Homeostasis And Resting Potential Flashcards
Who first suggested the idea of homeostasis and who coined the word “homeostasis”?
Claude Bernard, 1872
Walter Cannon
What maintains the body’s stability of extracellular fluid composition?
The body’s organ systems
Why is homeostasis not linked to temperature?
Because many animals are ectotherms and don’t control their body temperature
What are the ionic differences between the cytoplasm and the plasma bathing the cell?
The cytoplasm has a higher concentration of potassium and lower concentration of sodium, chloride and calcium
What is the difference between the electrical voltage in the cytoplasm compared to outside called?
Resting membrane potential
What is the inside cells resting potential in volts?
60-80mV negative to the outside
How can resting potential be measured?
By using an intracellular microelectrode (voltage of the electrode inside cell compared to voltage outside cell)
How is resting potential established and maintained?
Unequal distribution of K+ ions between inside and outside
Selective permeability to potassium
What two proteins that span the cell membrane are responsible for maintaining the resting potential?
Sodium potassium exchange pump
One type of potassium ion channel
What does the sodium potassium exchange pump do?
Uses ATP to move 3Na+ out and import 2K+ against a concentration gradient, making potassium concentration greater inside than outside
What does the potassium channel do?
Only allows potassium ions to pass through by diffusion
Doesn’t require energy
What did Hodgkin and Horowicz (1959) do to show resting potential?
Experimented on frog muscle cells by using an electrode to measure the V across a cell membrane
Found varying external potassium conc alters membrane potential in the way Nernst equation predicts
What determines the net direction in which a particular ion moves through open channels?
It’s electrochemical gradient
