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Cognitive Psychology > Action Potential > Flashcards

Flashcards in Action Potential Deck (34)
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1
Q

What is extracellular fluid

A

fluid outside the cell

2
Q

what is intracellular fluid

A

fluid inside the cell

3
Q

What are afferent signals?

A

incoming signals from receptors to the brain (sensory to brain)

4
Q

what are efferent signals?

A

outgoing signals must pass from motor areas to muscle groups (brain to muscles)

5
Q

What is the name for passing of signals among a nerve?

A

Intra-neuronal information transmission

6
Q

Where is information from other neurons received?

A

The dendrites

7
Q

What is the name of the cell body?

A

Soma

8
Q

What is the long ‘tail’ of a neuron called?

A

Axon

9
Q

What are the gaps called on the axon?

A

Nodes of Ranvier

10
Q

What are the coverings called on the axon?

A

Schwann cells (form the myelin sheath)

11
Q

What is the name of the end of the neuron where the message then leaves the neuron?

A

Axon terminal OR button

12
Q

What do the Nodes of ranvier do?

A

Allow membrane to contact extracellular fluid

13
Q

What is saltatory conduction?

A

Allows another action potential to occur at each node of ranvier gap, this repeats the signal at each stage at same intensity so the signal strength remains strong

14
Q

What does the fluid inside and outside the neuron contain?

A

Electrolytes. These contain positively and negatively charged ions of different chemicals

15
Q

What is the potential?

A

The difference between the positively and negatively charged ions

16
Q

What chemicals are in the extracellular fluid

A

Chloride (Cl-)
Sodium (Na+)
Potassium (K+)

17
Q

What chemicals are in the intracellular fluid

A

Chloride (Cl-)
Sodium (Na+)
Potassium (K+)
Protein (A-) - doesn’t cross membrane

18
Q

Where is there more K+?

A

intracellular fluid

19
Q

Where are more Na+ and Cl- chemicals located

A

Outside cell, extracellular fluid. More Na+ outside because of sodium-potassium pump

20
Q

What is the membrane potential?

A

When the difference between the intracellular fluid and extracellular fluid charge is 70mV.

The inside is negatively charged (-70mV) This stored charge is called the membrane or resting potential.

Footnote: If a positive charge is added across the membrane this is called depolarisation,

21
Q

What are the two forces at play that generate the membrane potential?

A

Diffusion - the movement of ions from an area of high concentration to an area of low concentration

Electrostatic pressure - opposite charges attract

22
Q

What does the sodium potassium pump do?

A

Imbalance of Na+ ions wanting to come IN to the cell.
Pumps which is a hole in the membrane wall works to move 3 x Na+ out, and push 2x K+ in.

2 K+ ions move into the cell against diffusion gradient by energetic process of ATP (bodies energy ‘currency’)

3 Na+ ions move outside of cell against diffusion gradient by energetic process of ATP.

Because of this, resting potential (stored charge) of cell is negative (-70mV) which is what we want.

If this didn’t happen, eventually the electrostatic pressure and diffusion would reach balance and there would be no membrane potential

23
Q

What are voltage dependent ion channels?

A

Channels along membrane wall that open in response to change in membrane potential. Open in response to diffusion and electrostatic charge.

This means the composition of the fluid inside and outside the cell is always changing and the balance of the forces is always changing

24
Q

What are the two voltage dependent ion channels?

A

Potassium VDI channels
Sodium VDI channels

Work on membrane alonside sodium potassium pumps

25
Q

What are the four stages of an action potential?

A
  1. Resting potential
  2. Depolarisation
  3. Repolarisation
  4. Hyperpolarisation

Each stage is defined by the voltage caused by the movement of ions across the membrane via the VDI channels.

26
Q

What happens if there is a stronger stimuli / input?

A

Input strength doesn’t change the AP as it is always the same size and duration but a stronger input can lead to more frequent AP release. Increased firing = stronger response

27
Q

What is stage 1: resting potential?

A
  1. neuron is inactive, it is in a state of being ‘ready to fire’ but no stimulus to membrane meaning the stored charge of -70mV remains and this Is called the resting potential
28
Q

What is depolarisation?

A

Influx of positive charge - membrane potential reaches state of EXCITATION (-55mV). At this threshold;

Na+ VDI channels open…influx of Na+ ions into cell because want to go in because it’s negatively charged and opposites attract, and also there’s less Na+ ions inside so they want to go diffuse across.

Because of this, K+ VDI channels open in response. Outflow of K+ ions from the cell due to diffusion at first (there are less outside so they want to go out), then they go out because the inside is becoming more positive, outside more negative, and because K+ is positive, electrostatic pressure force makes them go out, as the membrane potential becomes positive.

Membrane potential changes from -55mV to +40mV

29
Q

what happens at stage 3, repolarisation?

A

Na+ channels close, Na+ ions stop going IN to the cell

K+ ions continue to flow out, but fact sodium (+) is not going in, and K+ continues to go out, the membrane potential is going more negative.

K+ channels begin to close slowly at -55mV

Outflow of K+ ions due to diffusion brings the membrane potential back down to -70mV.

30
Q

What happens at stage 4, hyperpolarisation?

A

K+ channels still closing, allowing K+ ions to continue flowing out of the cell. This brings the inside of the cell more negative and increases the charge difference across the membrane.

The membrane potential falls below the level of the resting potential

Diffusion (and the sodium/potassium pump) then act to return the membrane potential back up to the resting potential (-70mV)

31
Q

What is the refractory period.

A

Everything after stage 2 depolarisation phase.
A period in which the neuron can’t generate another action potential

It is what makes the hops on the axon (between nodes of ranvier) directional

32
Q

What is the absolute refactory period?

A

Repolarisation - a new AP is impossible

33
Q

What is the relative refactory period?

A

Hyperpolarisation - a new AP is possible but would take a very large input of positive charge to get us back to threshold point.

34
Q

Clinical relevence of Action potential. What diseases are caused by issues with AP?

A

Multiple sclerosis is an autoimmune disease affecting myelination of nerve fibres. Means they are not formed properly and signal transmission via the action potential is impeeded