lecture 3- excitability pt 1 Flashcards
define excitability
the generation & conduction of electrical charge by specialized cells in human body
nerves and impulses are ___ cells, can display property of generating and conducting ___
excitable
electrical impulses
define excitable membranes
electrical impulse generated at surface of membrane of excitable cells and travels along membrane
excitable membranes share 2 electrical properties:
capacitance & conductance
___ is the ability of membrane to separate electrical charge one side from the other (positive charge on one side and neg charge on the other)
capacitance
___ is the ability of membrane to transport or move charge one side to the other
conductance
every nerve impulse is an ___
electrical current
name a few charged ions in solution
Na+
K+
Ca2+
Mg2+
Cl-
HCO3-
Pro-
electrical charge- contributes to electrical nature of membranes
describe the distribution of ions across typical nerve cell in mammalian body
sodium higher outside than inside, charge unequally separated across membrane
potassium higher inside than outside, charge unequally distributed across membrane
chlorine higher outside than inside
individual ions and charges separated
(entire total charge- can only tell if membrane has net charge on one side or the other if you measure it)
describe how you measure charge on a membrane
potentiometer (specific voltmeter)- 2 electrodes, put one on outside and one through membrane on inside of cell
- reference electrode sets its side of the membrane to zero
- recording electrode (sticks through membrane to inside) measures the difference in electrical charge b/w reference and recording electrode (inside & outside of membrane)
the inside of the membrane has a net negative charge relative to the outside
what is it? what is it called?
-70 mV
this charge on the membrane called:
potential difference
TMP (transmembrane potential)
resting potential
when you measure the transmembrane potential, how does it differ between nerve cell types?
it is fairly constant (-70 mV) on all nerve cell types –> so it is called resting potential (RP)- electrical charge on a nerve cell at rest, not active
where does the -70 charge exist in a nerve cell?
only at the inside surface of membrane
- relative pos charge only exists on outside surface of membrane at interstitial fluid
- if a fluid is large enough to be measured, going to be relatively neutral (surface of membrane is its own compartment, inside and outside of cell are neutral)
the membrane has the property of ___, unequal distribution of charge - pos on outside and neg on inside
polarity
excitable membrane generates this -70 mV charge by a combination of…
capacitance and conductance
name 3 factors that govern ion movement
concentration gradient
relative speed due to permeability
electrical gradient