Topic 6: Synaptic Transmission 📩

Describe electrical synapses

connect cytosol of adjacent neurons to allow flow of ions, signal transmission is very rapid (brain)

Describe chemical synapses

The cells are not touching and have a very small space between them. They have slower transmission. Action potential can only flow in one direction. They allow for the integration of information by chemical messengers

Which synapse has faster transmission?

electrical synapses

describe presynaptic neuron

the one sending the signal

describe postsynaptic neuron

the one receiving the signal

Describe an axosomatic synapse

axon attaches to cell body

describe axodendritic synapse

synapse between axon and dendrite

describe axoaxonal synapse

synapse between axon and axon

Describe the generation of synaptic response

1. AP arrives at axon terminal of presynaptic neuron

2. Calcium influx into axon terminal due to opening of voltage gated calcium channels

3. vesicles filled with chemical signals are released into synaptic cleft

4. Chemical messenger binds to receptors opening ion channels

5. triggering a graded potential the post-synaptic cell (excitatory or inhibitory)

6. The chemical messenger is either recycled, destroyed or diffused away

Define exocytosis

cells secrete large impermeable molecules dependant on ATP (e.g. release of neurotransmitters)

define endocytosis

molecules or particles move into cells dependant on ATP

What kind of channels does the post-synaptic membrane have?

chemically gated or receptor activated channels (no action potential is generated)

What determines how much neurotransmitter is released?

higher the frequency of the impulse, the more neurotransmitter is released

how would the amount of neurotransmitter released affect the size of graded potential?

the larger the amount of neurotransmitter, the larger the graded potential