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Neuropharmacology A.5 Some neurotransmitters excite nerve impulses in postsynaptic neurons and others inhibit them • Neurotransmitters (Excitatory) a. Released from the presynaptic neuron into the synaptic cleft. b. Bind to receptors in the post synaptic neuron causing channels to open. c. This depolarizes the neuron triggering an action potential. • Some neurotransmitters inhibit an action potential which inhibits nerve impulses. Nerve impulses are initiated or inhibited as a result of summation • One pre-synaptic neuron usually does not trigger an action potential. a. Can be hundreds or even thousands of presynaptic neurons. • Summation- the combined effects of excitatory and inhibitory neurotransmitters. a. Action potential depends on the balance of these two. Many different slow-acting neurotransmitters modulate fast synaptic transmission in the brain • Neuromodulators- slow acting neurotransmitters that take many milliseconds to have an effect. a. Usually affect groups of neurons. b. Ex. Dopamine and serotonin 1. Dopamine deficiency is linked to Parkinson’s Disease. 2. Serotonin is linked with depression, OCD, and anxiety. Memory and learning involve changes in neurons caused by slow acting neurotransmitters • Secondary messengers- promote synaptic transmission a. Increase the amount of receptors. b. Chemically modify the receptors to increase the speed. c. Can last for days and cause long-term potentiation (LTP). Psychoactive drugs affect the brain by either increasing or decreasing post-synaptic transmission • Psychoactive Drugs: 1. Excitatory a. Increase post synaptic transmission. b. Ex, Cocaine, nicotine 2. Inhibitory a. Decrease postsynaptic transmission. b. Ex: Alcohol, THC Stimulant drugs mimic the stimulation provided by the sympathetic nervous system • Stimulants- drugs that promote the activity of the nervous system. a. Increase heart rate, blood pressure. b. Make the body respond as though it is being stimulated by the sympathetic nervous system. Addiction can be affected by genetic predisposition, social environment and dopamine secretion • Three areas affecting addiction: a. Genetic predisposition 1. Genes increase chances a. Gene DRD2 codes for dopamine receptors. 1. People with one allele consumed more alcohol. b. Social environment: 1. Peer pressure, poverty c. Excess dopamine production 1. Dopamine is associated with feelings of well being and pleasure.