Week 3 Flashcards
What is the resting membrane potential?
Electrochemical gradient where the intro cellular ion concentration is different to the extra cellular ion concentration, which makes the potential to change.
What is neurophysiology?
The physiology of how neuroma produce action potential
What are cations?
Positively charged ions like sodium, potassium, calcium
What are anions?
Negative ions- chloride
Where does the electrochemical gradient in the phospholipid bilayer occur?
Between the intracellular fluid and the extracellular fluid
What is an action potential
Getting the presynaptic terminals to fire
What does the phospholipid bilayer do to the neurons?
Goes around it and maintains resting potential
What is the levels in the ecf?
High sodium low potassium
What is the levels in the icf
High potassium low sodium
What charge are the proteins in the cell and what do they do to the cell?
They are negative and make the cell negative, as well as chloride ions.
What is the overall charge in the inside of the cell?
Negative
What is the usual resting membrane potential?
-70 mV
Why can some ions move across the membrane?
Because of the difference in ICF and ECF, but only if the channels are open.
Why can potassium move across the membrane?
Because the channels are always open for potassium,
What happens if there is a negative ion on the other side and potassium is on the outside?
Potassium is going to want to move across the electrical gradient
What is the concentration gradient?
Where if there is a lot of ions in one place, other ions will traverse to where there is less ions
Ions go from high to low concentration
What happens when the electrons are at rest?
Potassium can float in and out depending on the concentration gradient
Why arnt the levels of potassium the same between the inside and out?
Because there is a sodium potassium pump that transfers 2 potassium in and brings out 3 sodium
What does the sodium potassium pump need to work?
ATP because it’s going against the gradient
When neuron is at rest, what does a sodium pump do?
It closes
When a neuron reaches a less negative charge, what happens?
Channels open for sodium channels. They will only open at certain membrane potentials = -70 to -50 V
When do voltage gated potassium pumps open?
+30 mV
Intracellular and extracellular electrodes measure what?
Action potentials on the inside and outside of cell
What is an action potential
A rapid reversal in potential
How does action potentials occur?
Neurons connect to dendrites and put positive charges in the cell. The axon hillock then decides whether the neuron is going to fire
What is the threshold of excitation.
The threshold for the neuron to fire
What does the change in the charge of an axon affect?
How the ion channels work. If you have more positive ions coming into the cell it will make the cell less negative, which will open the sodium channels. All sodium ions outside of the cell then rush into the cell and reverse the polarity from negative to positive. The polarity goes in a wave along the axon. After change has occurred membrane returns to its original resting potential
What is the voltage for the threshold of excitation
-50mv
What happens when the axon hillock receives a positive charge?
It brings the millivoltage up to -50 which opens the sodium channels, allowing sodium to rush in. Because it is more negative on the outside, some potassium ions leave and the sodium potassium pump closes
What is depolarisation?
Massive influx of sodium ions- going away from the negative
When does the sodium potassium pump close?
When depolarisation occurs and potassium ions leave the cell
What does the voltage of the cell become once the sodium potassium pump closes?
+30 mV
What happens at +30 mV
The voltage gated potassium channels open and the voltage gated sodium channels close. All the potassium that is inside can rush out and the cell becomes repolarised
What is the refractory period?
When the neuron can’t fire again because the voltage is too high
What happens when the potassium is released through the potassium channels?
The charge falls to -80 mV and the voltage gated potassium channels close
What is hyper polarisation?
When you go beyond the resting membrane potential e.g. -80mv more negative
What are the two types of refractory periods?
Absolute- at +30 mV- can never produce an action potential
Relative- unlikely to fire but still possible -80mv
What happens when the membrane is at -80 mV
Sodium potassium pump brings in potassium and pumps out sodium
What is the process of an action potential?
1- triggering event increases positive charge and mV towards the axon helix rise
2- reaches threshold of excitation at -50 mV and voltage gated sodium channels open and sodium rushes in, causing huge increase in positive charge which is called depolarisation
3- at the height of the action potential the voltage gated potassium channels open which let’s all the potassium flow out and you go back down to negative which is called repolarisation
4- hyperpolarisation occurs because it takes awhile to open the voltage gated potassium channels
5- absolute refractory period occurs at -30 mV
6- relative refractory period occurs
When the neuron is at rest what is the concentration like
High potassium low sodium
What channels are open at rest?
Potassium not sodium
What do glial cells and mylin do to neurons?
They wrap around the axon and speed up the conduction
What are the small gaps between the glial cells called?
Nodes of ranvier and help the conductance
What is saltatory conduction?
The propagation of the action potential as it jumps from place to place
Why can’t the action potential go in both directions?
Because of the absolute and relative refractory periods
