Campbell Biology Chapters 48/49

For the following question, refer to the graph of an action potential. The minimum graded depolarization needed to operate the voltage-gated sodium channels is indicated by the label A. B. C. D. E.

A.

For the following question, refer to the graph of an action potential. The membrane's permeability to sodium ions is at its maximum at label A. B. C. D. E.

B.

The figure shows an action potential triggered by a depolarization that reaches the threshold. The diagram shows the membrane potential as a function of time. The membrane potential is measured from minus 100 to 100 millivolts on the y-axis, while the time is measured from 0 to 6 milliseconds on the x-axis. The resting potential is minus 70 millivolts. The curve of the action potential goes up from minus 70 millivolts at 0 milliseconds to minus 55 millivolts at 2.5 milliseconds. The level of minus 55 millivolts is a threshold level. Then the curve goes up to 35 millivolts at 3.5 milliseconds. This peak is labeled as the action potential. Finally, the curve goes down to minus 75 millivolts at 5 milliseconds and then returns to the level of minus 70 millivolts. A Strong depolarizing stimulus is a part of diagram from 0 milliseconds to 3 milliseconds. Why is an action potential an all-or-none response to stimuli? Because a typical neuron receives signals through multiple dendrites but transmits signals through a single axon Because voltage-gated ion channels open when membrane potential passes a particular level Because neurons contain gated ion channels that are either open or closed

Because voltage-gated ion channels open when membrane potential passes a particular level

For the following question, refer to the graph of an action potential. The cell is not hyperpolarized; however, repolarization is in progress, as the sodium channels are closing or closed, and many potassium channels have opened at label A. B. C. D. E.

C.

For the following question, refer to the graph of an action potential. The neuronal membrane is at its resting potential at label A. B. C. D. E.

E.

The figure shows an action potential triggered by a depolarization that reaches the threshold. The diagram shows the membrane potential as a function of time. The membrane potential is measured from minus 100 to 100 millivolts on the y-axis, while the time is measured from 0 to 6 milliseconds on the x-axis. The resting potential is minus 70 millivolts. The curve of the action potential goes up from minus 70 millivolts at 0 milliseconds to minus 55 millivolts at 2.5 milliseconds. The level of minus 55 millivolts is a threshold level. Then the curve goes up to 35 millivolts at 3.5 milliseconds. This peak is labeled as the action potential. Finally, the curve goes down to minus 75 millivolts at 5 milliseconds and then returns to the level of minus 70 millivolts. A Strong depolarizing stimulus is a part of diagram from 0 milliseconds to 3 milliseconds. What causes the falling phase of the action potential? Select the best answer. Inactivation of voltage-gated sodium channels and the opening of voltage-gated potassium channels The opening of voltage-gated potassium channels The opening of voltage-gated sodium channels

Inactivation of voltage-gated sodium channels and the opening of voltage-gated potassium channels

A cation that is more abundant as a solute in the cytosol of a neuron than it is in the interstitial fluid outside the neuron is Cl-. HCO3 -. Ca2+. K+. Na+.

K+.

The plasma membrane of a neuron has voltage-gated sodium and potassium channels. What is the effect of membrane depolarization on these channels? Membrane depolarization first opens sodium channels and then opens potassium channels. Membrane depolarization opens sodium channels but closes potassium channels. Membrane depolarization opens sodium and potassium channels at the same time.

Membrane depolarization first opens sodium channels and then opens potassium channels.

ATP hydrolysis directly powers the movement of

Na+ out of cells.

Select all that apply. Potassium (K+) and sodium (Na+) gradients are maintained by active transport in a resting mammalian neuron. Neurons are the only cells that have a charge difference across their membranes. Concentration gradients of potassium (K+) and sodium (Na+) across the plasma membrane represent potential energy.

Potassium (K+) and sodium (Na+) gradients are maintained by active transport in a resting mammalian neuron. Concentration gradients of potassium (K+) and sodium (Na+) across the plasma membrane represent potential energy.

At the neuromuscular junction, the arrival of acetylcholine on the muscle most immediately causes _____. an inhibitory postsynaptic potential a single action potential a graded hyperpolarization the release of second messengers, such as cAMP a graded depolarization

a graded depolarization

If the membrane potential of a neuron decreases, the membrane potential _____. becomes less negative. remains unchanged. becomes more negative.

becomes less negative.

Acetylcholine receptors on skeletal muscles are described as being "ionotropic" receptors because _____. binding of acetylcholine to the receptor protein converts the protein to an open ion channel binding of acetylcholine to its receptor triggers release of a second messenger, e.g., cAMP, inside the muscle acetylcholine is an excitatory stimulus to the muscle these receptors have a corequisite binding of magnesium ions in order to function the receptors ionize as a result of binding acetylcholine, and this directly alters membrane potentials

binding of acetylcholine to the receptor protein converts the protein to an open ion channel

The simultaneous arrival of graded depolarization and a graded hyperpolarization of equal but opposite magnitude at a particular location on the dendritic membrane is likely to _____. cause depolarization, because graded depolarizations are more important to neuron function cancel each other out, making it appear as if there was no change in membrane potential cause hyperpolarization, because graded hyperpolarizations are more important to neuron function cause the apoptosis of the neuron allow only the entry of sodium ions into the neuron, and prevent potassium ions from exiting the neuron

cancel each other out, making it appear as if there was no change in membrane potential

The nucleus and most of the organelles in a neuron are located in the dendritic region. axon terminals. cell body. axon. axon hillock.

cell body.

