Chapter 6 & 7 Flashcards
What is the normal resting potential of a cell
-65 to -70 mV
What measures the resting potential of a cell
Oscilloscope
How does the oscilloscope measure the resting potential
One probe is in the intracellular fluid and the other is in the extracellular fluid
What are the major players in membrane and action potentials (5)
- K+
- Na+
- Cl-
- Ca++
- Proteins (A-)
Which of the major players are in greater concentration inside the cell (2)
- K+
2. A-
Which of the major players are in greater concentration outside the cell (3)
- Na+
- Cl-
- Ca++
What is equilibrium potential
A balance between diffusion and electrostatic pressure
What is the equation used to determine the equilibrium potential
Nernst equation
What is the Nernst equation
V= RT/zF ln([X]out/[X]in)
What is R
Gas constant 8.314
What is T
Temperature 298.15K (room temp)
What is F
Faraday’s constant 96500
What is z
Charge of ion
What are glial cells permeable to at rest
K+ only
What are neurons permeable to at rest
Na+ and K+
How many open channels are there for K+ and Na+ in a neuron (roughly)
K+: Many open channels
Na+: Only a few open channels
What does the Na+/K+ pump move
3 Na+ out and 2 K+ in
What is a graded potential
The stimuli is able to vary in size from small to big
What does depolarization at the dendrites give you
Only graded potentials
What does depolarization at the axon hillock/axon give you
Only action potentials
True or False:
A graded potential diffuses to nearby areas and leaks out of the neuron as it moves down the neuron
True
Where does the signal need to go in order to initiate an action potential
Axon hillock
What is an action potential
A nerve impulse that is an electrical signal that moves from the axon hillock down the axon to the terminal button
What is it called when you send a signal from the axon hillock to the terminal button
Internal neuronal communication
What are the 4 properties of an action potential
- Threshold
- All-or-none
- Does not diminish
- Followed by refractory period
What is the threshold
The point at which an AP will occur when the graded potential is big enough
What is all-or-none
When the threshold is met the action potential will be the same but if the threshold isn’t met no action potential is formed
True or False:
The action potential is the exact same at the start and end of the axon
True
What is the refractory period
Time during which an AP can’t occur or it is much harder to get an AP
What are 2 critical voltage gated channels for causing an AP
- Na+
2. K+
What happens when there is a conformational change in the voltage gated channel
An action potential occurs
What causes a conformational change in the voltage gated channel
Positively charged amino acids moving inside the voltage gated channel do to a big enough graded potential
What are 2 key differences between the Na+ and K+ voltage gated channels
- Na+ channel opens faster
2. Na+ channel becomes inactivated
When are the Na+ channels deactivated based on the graph
At the peak of the graph
What close the voltage gated Na+ channels
The ball and chain
What prevents the neuron from getting to +55 mV which is the equilibrium potential of Na+
K+ prevents it
What occurs once the Na+ channels close
K+ continues to leave the cell bringing the cell back to it’s negative potential
What causes the over shoot
The remaining K+ outside the cell makes the inside of the cell negative making it briefly hyperpolarized
What are the 6 steps of an action potential firing
- Na+ channels open and Na+ begins to enter the cell
- K+ channels open K+ begins to leave cell
- Na+ channels close so no more Na+ enters the cell
- K+ continues to leave the cell bringing the membrane potential back to normal
- K+ channels close and Na+ channels reset
- Extra K+ outside diffuses away
What is the absolute refractory period
The period of time following an action potential during which no stimulus can initiate another action potential
What mediates the absolute refractory period
The Na+ channels being inactivated by the ball and chain
What is the relative refractory period
The period of time following an action potential during which an action potential can be initiated but only by a stronger than normal stimulus
When does the relative refractory period occur
When the Na+ channels are de-inactivated (ball and chain is no longer closing channel)
What are at the axon hillock the cause an action potential
Voltage gated Na+ channels
Do dendrites have voltage gated Na+ channels
No
What does myelin do to an axon
Makes the conduction of the AP faster because cells can’t leak out
Where are there a lot of unmyelinated axons
Cerebrum
Which pain neuron is myelinated and unmyelinated
Myelinated: Sharp pain
Unmyelinated: Dull pain
How does MS prevent a neuron from conducting the impulse properly
The myelin on the neuron is lost and the AP diminshes because there are no voltage gated Na+ channels where the myelin was located.
Card #50
Good luck on the test
