SYNAPSE AND THE EFFECTS OF DRUGS

JASREENA LAURENCEHAMSAVATHANI SELVAN

DATCAINY MANIAMSARAH HO

HANIF HAMZAHMAH HAN FONG

NABIL AIMAN

What is synapse?

Synapses is specialized gap that

exist between neurons (axon-to-

dendrite) to transmit impulses from one neuron to another

Pre-synaptic neuron = neuron sending

impulses

Post-synaptic neuron = neuron receiving

impulses

How the impulses move from one neuron to another

? BY

NEUROTRANSMITTERS! NEUROTRANSMITTERS ARE

RESPONSIBLE FOR TRANSMITTING THE IMPULSES

ACROSS THE SYNAPSE

During transmission of the impulses, neurotransmitters runs in a cycle

•Synthesis•Storage•Release•Receptor interaction• Inactivation•Reuptake•Degradation (negative feedback mechanism)

Neural transmission problems if cycle disrupted (e.g., drugs) at any step!

THERE ARE MORE LIKELY AROUND 50

NEUROTRANSMITTERS IN HUMAN BODY, BUT

THE COMMONLY DISCUSSED ONES

ARE.. •Acetylcholine•Serotonin•Dopamine

Removal of neurotransmitter•Neurotransmitters must be clear-up from the synapse to ensure that the response to them is short-lived and precise.

• 3 methods neurotransmitter can be cleared out:

1. Diffusion- neurotransmitter diffuse away from the synaptic cleft.

2. Reuptake by cells- neurotransmitter are actively transported back into the neuron that release them.

3. Degradation by enzyme- inactivated through enzymatic degradation.eg: Acetyl cholinesterase breaks down acetylcholine.

•Acetylcholine, for example, the neurotransmitter that causes muscle contraction is broken down by an enzyme called acetyl cholinesterase.

•The presence of this enzyme ensures that when a neuron stimulates a muscle cell, the stimulus only lasts a second which allows the muscle to then relax immediately after it was stimulated.

•This allows precise, coordinated movements.

Among all the neurotransmitters, what is the master molecule of addiction and where

it is produced??

DOPAMINE is the master molecule of addiction.

ANDIt is made in the

brain and affects

primitive parts of the brain

The normal action of DOPAMINE

1. After being released into the synapse (the gap between nerve endings and receiver cells), dopamine binds to receptors on the next neuron

2. The dopamine is either quickly reabsorbed or broken down by the enzyme monoamine oxidase (MAO)

How actually drugs works?Drugs make their effects known by acting to enhance or interfere with the activity of neurotransmitters and receptors within the synapses of the brain. Some neurotransmitters carry inhibitory messages across the synapses, while others carry excitatory messages. Agonistic drugs enhance the message carried by the neurotransmitters; inhibitory neurotransmitters become more inhibitory, and excitatory neurotransmitters become more excitatory. Antagonistic drugs, on the other hand, interfere with the transmission of neurotransmitter messages; the natural action of neurotransmitters is interfered with so that their effects are lessened or eliminated.

BUT, Most of the drugs that get abused are agonists of various

neurotransmitters - they work to enhance the natural effect of

neurotransmitters!

How drug affect Dopamine level.

Cocaine blocks the normal absorption of dopamine. As a result, dopamine accumulates in the synapse, where is stimulates the receiver cell.

Amphetamines stimulate excess release of dopamine, overwhelming the processes of reuptake and enzyme breakdown.

Nicotine stimulates the release of dopamine, while another substance in cigarette smoke blocks the action of MAO.

Physiology of Addiction Drug enhances amount of dopamine in the

synapses Increased dopamine results in increased

feelings of pleasure Nervous system responds by reducing the

number of dopamine receptor sites Addict must take more drug to produce the

same “high” “So while addicts begin by taking drugs to

feel high, they end up taking them in order not to feel low.”

That’s all from us. Thank you.