Neural comms Flashcards
(15 cards)
What is known as the resting potential?
This is when the inside of the axon is less positive than the outside
How does the Sodium-potassium maintain the resting potential?
It pumps out 3 Na+ and takes in 2 K+ to balance out the movement caused by the electrochemical gradient
What is the action potential and how is it established?
NaKama
Upon the arrival of the positive charge of a nerve impulse, the voltage gated Na+ channel opens allowing them to flow inside of the axon.
when the threshold value is met and the inside is more + than the outside of the axon, that’s an action potential
What is meant by the threshold value?
The maximum positive charge needed to reach an action potential
What is the establishing of the action potential and example of?
Positive feedback
How is the resting potential established after reaching the action potential? (4) Hype
1)Voltage gated Na+ channels close
2)Voltage gated K+ channels open and K+ leaves the inside making it hyperpolarized as its now at the minimum positive charge (below resting potential)
3)Na+ enters the inside of the axon gain via Na+ channels
4)Na-K pump restores electrochemical gradient and resting potential
What is the speed of conductance and what are the 2 factors that affect it?
The speed that an action potential travels down an axon.
- axon diameter
- Temp - more diffusion of Na+ trigger action pot faster though denaturing can happen
What are 2 reasons why a wider axon diameter is better for a faster speed of conductance?
There’s less resistance as more space so more room to avoid obstacles
Steadier resting potential as less K+ diffuse out so faster to stim action pot
Where is the only place on myelinated axon where action potentials can be generated?
The nodes of Ranvier
What is it called when an action potential jumps from one node of Ranvier to another?
Saltatory conduction - these jumps are faster than traveling the whole length of the axon and why speed of conductance is faster on myelinated axons
What is the refractory period and its purpose? - sneaky uni
A period when no action potential can be triggered
To insure unidirectional and discrete (separated) impulses
What happens when an action potential arrive at eh presynaptic knob of a cholinergic synapse/neuromuscular junction?
1) It becomes depolarised stiming the the voltage gated Ca2+ channel to open
2)The presence of Ca2+ causes vesicles filled with neurotransmitters (Acetylcholine) to exocytosis
3) Neurotransmitters diffuse across the synaptic cleft and bind to receptors the the post synaptic membrane which leads to an action potential - stims opening of ligand gated Na+ depolarise then action pot
For Cholinergic synapses how is acetylcholine recycled?(what enzyme)
The enzyme Acetylcholinesterase breaks down acetylcholine into ethanoic acid and chlorine to be recycled and recombined in the presynaptic knob again as acetylcholine
What is Temporal Summation?
A Single presynaptic neurone releases neurotransmitter fast and repeatedly over a period of time
What is Spatial Summation?
Multiple presynaptic neurone releasing neurotransmitters all at once
