Neurons [AP 2] Flashcards
3 stages of passive spread
- Passive current spread inside and outside axon
- Local depolarisation subthreshold
- Depolarisation at adjacent parts of the membrane
5 stages of AP transmission
- Action potential
- Passive current spread
- Depolarisation or adjacent parts of membrane to threshold.
- Activation of voltage-gated Na+ channels.
- New (full size) AP generated on both sides of the initial AP.
How do myelinated axons increase AP spread?
Increase the efficiency of passive spread and APS do not need to be generated at every part of the cell membrane
Diameter and AP description and speed for non-myelinated axons
1Mm
Slow continuous
Speed 1m/sec
Diameter and AP description and speed for myelinated axons
Diameter 5-10Mm
Fast, salatory, discontinuous
Speed 20-100m/s
How is current etc. flowing in physiological conditions?
AP only conducts in one direction even though passive is both. Due to absolute refractory period (once this is over, AP has already moved on and can’t be regenerated in the old places. Channels have closed).
What are muscle spindles considered to be?
Receptors In sensory neurons
Describe the 3 things that happen in generation of APs in sensory neurons
- Stimulus causes Graded depolarisation in sensory endings, known as receptor potential.
- RP spreads passively to nearby trigger zone where APS are generated.
- APs are spread along the axon toward CNS.
What is info about the strength of the stimulus encoded in for sensory neurons?
The amplitude of the RP and the frequencies of AP.
What causes AP in the muscle spindles?
Muscle contains ion channels sensitive to stretch. Stretch opens some channels causing depolarisation therefore AP.
Concentrations of K+ and Na+ in / out of cell
Na+ in = 15
Na+ out = 150
K+ in = 100
K+ out = 5
