Chapter 8 Concept Check Questions Flashcards
Organize the following terms describing functional types of neurons into a map or outline: afferent, autonomic, brain, central, efferent, enteric, parasympathetic, peripheral, sensory, somatic motor, spinal, and sympathetic.
figure 8.1
Where do neurons that secrete neurohormones terminate?
Neurons that secrete neurohormones terminate close to blood vessels so that the neurohormones can enter the circulation.
What is the difference between a neuron and a nerve?
A neuron is a single nerve cell.
A nerve is a bundle of axons from many
Draw a chain of three neurons that synapse on one another in sequence. Label the presynaptic and postsynaptic ends of each neuron, the cell bodies, dendrites, axons, and axon terminals.
8.2 figure
Schwann Cells and Oligodendrocytes
Schwann cells in PNS and oligodendrocytes in the CNS support and insulate axons by forming myelin.
What is the primary function of each of the following: myelin, microglia, ependymal cells
Myelin insulates axon membranes.
Microglia are scavenger cells in the CNS.
Ependymal cells form epithelial barriers between fluid compartments of the CNS.
Name the two glial cell types that form myelin. How do they differ from each other?
Schwann cells are in the PNS and each Schwann cell forms myelin around a small portion of one axon. Oligodendrocytes are in the CNS, and one oligodendrocyte forms myelin around the axons of several neurons.
Given the values in Table 8.2, use the Nernst equation to calculate the equilibrium potential for
Express the concentrations as powers of 10 and use your knowledge of logarithms[p. A-38] to try the calculations without a calculator.
(61 *4) / (+2) = 122 mV
Would a cell with a resting membrane potential of -70 mV depolarize or hyperpolarize in the following cases? (You must consider both the concentration gradient and the electrical gradient of the ion to determine net ion movement.)
a. Cell becomes more permeable to Ca+2
b. Cell becomes less permeable to K+
a. depolarize
b. depolarize
Would the cell membrane depolarize or hyperpolarize if a small amount of Na+ leaked into the cell?
depolarize
Ohm’s law
current flow (I) is directly proportional to the electrical difference (in volts, V) between two points and inversely proportional to the resistance (R) of the system to current flow: I = V x 1 / R or
I = V / R
Match each ion’s movement with the type of graded potentialitcreates.
a. Na+ entry
b. Cl- entry
c. K+ exit
d. Ca+2 entry
- depolarizing
- hyperpolarizing
a. depolarizing
b. hyperpolarizing
c. hyperpolarizing
d. depolarizing
Identify the trigger zones illustrated in figure 8.2 if possible
look at figure 8.2
Trigger zone
Graded potentials that are strong enough eventually reach the region of the neuron known as the ___________.
What is the difference between conductance and conduction in neurons?
Conductance refers to the movement of ions across a cell membrane.
Conduction is the rapid, undiminished movement of an electrical signal down the axon of a neuron.
If you put ouabain, an inhibitor of the
pump, on a neuron and then stimulate the neuron repeatedly, what do you expect to happen to action potentials generated by that neuron?
There is no immediate effect, but they diminish with repeated stimulation and eventually disappear
The pyrethrin insecticides, derived from chrysanthemums, disable inactivation gates of channels so that the channels remain open. In neurons poisoned with pyrethrins, what happens to the membrane potential? Explain your answer.
The membrane potential depolarizes and stays depolarized
When Na+ channel gates are resetting, is the activation gate opening or closing? Is the inactivation gate opening or closing?
During resetting, the activation gate is closing, and the inactivation gate is opening
If you place an electrode in the middle of an axon and artificially depolarize the cell above the threshold, in which direction will an action potential travel:
The action potential will go in both directions because the Na+ channels around the stimulation site have not been inactivated by a previous depolarization.
Place the following neurons in order of their speed of conduction, from fastest to slowest:
(a) myelinated axon, diameter 20@mm
(b) unmyelinated axon, diameter 20@mm
(c) unmyelinated axon, diameter 200@mm
(a), (c), (b)
Hypokalemia
If blood K+ concentration falls too low – a condition known as hypokalemia – the resting membrane potential of cells hyperpolarizes, moving farther from the threshold.
When pharmaceutical companies design drugs, they try to make a given drug as specific as possible for the particular receptor subtype they are targeting. For example, a drug might target adrenergic b1-receptors rather than all adrenergic a- and b-receptors. What is the advantage of this specificity?
Because different receptor subtypes work through different signal transduction pathways, targeting drugs to specific receptor subtypes decreases the likelihood of unwanted side effects.
Which organelles are needed to synthesize proteins and package them into vesicles?
Proteins are synthesized on the ribosomes of the rough endoplasmic reticulum; then the proteins are directed into the Golgi apparatus to be packaged into vesicles.
What is the function of mitochondria in a cell?
Mitochondria are the primary sites of ATP synthesis.
How do mitochondria get to the axon terminals?
Mitochondria reach the axon terminal by fast axonal transport along microtubules
One class of antidepressant drugs is called selective serotonin reuptake inhibitors (SSRIs). What do these drugs do to serotonin activity at the synapse?
SSRIs decrease reuptake of serotonin into the axon terminal, thereby increasing the time serotonin is active in the synapse
How does the axon terminal make acetyl CoA for acetylcholine synthesis?(Hint: see p. 107.)
Acetyl CoA is made from pyruvate, the end product of glycolysis, and CoA.
Is Na+-dependent neurotransmitter reuptake facilitated diffusion, primary active transport, or secondary active transport? Explain your reasoning.
Neurotransmitter uptake is secondary active transport because it uses energy stored in the Na+ concentration gradient to concentrate neurotransmitters inside the axon terminal.
In Figure 8.24e, assume the postsynaptic neuron has a resting membrane potential of -70 mV and a of -55 mV. If the inhibitory presynaptic neuron creates an IPSP of -5 mV and the two excitatory presynaptic neurons have EPSPs of 10 and 12 mV, will the postsynaptic neuron fire an action potential?
The postsynaptic neuron will fire an action potential because the net effect would be a 17 mV depolarization to -70 - (-17) = -53 mV, which is just above the threshold of -55 mV.
In the graphs of Figure 8.24a, b, why doesn’t the membrane potential change at the same time as the stimulus?
The membrane potential does not change at the same time as the stimulus because the depolarization must travel from the point of
the stimulus to the recording point.
Why are axon terminals sometimes called “biological transducers”?
Axon terminals convert (transduce) the electrical action potential signal into a chemical neurotransmitter signal.
Why would depolarization of the membrane drive
Mg 2+ from the channel into the extracellular fluid?
Membrane depolarization makes the inside of the membrane more positive than the outside. Like charges repel one another, so the more positive membrane potential tends to repel Mg2 +.
