Concept explainers
Sequence the following list of events of a neuronal action potential by placing 1 next to the first event, 2 next to the second event, and so on.
a. _______ The activation gates of voltage-gated
b. _______
c. ________ Local potentials depolarize the membrane to threshold.
d. ________ The inactivation gates of voltage-gated
e. ________ Repolarization continues and Na+ channels return to resting.
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Human Anatomy & Physiology (2nd Edition)
- Assume presynaptic excitatory neuron A terminates on a postsynaptic cell near the axon hillock and presynaptic excitatory neuron B terminates on the same postsynaptic cell on a dendrite located on the side of the cell body opposite the axon hillock. Explain why rapid firing of presynaptic neuron A could bring the postsynaptic neuron to threshold through temporal summation, thus initiating an action potential, whereas firing of presynaptic neuron B at the same frequency and the same magnitude of EPSPs may not bring the postsynaptic neuron to threshold.arrow_forwardIn the figure to the left, name the 4 phases of the action potential (Note: you have to write in where phase 4 occurs). Describe what happens in each phase with a focus on Na+ and K+ flow through channels and the membrane potential. Discuss the importance of threshold. How does this relate to the concept of APs being all or none?arrow_forwardLocal anesthetic is often used in dentistry to lessen the sensation of pain during dental procedures. It prevents propagation of nerve conduction by decreasing the flow of ions. a. Describe how depolarization of an action potential can be blocked by the use of local anesthetic. b. Your classmate explained that once the threshold potential has been reached, the inside charge of the neuron is more positive than the outside charge. Is she correct? Can you compare the inside charge to the outside charge in an axon treated with local anesthetic?arrow_forward
- A neuron with a resting membrane potential of -75 mV receives multiple inputs giving rise to the following post-synaptic potentials: -15 mV, 20 mV, -5 mV, 7 mV, and 22 mV. The threshold is -50 mV. What will be the outcome? An action potential (AP) will be generated because there are more positive than negative inputs а. b. No action potential because the presence of a single IPSP is sufficient to prevent an AP О с. An action potential (AP) will be generated because the sum exceeds the threshold O d. An action potential (AP) will be generated because the sum of inputs is a positive value Ое. No action potential (AP) will be generated because the sum of inputs is below the thresholdarrow_forwardWhich of the following is TRUE regarding the absolute and relative refractory periods of the action potential (AP)? A. The absolute refractory period may be overcome if enough excitatory stimulation is applied to the neuronal membrane. B. The absolute refractory period is due the closing of the activation gate of voltage gated sodium channels at the peak of the AP. C. The relative refractory period is due to the closing of the activation gate of voltage gated potassium channels during the overshoot phase of the AP. D. The relative refractory period is due the closing of the inactivation gate of voltage gated sodium channels . E. All of the above statements are FALSE.arrow_forward1) A 100-um diameter nerve axon has the following properties: rm = 2.5 x 104 ohm x cm, ri = 1 x 105 ohm/cm, r0 = 0, cm = 3 x 10-8 F/cm. The permeability to Cl- is very high and Cl- ions are at resting potential Vm. A steady inward current is injected into the axon resulting in a Vm of -110 mV at the site of current injection. If the Vm 3 mm from the site of injection is -94.5 mV, what is the resting Vm?arrow_forward
- Can you explain to me why choice E is the correct answer and break down why the other options are false?Select the choice option that is TRUE regarding the absolute and relative refractory periods of the action potential (AP). A. The absolute refractory period occurs when the activation gate of voltage gated sodium channel closes at the peak of the AP B. The relative refractory period occurs when the inactivation gate of voltage gated sodium channels closes at the peak of the AP C. The relative refractory period occurs when the activation gate of voltage gated potassium channels opens at the peak of the AP D. The absolute refractory period may be overcome if enough excitatory stimulation is applied to the neuronal membrane E. All of the choice options are FALSE regarding the absolute and relative refractory periods of the AParrow_forwardwhich one of the following statements is incorrect? a. temporal summation occurs when a single synaptic input is activated twice in succession, with the second postsynaptic potential occurring before the first postsynaptic potential is over. b. blocking voltage-gated k* channels in the presynaptic membrane of a typical chemical synapse is likely to reduce the amount of neurotransmitter released in response to a single action potential in the presynaptic axon. c. in the optic tectum of the hunting rattlesnake, spatial summation is used to combine inputs from visual and thermoreceptive layers in order to make a decision whether to strike at a mouse-like object. d. a single type of neurotransmitter can have different postsynaptic actions depending on the type of receptor to which it binds.arrow_forwardImagine that a toxin creates pores that are permeable to Ca2+. Describe its immediate effect on the resting potential of the neuron: identify which ions diffuse across the membrane, which direction they diffuse (and why), and whether this brings the neuron closer to or further from threshold potential. asap pleasearrow_forward
- What type of synaptic potential (if any; be sure to indicate if any modification is occurring as well) would occur if: a.) An MAO inhibitor type of antidepressant is functioning at an active dopaminergic synapse that increases the rate of sodium flowing into the cell. b.) Prozac is present at an active serotonin synapse where receptor activation increases the flow of potassium out of the cell.arrow_forward+70 D A -70 Time in msec The diagram above shows the changes in membrane potential measured from a single point in a typical mammalian motor neuron that has been artificially stimulated to threshold. Membrane potential in mV Barrow_forwardexcitatory and 15 inhibitory postsynaptic potentials appear simultaneously on the plasmatic membrane of motoneuron. Answer the question A and fulfill the task B:A) Will this neuron generate the efferent nervous impulses if the amplitude of single EPSP and IPSP appeared on the axonal hillock`s membrane equals 1 mV? Why?B) Name the state of this neuron and name the type of summationarrow_forward
- Human Physiology: From Cells to Systems (MindTap ...BiologyISBN:9781285866932Author:Lauralee SherwoodPublisher:Cengage Learning