Topic 8: Synapses & Drugs

Synapses

1. An action potential reaches the presynaptic neuron, causing Ca²⁺ channels to open and Ca²⁺ to enter.

2. This triggers vesicles to release NT into the synaptic cleft.

3. The NT binds to receptors on Na⁺ channels of the postsynaptic membrane, allowing Na⁺ in and possibly triggering a new action potential.

4. Enzymes then break down the NT, resetting the synapse for the next signal.

drugs that are stimulates by an agonist

• increase NT synthesis & release

• bind to receptors & activate them

• stop NT from degrading or being taken up

drugs that are repressed by an antagonist:

• blocking NT synthesis & release

• blocks receptors & stops NT binding

nicotine (stimulant)

binds to ACh receptors on the postsynaptic membrane. It triggers an action potential but temporarily desensitizes the receptor to further stimulation. Nicotine also increases heart rate, blood pressure, and dopamine release.

lidocaine (anesthetics)

• blocks voltage Na+ channels on the post synaptic neuron

• stops action potential

• no pain is felt

cobra venom (represent)

• binds to post-synaptic receptors

• stops transmission across synapses including at the NMJ

• muscles don’t contract = paralysis