Lecture 16- Homeostasis Flashcards
Does blood pressure change over a long period of time?
-no remains very similar despite stress and eating, exercise etc.
Does blood pressure change very much in response to intake of salt?
-no -still remains constant (reasonably) -homeostasis
How is heart beat and blood pressure affected in a rat with sinoartic denervation?
- heart rate is stable as it is not receiving the signal to change -the blood pressure is all over the place, every time it moves etc causes dramatic change in bp -due to loss of reflex circuitory
What is the relationship of heart beat and blood pressure?
-heart beat changes to keep blood pressure within normal range
Why is blood pressure dangerous?
-life expectancy is short= the variation in bp causes hypertrophy of the muscle, becomes floppy and can cause a dislodgement of clot with high spike in blood pressure
What is the role of insulin?
-brings levels of glucose down after a meal
What are the two types of homeostasis we can consider?
-whole body -cellular
Why do you not want change in neuronal excitability?
-control breathing etc.
What determines the excitability of neurons?
-the ion channels they express
How often are the ionic channels in neurons recycled?
-every few weeks
What are the two types of maintaining the excitability in neurons?
-activity dependent expression -activity independent coupled expression
Does the excitability of a neuron remain stable over a lifetime?
-yes
What is the activity dependent neuronal homeostasis mechanism?
-if new channel is expressed on the membrane that alters the excitability of the cell then within a very short period of time (minutes) will lead to expression of ion channels that will bring the cell’s activity back to normal -happens too quickly to be genetic expression, there must be channels ready to respond to change!
What is the activity independent neuronal homeostasis mechanism?
- activity independent coupled expression
- certain channels responsible for cellular excitability that if expression of one goes up, this one goes up, so at genetic level cell is looking to decrease the changes
- so have positive go up in expression, negative will also go up in expression so that you come down to zero sum
What will happen here?
- two chambers, semi-permeable membrane only to H2O not NaCl, higher concentration of NaCl in one half and H2O will move there so end up with equal ionic concentration
- but if this happens in a closed chamber then also increase pressure= volume!
What happens to a cell when more solute enters?
-with solute comes more water= larger volume thus the cell swells
What happens to a cell when solute leaves?
-with solute leaves water= thus smaller volume and the cell will shrink
What is regulatory volume decrease and increase?
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