Lecture 3: Interactions between cells and extracellular environment

Depolarized, polarized, hyerpolarized 1. The cell membrane of a resting neuron is described as being ____. 2. If the membrane potential becomes more negative than the resting membrane potential, the membrane is ____. 3. If the membrane potential becomes less negative than the resting membrane potential, the membrane is ____.

1. polarized 2. hyperpolarized 3. depolarized

The alpha subunit's separatism from the remainder of the G-protein can be repeated as long as the ligand is bound to the receptor. A) True B) False

A) True

The area between the pre-synaptic nerve cell and the post-synaptic muscle cell is termed the synaptic cleft. A) True B) False

A) True

The nerve impulse is an electrical current that travels along dendrites or axons. A) True B) False

A) True

The sodium channels in the cell membrane have receptor sites for acetylcholine. A) True B) False

A) True

The sodium-potassium pump is involved in establishing the resting membrane potential. A) True B) False

A) True

Threshold is the minimum current required for the cell membrane to generate an action potential. A) True B)False

A) True

Which of the following statements about the protein calmodulin is TRUE? A) It interacts directly with the ligand receptor. B) It binds to Ca 2+ ions to mediate a cellular response. C) It induces ATP hydrolysis. D) It interacts directly with the G protein. E) It binds to the Ca 2+ ion channel causing it to close.

B) It binds to Ca 2+ ions to mediate a cellular response.

Acetylcholine is actively transported from the pre-synaptic membrane to the post-synaptic membrane. A) True B) False

B) False

Action potentials can travel in both directions on the axon. A) True B) False

B) False

EPSPs and IPSPs have a long term effect on a neuron. A) True B) False

B) False

IPSPs always open K+ channels. A) True B) False

B) False

Receptors that bind the neurotransmitter at the post-synaptic cell membrane are voltage-gated. A) True B) False

B) False

The activity of the G protein mainly resides in the Beta subunit. A) True B) False

B) False

The sodium-potassium pump uses bulk transport to move the sodium and potassium ions. A) True B) False

B) False

What structures are used for direct cell to cell signaling? A) desmosomes B) gap junctions C) exocytosis vesicles D) tight junctions

B) Gap junctions

Phosphorylase activity removes a phosphate from GTP. A) True B) False

A) True

Arrange the following in the proper order in which they occur. 1. Binding of ligand to receptor site 2. Dissociation of G protein subunits 3. Diffusion of calcium ions into the cell

1, 2, 3

Inactivation of the alpha subunit occurs when its own phosphorylase activity removes a phosphate from the GTP. A) True B) False

A) True

Which of the following is NOT true of cyclic AMP? A) It is found on the outside of a plasma membrane. B) It is a second messenger for polar regulatory molecules. C) It activates enzymes inside a cell to produce the desired effect. D) It is made from ATP.

A) It is found on the outside of a plasma membrane.

After the passage of the action potential, the sodium-potassium pump reestablishes the resting membrane potential. A) True B) False

A) True

If the post-synaptic membrane potential reaches threshold level, an action potential will be produced. A) True B) False

A) True

Nicotinic receptors are also ion channels. A) True B) False

A) True

Depolarization occurs because... A) more sodium ions diffuse into the cell than potassium ions diffuse out of it. B) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value. C) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases. D) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close. E) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.

A) more sodium ions diffuse into the cell than potassium ions diffuse out of it.

During depolarization, which of the following statements about voltage-gated ion channels is TRUE? A) Na+ and K+ gates open at the same time B) Na+ gates open before K+ gates C) K+ gates open while Na+ gates remain closed D) Na+ gates open while K+ gates remain closed E) K+ gates open before Na+ gates

B) Na+ gates open before K+ gates

The neurotransmitter at the neuromuscular junction is A) histamine. B) acetylcholine. C) dopamine. D) serotonin. E) adrenaline.

B) acetylcholine

Hyperpolarization, or afterpotential occurs because... A) more sodium ions diffuse into the cell than potassium ions diffuse out of it. B) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level. C) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases. D) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close. E) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value.

B) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.

An action potential arriving at the presynaptic terminal causes _____. A) acetylcholine to diffuse into the cell. B) voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell. C) voltage-gated sodium ion channels to open, and sodium ions to diffuse into the cell. D) voltage-gated sodium ion channels to open, and sodium ions to diffuse out of the cell. E) ligand-gated sodium channels to open, and sodium ions to diffuse out of the cell.

B) voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell.

The activation/inactivation of G proteins occurs as a result of ___________________. A) binding and release of Ca2+ ions. B) synthesis and hydrolysis of GTP. C) GDP/GTP exchange and GTP hydrolysis. D) binding and release of the ligand. E) binding and release of extra G protein subunits.

C) GDP/GTP exchange and GTP hydrolysis.

Acetylcholine has which effect on the post-synaptic neuron? A) Ligand gated calcium ion channels open and calcium diffuses in. B) Voltage gated sodium ion channels open and sodium diffuses in. C) Ligand gated sodium ion channels open and sodium diffuses in. D) Terminal vessels migrate to the plasma membrane. E) Voltage gated calcium ion channels open and calcium diffuses in.

C) Ligand gated sodium ion channels open and sodium diffuses in.

