Membrane Potentials Flashcards
What are the 4 effects of caffeine?
- CNS stimulant.
- Diuretic.
- Phosphodiesterase inhibitor.
- Non-selective antagonist of adenosine receptors, therefore a competitive inhibitor of adenosine.
What can caffeine do that not many substances can?
It can cross the blood brain barrier (BBB).
What happens in the brain with continued caffeine intake?
An increased number of adenosine receptors are formed.
How does stress lead to glucose release?
- Stress results in the release of epinephrine from the adrenal medulla.
- Epinephrine binds to B2 receptors in the liver.
- Adenylyl cyclase is activated.
- ATP is converted into cAMP.
- cAMP stimulates the activation of protein kinase.
- Protein kinase activates phosphorylase b.
- Phosphorylase b acts on glycogen.
- Glycogen is converted into glucose-1-phosphate.
- Glucose-1-phosphate becomes glucose.
What does phosphodiesterase convert cAMP into?
5AMP.
What caffeine derivative inhibits phosphodiesterase?
Methyl xanthine.
What is membrane potential?
The electrical gradient across the cell membrane.
What 2 systems is membrane potential particularly important in?
- Nervous system.
- Muscular system.
What animal was first used to study membrane potential? Why?
- The giant squid.
- Few, large neurons that are easy to remove.
What 3 factors effect the electrical gradient of cells?
- Na+/K+ ATPase Pump.
- Differential membrane permeability.
- Non-diffusible anions inside the cell.
What is the membrane more permeable to: Na+ or K+?
K+.
What 2 diffusible anions are present in the cell?
- Phosphates (ATP).
- Amino acids (Proteins).
What are the functions of a nerve cell?
- Rapid depolarization of membranes.
- Conveying a message.
Where does the action potential originate?
In the cell body before traveling down the axon.
What is an action potential?
Rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane.
What two changes occur to allow for the transmission of the action potential down the axon?
- Depolarization.
- Repolarization.
What is the average RMP of a nerve?
-70 to -90 mV.
What does the - in front of the mV when measuring RMP mean?
That the potential inside the membrane is 90 mv more negative than the potential in the ECF.
How does the Na+/K+ ATPase pump contribute to the RMP?
It pumps more positive ions out of the membrane than it brings in, resulting in a negative RMP.
*Is an electrogenic pump.
What is an electrogenic pump?
A pump that moves ions across a cell membrane creating a charge difference.
What is the concentration gradient for Na+?
0.1.
What is the concentration gradient for K+?
35.
How does K+ and Na+ leak through the membrane?
Through Na+-K+ channels.
How many times more permeable is the channel to K+ than to Na+?
50x-100x.