Action and Resting Potentials Flashcards
1
Q
Ionic Composition of Intracellular and Extracellular fluids
A
Inside is More negatively charged than the outside
2
Q
NA+
A
Sodium Ion
3
Q
Cl-
A
Chloride Ion
4
Q
K+
A
Potassium Ion
5
Q
Extracellular Fluids
A
- Large concentration of sodium and chloride ions, and small concentration of potassium ions
- More Positive
6
Q
Intracellular Fluids
A
- A lot of potassium ions
- Few sodium and chloride ions
- Contain large negatively charged proteins in ion form
- Therefore, Inside is More negatively charged than the outside
7
Q
Ions
A
charger molocules
8
Q
Ion Channels and Ion Pumps
A
- Ion Channels – when open, passively allow certain ions like Sodium (Na+) or Chlorine (Cl-) to pass through the membrane.
- Ion Pumps – actively push out sodium ions and draw in potassium (K+) ions, or actively push out calcium (Ca++) ions.
- Requires 20-40% of the energy used by the brain! Because this pump is so important
- The pump has no diffusion at all so
- 3 Na+ in for every two K+ out
9
Q
Membrane and ATP
A
- The membrane is a phosphide lipid bilayer
- The protein structure on the inside has two binding sites- one for sodium and one for potassium- it takes sodium from inside puts it outside and potassium from outside and puts it inside RP
- Adenosine Triphosphate (ATP) – the cell’s energy source – phosphorylates the protein of the pump, changing its shape
10
Q
voltage
A
The energy available as a result of the separated difference in electric charge
11
Q
Factors That Move Ions/Molocules
A
- Diffusion
- Electrostatic Pressure
12
Q
Diffusion
A
- force that moves molecules from areas of higher concentration to lower concentration (more crowded to less crowded)
13
Q
Electrostatic pressure
A
force that moves molecules with like electrical charges apart and molecules with opposite electrical charges together (like magnets)
14
Q
Driving forces for K+ Cl- and Na+
A
Chloride
- Diffusion for chloride, which is outside, says in
- EP for chloride and the interior proteins inside, say out!
Potassium
- Diffusion says out
- EP says in
Sodium
- Diffusion says in (huge driving force for sodium)
- If it was wide open, ALL the sodium would RUSH into the cell
Remember new H&M video
15
Q
Resting Potential
A
- the measurement of the electrical charge across the neural membrane when the cell is not processing information
- Allows potassium to cross freely
- Sodium and potassium pumps have sodium outside and inside have a lot of potassium
- Na+ and Cl- wherever one goes the other follows. As we see in the extracellular fluid, we have lots of chloride (because it follows sodium) and sodium
- Usually rests at -70 mV
- In this state, Inside is negative and outside is positive
16
Q
Action Potential- explain the process
A
- Resting State: Inside more negative than outside. K+ and Negative proteins inside and Na+ and Cl- outside
- neurotransmitters from other cells (post synaptic) were accepted by dendrite receptors
- Neurotransmitters have passive spreads until they reach the axon hillock (AKA positive ions are received and get to AH)
- passive spread of ions you see positive ions traveling and the integration zone is where it reaches the threshold which happens at the axon hillock
- We get to axon hillock which is the point of decision
- Once in a while at membrane of axon hillock there are enough positive ions to push through the threshold (when we reach -65mV) which causes more opening of sodium channels and then boom action potential is shot
- At start of action potential, the channels are alerted
- Takes potassium a whole to wake up
- Sodium opens faster
-
Depolarization: With the rush of sodium inside, it gets up to 40+ mV which means that the neuron is now positively charged relative to the Extracellular fluid- which is the opposite of resting
- This is depolarization- when the sodium channels open
- At this peak, potassium leaves the cell:
- Because now with all the positive sodium inside the driving force tells the potassium to get out
- It jumps from node of Ranvier to the next node of Ranvier until it gets to axon terminal and releases Neurotransmitters
- When we lose the positive potassium charged ions it becomes negative inside again which is called repolarization
- We have the undershoot because of potassium leak channels
- And the potassium pumps are removing sodium from inside the cell as well, which makes the dip
17
Q
What causes the voltage to go up and down?
