Neuronal Cell Membrane and Membrane Potential
15. At rest, which direction do potassium ions move?
1. At rest, potassium ions (which are positive) move INTO the cell because the inside of the cell is negative (remember?). This would be a result of ELECTROSTATIC PRESSURE, because potassium (positive) is flowing to an oppositely charged area (the inside, which is negative). Opposites attract!
13. What are gated channels? What do they open and close to?
1. GATED CHANNELS are channels that open and close in response to voltage changes, chemicals (like neurotransmitters), and mechanical action.
14. What does it mean when we say neurons are selectively permeable?
1. SELECTIVELY PERMEABLE means some things pass freely, like POTASSIUM (K+), while other things like proteins do not.
18. How permeable is the membrane to sodium ions (Na+)?
1. SLIGHTLY permeable. Sodium ions slowly leak in
12. Why is the inside of the cell negative?
1. There are proteins stuck inside. Proteins are negative.
19. How much of Sodium, Potassium, Chloride, Calcium, and Proteins do you have outside the cell?
2. You have a lot of Sodium, Chloride, and Calcium outside the cell, but few Potassium and Proteins.
20. How much of Sodium, Potassium, Chloride, Calcium, and Proteins do you have inside the cell?
3. You have a lot of Potassium and Proteins, but not a lot of Sodium, Chloride, and Calcium.
21. Why should you beware of cheap Japanese restaurants?
4. If the puffer fish isn't cleaned out properly, tetradoxin, which blocks nerve action by blocking voltage-gated SODIUM CHANNELS, might be present. You need sodium for your neurons to fire. If tetradoxin blocks sodium, you might die. When your neurons stop firing, you paralyze your muscles, specifically your diaphragm, and stop breathing.
22. What is the purpose of the sodium-potassium pump?
5. To pump 3 SODIUM out and 2 POTASSIUM in to maintain resting potential. You have a net loss of -1 charge.
23. What percentage of brain energy operates this pump?
6. 40%!!!
A. Ion channels are made of...
A. Protein
A. The substance in pufferfish is useful for studying the ionic mechanisms of the neuron because it
A. Selectively blocks sodium channels
16. As potassium ions build up inside the cell, which direction do they move?
As potassium ions build up inside the cell, they diffuse OUT of the cell along the CONCENTRATION GRADIENT, going from high concentration to low concentration.
11. The cell membrane is a ....
LIPID BILAYER, and repels water, which surrounds ions. If ions want to go through the membrane, they have to use ION CHANNELS. The lipid bilayer is also known as the charge separator.
17. When is equilibrium reached?
When ion movement out is balanced by ion movement in.
