Flashcards in Cellular Physiology (Part 2) Deck (97)
What is resting membrane potential?
The potential difference that exists across the membrane of excitable cells, such as nerve and muscle, in the period between action potentials
The resting membrane potential is established by what?
diffusion potentials, which result from the concentration differences for various ions across the cell membrane
Which ions will make the greatest contributions to the resting membrane potential?
Ions with the highest permeabilities at rest
Resting membrane potential of excitable cells falls in the range of −__ to −__mV
−70 to −80mV
What is the resting membrane potential close to?
The equilibrium potentials for K+ and Cl- because the permeability to these ions at rest is high
What is the resting membrane potential far from?
The equilibrium potentials for Na+ and Ca2+ because the permeability to these ions at rest is low
What role does the Na+ - K+ APTase play in creating the resting membrane potential?
It creates and maintains the K+ concentration gradient, which establishes the resting membrane potential
What is an action potential?
A phenomenon of excitable cells, such as nerve and muscle, and consists of a rapid depolarization (upstroke) followed by repolarization of the membrane potential
What is the basic mechanism for transmission of information in the nervous system and in all types of muscle?
an action potential
What is depolarization?
the process of making membrane potential less negative
What is repolarization?
The process by which the membrane potential returns the membrane potential to a negative value after the depolarization phase of an action potential
What is hyperpolarization?
the process of making the membrane potential more negative
What is inward current?
The flow of positive ions from the ECF into the ICF
What is an example of inward current?
The flow of sodium into the cell during the upstroke of the action potential
What is outward current?
The flow of positive ions from the ICF to the ECF
What is an example of outward current?
The flow of potassium out of the cell during the repolarization phase of the action potential
Inward currents _____ the membrane potential and outward currents ______ the membrane potential.
What is threshold potential?
the membrane potential at which occurrence of the action potential s inevitable
An ____ current is required to depolarize the membrane potential to threshold
The portion of the action potential where the membrane potential is positive is called what?
The portion of the action potential, following repolarization, where the membrane potential is actually more negative than it is at rest is called what?
What is the refractory period?
a period during which another normal action potential cannot be elicited in an excitable cell
Each normal action potential for a given cell type looks ____, depolarizes to the same potential, and repolarizes back to the ___ resting potential.
Describe the propagation of an action potential
An action potential at one site causes depolarization at adjacent sites, bringing those adjacent sites to threshold.
* This propagation is nondecremental
What channel is responsible for the upstroke of the action potential in nerve and skeletal muscle?
the voltage-gated Na+ channel
What are the 2 types of gates on the Na+ channel?
activation and inactivation gates
In order for Na+ to move through the Na+ channel what gate must be open?
How do the gates on the Na+ channel respond throughout the course of an action potential?
1) during rest the activation gate is closed and the inactivation gate is open
2) during the upstroke of the action potential, the activation gate opens quickly (the inactivation gate is still open) allowing Na+ to flow through the channel
3) at the peak of the action potential the inactivation gate closes, stopping the passage on Na+ and repolarization begins
What are the 2 types of refractory periods?
Absolute or Relative