Depolarization occurs because A) more K+ diffuse into the cell than Na+ diffuse out of B) more K+ diffuse out of the cell than Na+ diffuse into it C) more Na+ diffuse into the cell than K+ diffuse out of it D) both Na+ and K+ diffuse into the cell E) more Na+ diffuse out of the cell than K+ diffuse into it

C) more Na+ diffuse into the cell than K+ diffuse out of it

Repolarization occurs because... A) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value. B) more sodium ions diffuse into the cell than potassium ions diffuse out of it. C) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close. D) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level. E) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases.

C) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close.

As a result of question number one _____. A) acetylcholine is actively transported to the post synaptic neuron. B) sodium ions diffuse into the cell. C) synaptic vessels migrate to the plasma membrane and release acetylcholine. D)acetylcholine is actively transported from the pre-synaptic neuron. E) ligand-gated sodium channels open.

C) synaptic vessels migrate to the plasma membrane and release acetylcholine.

An inhibitory post synaptic potential (IPSP)... A) will make the membrane potential of a neuron's inner cell membrane more positive. B) will make the membrane potential of a neuron's outer cell membrane more negative. C) will make the membrane potential of a neuron's inner cell membrane more negative. D) will make the membrane potential of a neuron's outer cell membrane more positive. E) will lower the membrane threshold potential of a neuron.

C) will make the membrane potential of a neuron's inner cell membrane more negative.

A ligand is _________________________. A) a large molecule that binds to the alpha subunit of the G-protein. B) a large molecule that binds to a membrane-bound receptor. C) a small molecule that binds to a G-protein. D) a small molecule that binds to a membrane-bound receptor. E) a small molecule that binds to the alpha subunit of the G-protein.

D) a small molecule that binds to a membrane-bound receptor.

An action potential _____. A) causes the inside of the neuron cell membrane to become negatively charged in reference to the outside. B)causes the outside of the neuron cell membrane to become positively charged in reference to the inside. C)causes the inside of the neuron cell membrane to become neutrally charged in reference to the outside. D) causes the inside of the neuron cell membrane to become positively charged in reference to the outside. E) causes the neuron cell membrane to become unable to alter its charge.

D) causes the inside of the neuron cell membrane to become positively charged in reference to the outside.

As a result of the ligand binding to its site... A) the G-protein changes conformation and the alpha subunit separates from the beta and gamma subunits. B) the G-protein changes conformation and GTO replaces the GTP on the alpha subunit. C) the G-protein changes conformation and GDP replaces the GTP on the alpha subunit. D) the G-protein changes conformation and GTP replaces the GDP on the alpha subunit. E) the G-protein changes conformation and the alpha subunit rejoins the beta and gamma subunits.

D) the G-protein changes conformation and GTP replaces the GDP on the alpha subunit.

Which of the following statements about the resting membrane potential is TRUE? A) the exterior of the cell has a net positive charge and the interior is neutral B) the exterior of the cell has a net negative charge and the interior has a net positive charge C) the exterior of the cell is neutral and the interior has a net negative charge D) the exterior of the cell has a net positive charge and the interior has a net negative charge E) the exterior of the cell has a net negative charge and the interior is neutral

D) the exterior of the cell has a net positive charge and the interior has a net negative charge

When the acetylcholine binds to the receptor sites... A) sodium ions diffuse through and leave the cell. B) sodium ions diffuse through and enter the cell. C) a ligand is formed. D) the sodium channels open. E) the sodium channels remain closed.

D) the sodium channels open.

Initially, bound to the alpha subunit of the G-protein is ____________________. A) a GTO molecule. B) a GTP molecule. C) a ligand. D) an ADP molecule. E) a GDP molecule.

E) a GDP molecule.

Absolute refractory period causes... A) action potential propagation to begin B) action potential propagation to occur in both directions C) action potential propagation to increase D) action potential propagation to cease E) action potential propagation to occur in one direction

E) action potential propagation to occur in one direction

An EPSP will cause... A) sodium gates to open, allowing sodium to diffuse out of the cell. B) potassium gates to open, allowing potassium to diffuse into the cell. C) potassium gates to open and allow potassium to diffuse out of the cytosol. D) chloride gates to open and allow chloride ions to diffuse into the cytosol. E) both sodium and potassium gates to open, allowing sodium to diffuse into the cell and potassium to diffuse out of the cell.

E) both sodium and potassium gates to open, allowing sodium to diffuse into the cell and potassium to diffuse out of the cell.

An action potential generates local currents that tend to _____ the membrane immediately adjacent to the action potential. A) stabilize B) neutralize C) repolarize D) hyperpolarize E) depolarize

E) depolarize

Once acetylcholine binds to the receptor, it causes _____________________. A) a ligand to be formed. B) the sodium channels to open. C) the sodium channels close. D) sodium ions to diffuse through and leave the cell. E) sodium ions to diffuse through and enter the cell.

E) sodium ions to diffuse through and enter the cell.

When the acetylcholine receptor sites are not occupied _____. A) the sodium channels open. B) a ligand is formed. C) sodium ions diffuse through and enter the cell. D) sodium ions diffuse through and leave the cell. E) the sodium channels remain closed.

E) the sodium channels remain closed.

An excitatory post synaptic potential (EPSP)... A) will lower the membrane threshold potential of a neuron. B) will make the membrane potential of a neuron's inner cell membrane more negative. C) will make the membrane potential of a neuron's outer cell membrane more positive. D) will make the membrane potential of a neuron's outer cell membrane more negative. E) will make the membrane potential of a neuron's inner cell membrane more positive.

E) will make the membrane potential of a neuron's inner cell membrane more positive.