 3 handout.

Cocaine is a powerfully addictive stimulant drug made from the leaves of the coca plant native to South America. As a street drug, cocaine looks like a fine, white, crystal powder or it is processed to a make rock crystal.

Cocaine acts as a dopamine reuptake inhibitor. Therefore, cocaine will:

  

decrease dopamine inside the postsynaptic neuron.

 

  

increase dopamine in the axon terminal.

 

  

increase dopamine receptor stimulation.

 

  

increase dopamine receptor stimulation.

 

Correct. Less reuptake means more dopamine remains in the cleft and is available to stimulate dopamine receptors.

  

decrease dopamine in the synaptic cleft.

 

Incorrect. Less reuptake means more dopamine remains in the cleft.

Question 10

1 / 1 pts

The refractory period of an action potential...

  

Allows bidirectional flow of the action potential

 

  

Is not a component of every action potential

 

  

Prevents flow of action potential toward cell body

 

  

Has no effect on direction of action potential propagation

 

Question 3

1 / 1 pts

Funnel-web spiders are found in southeast Australia, around Sydney. Others are found in Europe, New Zealand, and Chile. They are not native to the United States, although some people may keep them as exotic pets.

Their bites are very painful and dangerous. They have been known to cause serious symptoms, such as agitation, confusion, numbness of mouth and lips, and even coma and death.

Funnel-web spider venom is a neurotoxin that blocks gated calcium channels. Its effect would be a/an:

  

increased production of neurotransmitter.

 

  

decreased neurotransmitter release.

 

  

increased neurotransmitter release.

 

  

decreased production of neurotransmitter.

 

Question 2

1 / 1 pts

Some neurotransmitter receptors are ion channels that open when the neurotransmitter binds to them. Those receptors are called:

  

voltage-gated ion channels.

 

  

ligand-gated ion channels.

 

  

light-gated ion channels.

 

  

mechanically gated ion channels.

 

Question1                                                                                                    1 / 1 pts

Chlorpromazine (marketed under brand names Thorazine and Largactil) is a drug used to treat psychotic disorders such as schizophrenia or manic-depression in adults. Chlorpromazine was developed in the 1950s and its introduction as the first antipsychotic on the market has been labeled as one of the great advances in the history of psychiatry.

Chlorpromazine blocks postsynaptic receptors for several different neurotransmitters, such as dopamine and serotonin. Predict the effect of chlorpromazine on synaptic transmission by selecting all of the steps it will directly inhibit in the picture below.

  

2

 

  

1

 

  

5

 

  

3

 

  

4