BIO 191 CH 37 HW

What is the lowest concentration of morphine that blocked naloxone binding, in standard notation? 0.000000006 M 0.00000002 M 0.000006 M 0.000009 M

0.000000006 M 10-9 is 0.000000001, so 6 × 10-9 M is 0.000000006 M.

Answer questions 1-4 by selecting only from the three answer choices to the left of each question. Drag the correct answer to the right of each question.

1) In what direction will the K+ ions move through the artificial channel? OUT OF THE CELL 2) Does the K+ concentration gradient promote or impede the movement of K+ ions through the artificial channel? PROMOTE 3) Does the membrane potential promote or impede the movement of K+ ions through the artificial channel? IMPEDE 4) How does the movement of K+ ions through the artificial channel affect the membrane potential? CAUSES A HYPERPOLARIZATION At resting potential, the pumping of K+ ions into the cell by the sodium-potassium pump is balanced by the movement of K+ ions out of the cell through non-gated K+ channels. If an artificial K+ channel is inserted into the membrane at resting potential, K+ ions will also move out of the cell through that channel. The K+ ions moving through the artificial channel move along their concentration gradient, but against the membrane potential. The K+ movement further decreases the positive charge inside the cell, so the membrane potential becomes more negative (hyperpolarization).

Match the letter of each location along the axon with the correct description of what is occurring at that position.

1. At location (C), the membrane potential changes sign (from a positive value to a negative value) and the voltage-gated K+ channels are open. 2. At location (F), the axon membrane reaches threshold and the voltage-gated Na+ channels open. 3. At location (A), the voltage-gated Na+ channels reactivate. 4. At location (D), the voltage-gated Na+ channels are inactivating and the voltage-gated K+ channels are opening. 5. At location (G), the axon membrane is at resting potential. 6. At location (B), the voltage-gated K+ channels are closing. 7. At location (E), the membrane potential changes sign (from a negative value to a positive value) and the voltage-gated Na+ channels are open. As an action potential moves along an axon, one location reaches the rising phase of the action potential, while a nearby location reaches the peak, while another location reaches the falling phase, and so on. You can use the familiar graph of an action potential to pinpoint the stage of the action potential occurring at various locations on the axon as the action potential moves along. For example, at location (f), the action potential has just started—the membrane has reached threshold and the voltage-gated Na+ channels open. At location (d), the action potential is at its peak—the voltage-gated Na+ channels inactivate and the voltage-gated K+ channels open.

Which statement correctly describes what causes the second voltage-gated Na+ channel to open? As Na+ ions enter the cell through the first channel, they spread out from the channel. When these Na+ ions reach the second channel, it opens. As Na+ ions enter the cell through the first channel, Na+ ions outside the cell move toward the open Na+ channel. When the concentration of Na+ ions near the second channel becomes low enough, the second channel opens. After the first channel opens, the movement of Na+ ions (both inside and outside the cell) alters the Na+ ion distribution across the membrane near the second channel, causing it to open. After the first channel opens, the movement of many types of ions (both inside and outside the cell) alters the distribution of charges near the second channel, causing it to open.

After the first channel opens, the movement of many types of ions (both inside and outside the cell) alters the distribution of charges near the second channel, causing it to open. When Na+ ions enter the cell through the first channel, the charge distribution across the membrane changes. Inside the cell, the increase in Na+ ions near the first channel makes that region more positive; as a result, negative ions are attracted to the region, while positive ions are repelled. Conversely, outside of the cell, the loss of Na+ ions makes the region near the first channel more negative; as a result, positive ions are attracted to that region, while negative ions are repelled. Together, all of these ion movements alter the charge (and thus the membrane potential) at the neighboring channel, allowing it to reach threshold.

Would phenobarbital, atropine, or serotonin have blocked naloxone binding at a concentration of 10-5 M? Phenobarbital would have blocked naloxone binding at 10-5 M, but atropine and serotonin would not have. It is impossible to tell from the data. All of these drugs would have blocked naloxone binding at 10-5 M. None of these drugs would have blocked naloxone binding at 10-5 M.

None of these drugs would have blocked naloxone binding at 10-5 M. None of these drugs had an effect at a concentration of 10-4 M, which is higher than 10-5 M. If they had no effect at the higher concentration, they would certainly not have had an effect at the lower concentration.

