Neural Physiology

The period after an initial stimulus when a neuron is NOT sensitive to another stimulus is the/a

• Resting potential

• Absolute refractory Period

• Depolarization period

• Repolarization period

• Graded potential

Which of the following is TRUE about graded potentials?

• They travel down axons.

• They lose strength as they move towards the axon hillock.

• They lose strength as the move towards the terminal endings.

• The speed of the graded potential depends on how much myelin is covering the axons or dendrites.

• A threshold must be established before a graded potential will fire.

What cellular process(es) is/are present in the figure to the right?

• Action potential

• Resting potential

• Graded potential

• Action potential and resting potential

• Action potential, graded potential and resting potential

In the figure above, what is occurring at step #4?

• Neuron receives enough stimulation (15 mV), threshold is reached (-55mV)

• Na+ voltage channels open allowing Na+ to diffuse inward, depolarizing the membrane

• K+ voltage channels open and Na+ voltage channels open

• K+ voltage channels open allowing K+ to diffuse out, repolarizing the membrane.

• Hamsters. Massive amounts of hamsters

You are in a dark room and are unable to see anything. Which of the following best explains what is happening in the neurons of your retina (the photo-sensitive part of your eye)?

• The graded potentials are not strong enough to trigger an action potential.

• The graded potentials are strong enough to trigger an action potential

• The action potentials are not strong enough to trigger a graded potential

• The action potentials are strong enough to trigger a graded potential.

• Hamsters are gnawing on your optic nerve. You should probably have this checked by a doctor.

Which of the following does NOT occur during an action potential?

• Na⁺ (sodium) voltage channels open allowing Na⁺ to diffuse inward, depolarizing the membrane

• K⁺ (potassium) diffuse outward, repolarizing the membrane

• Neuron is hyperpolarized and enters a refractory period

• All of the Na⁺ channel proteins and and most of the K⁺ channel proteins are closed and resting membrane potential has been reestablished

During rapid depolarization of an action potential the current flow (charge of the membrane potential) is dominated by

• The inward movement of K⁺

• The outward movement of K⁺

• The inward movement of Na⁺

• The outward movement of Na⁺

Certain snake venoms cause K⁺ channels to remain open. This will prevent the neurons from firing action potentials. This occurs because

• K⁺ will leave the cell, hyperpolarizing the neuron

• K⁺ will enter the cell, hyperpolarizing the neuron

• K⁺ will leave the cell, depolarizing the neuron

• K⁺ will enter the cell, depolarizing the neuron

Refer to the previous question on snake venom. The snake venom mimics neurotransmitters and can attach to receptor proteins on the postsynaptic cell. Therefore, what type of graded potential does the snake venom initiate?

• EPSP

• IPSP

• Action Potential

The influx of Ca²⁺ is initiated by

• EPSPs

• IPSPs

• Action potential

• Graded potential