Lecture 11.2 main points Flashcards
describe excitable cells in their resting state. What are ions, what do opposite charges do? what do some charges do?
excitable cells in their resting state have a negative charge on the inside of the membrane (-70mV is the average for neurons) compared to the outside (0mV)
Ions are charged atoms, or molecules, that have lost or gained electrons
opposite charges attract
like charges repel
define electric potential
separated electrical charges of opposite sign have the potential to do work if they are allowed to come together
define membrane potential
voltage of the intracellular region of the membrane compared to the extracellular
what does it mean for the membrane voltage to increase/ decrease membrane potential
increasing the membrane potential - excite the call - makes it more positive
decrease the membrane potential - inhibit the cell - make it more negative
define potential difference
the difference in potential (charge) between the outside of the cell and the inside
what does it mean for the membrane voltage to increase/ decrease potential difference
increasing the potential difference of a resting membrane voltage - make it more negative
decrease the potential difference - make it more positive
define conductance? what is the shorthand?
the permeability of the membrane to an ion
represented by the lowercase g
gK= conductance of potassium
can charge/polar chemicals pass easily directly through the membrane
the plasma membrane is relatively impermeable to charge atoms and molecules
how is the membrane conductance for charged or polar chemicals altered?
ions must travel through transmembrane protein, when more are open, the greater the conductance for that ion
define current? what is the shorthand representation?
current is the actual movement (flow) of ions through membrane channels
represented by a capital I
INa= current for sodium
IK= current for potassium
what does it mean to increase/ decrease current
increase current means high flow of ions across the membrane
what does it mean to have positive/negative current
positive current means ions flowing out of the cell
negative current means ions flowing into the cell
sodium concentration inside v outside
cation, higher outside the cell
chloride concentration inside v outside
an anion, higher concentration outside
calcium concentration inside v outside
cation, higher outside
potassium concentration inside v outside
cation, higher concentration inside the cell
phosphate concentration inside v outside
polyatomic ion, higher inside the cell
majority of phosphate bound to proteins and ATO
shorthand representation for concentration of intracellular/ extracellular potassium, sodium?
[K]o or [K]e for extracellular
[K]I for intracellular
describe concentration differences intra vs extracellular K and Na
intracellular K > intracellular Na
extracellular Na > extracellular K
define diffusion
movement of an atom or molecule from a region of high concentration to a region of low concentration
where does sodium want to go? inside or outside the cell? does it flow up or down its concentration gradient
sodium wants to flow into the cell, down its concentration gradient
describe the charge of the extracellular region by the membrane vs intracellular region by the membrane
extracellular region is more positive than intracellular region
why would sodium want to flow into the cell at typical neuronal resting membrane potential
sodium wants to flow from the positive extracellular into the negative intracellular at resting membrane voltage
when sodium flows from a positive region to a more negative one, it is said to flow up or down its concentration gradient
down its concentration gradient