describes the ability of an antimicrobial to kill or inhibit the growth of a microbe without damaging host cells. Half-life Therapeutic index Broad-spectrum Selective toxicityDescribe the sequence of events that takes place when a nerve impulse arrives at a synapse. (4 marks) (b) The diagrams below show the changes in membrane potential in a presynaptic neurone and postsynaptic neurone when an impulse passes across a synapse. +40 Synaptic -20 20 140 pepo neurone neurone 0 20 membrane golenial membrane potentiam -40 -40 80 2. 3 time milliseconds 1 ?????? ??????? seconds GCE A level (Part 2) Blology Section 8 Assignment 8 0 0 Explain how depolarisation occurs in the presynaptic neurone. (3 marks) (ii) The maximum depolarisation in the presynaptic neurone is +40 mV. State the maximum depolarisation in the postsynaptic neurone. (1 mark) (iii) Calculate the length of the delay between the maximum depolarisation in the presynaptic and postsynaptic neurones. (1 mark) (iv) Give a reason for this delay. (1 mark) c) Describe how ecstasy affects synaptic transmission. (2 marks) (Total 12 marks)

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