A
- Sodium makes go up
- Potassium makes it go down
18
Q
4 phases of membrane potential
A
- Resting
- Depolarizing phase
- Repolarizing phase
- Undershoot
19
Q
Differences between Sodium and potassium channels
A
-
Sodium
- Open rapidly
- Remain open briefly and are inactive until the cell reaches resting potential again
-
Potassium
- Open slowly
- Remain open for a longer time
20
Q
tetrodotoxin
A
- a toxin by puffer fish that blocks sodium channels and then you die since sodium can’t get into cell
21
Q
Refractory Periods
A
-
Absolute refractory period- where no stimulus can produce another action potential until the membrane is repolarized AKA back to resting potential
- This is all because the sodium channels can’t open a second time until the membrane is near resting levels
- Relative refractory period- it can respond only when there is larger than normal input
- it gets to -50mV after hyperpolarization so sodium channels open but smaller. since its hyperpolarized and there are less sodium, it needs 10 – 15 mV’s of depolarization (more than usual)
- these ensure it can’t go backwards
22
Q
Conduction velocity
A
- the speed of action potentials – varies with diameter
23
Q
Nodes of Ranvier
A
- small gaps in the insulating myelin sheath
24
Q
Passive Conduction
A
- non myelinated axon
- Sodium starts to rush into cell
- These don’t have insulation, so sodium leaks, and goes through the axon thru diffusion and electrostatic pressure,
- The next segment is still negative because there was no action potential so it travels and reaches there- because its positively charged it makes polarization and that’s why more sodium rushes into cell and goes on and on
- Even thought sodium leaks out it still gets to the end
- There are no pumps here- its more just being pushes
- It’s happening at every segment along the axon, since there are no nodes
25
Saltatory conduction
* **_myelinated –_** the action potential travels inside the axon and jumps from node to node
* The myelin is basically a patch, so we have usual depolarization, and sodium is positive so it depolarizes the next segment which makes more sodium channels to open and more action potential and the sodium can’t leave and it goes until then end.
* It’s called saltatory because it jumps from place to place
26
Inside is More negatively charged than the outside
Ionic Composition of Intracellular and Extracellular fluids
27
Sodium Ion
NA+
28
Chloride Ion
Cl-
29
Potassium Ion
K+
30
* Large concentration of sodium and chloride ions, and small concentration of potassium ions
* More Positive
Extracellular Fluids
31
* A lot of potassium ions
* Few sodium and chloride ions
* Contain large negatively charged proteins in ion form
* Therefore, Inside is More negatively charged than the outside
Intracellular Fluids
32
charger molocules
Ions
33
* **_Ion Channels_** – when open, **passively** allow certain ions like Sodium (Na+) or Chlorine (Cl-) to pass through the membrane.
* **_Ion Pumps_** **– actively** push out sodium ions and draw in potassium (K+) ions, or actively push out calcium (Ca++) ions.
* Requires 20-40% of the energy used by the brain! Because this pump is so important
* The pump has no diffusion at all so
* 3 Na+ in for every two K+ out
Ion Channels and Ion Pumps
34
* The membrane is a phosphide lipid bilayer
* The protein structure on the inside has two binding sites- one for sodium and one for potassium- it takes sodium from inside puts it outside and potassium from outside and puts it inside **RP**
* **_Adenosine Triphosphate (ATP) –_** the cell’s energy source – *_phosphorylates_* the protein of the pump, changing its shape
Membrane and ATP
35
The energy available as a result of the separated difference in electric charge
voltage
36
1. Diffusion
2. Electrostatic Pressure
Factors That Move Ions/Molocules
37
* force that moves molecules from areas of higher concentration to lower concentration (more crowded to less crowded)
Diffusion
38
force that moves molecules with like electrical charges apart and molecules with opposite electrical charges together (like magnets)
Electrostatic pressure
39
Chloride
* Diffusion for chloride, which is outside, says in
* EP for chloride and the interior proteins inside, say out!
