Physiological Ecology 1. In the background section the authors wrote “Homeostati
ID: 3518575 • Letter: P
Question
Physiological Ecology
1. In the background section the authors wrote “Homeostatic regulation of blood flow in the cochlear capillary beds is achieved by the dynamic adjustment of the vascular diameter or “tone” of pre-capillary arteries and arterioles against systemic changes of pressure, nerve and metabolic activity.” What vascular diameter, small or large, would be needed to increase pressure? (1 point)
2. What vascular diameter, small or large, would be needed to decrease pressure? (1 point)
3. In the background section the authors wrote “In most smooth muscle cells, Ca2+ sparks activate BK channels, leading to membrane hyperpolarization ...” What kind of ion must be on the influx and what kind of ion must be on the efflux for this to happen? (1 point)
4. What word in question 3 did you use to answer question 3? (1 point)
5. In the background section the authors wrote “In this study, we investigate whether Ca2+ sparks regulate the global Ca2+ and vascular diameter in the SMA. Our results demonstrate that Ca2+ sparks are also present in the pressurized SMA but do not regulate vasodilation of the SMA by activating BK channels. Instead, the effects produced by ryanodine, which eliminates Ca2+ sparks are dictated by the pressure-dependent changes in the Ca2+ sensitivity of contraction.” What does ryanodine do to eliminate Ca2+ sparks? (1 point)
6. How do you know that your answer to question 5 is correct? (1 point)
7. In the “Ca2+ sparks in the pressurized spiral modiolar artery” section of the results section the authors wrote “Ca2+ sparks were completely eliminated in the presence of 10 µM ryanodine and significantly decreased in frequency in the presence of 100 µM tetracaine.” Why do you think ryanodine does this? (1 point)
*reference*
https://bmcphysiol.biomedcentral.com/articles/10.1186/s12899-016-0026-z
Explanation / Answer
1. Small vascular diameter is needed to increase pressure. This is because lesser the diameter, more blood cells hit against the walls of the blood vessels due to less cross section area which increases the pressure.
2. Larger vascular diameter decreases pressure. This is because larger the diameter, more area is available for the blood cells to move inside the vessel and less blood cells hit the walls of the blood vessels which reduces pressure.
3. BK Channels allow efflux of potassium ions and influx of calcium ions for repolarization of the membrane.
4. The word used is repolarization which means that ions which are at higher concentration on either side of the membrane move to the opposite side to change the polarity of the membrane.