Flashcards
Homeostasis and Resting Potentials
Cards in this deck (19)
- 1Who came up with the idea of homeostasis?Claude Bernard 1872
"Constancy of the internal environment is the condition of free life" - 2Why do cells need a stable internal environment?To protect them from harsh conditions and changing external environments
- 3How is the inside of the cell different from the outside?Inside is ideal for biological molecules to work:
High potassium
Low Sodium
Low Chloride
Low Calcium
Compared to mammal plasma and seawater - 4What is the cell resting potential?The difference in electrical voltage across a cell membrane.
Applies to almost all animal cells
Inside of the cell is usually maintained at -60mV -> -80mV negative to the outside - 5What is the cell resting potential a good example of?Homeostasis
- 6Why does the cell resting potential matter?The electrical energy created can be used to:
1. make electrical signals
2. move things across the membrane (e.g. absorption in gut) - 7How can cell resting potential be measured?Using an INTRACELLULAR MICROELECTRODE (made of a thin piece of capillary tubing with a v. sharp tip)
Shows a small voltage difference btwn the electrode placed inside and electrode outside axon. - 8How is cell resting potential established and maintained?2 factors involved in establishing resting potential:
1. Unequal distribution of K+ ions btwn inside and outside of cell (more inside)
2. Selective permeability of the resting cell membrane so K+ can pass through but others cannot - 9What are the two proteins that span the membrane that are responsible for the resting potential?1. Sodium-Potassium pump
2. Potassium ion channel - 10What do ion pumps do?Use ATP to move ions AGAINST their electrochemical gradients
- 11What happens in the Na:K pump?Na+ is expelled from the cell while K+ is imported
Ratio of 3Na+ : 2K+ - 12Where is there more K+?INSIDE THE CELL
- 13Properties of ion channels?Contain an aqueous pore and generally a GATE (not in K+ channel - always open)
When the channel is open, particular ions can move through the pore by DIFFUSION
Therefore the direction which an ion moves is influenced by its electrochemical gradient - 14What is an electrochemical gradient?-Difference in conc. across membrane AND
-The voltage across the membrane - 15As well as a potassium channel, there is also a...VOLTAGE-GATED Na+ channel
- 16What is the equilibrium potential for K+ and what does it mean?It is -60mV -> -80mV and is the voltage difference that balances the concentration difference
- 17What causes the voltage difference?Because K+ is more conc. inside the cell, it tends to diffuse out.
Each K+ carries a positive charge
SO the diffusion establishes a voltage difference - 18Why doesn't Na+ contribute (as much) to the resting potential?Even though Na+ is also unequally distributed, it cannot travel through open channels as K+ can. If voltage gated Na+ channels were open, it would enter the cell and inside would become less negative
- 19How can the value of the K+ equilibrium be calculated?Using the NERNST equation
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- 2nd Year Biology (Animal Physiology) Flashcards on Homeostasis and Resting Potentials, created by Phoebe Stockton on 18/08/2016.
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- Phoebe Stockton
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