nervous-system-drugs - Today’s Lesson Today’s Nervous...

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Unformatted text preview: Today’s Lesson Today’s Nervous System and Nervous Drug Addiction Drug Overview of Lesson • Nervous system • Synapses and neurohormones • Drug addiction Neuron Based on: Raven et al., Biology, McGraw-Hill Types of Neurons Based on: Mader, S., Inquiry Into Life, McGraw-Hill •Sensory neurons - carry impulses to the interneurons of the brain interneurons •Interneurons of the brain - interpret impulses •Motor neurons - carry impulses to the muscles Nerve Impulse Nerve •Stimulation of neuron, opens channels so that sodium (Na+) goes in, depolarizing the that membrane membrane •The adjacent section of membrane allows The Na+ to go in, depolarizing it Na+ •This wave of depolarization continues at a rapid rate down the neuron, resulting in a rapid nerve impulse traveling to the brain in nerve milliseconds milliseconds Neuron at Rest: Polarized Membrane Neuron +++++++++ ----------Inside of Neuron Outside of Outside neuron is positively charged due to positive sodium ions ions Inside of neuron Inside is negatively charged due to negative ions negative ++++++++ ---------Neuron Nerve Impulse Polarized membrane Polarized of resting neuron of ++++++++ ---------Neuron 0000 Nerve impulse +++++ -----Neuron Sodium (Na) moves Sodium inside to depolarize inside Nerve impulse is wave Nerve of depolarization moving down neuron moving Depolarization and Repolarization Based on: Starr, C., Biology: Concepts and Connections, Brooks/Cole Sodium Pump •Operates when neuron is at rest or Operates not transmitting nerve impulse not •Pump is a membrane protein •The protein actively transports Na out The of the axon to re-establish polarity of membrane membrane Overview of Lesson • Nervous system • Synapses and neurohormones • Drug addiction There are gaps or junctions between neurons called synapses Based on: Mader, S., Inquiry Into Life, McGraw-Hill Synapses Based on Harvard Medical School Family Health Guide Neurotransmitter being released into synapse and attaching to receptors on dendrite 50 Known Neurotransmitters • Examples include: – Acetylcholine – Dopamine – Serotonin Why do we need a neurotransmitter like dopamine? Importance of Dopamine Human behavior is controlled by natural chemical reward systems in the body chemical For example, we like to eat fatty foods For because it make us feel good because It is the release of dopamine that is the It chemical reward system responsible for the good feeling good Dopamine “reinforces behaviors essential to Dopamine our survival.” our Synapses must be cleaned up After neurotransmitter stimulates the postsynaptic membrane, it is removed by an enzyme or transported out of synapse synapse For example, acetylcholine is removed For from synapses by an enzyme called acetylcholinesterase acetylcholinesterase Overview of Lesson • Nervous system • Synapses and neurohormones • Drug addiction Price of Drug Addiction in U.S. •Cigarettes contribute to death rates from Cigarettes cancer and heart disease cancer •Alcohol is the leading cause of violence •Needles are spreading AIDS •Addiction to drugs, cigarettes and alcohol Addiction account for a third of all hospital admissions, and a majority of all crimes and •Drug use costing us excess of 240 billion Drug dollars annually dollars According to scientists, what is the master molecule of addiction and where is it produced? and Dopamine is thought to be the master molecule of addiction It is made in the brain and affects primitive parts of the brain Based on Time, May 5, 1997 Dopamine’s Normal Action Based on Time, May 5, 1997 1. After being released into the synapse (the gap 1. After between nerve endings and receiver cells), dopamine binds to receptors on the next neuron dopamine 2. The dopamine is either quickly reabsorbed or The broken down by the enzyme monoamine oxidase (MAO) (MAO) How Drug Affect Dopamine Levels Based on Time, May 5, 1997 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 Physiology • Drug enhances amount of dopamine in the Drug synapses synapses • Increased dopamine results in increased Increased feelings of pleasure feelings • Nervous system responds by reducing the Nervous number of dopamine receptor sites number • Addict must take more drug to produce Addict the same “high” the • “So while addicts begin by taking drugs to So feel high, they end up taking them in order not to feel low.” not Withdrawal Withdrawal • Physiological response to lack of drug Physiological effects, especially the drug’s substitution for naturally produced neurotransmitter for • Withdrawal effects can be intense at first, Withdrawal especially if the drug addict quits abruptly especially • Eventually the body’s physiology returns Eventually to normal, and the person will stop craving the drug the Treatment for Heroin Addicts Treatment • Heroin addicts are put on methadone to wean Heroin them off of heroin • Methadone replaces the heroin without giving Methadone the “rush” the • If the addict tries to take heroin, the If methadone blocks the euphoric effects of it methadone • Eventually the addict’s neurotransmitter Eventually production returns to normal if they can avoid taking heroin taking So how has the scientific view of the cause of drug addiction and treatment changed? treatment Changing View of Drug Addiction Changing • Drug addiction has been viewed as a Drug failure of character and combated with criminal laws and imprisonment criminal • Now some scientists feel drug addiction Now may be a disorder of the brain no different from other forms of mental illness from – May be caused by deficiency in May neurotransmitters neurotransmitters – May be genetically based This powerpoint was kindly donated to is home to over a thousand powerpoints submitted by teachers. 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This note was uploaded on 11/07/2011 for the course BIOLOGY 100 taught by Professor Staff during the Winter '08 term at BYU.

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