Download Neuron Physiology: Resting Membrane Potential and Action Potential Exercises and more Exams Advanced Education in PDF only on Docsity!
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A resting neuron is an unstimulated neuron that is not presently generating an action potential. The resting membrane potential is the separation of the relative positive and negative charges across the membrane of a cell at rest. Drag the charges to the correct side of the membrane to represent the resting membrane potential of a typical neuron. - correct answer The separation of charges creates a voltage (electrical potential difference), which can be measured using a voltmeter. The resting membrane potential of a neuron averages -70mV (millivolts). All neural activities begin with a change in the resting membrane potential of a neuron. The resting membrane potential is dependent upon two important factors: 1) differences in sodium and potassium concentrations across the membrane (electrochemical gradients) and 2) differences in sodium and potassium membrane permeability. This activity will help you to review how the resting membrane potential of cells are generated and maintained. Use the provided ions to correctly complete each sentence about the resting membrane potential. Ions may be used more than once, or not at all. - correct answer All living cells have a membrane potential that varies depending on its cellular activities. Drag and drop the correct concentrations and the direction of the concentration gradient in a cell at RMP. Answers may be used more than once or not at all. The appropriate arrow should be placed on the plasma membrane—the targets appear on either side of the pumps. - correct answer The Na+ concentration is higher outside of the cell, while the concentration of K+ is higher inside the cell. Which choice best characterizes K+ leakage channels? - correct answer transmembrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy Assume you have a membrane with only potassium leakage channels. The RMP is - 90mV. Predict the RMP if we add Na+ leakage channels.The most likely RMP value of Na+ is __________. - correct answer -70 mV
Imagine that the cell membrane from the previous problem becomes more permeable to Na+. Predict how this will affect the RMP. - correct answer The RMP will be more positive. Complete the following sentence. The operation of the Na+−K+ ATPase pump __________. - correct answer moves 3 Na+ to the ECF and 2 K+ to the cytoplasm -The pumps move more Na+ than K+, which counteracts the effect of the membrane's being more permeable to K+ (more K+ leak channels than Na+). 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? - correct answer The cell's Na+-K+ ATPase pumps have stopped functioning. -Yes! Since the RMP eventually becomes zero, the concentration of ions on either side of the membrane would be roughly equal. Without active processes to maintain concentration gradients, we would expect the concentration of ions on either side of the membrane to equilibrate. Cl− is a common, negatively charged extracellular ion. Predict the effect on the RMP if many Cl− gated channels are suddenly opened - correct answer A more negative RMP would result. -Correct! Cl− is negatively charged and has a higher concentration in the ECF. The opening of Cl− channels would allow more negative charge to attempt to enter the cytoplasm. If the cell's normal RMP were -70mV, it would now become more negative. The farther away the RMP is from zero, either in the positive or in the negative direction, the greater the separation of charges is. This is called hyperpolarization. When the RMP moves closer to 0 mV, depolarization occurs.Congratulations! You've successfully examined the construction of the resting membrane potential, an important concept in any human cell. The small space between the sending neuron and the receiving neuron is the - correct answer Synaptic Cleft -The synaptic cleft is the small space between the sending neuron and the receiving neuron.
An action potential is self-regenerating because __________. - correct answer depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment -Yes! The Na+ diffusing into the axon during the first phase of the action potential creates a depolarizing current that brings the next segment, or node, of the axon to threshold. Why does regeneration of the action potential occur in one direction, rather than in two directions? - correct answer The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential. -Yes! At the peak of the depolarization phase of the action potential, the inactivation gates close. Thus, the voltage-gated Na+ channels become absolutely refractory to another depolarizing stimulus. What is the function of the myelin sheath? - correct answer The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals. -Yes! The myelin sheath increases the velocity of conduction by two mechanisms. First, myelin insulates the axon, reducing the loss of depolarizing current across the plasma membrane. Second, the myelin insulation allows the voltage across the membrane to change much faster. Because of these two mechanisms, regeneration only needs to happen at the widely spaced nodes of Ranvier, so the action potential appears to jump. What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization? - correct answer Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open. -Yes! Closing of voltage-gated channels is time dependent. Typically, the inactivation gates of voltage-gated Na+ channels close about a millisecond after the activation gates open. At the same time, the activation gates of voltage-gated K+ channels open. In which type of axon will velocity of action potential conduction be the fastest? - correct answer Myelinated axons with the largest diameter -Yes! The large diameter facilitates the flow of depolarizing current through the cytoplasm. The myelin sheath insulates the axons and prevents current from leaking across the plasma membrane.
