BIOL 2410 – Quiz 3 – Flashcards

The membrane potential of most cells __________. is negative at all times is negative, except when there is a change in membrane permeability to ions determined primarily by sodium results in a net negative electrical charge in the body

Why is the resting membrane potential (Vm) approximately - 70 mV for most cells? Most membranes are 40 times more permeable to K+ than to Na+. The large concentration of proteins in the interstitial space draws Na+ out of the cell making it negatively charged. Most membranes are 10 times more permeable to Na+ than to K+. Most cells contain a large concentration of Cl- making them negatively charged.

assuming a resting membrane potential of -70 mV. A. electrical polarization B. hyperpolarization C. depolarization D. repolarization E. more than one of the answers to +30 mV from resting potential

Membrane protein pores that can be opened and closed are called ________ channels. gated variable carrier open

The part of the neuron that receives most of the incoming signals is the __________. axon dendrite soma cell body

What would the sudden increase in axonal permeability to sodium cause? Repolarization following an action potential The rising phase of an action potential Hyperpolarization of the axon membrane The falling phase of an action potential

The region where the axon terminal meets its target cell is called the collateral. synapse. dendrites. nerve. hillock.

Myelin is formed by axons only. oligodendrocytes only. Schwann cells only. Schwann cells and oligodendrocytes.

Which is the correctly written Nernst equation? 61/z × log [ion]out / [ion]in log 61/z × [ion]out / [ion]in log 61/z × [ion]in / [ion]out 61/z × log [ion]in / [ion]out

Which ion(s) is/are higher in concentration inside the cell compared to outside? calcium chloride potassium sodium More than one of the answers is correct.

The rising phase of the action potential is due to K+ flow out of the cell only. Na+ flow into the cell only. Na+ flow out of the cell only. K+ flow into the cell only. Na+ flow out of the cell and K+ flow into the cell.

The falling phase of the action potential is due primarily to Na+ flow out of the cell only. K+ flow into the cell only. Na+ flow out of the cell and K+ flow into the cell. K+ flow out of the cell only. Na+ flow in the cell only.

Choose all of the items that are incorrectly matched. Check all that apply. activation gate opened at rest inactivation gate closed at rest activation gate opens during depolarization inactivation gate closed during repolarization

All of the following must occur before a second action potential can begin, EXCEPT the Na+ and K+ ions that moved in/out of the cell must move back to their original compartments. the absolute refractory period must occur. the Na+ and K+ ions that moved in/out of the cell must move back to their original compartments; the Na+ inactivation gate must open; and the Na+ activation gate must close. the Na+ inactivation gate must open and the Na+ activation gate must close. None of the answers are correct.

The sodium-potassium exchange pump transports potassium ions out of the cell during repolarization. requires ATP to function. transports sodium ions into the cell during depolarization. moves sodium and potassium in the direction of their chemical gradients. must re-establish ion concentrations after each action potential.

The all-or-none principle states that all stimuli will produce identical action potentials. only sensory stimuli can activate action potentials. only motor stimuli can activate action potentials. all stimuli great enough to bring the membrane to threshold will produce action potentials of identical magnitude. the greater the magnitude of the stimuli, the greater the intensity of the action potential.

Some neurotoxins work essentially the same way as some local anesthetics, which is to inactivate the enzyme that destroys the neurotransmitter only. bind to Na+ channels and inactivate them and prevent depolarization by blocking Na+ entry into the cell. prevent depolarization by blocking Na+ entry into the cell only. bind to Na+ channels and inactivate them only. inactivate the enzyme that destroys the neurotransmitter and bind to Na+ channels and inactivate them.

The period of time during which an excitable membrane can respond again, but only if the stimulus is greater than the initial stimulus is the absolute refractory period. relative refractory period. resting membrane potential. excessive period.

If a stimulating electrode is placed in the middle of a resting axon and an above-threshold voltage is applied to the electrode action potentials will start at that point and proceed only toward the cell body. will start at that point and proceed only toward the axon terminal. will not occur. will start at that point and travel in both directions in the axon.

Conduction speed is (or can be) enhanced by myelin and increasing the temperature. increasing the temperature. myelin. altering extracellular sodium concentration. altering extracellular potassium concentration.