Neurobiology/ Behavior Lesson E.4.3 -E.4.6 Emma Burton Roshini Jayasankar

E.4.3 Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing postsynaptic transmission. The postsynaptic membrane contains receptors for the normal neurotransmitters. Normally when the neuro transmitter attaches to these receptors it either: Depolarise the postsynaptic neuron resulting in an action potential Hyperpolarize the postsynaptic neuron resulting in no action potential A drug can therefore change postsynaptic output by: Blocking or enhancing the depolarising neurotransmitter Blocking or enhancing the hyperpolarize neurotransmitter This provides a complex of possible effects. The important issue however is to consider the type of receptor in the postsynaptic membrane and its associated normal effect on the mind. Psychoactive drugs are those that alter the state of mind by changing (stopping or enhancing ) the activity at the postsynaptic neuron.

E.4.4 List three examples of excitatory and three examples of inhibitory psychoactive drugs. Excitatory psychoactive drugs are drugs which increase the activity of the nervous system Inhibitory psychoactive drugs are drugs which decrease the activity of the nervous system Examples of Excitatory psychoactive drugs 1) Cocaine 2) Nicotine 3) Amphetamine Examples of Inhibitory psychoactive drugs 1) Benzodiazepines 2) Alcohol 3) Cannabis( THC: Tetrahydrocannabinol)

E.4.6 Discuss the effects of THC and cocaine in terms of their action at synapses in the brain. E.4.5 Explain the effects of THC and cocaine in terms of their action at synapses in the brain.

E.4.5 and E.4.6 THC What is it? THC stands for Tetrahydrocannabinol and comes from Cannabis sativa plant specifically the plants leaves and buds which are known better as Marijuana. THC is the plants main psychoactive chemical. THC is responsible for most of Marijuanas psychological effects.THC changes behavior by binding to receptors on Nerve cells, which responds by a change in activity.

E.4.5 and E.4.6 —Cannabinoid receptors are activated by a neurotransmitter called anandamide.They are found in areas of the brain that affect thinking, memory, pleasure, coordination and time perception. —Anandamide belongs to a group of chemicals called cannabinoids. THC is also a cannabinoid chemical. THC mimics the actions of anandamide, meaning that THC binds with cannabinoid receptors and activates neurons, which causes adverse effects on the mind and body THC stimulates cells in the brain to release dopamine, creating euphoria. It also interferes with how information is processed in the hippocampus, which is part of the brain responsible for forming new memories. THC can induce hallucinations, change thinking and cause delusions.

E.4.5 and E.4.6 Effects of THC THC affects brain’s short-term memory —THC affects motor coordination & appetite —THC increases heart rate and raises levels of anxiety —THC contains cancer-causing chemicals similar to those in tobacco —THC affects higher order thinking —THC users report feeling mellow and calm —THC mimics the neuro-receptor anandamide —THC binds to the post synaptic membrane receptors for anandamide called Cannabinoid Receptor —THC effect is to hyperpolarise the post synaptic neuron inhibiting generation of an action potential.

E.4.5 and E.4.6

Cocaine E.4.5 and E.4.6 What is it? —Cocaine:- a powdered drug that is made from the leaves of the coca plant grown primarily in South America. Cocaine stimulates transmission at synapses in the brain that use dopamine as a neurotranmitter. Cocaine binds to membrane proteins that pump dopamine back into the pre-synaptic neurons thus causing a build-up of dopamine in the synapse.

E.4.5 and E.4.6 Cocaine blocks the dopamine reuptake pump in the presynaptic terminal Consequently, dopamine remains active in the synapse, continuing to bind to postsynaptic receptors and causing excitation

E.4.5 and E.4.6 Effects of Cocaine —cocaine is an excitatory psychoactive drugs that increases synaptic transmission —on post synaptic membrane receptor, it prevents the removal of acetylcholine —on pre-synaptic membrane, it prevents the recycling of acetylcholine —both effects maintain the stimulation of the post synaptic membrane —cocaine also blocks the recycling of Dopamine at the Pre-synaptic membrane, making dopamine to remain active in the synapse —dopamine is associated with a feeling of pleasure , thus cocaine creates a mood of euphoria Suppresses appetite and enhances endurance / energy levels Long-term use associated with medical complications and severe mental disorders

Works cited Burrell, John. "Click4Biology: E4 Neurotransmitters." Click4Biology. N.p., n.d. Web. 17 Nov. 2013. Allott, Andrew. "Biology for the IB Diploma: Standard and Higher Level." Google Books. N.p., 2001. Web. 17 Nov. 2013 Cox, Lauren. "What Is THC?" LiveScience.com. Tech Media Network, n.d. Web. 17 Nov. 2013. NIH. "Cocaine: Abuse and Addiction." What Is Cocaine? National Institute on Drug Abuse, Sept. 2010. Web. 18 Nov. 2013. Cornell, Brent. "E4 Neurotransmitters and Synapses." E4 Neurotransmitters and Synapses. N.p., n.d. Web. 18 Nov. 2013. "E.4: Lecture Notes." E.4: Lecture Notes. N.p., n.d. Web. 18 Nov. 2013.