CHP 11 – Flashcards

Which of the following is NOT a difference between graded potentials and action potentials? Greater stimulus intensity results in larger graded potentials, but not larger action potentials. Graded potentials can result from the opening of chemically gated channels; action potentials require the opening of voltage-gated channels. Spatial summation is used to increase the amplitude of a graded potential; temporal summation is used to increase the amplitude of an action potential Graded potentials occur along dendrites, whereas action potentials occur along axons.

What characterizes repolarization, the second phase of the action potential? Once the membrane depolarizes to a threshold value of approximately -55 mV, it repolarizes to its resting value of -70 mV. Before the membrane has a chance to reach a positive voltage, it repolarizes to its negative resting value of approximately -70 mV. Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV. As the membrane repolarizes to a negative value, it goes beyond the resting state to a value of -80 mV.

What event triggers the generation of an action potential? The membrane potential must hyperpolarize from the resting voltage of -70 mV to the more negative value of -80 mV The membrane potential must depolarize from the resting voltage of -70 mV to its peak value of +30 mV. The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

What is the first change to occur in response to a threshold stimulus? Voltage-gated K+ channels change shape, and their activation gates open. Voltage-gated Na+ channels change shape, and their inactivation gates close. Voltage-gated Ca2+ channels change shape, and their activation gates open Voltage-gated Na+ channels change shape, and their activation gates open.

An action potential is self-regenerating because __________. depolarizing currents established by the influx of K+‎ flow down the axon and trigger an action potential at the next segment repolarizing currents established by the efflux of Na+‎ flow down the axon and trigger an action potential at the next segment depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment repolarizing currents established by the efflux of K+‎ flow down the axon and trigger an action potential at the next segment

Why does regeneration of the action potential occur in one direction, rather than in two directions? The inactivation gates of voltage-gated K+‎ channels close in the node, or segment, that has just fired an action potential. The activation gates of voltage-gated K+‎ channels open in the node, or segment, that has just depolarized. The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential. The activation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just depolarized.

What is the function of the myelin sheath? The myelin sheath increases the insulation along the entire length of the axon. The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals. The myelin sheath decreases the resistance of the axonal membrane to the flow of charge. The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

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

In which type of axon will velocity of action potential conduction be the fastest? Unmyelinated axons of the shortest length Myelinated axons with the largest diameter Myelinated axons with the smallest diameters Unmyelinated axons with the largest diameter

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you? The inside surface of the plasma membrane is much more positively charged than the inside surface. The outside surface of the plasma membrane is much more negatively charged than the inside surface. There is no electrical potential difference between the inside and the outside surfaces of the plasma membrane. The inside surface of the plasma membrane is much more negatively charged than the outside surface.

The plasma membrane is much more permeable to K+ than to Na+. Why? The Na+-K+ pumps transport more K+ into cells than Na+ out of cells. Ligand-gated cation channels favor a greater influx of Na+ than K+. There are many more K+ leak channels than Na+ leak channels in the plasma membrane. There are many more voltage-gated K+ channels than voltage-gated Na+ channels

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors. The presence of concentration gradients and voltage-gated channels The presence of a resting membrane potential and leak channels The presence of concentration gradients and leak channels The presence of concentration gradients and Na+-K+ pumps

What prevents the Na+ and K+ gradients from dissipating? Na+-K+ ATPase H+-K+ ATPase Na+ and K+ leaks Na+ cotransporter

Which statement best characterizes a K+ leak channel? Trans-membrane channels that use energy to allow the movement of K+ across the membrane. Chemically gated K+ channels that open and close according to the binding of other molecules. Trans-membrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy. Common trans-membrane channels are always open for any ion to move through in the presence of K+.

The most likely RMP value of Na+ is __________. -90 mV -70 mV +70 mV +90 mV -50 mV

Imagine that the cell membrane from the previous problem becomes more permeable to Na+. Predict how this will affect the RMP. The RMP will be zero. The RMP will be more negative. The RMP will be unaffected. The RMP will be more positive

Complete the following sentence. The operation of the Na+−K+ ATPase pump __________. releases 3 K+ to the ECF releases 1 Na+ to the ECF and 1 K+ to the cytoplasm moves 3 Na+ to the ECF and 2 K+ to the cytoplasm moves 2 Na+ to the ECF and 3 K+ to the cytoplasm

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+ and K+ are the major determinants of RMP in this cell, which of the following could best explain your results? The cell is becoming depleted of Na+. The cell's K+ leak channels have stopped functioning. The cell is becoming depleted of K+. The cell's Na+−K+ ATPase pumps have stopped functioning. The cell's Na+ leak channels have stopped functioning.

