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E.4

E.4. Neurotransmitters and Synapses. E4.1 Postsynaptic Responses. Pre-synaptic neurons can inhibit or excite the post synaptic neuron by releasing excitatory or inhibitory neurotransmitters

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E.4

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  1. E.4 Neurotransmitters and Synapses

  2. E4.1 Postsynaptic Responses • Pre-synaptic neurons can inhibit or excite the post synaptic neuron by releasing excitatory or inhibitory neurotransmitters • Excitatory neurotransmitters will cause an excitatory post-synaptic potential (EPSP) that will open Na+ channels and depolarize the membrane. The neuron will get closer to threshold and reaching an Action Potential (AP)

  3. E4.1 and E4.2 • Inhibitory Neurotransmitters will cause K+ channels or CL- channels to open and polarize the postsynaptic neuron, which can lead to hyperpolarization of the neuron • EPSP’s and IPSP’s caused by various presynaptic neurons will combine in the process of summation • Summation and IPSP’s explain why some neurons fire and others don’t as an action potential is passed through a network of neurons.

  4. E4.3 • Psychoactive drugs affect personality by influencing the mechanisms that control neurotransmitters and what goes on in a synapse • They can mimic the effect of certain neurotransmitters • They can affect the receptor sites of neurotransmitters on the neurons

  5. E.4.4 • Inhibitory Drugs • Mimic inhibitory neurotransmitters • E.g. alcohol mimics GABA • Block excitatory recptors • E.g. heroin blocks pain and stress neurotransmitter receptors. • Excitatory Drugs • Mimic Excitatory neurotransmitters • E.g. Nicotine • Block neurotransmitter retake gates in presynaptic neuron • E.g. Cocaine keeps dopamine in the synaptic cleft • Block inhibitory neurotransmitter ports • E.g. Caffeine

  6. E4.5 • Cocaine affects mood by increasing the amount of dopamine related neuron transmissions. • Normally, neurons re-absorb dopamine through dopamine reuptake pumps for re-use • Cocaine blocks these pumps • Dopamine remains in the synaptic cleft • The post-synaptic neuron continues to fire • Dopamine is related to causing pleasure The neurons that can receive dopamine are usually associated with pleasure processing. When Cocaine causes these neurons to repeatedly fire, it enhances feelings of pleasure and euphoria With consistent use, the body starts to reduce its own dopamine production, leading to depression.

  7. E4.5 • THC (tetrahydrocannabinol) is the active drug in marijuana • It inhibits the release of inhibitory neurotransmitters • It mimics anandamide, which causes the release of GABA • GABA inhibits the release of dopamine • THC inhibits the release of GABA • So, dopamine release is not inhibited and uncontrolled Anti-Dopamine inhibitory Neurotransmitters It creates a feeling of intoxication Increased feelings of pleasure THC mimics anandamide, which has been linked to the removal of unnecessary short term memories. Thus, THC is known to cause memory problems.

  8. E4.6- Addiction • In the center of the brain is the reward pathway • It is responsible for feelings of pleasure and motivation • It is also responsible for reinforcing behaviors • Dopamine is the main neurotransmitter used in the reward pathway • Drugs that stimulate the reward pathway and increased dopamine related neuron firings are more addictive

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