Action potential Flashcards
What are neurone
Cells responsible for generation, transmission and processing of nervous impulses
Structure of a neuron
Axon, cell body, dendrite
What direction do impulses pass from in a neuron
Dendrite to axon
What is action potential
The change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell
Function of an ion channel
Provide a mechanism for the diffusion of ions across a membrane
Range of resting potential
-60 to -70m V
Phases of an action potential
1) Initial phase (Depolarisation)
2) Second phase (Repolarisation)
3) Third phase (Hyperpolarisation)
Sequence of an action potential
- Mini depolarisations until a threshold potential is reached
- “All or nothing” threshold : depolarisation (Na+ channels are open, influx of Na+ in and K+ out)
- Repolarisation (Na+ channels are closed, influx of K+ in, Na+ out)
Hyperpolarisation (when cell is so -ve it overshoots the initial resting potential)
What does depolarisation do
Makes the cell more +ve
What does repolarisation do
Makes the cell more -ve
What is myelination
An increase in the fatty sheath surrounding neurone and fibres that increases the efficiency of electrical transmission
What is saltatory conduction
The way an electrical impulses skips from node to node down the full length of an axon. This speeds up the arrivals of the impulse
Ab fibres
6%
5-12 mm
Sharp pain sensations, myelinated
Carry information related to touch
Ad fibres
2-5 mm
Sharp pain sensations, myelinated
Carry information related to pain and temperature (mechanical and thermal)
C fibres
0.3- 1.2mm
Dull pain, thin and unmyelinated
Carry information related to pain, temperature and itch (mechanical, thermal and chemical)
