A sedative drug affects nerve transmission by slowing down the movement of neurotransmitters. Taking this sedative can cause drowsiness and significantly slower reaction times.
The diagram below shows a synapse between two neurones in the brain:
A neurotransmitter diffuses across the 24 nanometre24\text{ nanometre}24 nanometre synaptic gap.
In the presence of the sedative drug, the time taken for the neurotransmitter to diffuse between the two neurones is 8.0×10−7 s8.0 \times 10^{-7}\text{ s}8.0×10−7 s.
1 metre=109 nanometres1\text{ metre} = 10^9\text{ nanometres}1 metre=109 nanometres.
Calculate the speed of diffusion of the neurotransmitter when the sedative is present. Use the formula: speed=distancetime\text{speed} = \frac{\text{distance}}{\text{time}}speed=timedistance Give your answer in metres per second (m/s\text{m/s}m/s).
In a healthy brain without the sedative, the speed of diffusion is 0.12 m/s0.12\text{ m/s}0.12 m/s. Explain how your result from part (a) accounts for the symptom of slowed reaction times.