9.6 - effects of drugs on the nervous system

Question 1

what drugs affect the function of synapses/nervous system

Answer 1

• nicotine
• lidocaine
• cobra venom

Question 2

ways in which drugs affect synapses - increasing response

Answer 2

1. increases amount of neurotransmitter synthesised
2. increases release of neurotransmitter from vesicles at presynpatic membrane
3. binds to postsynaptic receptors & either activates them or increases effect of normal neurotransmitter
4. prevents the degradation of neurotransmitter by enzymes or prevents reuptake into presynaptic knob

Question 3

ways in which drugs effect synapses - decreasing response

Answer 3

1. blocks synthesis of neurotransmitter
2. causes neurotransmitter to leak vesicles & be destroyed by enzymes
3. prevents release of neurotransmitter from vesicles
4. blocks receptors & prevents neurotransmitter binding

Question 4

nicotine

Answer 4

• affects synapses of the brain and PNS
• synapses have nicotinin acetylcholine (ACh) receptors
• can cause increased heart rate and blood pressure due to nerve stimulation
• dopamine is released in the brian → causes feeling of well-being

Question 5

lidocaine

Answer 5

• an anaesthetic
• prevents impulses from being conducted along nerve fibres that are responsible for causing pain sensations

Question 6

how does lidocaine work

Answer 6

• voltage dependant Na+ ion channels in postsynaptic membrane is blocked
• Na+ ions cannot enter the cell when the neurotransmitter binds
• action potential cannot form

Question 7

cobra venom

Answer 7

• causes paralysis

Question 8

how does cobra venom work

Answer 8

• binds to acetylcholine receptors
• prevents transmission of impulses across synapse
• if nerves that stimulate breathing are affected, muscles not stimulated to contract leading to paralysis
• when toxins reach muscles involved in breathing, the person can die

Question 9

describe the events that lead to the release of acetylcholine at a synapse (3marks)

Answer 9

• action potential/impulse arrives at presynaptic knob
• calcium channels open and calcium ions diffuse in
• vesicles move to membrane
• vesicles fuse with membrane and release acetylcholine

Question 10

Neurone A releases the excitatory neurotransmitter acetylcholine.
- Describe the sequence of events that leads to an excitatory postsynaptic potential
(EPSP) in the postsynaptic neurone after stimulation of neurone A.