Ch 11 HW Assignment

Cl−Cl− is a common, negatively charged extracellular ion. Predict the effect on the RMP if many Cl−Cl− gated channels are suddenly opened.

A more negative RMP would result.

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

Imagine that the cell membrane from the previous problem becomes more permeable to Na+Na+. Predict how this will affect the RMP.

The RMP will be more positive.

You are going to record RMP from a cell using an electrode. You place your electrode and record a resting membrane potential every millisecond. You record an initial value of -70mV; however, over time you notice that your recordings become more and more positive until the RMP reaches 0mV. Assuming that Na+Na+ and K+K+ are the major determinants of RMP in this cell, which of the following could best explain your results?

The cell's Na+Na+-K+K+ ATPase pumps have stopped functioning.

Why does regeneration of the action potential occur in one direction, rather than in two directions?

The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

Which mechanism allows the rabies virus to gain access to the central nervous system (CNS)?

The rabies virus uses retrograde movement along the neuronal axon.

A molecule that carries information across a synaptic cleft is a

neurotransmitter.

In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________.

oligodendrocytes

Let's consider a scenario in which the resting membrane potential changes from −−70 mVmV to +70 mVmV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+Na+. The electrical gradient for Na+Na+ would tend to move Na+Na+ __________ while the chemical gradient for Na+Na+ would tend to move Na+Na+ __________.

out; in

The small space between the sending neuron and the receiving neuron is the

synaptic cleft.

If a signal from a sending neuron makes the receiving neuron more negative inside,

the receiving neuron is less likely to generate an action potential.

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

Which choice best characterizes K+K+ leakage channels?

transmembrane protein channels that are always open to allow K+K+ to cross the membrane without the additional input of energy

The generation of an action potential in a neuron requires the presence what type of membrane channels?

voltage-gated channels

Complete the following sentence. The operation of the Na+−K+Na+−K+ ATPase pump __________.

moves 3 Na+Na+ to the ECF and 2 K+K+ to the cytoplasm

Assume you have a membrane with only potassium leakage channels. The RMP is -90mV. Predict the RMP if we add Na+Na+ leakage channels.The most likely RMP value of Na+Na+ is __________.

-70 mV

What type of conduction takes place in unmyelinated axons?

Continuous conduction

People who have hydrocephaly often have an issue with which of these glial cell types?

Ependymal cells

People with multiple sclerosis (MS) experience many challenging symptoms. Which statement best explains one cause of these difficulties?

Loss of oligodendrocytes in the central nervous system results in absence of the myelin sheath of neuronal axons, impairing rapid saltatory conduction.

In which type of axon will velocity of action potential conduction be the fastest?

Myelinated axons with the largest diameter

The concentrations of which two ions are highest outside the cell?

Na+ and Cl−

Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. Which of the following is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth?

anterograde transport

An action potential is self-regenerating because __________.

depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

ion channels in the plasma membrane of the receiving neuron open.