Nerve Impulses and Synapses Flashcards
What is the correct name for a nerve impulse down the axon?
Action potential
When a neurone is at rest, there are more … ions outside the axon than … ions inside the axon. And what is this controlled by?
- sodium Na+
- potassium K+
This is controlled by the sodium potassium pump.
What proteins is the sodium potassium pump and where are they found?
- carrier proteins
- they are found in the cell membranes of the neurones.
How does the sodium ions and potassium ions move across the membrane?
Active transport
Does active transport need ATP and why?
Yes as the process is active.
How many of each ions are moved in and out of the cell?
-3 sodium ions are moved out of the cell
- 2 potassium ions are moved into the cell
Why is the axon more negatively charged in the inside than the outside of the axon?
As there are fewer potassium ions moving inside the axon than the sodium ions out of the cell.
How can we remember the role of the sodium potassium pump?
123 12
Na+ K+
OUT IN
What is depolarisation?
When stimulated, there is a rapid influx of sodium ions into the axon, depolarising it, as the inside of the membrane becomes more positive)
How does depolarisation spread down the axon?
Depolarisation in one area causes it in the next region and so on till it has moved all down the axon.
What is repolarisation?
The potassium ions move rapidly out of the axon, repolarising it.
What is the refractory period?
No new action potentials can be transmitted during this period until the sodium potassium pump restores resting potential.
When as axon is myelinated ( has … cells which create a … shealth, with the gaps between them being the … of …) the transmission of the action potential is much … as you only need to depolarise the Nodes of Ranvier.
- Schwann
- myelin
- Node of Ranvier
- faster
What is it called when the action potential leaps from one Node of Ranvier to another?
Salutatory Conduction
How fast can unmyelinated axons transmit nerve impulses?
0.5-10m/s
How fast can myelinated axons transmit nerve impulses?
up to 150m/s
What is a synapse?
A small gap between 2 neurones, a chemical neurotransmitter carries the message across the gap.
Why are there lots of mitochondria in the presynaptic neurone?
Provides energy for active transport, protein synthesis and exocytosis
What are the vesicles on a synapse filled with?
Neurotransmitters: acetylcholine
Only on 1 side so pulse can only travel one direction.
What happens when an action potential arrives at the end of the axon?
- Calcium ions: influx, channels open.
- Calcium ions: vesicles - neurotransmitters - moves to the presynaptic membrane.
Why is the left synaptic cleft very narrow?
- Diffusion
- Short distance
- Speed up
What do the neurotransmitters bind to on the postsynaptic neurone?
The receptors on the postsynaptic membrane.
What happens when enough neurotransmitters bind to the postsynaptic neurone?
The sodium channels open and causes depolarisation and therefore action potential.
