Neurotransmission (2) Flashcards
What does propagate mean?
Transmit
What is the action potential propagation speed?
0.1m/s to 100m/s
What are the two factors that affect how fast membrane potential changes?
1. Affected by r____ of m____
2. Affected by c____ of c____
- Affected by resistance of membrane (slower if more charge can leak out)
- Affected by capacitance of cell (how easy it is to change the membrane voltage)
What are the two factors that affect how far depolarisation can spread along the axon?
1. M____ r____
2. D____
- Affected by membrane resistance - more leaky membrane -> depolarisation spreads less far
- Affected by diameter (internal resistance to flow down the axon) - big diameters conduct faster
How does myelination result in less charge loss?
Myelin insulates membrane
What is meant by saltatory conduction?
A____ p____ travelling from one n____ of r____ to the next
Action potentials travelling from one node of ranvier to the next
What is the synapse?
A tiny gap between neurons
What are the six steps of synaptic transmission?
1. Action potential arrives at a____ t____
2. Membrane depolarisation opens v____-gated c____ channels
3. C____ inside cell causes v____ of neurotransmitter to f____ with membrane
4. Neurotransmitter d____ through synaptic c____
5. Neurotransmitter binds to l____-gated i____ channel
6. Ions flow through the channel, d____ or h____ the post-synaptic membrane
- Action potential arrives at axon terminal
- Membrane depolarization opens voltage- gated calcium channels
- Calcium inside cell causes vesicles of neurotransmitter to fuse with membrane
- Neurotransmitter diffuses through synaptic cleft
- Neurotransmitter binds to ligand-gated Ion channel (a channel that opens when a molecule binds to it)
- Ions flow through the channel, depolarizing or hyperpolarizing the post-synaptic membrane.
What is meant by an excitatory synapse?
If the i____ channels allow s____ in, the membrane potential becomes more d____ - the p____ synaptic cell is nearer to the t____ for opening voltage gated s____ channels, the cell is more likely to f____ an a____ p____. This is an excitatory snapse.
If the ion channels allow sodium in, the membrane potential becomes more depolarized – the post synaptic cell is nearer to the threshold for opening voltage gated sodium channels – the cell is more likely to fire an action potential. This is an excitatory synapse
What is meant by an inhibitory synapse?
If the i____ channel lets c____ in, the membrane potential will be held near the c____ resting potential - b____ threshold for firing action potentials. This makes the cell l____ likely to fire an ction potential - the synapse is inhibitory
If the ion channel lets chloride in, the membrane potential will be held near the chloride resting membrane potential - below threshold for firing action potentials. This makes the cell less likely to fire an action potential - the synapse is inhibitory
Depolarisation of dendrites by ion flow through glutamate receptors generates what?
An e____ p____-s____ p____ (EPSP) - drives m____ potential towards t____ for action potential f____.
An excitatory post-synaptic potential (EPSP) - drives membrane potential towards the threshold for action potential firing
Glutamate opens cation (positive ion) channels. Which ions does it allow through?
Na+ and K+
What happens during feedforward excitation?
An e____ cell a____ the next cell, which p____ on that e____
An excitatory cell activates the next cell, which passes on that excitation
What happens during lateral inhibition?
Excitatory cells activate inhibitory neurons that inhibit adjacent excitatory neurons
With lateral inhibition, there is a bigger change in perceived light at boundaries. Why is this?
Because the high firing neurons inhibit their neighbours. At the boundary, the high firing rate light-activated neuron receives less inhibiton than the high firing rate neurons far from the boundary, and the low firing rate neurons are more inhibited near the boundary than those further from the boundary
