Neurophysiology of Nerve Impulses. Physioex 3 2023/2024 updated to pass

Neurophysiology of Nerve Impulses. Physioex 3 1. Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels. - correct answer Increasing the extracellular K+ reduces the steepness of the concentration gradient and so less K+ diffuses out of the neuron. 2. Explain why increasing the extracellular K+ causes the membrane potential to change to a less negative value. - correct answer The membrane potential became less negative because less K+ diffused out. If more K+ stays in, it is more positive of less negative. 3. Explain why a change in extracellular Na+ did not significantly alter the membrane potential in the resting neuron? - correct answer There are less Na+ leakage channels than K+ leakage channels, and more K+ leakage channels are open. 4. Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron. - correct answer The resting neuron is approximately 4-5 times more permeable to K+ because of the increased number of K+ leakage channels. 5. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential. - correct answer A change in K+ conductance would have a greater effect of the resting membrane potential than a change in Na+ conductance would due to the greater number of K+ channels. 1. Sensory neurons have a resting potential based on the efflux of potassium ions. What passive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle, and in the membrane of the free nerve endings? - correct answer The efflux of potassium is a key factor of resting potential, so there will be a potassium channel. 2. What is meant by the term graded potential? - correct answer Graded potentials are brief, localized changes in the membrane potential than can be either depolarizing or hyperpolarizing. 3. Identify which of the stimulus modalities induce the largest amplitude receptor potential in the Pacinian corpuscle. - correct answer The moderate intensity pressure modality induced a receptor potential of the largest amplitude in the Pacinian corpuscle. 4. Identify which of the stimulus modalities induced the largest-amplitude receptor potential in the olfactory receptors. - correct answer The moderate intensity chemical modality causes a receptor potential in the olfactory receptors. 5. The olfactory receptor also contains a membrane protein that recognizes isoamyl acetate and, via several other molecules, transduces the odor stimulus into a receptor potential. Does the Pacinian corpuscle likely have this isoamyl acetate receptor protein? Does the free nerve ending likely have this isoamyl acetate receptor protein? - correct answer The Pacinian corpuscle and the free nerve ending are not likely to have the isoamyl acetate receptor because they did not respond to chemical stimuli. 6. What type of sensory neuron would likely respond to a green light? - correct answer Photosensory neurons. 1. Define the term threshold as it applies to an action potential. - correct answer Threshold is the voltage that must be reached in order to generate an action potential. 2. What change in membrane potential (depolarization or hyperpolarization) triggers an action potential? - correct answer A depolarization in the membrane potential results in an action potential. The membrane potential must become less negative to generate an action potential. 3. How did the action potential at R1 (or R2) change as you increased the stimulus voltage above the threshold voltage? - correct answer The action potential didn't change as the stimulus voltage increased. This is because once threshold is met, the event it all or none, not graded. 4. An action potential is an "all or nothing" event. Explain what is meant by this phrase. - correct answer This means that once threshold is met, an action potential occurs. If the stimulus is too small, an action potential does not occur. 5. What part of a neuron was investigated in this activity? - correct answer The trigger zone was investigated. This is where the axon hillock and the initial segment come together.