Chapter 2 Flashcards
negative current
positive ion flowing in or negative flowing out
positive current
negative ion flowing in or positive flowing out
What causes a membrane potential difference?
Separation of charge
Is the inside of the cell negative or positive?
negative
what is the resting mb potential?
-70 mV
what charge do “bulk” have?
electroneutral
What can get across the mb?
gases and lipophilic/hydrophobic molecules
What cannot get across the mb?
charged or large particles/molecules
What ions have a greater concentration outside of the cell?
Na+ and Cl-
What ion has a greater concentration inside the cell?
K+
What does the Na/K pump do?
Pumps 3 Na+ out and 2 K+ in
Does Ca+ contribute to resting mb potential?
No because it is a signaling molecule
What are channels?
Water-filled and allow ions to flow down their electrochemical gradient
Leak/passive channels
always/almost always open at resting mb potential (many for K+, some for Cl-, very few for Na+)
equilibrium potential
balance of chemical and electrical forces; a type of reverse potential
resting mb potenital for K+
-80 mV
resting mb potential for Na+
+60 mV
resting mb potential for Cl-
-60 mV
resting mb potential for Ca+
135
Nerst equation
- calculation for determining the equilibrium potential of an ion
- need the concentration of the ion inside and outside of the cell
Goldman equation
- each ion moving down own electrochemical gradient
- need membrane permeability of each ion, concentration gradient of each ion, and valence of each ion
What is a graded potential?
makes communication between nerve cells possible
How are electrical signals generated? (change from resting mb potential)
changes in mb permeability generated by:
- chemical/ligand binding
- voltage change
- stretch/pressure (physical force)
- light and heat (mechanical forces)
EPSPs
excitatory; bring mb potential closer to action potential threshold
IPSPs
inhibitory; makes mb potential more negative
What happens if you increase external ion concentration?
Equilibrium potential increases
Does negative current depolarize or polarize?
depolarize (think negative out, so becoming more positive)
What does the frequency of an action potential relfect?
The frequency of the stimulus
In HH experiments, what does decreasing extracellular Na+ do?
decreases the amplitude of the action potential
