Lecture 8 - Part 1 - Neural Transmission Flashcards
What is an action potential
Response to neurone to depolerisation of 15mV - all or nothing
What happens if threshold is reached
Action potential transmitted along neurone = depolerisation
What is the 1st positive shape of action potential due to
Influx of sodium into neuron
What is charge outside neuron
Positive
What is charge inside
Negative
How does neuron become negative after being positive by Na entering
Potassium moves out of neuron by opening potassium ion channels
How is resting potential restored
Sodium potassium pump - pumps K+ back in neurone and Na+ back out
What forces are acting on K+ when the neuron is depolarised during the action potential?
Both the electrical and chemical forces are acting to push potassium
out of the neuron.
Electrical force is pushing it out as inside has become positive and K is positive
Chemical force - a lot of K inside, not outside
What act as ion channels
Proteins inside plasma membrane of a cell which change shape to let ion through
Examples of ion channels
Sodium and potassium ion channels - open and close depending on voltage
What happens to ion channels when membrane is depolerised
Changes shape
open Na channels = Na into neuron
Then Na channel shuts
K channel opens - K out of neuron
What happens when sodium conductance increases
Na+ channel open
What happens when potassium conductance increases
K+ channel open
What happens when sodium conductance decreases
Na+ channel closes
What happens when K+ rises much later
Fall of action potential
What do Na+/k+ channels form
Alpha helices
What are alpha helices
Long chains of proteins that change shape to open/close - pore/hole in middle = ion goes through
How do channels open/close
Due to charge = repulsion/attraction within amino acids makes repulsion
What happens to channels during negative resting neuron and why
Close
Negative attract the positive
What happens to channels during action potential and how is triggered
Inside becomes + = opens Na+ channel
Positive charge inside neuron repels positive bit of protein = molecule flip = open channel = Na move
What property does axoplasm have
High resistance to current spread
What happens as a result of axoplasm having high resistance to current spread
Local (electrotonic) potentials will therefore diminish in size and not be propagated along (longer) neurons = die out
Small potential at one end of neuron will never get to far end of neuron
Do action potentials diminish in size as they travel along neuron
No
What happens to action potentials as they go along nueron
Regenerated
How is action potential transmitted - moved
Inside = positive = Na channel opens = Na pushes in = positive inside = action potential
What happens to action potential when neuron positive
It freezes
What are local circuits
Action potential triggers next bit of axon to produce new action potential
How are local circuits trasnmitted
Positive ions surrounding axoplasm attracted forward to part of neuron that is not stimulated ( opposites attract ) = action potential triggers next bit of axon to produce new action potential
Na+ moves in = attracted to next bit of neuron = opens more Na+ channels = another action potential