Compare the concentrations for methadone (2 × 10-8 M) and phenobarbital (10-4 M). Which concentration is higher and by how much? Phenobarbital's concentration is 500 times higher. Phenobarbital's concentration is 2,000 times higher. Methadone's concentration 20,000 times higher. Phenobarbital's concentration is 5,000 times higher.

Phenobarbital's concentration is 5,000 times higher. The concentration of phenobarbital is 10-4 M, whereas the concentration of methadone is 2 × 10-8 M. The concentration of phenobarbital is higher by 10-4/(2 × 10-8) = 5 × 103 or 5,000 times.

What type of cell makes up the myelin sheath of a motor neuron? astrocytes microglial cells Ranvier cells ependymal cells Schwann cells

Schwann cells Myelin sheaths are formed when Schwann cells wrap around the axons of motor neurons.

There are two properties that affect the conduction speed of an action potential along an axon: the axon's diameter and whether or not the axon is myelinated. Rank the axons from slowest to fastest conduction speed. If two axons have the same conduction speed, place one on top of the other.

Slowest non-myelinated invertebrate axon (20um diatmeter) non-myelinated invertebrate axon (30um diameter) non-myelinated invertebrate axon (40um diameter) Myelinated vertebrate axon (30um diameter) Fastest For non-myelinated axons, the larger the diameter of the axon, the faster the conduction speed of an action potential. However, even the smallest myelinated axons are much faster than the largest non-myelinated axons (the squid axon, for example).

When the researchers repeated the experiment using tissue from mammalian intestinal muscles rather than brains, they found no naloxone binding. What does this result suggest about opiate receptors in mammalian intestinal muscle tissue? There are no naloxone receptors in mammalian intestinal muscle tissue, but there are opiate receptors. There are no opiate receptors in mammalian intestinal muscle tissue. There are opiate receptors in mammalian intestinal muscle tissue. There may be opiate receptors in mammalian intestinal muscle tissue. Further experiments are needed to be sure.

There are no opiate receptors in mammalian intestinal muscle tissue.

Morphine, methadone, and levorphanol blocked naloxone binding in this experiment. What do these results indicate about the brain receptors for naloxone? They are specific for both opiate and non-opiate drugs. They are specific for opiate drugs. They are specific for the non-opiate drugs used in the experiment. They are specific for morphine.

They are specific for opiate drugs. The three opiates blocked naloxone binding, whereas the three non-opiates did not block naloxone binding. These results indicate that the receptors for naloxone are specific for opiates.

Drag the appropriate labels onto the graph to indicate the status (open or closed) of the voltage-gated Na+ and K+ channels during each phase of an action potential. Labels may be used once, more than once, or not at all.

a. Na+ channels closed K+ channels closed b.Na+ channels open K+ channels closed c. Na+ channels closed K+ channels open d. Na+ channels closed K+ channels open e. Na+ channels closed K+ channels closed During the rising phase, the membrane potential becomes less negative because voltage-gated Na+ channels are open and Na+ ions enter the cell. During the falling and undershoot phases, the membrane potential becomes more negative because voltage-gated K+ channels are open (while voltage-gated Na+ channels are closed) and K+ ions leave the cell. At resting potential, both types of voltage-gated channels are closed and no ions move through the voltage-gated channels.

Drag the labels to their appropriate locations on the diagram of the neurons below. Use only the pink labels for the pink targets (which indicate the locations of gated ion channels).

a. cell body b. myelin sheath c. synaptic terminal d. axon hillock e. nucleus f. location of voltage-gated channels g. location of ligand-gated channels h. axon i. dendrite The structures of a neuron play specific roles in receiving information from one cell, generating and propagating an action potential (sometimes over very long distances), and then passing the information along to another cell.

The diagram below shows the five main transport proteins that control the distribution of Na+ and K+ ions across the plasma membrane of an axon. Assume that the membrane is at resting potential---the membrane potential of the axon remains constant at about -70 mV. Drag the arrows onto the diagram to show the direction of Na+ (gray arrows) and K+ (red arrows) movement through each transport protein at resting potential. If no ions move through a transport protein at resting potential, leave that target blank.

a. voltage-gated Na+ channel blank b. voltage-gated K+ channel blank c. sodium-potassium pump Na+ out, K+ in d. non-gated K+ channel K+ out e.non-gated Na+ channel Na+ in At resting potential, the membrane potential remains constant at about -70 mV. This means that there is no net movement of ions across the membrane. Assuming that Na+ and K+ are the only ions that move at resting potential, Na+ movement out of the cell through the sodium-potassium pump is balanced by an influx of Na+ through the non-gated Na+ channels. Conversely, K+ movement into the cell through the sodium-potassium pump is balanced by an outward movement of K+ through the non-gated K+ channels.