The coordination of groups of skeletal muscles is driven by activity in the cerebrum. thalamus. hypothalamus. cerebellum. medulla oblongata.

cerebellum.

As vertebrates evolved, the increasingly complex structure of the brain conferred increasingly complex function, especially apparent in the _____. brainstem, which in most vertebrates, controls homeostasis and basic bodily function forebrain, which is a small brain region that arises early in development medulla oblongata, which controls automatic functions sleep-wake cycles of birds and mammals cerebral cortex, which is greatly expanded in humans, other primates, and cetaceans

cerebral cortex, which is greatly expanded in humans, other primates, and cetaceans

Calculation, contemplation, and cognition are human activities associated with increased activity in the cerebellum. spinal cord. pituitary gland. hypothalamus. cerebrum.

cerebrum.

The "information receiving" section of a neuron is its _____. Schwann cells axon terminal dendrites glia

dendrites

Of these choices, neuronal communication between the brain and the muscles of the leg is best conceptualized as _____. the transcription of genes electrical signaling electrical and chemical signaling the transcription and translation of genes chemical signaling

electrical and chemical signaling

Neurotransmitters are released from axon terminals via diffusion. transcytosis. osmosis. exocytosis. active transport.

exocytosis.

Neurotransmitters categorized as inhibitory are expected to open sodium channels. close chloride channels. close potassium channels. hyperpolarize the membrane. act independently of their receptor proteins.

hyperpolarize the membrane.

Central coordination of vertebrate biological rhythms in physiology and behavior reside in the cerebrum. cerebellum. pituitary gland. thalamus. hypothalamus.

hypothalamus

A simple nervous system includes a minimum of 12 effector neurons. has information flow in only one direction: toward an integrating center. has information flow in only one direction: away from an integrating center. must include chemical senses, mechanoreception, and vision. includes sensory information, an integrating center, and effectors.

includes sensory information, an integrating center, and effectors.

Most of the neurons in the human brain are sensory neurons. motor neurons. auditory neurons. interneurons. peripheral neurons.

interneurons.

The "threshold" potential of a membrane is the lowest frequency of action potentials a neuron can produce. is the peak amount of depolarization seen in an action potential. is the minimum depolarization needed to operate the voltage-gated sodium and potassium channels. is the minimum hyperpolarization needed to prevent the occurrence of action potentials. is the point of separation from a living to a dead neuron.

is the minimum depolarization needed to operate the voltage-gated sodium and potassium channels.

The activity of acetylcholine in a synapse is terminated by its diffusion across the presynaptic membrane. its active transport across the presynaptic membrane. its diffusion across the postsynaptic membrane. its degradation by a hydrolytic enzyme on the postsynaptic membrane. its active transport across the postsynaptic membrane.

its degradation by a hydrolytic enzyme on the postsynaptic membrane.

Saltatory conduction is a term applied to an action potential that skips the axon hillock in moving from the dendritic region to the axon terminal. jumping from one neuron to an adjacent neuron. jumping from one node of Ranvier to the next in a myelinated neuron. conduction of impulses across electrical synapses. rapid movement of an action potential reverberating back and forth along a neuron.

jumping from one node of Ranvier to the next in a myelinated neuron.

Emotion, motivation, olfaction, behavior, and memory, in humans, are mediated by the _____. temporal lobes of the cerebral cortex limbic system frontal lobe of the cerebral cortex occipital lobes of the cerebral cortex cerebellum

limbic system

The unconscious control of respiration and circulation are associated with the cerebellum. thalamus. cerebrum. medulla oblongata. corpus callosum.

medulla oblongata.

Action potentials move along axons more slowly in axons of large than in small diameter. by reversing the concentration gradients for sodium and potassium ions. by activating the sodium-potassium "pump" at each point along the axonal membrane. more rapidly in myelinated than in non-myelinated axons. by the direct action of acetylcholine on the axonal membrane.

more rapidly in myelinated than in non-myelinated axons.

The fundamental excitable cell in the nervous system is the _____. dendrite cell body neuron axon nephron

neuron

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels open and close depending on chemical messengers, and are nonspecific as to which ion can traverse them. open and close depending on stimuli, and are specific as to which ion can traverse them. are always closed, but ions move closer to the channels during excitation. are always open, but the concentration gradients of ions frequently change. open in response to stimuli, and then close simultaneously, in unison.

open and close depending on stimuli, and are specific as to which ion can traverse them.

The "selectivity" of a particular ion channel refers to its ability to change its size depending on the ion needing transport. permitting passage only to a specific ion. permitting passage by negative but not positive ions. permitting passage by positive but not negative ions. binding with only one type of neurotransmitter.

permitting passage only to a specific ion.

