Exam 2 Lecture - Membrane Potential Flashcards
What is the resting membrane potential (RMP)?
-65 mV
What does the RMP represent?
reflects the uneven distribution of ions across the plasma membrane by the electrochemical gradients
What are the electrochemical gradients created by?
- the sodium/potassium pump
- K and Cl: non-gated or leak channels
- Na: a few nongated or some other channels for Na
- intracellular anions that are too large to exit the cell
What is sensory receptor signal transduction?
conversion of the sensory stimulus
What does the sensory stimulus open?
- Mechano-gated Na channels
- Heat-gated Na channels
- Cold-gated Na channels
What does opening stimulus specific Na channels lead to?
depolarizing of the receptor membrane
What is a potential produced by sensory transduction?
a depolarizing event resulting from inward current flow
What is depolarizing potential of receptor membrane referred to as?
receptor potential
What does receptor potential lead to?
action potential
When is an action potential created?
When the receptor potential goes over the threshold potential
What is the threshold potential?
(-55mV)
What does the generation of action potential require?
- Voltage gated Na channels
- Voltage gated K channels
What is depolarization?
the decrease in the potential difference across the plasma membrane, going more positive, approaching 0mV
What is overshoot?
When the difference goes over 0mV
What is repolarization?
the return of membrane potential to its normal RMP
What is hyperpolarization?
the increase in the potential difference across the membrane, going more negative, away from the RMP
Explain the importance of the threshold membrane potential.
an action potential will only be generated if the receptor potential goes over -55 mV
When will Na cross the membrane?
only at the activated state (-55 mV), not during resting or inactivated
When do the voltage gated channels open?
Once the receptor potential reaches threshold
What direction does Na flow when its voltage gated channel is open?
in
What direction does K flow when its voltage gated channel is open?
out
What ion channel is involved with generating depolarization?
opening stimulus of specific Na channels lead to depolarization
What ion channels are involved with generating overshoot and repolarization?
Voltage gated Na and K channels
What ion channels are involved with generating hyperpolarization?
K tries to reach equilibrium potential of -80 mV but cannot because the channel closes before it can do so