synaptic transmission

Question 1

chemical transmission

Answer 1

neurons communicate with each other within groups known as neural networks

each neuron is separated from the next by a gap called the synapse

signals within neurons are transmitted electrically

however signals between neurons are transmitted chemically across the synapse

when the electrical impulse reaches the end of the neuron (the presynaptic terminal) it triggers the release of neurotransmitter from synaptic vesicles

Question 2

neurotransmitters

Answer 2

neurotransmitters are chemicals that diffuse across the synapse to the next neruon in the chain

once the neurotransmitter crosses the gap it is taken up by the postsynaptic receptor site on the dendrites of the next neuron

axons take signals tot he synapse dendrites take signals away

here chemical message is converted back into an electrical impulse and the process of transmission begins again in this other neruon

direction of travel can only be one way - because neurotransmitters are released form the presynaptic neruon terminal and received by the postsynapitic neuron

each different neruotransmitter has its own specific molecular structure that fits perfectly into a postsynaptic receptive site

similar to lock and key

also have specialist function

Question 3

excitation and inhibitation

Answer 3

neurotransmitters have either an excitory or inhibitory effect on the neighbouring neuron

such as the neurotransmitter serotonin causes inhibitation in the receiving neuron resulting in the neruon becoming more negatively charged and less likely to fire

adrenaline causes excitation of the postsynatic neuron by increasing its positive charge and making it more likely to fire

Question 4

summation

Answer 4

whether a postsynaptic neruon fires is decided by the process of summation

the excitatory and inhibitory influences are summed

if the net effect on the postsynapitic neuron is inhibitory then the postsynaptic neuron is less liekly to fire

if the net effect is excitory it is more likley to fire

once the electircal impulse is created it travels down the neruon

therefore the action potential of the postsynaptic neruon is only triggered if the sum of the excitory and inhibitory signals at any one time reaches the threshold