A nerve impulse moves away from a neuron's cell body along _____. dendrites Nissl bodies synapses axon glia

axon Axons conduct a nerve impulse away from the cell body.

Enter the sequence in which the action potential would pass through the points. Enter the letters in the correct order separated by commas. For example if the order is point (c), then (b), then (a), enter c, b, a. If the action potential would not pass though a point, do not include that point in your answer.

b,a,c Under the artificial conditions, the axon membrane is initially at resting potential everywhere except at the location indicated by the red arrow (where the membrane is artificially brought to threshold). Voltage-gated Na+ channels at that location open and Na+ ions rush into the cell. The depolarization caused by this influx of Na+ ions is "felt" both to the right and left of the open channels. Voltage-gated Na+ channels on both sides open, resulting in an action potential that moves in both directions. It reaches nearby locations (on both sides) first, then locations farther away.

A neuron's nucleus is located in its _____. cell body axon myelin sheath dendrite synaptic terminals

cell body The cell body is the region of a neuron where the nucleus is found.

A nerve impulse moves toward a neuron's cell body along _____. dendrites synaptic terminals oligodendrocytes axons nodes of Ranvier

dendrites Dendrites conduct an impulse from a synapse toward the cell body.

Which of the following characteristics determines when the refractory period ends? View Available Hint(s) how low the membrane potential drops below resting potential during the undershoot phase how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential how long it takes for the voltage-gated Na+ channels to close at the end of an action potential how long it takes for the membrane potential to return to resting potential after the undershoot phase how long it takes for the voltage-gated K+ channels to close during the undershoot phase

how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential During the refractory period, an action potential cannot be triggered even if the membrane potential reaches threshold because the voltage-gated Na+ channels are inactive. The Na+ channels must reactivate before Na+ ions can move into the cell again, and the rising phase of the second action potential can begin. In this way, the refractory period determines how closely one action potential can follow another.

Drag the labels onto the flowchart to show the sequence of events that occurs once the membrane potential reaches threshold. You may use a label once or not at all.

membrane potential reaches threshold a. many voltage-gated Na+ channels open b. Na+ ions rush into the cell c. membrane potential rises (depolarizes) rapidly Once the membrane potential reaches threshold, the voltage-gated Na+ channels open and the Na+ ions move into the cell (moving down their electrochemical gradient). This influx of positive ions makes the inside of the cell less negative compared to the outside, and the membrane potential rises (depolarizes) rapidly.

Which drugs blocked naloxone binding in this experiment? morphine, methadone, levorphanol, phenobarbital, atropine, and serotonin morphine, methadone, and serotonin only morphine, methadone, and levorphanol only morphine and methadone only

morphine, methadone, and levorphanol only

Axons insulated by a(n) _____ are able to conduct impulses faster than those not so insulated. node of Ranvier synaptic terminal myelin sheath layer of asbestos astrocytes

myelin sheath Myelin sheaths, formed when Schwann cells wrap around an axon, allow such neurons to conduct impulses more rapidly than unmyelinated axons.

What result did the researchers obtain for atropine, in standard notation? no effect at 0.0001 M no effect at 0.0004 M no effect at 0.001 M no effect at 10,000 M

no effect at 0.0001 M 10-4 is 0.0001.

An impulse relayed along a myelinated axon "jumps" from _____ to _____. oligodendrocyte ... Schwann cell node of Ranvier ... Schwann cell node of Ranvier ... node of Ranvier Schwann cell ... Schwann cell Schwann cell ... node of Ranvier

node of Ranvier ... node of Ranvier In myelinated neurons the impulse jumps from node of Ranvier to node of Ranvier.

What part of a neuron relays signals from one neuron to another neuron or to an effector? dendrite axon hillock synaptic terminal axon node of Ranvier

synaptic terminal Synaptic terminals contain neurotransmitter molecules that relay the nerve impulse across a synapse.