Cl− is a common negatively charged extracellular ion. Predict the effect on the RMP if many Cl− gated channels are suddenly opened. The membrane would become hypopolarized or have less charge separation across the membrane. A more negative RMP would result. There would be no change in the RMP. The RMP would become more positive.

Following repolarization, the neuron may become slightly hyperpolarized before it re-establishes its resting membrane potential. Hyperpolarization is due to a difference between how the voltage-gated Na+ and K+ channels work. What is this difference? Voltage-gated Na+ channels stop the flow of Na+ relatively quickly, while voltage-gated K+ channels are slow to close, resulting in the overshoot. Voltage-gated K+ channels possess an inactivation gate that keeps them closed until repolarization is almost complete. Voltage-gated Na+ channels are responsible for depolarization, while voltage-gated K+ channels return K+ to their original location. Voltage-gated Na+ channels can open much faster than voltage-gated K+ channels.

Based on your knowledge of action potentials in neurons, what can you conclude about how they occur in cardiac muscle fibers? Cardiac muscle fibers repolarize much faster than neurons. The time frame of the action potential in cardiac muscle is much shorter than in neurons. Cardiac muscle fibers have the same resting membrane potential as neurons. Cardiac muscle fibers depolarize more quickly and spend more time depolarized than neurons do.

Which of the following is NOT a type of circuit? pre-discharge circuits diverging circuits converging circuits reverberating circuits

What type of stimulus is required for an action potential to be generated? hyperpolarization multiple stimuli a threshold level depolarization a suprathreshold stimulus

The __________ is due to the difference in K+ and Na+ concentrations on either side of the plasma membrane, and the difference in permeability of the membrane to these ions. dendrite potential resting membrane potential intermittent membrane potential active potential

When calcium ions enter the synaptic terminal, the inside of the receiving neuron becomes more positive. neurotransmitter molecules are quickly removed from the synaptic cleft. they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron. the inside of the receiving neuron becomes more negative. they cause an action potential in the sending neuron.

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron, ion channels in the plasma membrane of the sending neuron open. the receiving neuron becomes more positive inside. the receiving neuron becomes more negative inside. vesicles in the synaptic terminal fuse to the plasma membrane of the sending neuron. ion channels in the plasma membrane of the receiving neuron open.

If a signal from a sending neuron makes the receiving neuron more negative inside, the sending neuron becomes more positive inside. the receiving neuron is more likely to generate an action potential. the receiving neuron is less likely to generate an action potential. the receiving neuron immediately generates an action potential. the sending neuron becomes more negative inside.

Which of the following best characterizes depolarization? mass movement of Na+ into the axon cytoplasm from the cell body to the terminal small consecutive steps of Na+ penetration into the axon along its length small consecutive steps of Na+ exit from cytoplasm into extracellular fluid small consecutive steps of K+ entering the cytoplasm

When an action potential arrives at the end of the axon terminal, a series of events take place that result in the release of neurotransmitter from the presynaptic axon. Select the answer that correctly describes the primary stimulus for vesicles to move towards the cell membrane and eventually release their contents. axonal Ca+2 is increased because endoplasmic reticulum voltage-gated calcium channels open and Ca+2 enters the cytoplasm. voltage-gated channels open, and K+ exits to the extracellular fluid, decreasing intracellular K+. voltage-gated membrane channels open, and multiple types of ions enter the cytoplasm, increasing the intracellular positive charge voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium

Which statement best describes exocytosis? Membrane organelles fuse together and mix neurotransmitter. Sodium from the action potential fuses with the membrane vesicle and releases the neurotransmitter in the cytoplasm, which can then diffuse out to the extracellular fluid. Membrane organelles fuse with the membrane and release contents out of the cell. Membrane organelles fuse with the membrane and release contents inside the cell

What conditions will increase the diffusion of molecules, such as neurotransmitters? An increase in number of postsynaptic receptors. An increase in the amount of neurotransmitter exocytized by the presynaptic axon. An increase in the distance between the neurons. An increased viscosity of the fluid between neurons.

If the membrane of a postsynaptic dendrite is setting up a graded potential, what must have happened after neurotransmitter was released by the presynaptic terminal? The neurotransmitter: bound at postsynaptic receptors to open postsynaptic ion channels. was reabsorbed by the presynaptic membrane before it diffused away. was degraded by enzymes before arriving at the postsynaptic membrane. bound at postsynaptic receptors to initiate an action potential.

Select the correct statement regarding synapses. The synaptic cleft prevents an impulse from being transmitted directly from one neuron to another. Neurotransmitter receptors are located on the axons terminals of cells. The release of neurotransmitter molecules gives cells the property of being electrically coupled. Cells with gap junctions use chemical synapases.

What is the role of acetylcholinesterase? act as a transmitting agent stimulate the production of acetylcholine destroy ACh a brief period after its release by the axon endings amplify or enhance the effect of ACh