B15 - Nervous Coordination Flashcards
Describe the cell body of a neuron
Contains large amounts of RER. Production of proteins and neurotransmitters
What are Schwann Cells?
These surround the axon
What covers the axon?
Myelin Sheath
What is the value of the resting potential?
-65mV
What is the state of the sodium ion channels when at resting potential?
They are closed
What is the state of the potassium ion channels when at resting potential?
Open so that K ions can diffuse back out of the axon
Role of Na/K pump when at resting potential?
Actively transports 2K into the axon membrane and 3 Na out of the axon.
How is an electrochemical gradient established?
Negative electrical charge inside the axon - the axon is polarised.
How do voltage-gated channels come about?
Open or closed as their shape changes. This is due to the change of potential difference.
What happens when a stimulus is introduced (action potential)?
Voltage-gated sodium channels open rapidly - influx of Na ions within the axon
What happens once 40mV has been established?
Sodium voltage gates close, so do potassium.
What happens after the 40mV has been reached?
Reversed: More K voltage gates begin to open
Why does the p.d become more negative?
Hyper-polarisation - K channels close slowly.
What is saltatory conduction?
In myelin sheaths - allows the action potential to jump from node to node. Speeds up impulses to 100ms.
Why is transmission slower in unmyelinated sheaths?
Depolarisation takes place the whole way along the axon - making transmission slower
