Communication with the Neuron Flashcards
Which ions are higher in concentration outside the axon compared to inside the axon during polarisation?
Sodium Na+
Which ions are higher in concentration inside the axon compared to outside the axon during polarisation?
Potassium, K+ ions.
What occurs during polarisation?
The sodium-potassium pump causes the diffusion of sodium ions from the outside to the inside of the axon and of potassium ions in the opposite direction, against their concentration gradient. This occurs to establish resting potential.
What is the resting potential of the neuron?
-70mv.
What causes voltage gated sodium channels in the axon membrane to open?
Depolarisation in previous axon spaces.
What occurs when voltage gated sodium channels in the axon open?
Sodium ions diffuse into the axon and potassium ions diffuse out, along their respective concentration gradients.
= Depolarisation
How does the charge inside the axon change when depolarisation occurs?
It becomes more positive.
At what charge do the sodium channels close after depolarisation?
Around +40mv
After depolarisation, which channels open after sodium channels close?
Potassium channels.
What is the effect on charge that occurs when potassium channels open after depolarisation and why?
The axon becomes more negative because potassium K+ ions diffuse out of the axon.
What is repolarisation?
The way in which the axon becomes more negative again, after potassium ions diffuse out of the cell.
What occurs after repolarisation?
Hyperpolarisation
Why does hyperpolarisation occur?
Potassium channels open and close very slowly.
How is resting potential restored after hyperpolarisation?
Sodium and potassium ions leak back through the axon by diffusion, along their concentration gradient.
What is the refractory period?
The amount of time that the membrane/axon is hyperpolarised.
Why is the refractory period important?
It ensures that the action potential only travels in one direction, as no action potential can occur during the refractory period.
What percentage of a neuron’s metabolic resources does the sodium potassium pump use for exchange?
40%
What is another term for depolarisation?
Hypopolarisation
What are the two types of ion channel?
Voltage gated and ligand gated.
What is the threshold of excitation?
The charge at which sodium channels open: -60mv
What does the all or none law suggest?
That an action potential either occurs or does not occur - there is no in-between.
What is rate law?
The rate of firing of a neuron codes for stimulus strength
What is salutatory conduction?
The increased speed of conduction due to the ‘jumping’ of an action potential at each node of ranvier. Occurs in insulated axons.
Myelin sheath/insulated axon increases conduction speed. What is the other factor that can influence conduction speed and how?
The diameter of an axon.
The larger the diameter, the faster the conduction.
What are the two types of glia?
Oligodendrocytes and Astrocytes.
What do Oligodendrocytes do?
Lay down myelin sheath in the brain.
What do Astrocytes do?
Form the blood brain barrier.
