synaptic transmission

Question 1

what is a synapse?

Answer 1

small gaps which separate each neuron from the next

Question 2

how are signals transmitted within and between neurons?

Answer 2

• electrically
• chemically

Question 3

what happens when the electrical impulse reaches the end of the neuron?

Answer 3

at presynaptic terminal, release of neurotransmitters from synaptic vesicles is triggered

Question 4

what is synaptic transmission?

Answer 4

process by which neighbouring neurons communicate with each other by sending chemical messages across the synapse that separates them

Question 5

what happens once a neurotransmitter crosses the gap?

Answer 5

• taken up by postsynaptic receptor on dendrites of next neuron
• chemical message converted back into electrical impulse
• process of transmission begins again in this neuron

Question 6

what is the difference between where axons and dendrites take signals?

Answer 6

• axons take signals to synapse
• dendrites take signals away from synapse

Question 7

why can the direction of travel only be one-way?

Answer 7

neurotransmitters are released from presynaptic neuron terminal and received by postsynaptic neuron at receptor sites

Question 8

what are neurotransmitters?

Answer 8

chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another

Question 9

what are 2 types of neurotransmitter?

Answer 9

• excitatory
• inhibitory

Question 10

what is excitation?

Answer 10

• when a neurotransmitter, such as adrenaline, increases the positive charge of the postsynaptic neuron
• this increases the likelihood that the postsynaptic neuron will pass on the electrical impulse

Question 11

what is inhibition?

Answer 11

• when a neurotransmitter, such as serotonin, increases the negative charge of the postsynaptic neuron
• this decreases the likelihood that the postsynaptic neuron will pass on the electrical impulse

Question 12

what is summation?

Answer 12

process which decides whether a postsynaptic neuron is fired or not

Question 13

describe the process of summation

Answer 13

• excitatory and inhibitory influences are summed
• if net effect on postsynaptic neuron is inhibitory/excitatory then the postsynaptic neuron is more/less likely to fire
• electrical impulse is created when inside of postsynaptic neuron momentarily becomes positively charged
• positive impulse travels down neuron

Question 14

when is the action potential of the postsynaptic neuron only triggered?

Answer 14

if sum of excitatory and inhibitory signals at any one time reaches the threshold

Question 15

describe the reflex arc using the knee-jerk reflex as an example

Answer 15

• stimulus (hammer) hits knee
• stimulus is detected by sense organs in PNS
• message is conveyed along a SN
• message reaches CNS, where it connects with RN
• RN transfers message to MN
• MN carries message to an effector (muscle) which causes muscle to contract so knee jerks