Intro to Electrophysiology Flashcards
A voltage difference or separation of charge between the internal and external surfaces of the plasma membrane
Membrane potential
At rest, the membrane is
Polar
In general, the internal surface region of the plasma membrane has what charge?
Negative
In general, the extracellular surface region of the plasma membrane has what charge?
Positive
The inner surface of the plasma membrane is negative relative to the
-does not mean it is loaded with negative charge
Extracellular surface
The resting membrane potential of a large nerve is maintained at approximately
- 90 mV
- means inner membrane is 90 mV less positive than outer
The flow of charge (ions)
Current
The resting membrane potential is due in large part to the membrane distribution of
Na+ and K+
Located inside the cell and help establish the resting membrane potential
Negatively charged proteins and Cl-
Generated any time an ion translocates across the cell membrane
Current (I)
Cell and tissue function is controlled by
Ion flux
In a resting motor neuron, there is a high intracellular concentration of K+ as compared to a high extracellular concentration of
Na+
Because of its chemical concentration gradient, there is a strong driving force for the translocation of K+ out of the cell through
K+ leak channels
Na+ and K+ are moved across the membrane against their concentration gradients by the
-maintains net negative charge on inner face of membrane
Na+/K+ ATPase (3 Na+ out, 2 K+ in)
How many ATP molecules are used during each ATPase cycle?
One
The tendency for an ion to move in one direction or another
Electromotive Force (EMF)
Dependent on the intra- and extracellular concentrations of Na+, K+, and Cl-, as well as membrane permeability of these ions
EMF
By maintaining RMP at around -90 mV, there exists a tremendous electrochemical gradient for the movement of Na+ inward, which is the defining characteristic of
Membrane depolarization during action potential
What are four electrogenic tissues that are dependent oupon anions (Cl-) and cations (Na+, K+, Mg2+, and Ca2+) for electrogenecity?
Heart, Skeletal muscle, Neurons, Vascular smooth muscle, and GI smooth muscle
The resting membrane potential is set by the membranes concentration gradient for
K+ out of the cell
The larger the K+ concentration gradient (i.e. the ratio of intracellular K+ to extracellular K+), the greater the
Nagtivity in the cell
When the the plasma [K+] is elevated (i.e. during hyperkalemia), the concentration gradient across the cell membrane is lowered; and this drives the
Resting membrane potential to be less negative (Membrane depolarizes)
Neurons communicate via the electrochemical phenomenon known as an
Action potential
The plasma membranes of neural and muscle cells contain voltage-gated Na+, K+, Cl-, and/or Ca2+ channels that open/close when there is a specific change in
Membrane potential