Choose the set that includes the most charged compounds that are more abundant inside neurons, in the cytosol, than outside the neurons, in the extracellular fluid. chloride ions and proteins sodium and potassium ions sodium and chloride ions potassium ions and proteins proteins and sodium ions

potassium ions and proteins

An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to sodium ions. potassium ions. all neurotransmitter molecules. ATP. calcium ions.

potassium ions.

The surface on a neuron that discharges the contents of synaptic vesicles is the postsynaptic membrane. presynaptic membrane. axon hillock. node of Ranvier. dendrite.

presynaptic membrane.

A nerve poison that blocks acetylcholine receptors on dendrites would _____. reduce the binding of acetylcholine to its receptors on the postsynpatic membrane inhibit the regeneration of acetylcholine for use by the presynaptic terminals cause continued stimulation of the postsynaptic membrane inactivate acetylcholinesterase, allowing acetylcholine to persist in the synapse cause an immediate and enduring depolarization

reduce the binding of acetylcholine to its receptors on the postsynpatic membrane

Immediately after an action potential passes along an axon, it is not possible to generate a second action potential; thus, we state that the membrane is briefly hyperexcitable. fully depolarized. above threshold. at the equilibrium potential. refractory.

refractory.

Although the membrane of a "resting" neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also highly permeable to chloride ions. slightly permeable to sodium ions. fully permeable to calcium ions. fully permeable to sodium ions. impermeable to sodium ions.

slightly permeable to sodium ions.

The operation of the sodium-potassium "pump" moves sodium ions out of the cell and potassium ions into the cell. sodium ions into the cell and potassium ions out of the cell. sodium and potassium ions into the mitochondria. sodium and potassium ions out of the cell. sodium and potassium ions into the cell.

sodium ions out of the cell and potassium ions into the cell.

In a neuron, during the depolarization phase that may trigger an action potential _____. most voltage-gated sodium channels are open most voltage-gated sodium channels become inactivated most voltage-gated potassium channels are open some voltage-gated sodium channels are open most voltage-gated sodium and potassium channels are open

some voltage-gated sodium channels are open

When several EPSPs arrive at the axon hillock from different dendritic locations, depolarizing the postsynaptic cell to threshold for an action potential, this is an example of tetanus. temporal summation. spatial summation. an action potential with an abnormally high peak of depolarization. the refractory state.

spatial summation.

The "undershoot" phase of after-hyperpolarization is due to rapid opening of voltage-gated calcium channels. slow restorative actions of the sodium-potassium ATPase. slow opening of voltage-gated sodium channels. ions that move away from their open ion channels. sustained opening of voltage-gated potassium channels.

sustained opening of voltage-gated potassium channels.

When several IPSPs arrive at the axon hillock rapidly in sequence from a single dendritic location, hyperpolarizing the postsynaptic cell more and more and thus preventing an action potential, this is an example of spatial summation. tetanus. the refractory state. temporal summation. an action potential with an abnormally high peak of depolarization.

temporal summation.

In a simple synapse, neurotransmitter chemicals are received by the dendritic membrane. axon hillocks. the presynaptic membrane. cell bodies. ducts on the smooth endoplasmic reticulum.

the dendritic membrane.

After the depolarization phase of an action potential, the resting potential is restored by a decrease in the membrane's permeability to potassium and chloride ions. the opening of sodium activation gates. the opening of more voltage-gated sodium channels. the opening of voltage-gated potassium channels and the closing of sodium channels. a brief inhibition of the sodium-potassium pump.

the opening of voltage-gated potassium channels and the closing of sodium channels.

In a simple synapse, neurotransmitter chemicals are released by the presynaptic membrane. ducts on the smooth endoplasmic reticulum. axon hillocks. the dendritic membrane. cell bodies.

the presynaptic membrane.

The point of connection between two communicating neurons is called the cell body. the dendrite. the glia. the axon hillock. the synapse.

the synapse.

Ions move in the direction opposite to that favored by the chemical concentration gradient when _____. proteins leak out of a neuron simple diffusion operates after active transport has been permanently halted by being poisoned potassium ions exit the neuron during the repolarization phase of an action potential they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them sodium ions enter a neuron during the depolarization phase of an action potential

they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them

Select the choice that describes neurons with the fastest conduction velocity for action potentials. thin, myelinated neurons thin, nonmyelinated neurons thick, nonmyelinated neurons thick, myelinated neurons All of these choices conduct action potentials at the same velocity.

thick, myelinated neurons

The fastest possible conduction velocity of action potentials is observed in thick, myelinated neurons. thin, non-myelinated neurons. thin, myelinated neurons. thick, non-myelinated neurons.

thick, myelinated neurons.

Action potentials are normally carried in only one direction: from the axon hillock toward the axon terminals. If you experimentally depolarize the middle of the axon to threshold, using an electronic probe, then no action potential will be initiated. an action potential will be initiated and proceed only in the normal direction toward the axon terminal. two action potentials will be initiated, one going toward the axon terminal and one going back toward the hillock. an action potential will be initiated and proceed only back toward the axon hillock. an action potential will be initiated, but it will die out before it reaches the axon terminal.

two action potentials will be initiated, one going toward the axon terminal and one going back toward the hillock.