Yes! The large diameter facilitates the flow of depolarizing current through the cytoplasm. The myelin sheath insulates the axons and prevents current from leaking across the plasma membrane. - correct answer anterograde transport -This transport mechanism defines movement of material from the cell body (soma) of a neuron toward the axon terminals (synaptic knobs). In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________. - correct answer oligodendrocyte -Oligodendrocytes are a type of neuroglial cell that function to form the myelin sheath around the axons of neurons within the central nervous system. These are the glial cells targeted by the immune system in people who have MS. Part complete The concentrations of which two ions are highest outside the cell? - correct answer Na+ and Cl− Let's consider a scenario in which the resting membrane potential changes from −70 mV to +70 mV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+. The electrical gradient for Na+ would tend to move Na+ __________ while the chemical gradient for Na+ would tend to move Na+ __________. - correct answer out; in =If the inside of the cell is positively charged compared to the outside, the electrical gradient will favor movement of positively charged sodium ions out of the cell. Drag the resting membrane determinants to their appropriate locations in the figure. Answers may be used once, or not at all. Drag the appropriate labels to their targets. Note that pink labels should go in pink targets, blue labels should go in blue targets, and green labels should go in green targets. - correct answer For each of the following, indicate whether the condition will cause the membrane potential to become more positive, more negative, or largely unchanged when compared to the normal physiological resting membrane potential. Drag the appropriate items to their respective bins. - correct answer
People who have hydrocephaly often have an issue with which of these glial cell types? - correct answer Ependymal cells -These cells are responsible for the production and circulation of cerebrospinal fluid, and if they are overactive, it can lead to hydrocephaly. What effect did increasing the extracellular potassium have on the resting membrane potential? - correct answer The resting membrane potential became less negative. What effect did decreasing the extracellular sodium have on the resting membrane potential? - correct answer Only a small change occurred, because the resting neuron is not very permeable to sodium. The channels that provide for the movement of potassium in the resting neuron are _______. - correct answer leakage Establishing the resting membrane potential requires energy through the use of the _______. - correct answer sodium-potassium pump Which of the following was able to detect pressure? - correct answer the Pacinian corpuscle and the free nerve ending Which of the following does NOT describe graded potentials? - correct answer They are always depolarizing. Which of the following responded to a chemical stimulus? - correct answer olfactory receptor When the intensity of the appropriate stimulus was increased, the amplitude of the response _______. - correct answer increased The minimum voltage that is required to generate an action potential is called the _______. - correct answer threshold voltage
Increasing the voltage resulted in which of the following? - correct answer no change to the action potential An axon that is more negative than the resting membrane potential is said to be _______. - correct answer hyperpolarized If an increase in extracellular potassium hyperpolarizes a neuron, which of the following would be correct? - correct answer It would change the membrane potential to a more negative value. Which of the following occurred in the presence of tetrodotoxin? - correct answer The number of action potentials decreased. Which of the following occurred in the presence of tetrodotoxin? - correct answer An action potential was always seen at R1. In the presence of lidocaine, the action potential was NOT affected at R1 because _______. - correct answer lidocaine was applied downstream of R The effects of lidocaine and tetrodotoxin were _______. - correct answer similar, but tetrodotoxin had a greater effect Why does the threshold increase when the interval between the stimuli decreases? - correct answer Some sodium channels have been inactivated and cannot be reopened immediately. During the relative refractory period, _______. - correct answer another action potential can be generated provided the stimulus is large enough. When the interval between the stimuli decreases, _______. - correct answer a second action potential is generated until the interval reaches the absolute refractory period
When magnesium was added to the extracellular solution, _______. - correct answer the amount of neurotransmitter released decreased Calcium and magnesium are both _______. - correct answer divalent cations A weak, subthreshold stimulus will result in _______. - correct answer a small depolarization at the receiving end of the neuron Which stimulus was at or above threshold? - correct answer the moderate and strong stimuli Increasing the strength of the stimulus applied to the sensory receptor increased _______. - correct answer the frequency of action potentials in the sensory neuron, the amount of neurotransmitter released at the axon terminal of the sensory neuron and the frequency of action potentials in the interneuron An excitatory postsynaptic potential occurs _______. - correct answer at the receiving end of the interneuron
