Lecture 17 Flashcards
What is the membrane potentials for the ECF
High Na+ and Low K+
What is the membrane potentials for the ICF
High K+ and low Na+
What is the voltage at a close channel?
-70mV
What is the voltage at an open channel?
-60mV
What is the voltage at an inactivated channel?
+30mV
What is the resting membrane potential?
-70mV
What does it mean if there is a depolarisation of the membrane?
The membrane is becoming more positive
When does the gate close?
When the membrane becomes very positive.
What does the inactivation gate do?
It allows the inactivation gate to close very rapidly and eventually the activation gate will close too.
What is the first step in the action potential of a myelinated axon?
A local or graded change in membrane potential occurs sufficient to depolarise the cell and open voltage gated Na+ channels.
What is the second step in the action potential of a myelinated axon?
Voltage gated Na+ channels open and Na+ ions flow through.
What is the third step in the action potential of a myelinated axon?
The membrane rapidly depolarises and then they close and at the same time voltage gated K+ channels open.
What is the fourth step in the action potential of a myelinated axon?
Voltage gated K+ channels close and membrane repolarises to RMP
What are the statuses of the gates at resting membrane potentials?
They are both shut and a few membrane channels open
What does it mean when the membrane is at absolute refraction period?
Absolutely nothing else can occur at that membrane, no other action potentials can occur.
What happens at the initiation point?
Membrane starts to depolarise
What happens when the cell depolarises above the threshold value?
Voltage gated sodium channels open, making it positive inside and goes to +30mV.
What occurs at +30mV?
Sodium gate inactivate/ close and at the same time voltage gated potassium ions channels open.
What does the axon hillock control?
It controls whether or not to pass on action potentials. By the action potential being large enough to over come the axon hillock.
What is the first step in action potential for an unmyelinated axon?
As an action potential develops at the initial segment, the membrane potential at this site depolarises to +30mV
What is the second step in action potential for an unmyelinated axon?
As the sodium ions entering at spread away from the open voltage-gated channels, a graded depolarisation quickly brings the membrane in segment 2 to threshold
What is the third step in action potential for an unmyelinated axon?
An action potential develops in segment 2.
The initial segment begins repolarisation (and is now refractory)
What is the fourth step in action potential for an unmyelinated axon?
As the sodium ions entering at segment 2 spread laterally a graded depolarisation quickly brings the membrane segment 3 to threshold
How do we increase our conduction speed?
Myelinating- Schwann cells, meaning it gets regenerated at each node.
