The effect of drugs on the synapse

• WALT

• That different drugs affect the synapse in different ways

• To research different drugs and their effects on the synapse

Research the following drugs and describe their effects on the

synapse

• Nictoine

• Atropine

• Betablockers

• Curare

• Prozac

Drugs and the synapse

• Almost all drugs taken by humans (medicinal and recreational) affect the nervous system.

• From our understanding of the human nervous system we can understand how many common drugs work

Drugs can affect the nervous system in various ways, shown in

this table:Mimic a neurotransmitter Switch on a synapse

Stimulate the release of a neurotransmitter

Switch on a synapse

Open a neuroreceptor channel Switch on a synapse

Block a neuroreceptor channel Switch OFF a synapse

Inhibit the breakdown enzyme Switch on a synapse

Inhibit the Na+K+ATPase pump Stop action potentials

Block the Na+ or K+ channels Stop action potentials

Excitatory drugs:

These amplify the process of synaptic transmission by

1. mimicking the transmitter substance

2. stimulating the release of more of the natural transmitter

3. slowing or preventing the breakdown of the transmitter examples: amphetamines, caffeine, nicotine

Inhibitory drugs:

These decrease the process of synaptic transmission by

1. Preventing the release of the synaptic transmitter

2. Blocking the action of the transmitter at the receptor molecules on the postsynaptic neuron

example: atropine

Agonists/ Antagonists

Agonists:

• Drugs that stimulate a nervous system are called agonists

Antagonists:

• Drugs that inhibit a system are called antagonists

Nicotine

• Nicotine is a similar shape to acytylacholine and so competes with acetylcholine to bind with its receptors

• Once it has bound to the receptors it opens the sodium channels cusasing an action potential to be generated

Atropine

• Parasympathetic antagonists like atropine binds to the acetylcholine receptors but blocks the receptors so inhibiting the muscarinic acetylcholine receptors in parasympathetic system, and are used as eye drops to relax the ciliary muscles in the eye.

Beta Blockers

• Sympathetic antagonists like the beta blockers block the noradrenaline receptors in the sympathetic nervous system.

• They cause dilation of blood vessels in the treatment of high blood pressure and migraines, and reduce heartbeat rate in the treatment of angina and abnormal heart rhythms.

Curare

• Used as a muscle relaxant in abdominal surgery

• It competes with acetylcholine at the neuromuscular junctions preventing the muscles from contracting.

• South American Indians use it as a poison to catch animals by smearing theor arrow tips with it

Prozac

• Serotonin is a neurotransmitter in the brain

• Prozac works by inhibiting the uptake of serotonin

• This means there is an increased concentration of serotonin at the synaspes

• Making the patient feel happier and more relaxed!!