Potassium
* Diffusion says out
* EP says in
Sodium
* Diffusion says in (huge driving force for sodium)
* If it was wide open, ALL the sodium would RUSH into the cell
Remember new H&M video
Driving forces for K+ Cl- and Na+
40
* the measurement of the electrical charge across the neural membrane when the cell is not processing information
* Allows potassium to cross freely
* Sodium and potassium pumps have sodium outside and inside have a lot of potassium
* Na+ and Cl- wherever one goes the other follows. As we see in the extracellular fluid, we have lots of chloride (because it follows sodium) and sodium
* Usually rests at -70 mV
* In this state, Inside is negative and outside is positive
Resting Potential
41
1. Resting State: Inside more negative than outside. K+ and Negative proteins inside and Na+ and Cl- outside
2. neurotransmitters from other cells (post synaptic) were accepted by dendrite receptors
3. Neurotransmitters have passive spreads until they reach the axon hillock (AKA positive ions are received and get to AH)
1. passive spread of ions you see positive ions traveling and the integration zone is where it reaches the threshold which happens at the axon hillock
4. We get to axon hillock which is the point of decision
5. Once in a while at membrane of axon hillock there are enough positive ions to push through the **_threshold_** (when we reach -65mV) which causes more opening of sodium channels and then boom action potential is shot
6. At start of action potential, the channels are alerted
1. Takes potassium a whole to wake up
2. Sodium opens faster
7. **_Depolarization:_** With the rush of sodium inside, it gets up to 40+ mV which means that the neuron is now positively charged relative to the Extracellular fluid- **which is the opposite of resting**
1. **This is depolarization- when the sodium channels open**
8. At this peak, potassium leaves the cell:
1. Because now with all the positive sodium inside the driving force tells the potassium to get out
9. It jumps from node of Ranvier to the next node of Ranvier until it gets to axon terminal and releases Neurotransmitters
10. When we lose the positive potassium charged ions it becomes negative inside again which is called **_repolarization_**
11. We have the **undershoot** because of potassium leak channels
1. And the potassium pumps are removing sodium from inside the cell as well, which makes the dip
Action Potential- explain the process
42
* Sodium makes go up
* Potassium makes it go down
What causes the voltage to go up and down?
43
1. Resting
2. Depolarizing phase
3. Repolarizing phase
4. Undershoot
4 phases of membrane potential
44
* **_Sodium_**
* Open rapidly
* Remain open briefly and are inactive until the cell reaches resting potential again
* **_Potassium_**
* Open slowly
* Remain open for a longer time
Differences between Sodium and potassium channels
45
* a toxin by puffer fish that blocks sodium channels and then you die since sodium can’t get into cell
tetrodotoxin
46
* **_Absolute refractory period-_** where no stimulus can produce another action potential until the membrane is repolarized AKA back to resting potential
* This is all because the sodium channels can’t open a second time until the membrane is near resting levels
* * **_Relative refractory period_**- it can respond only when there is larger than normal input
* it gets to -50mV after hyperpolarization so sodium channels open but smaller. since its hyperpolarized and there are less sodium, it needs 10 – 15 mV’s of depolarization (more than usual)
* these ensure it can’t go backwards
Refractory Periods
47
* the speed of action potentials – varies with diameter
Conduction velocity
48
* small gaps in the insulating myelin sheath
Nodes of Ranvier
49
* non myelinated axon
* Sodium starts to rush into cell
* These don’t have insulation, so sodium leaks, and goes through the axon thru diffusion and electrostatic pressure,
* The next segment is still negative because there was no action potential so it travels and reaches there- because its positively charged it makes polarization and that’s why more sodium rushes into cell and goes on and on
* Even thought sodium leaks out it still gets to the end
* There are no pumps here- its more just being pushes
* It’s happening at every segment along the axon, since there are no nodes
Passive Conduction
50
* **_myelinated –_** the action potential travels inside the axon and jumps from node to node
* The myelin is basically a patch, so we have usual depolarization, and sodium is positive so it depolarizes the next segment which makes more sodium channels to open and more action potential and the sodium can’t leave and it goes until then end.
* It’s called saltatory because it jumps from place to place
Saltatory conduction
