Nervous System Drugs

8/6/2019 Nervous System Drugs

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Todays LessonTodays Lesson

Nervous System andNervous System and

Drug AddictionDrug Addiction


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Overview of Lesson

Nervous system

Synapses and neurohormones

Drug addiction


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Neuron

Based on: Raven et al., Biology, McGraw-Hill


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Sensory neuronsSensory neurons -- carry impulses to thecarry impulses to the

interneuronsinterneurons of the brainof the brain

InterneuronsInterneurons of the brainof the brain -- interpret impulsesinterpret impulses

Motor neuronsMotor neurons -- carry impulses to the musclescarry impulses to the muscles

Types of Neurons

Based on: Mader, S., InquiryInto Life, McGraw-Hill


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Nerve ImpulseNerve ImpulseStimulation of neuron, opens channels soStimulation of neuron, opens channels so

that sodium (Nathat sodium (Na++) goes in, depolarizing the) goes in, depolarizing the

membranemembrane

The adjacent section of membrane allowsThe adjacent section of membrane allows

Na+ to go in, depolarizing itNa+ to go in, depolarizing it

This wave of depolarization continues at aThis wave of depolarization continues at a

rapid rate down the neuron, resulting in arapid rate down the neuron, resulting in a

nerve impulse traveling to the brain innerve impulse traveling to the brain in

millisecondsmilliseconds


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Neuron at Rest: Polarized MembraneNeuron at Rest: Polarized Membrane

Outside ofOutside of

neuron isneuron is

positivelypositively

charged due tocharged due topositive sodiumpositive sodium

ionsions

Inside of neuronInside of neuron

is negativelyis negatively

charged due tocharged due to

negative ionsnegative ions

+ + + + + + + + +

- - - - - - - - - - -

Inside of Neuron


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+ + + + + + + +

- - - - - - - - - -

+ + + + + + + +- - - - - - - - - -

+ + + + +

- - - - - -0 0 0 0

Neuron

Neuron

Neuron

Polarized membranePolarized membraneof resting neuronof resting neuron

Sodium (Na) movesSodium (Na) moves

inside to depolarizeinside to depolarize

Nerve impulse is waveNerve impulse is wave

of depolarizationof depolarization

moving down neuronmoving down neuronNerve

impulse

Nerve ImpulseNerve Impulse


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Operates when neuron is at rest orOperates when neuron is at rest or

not transmitting nerve impulsenot transmitting nerve impulse

Pump is a membrane proteinPump is a membrane protein

The protein actively transports Na outThe protein actively transports Na outof the axon to reof the axon to re--establish polarity ofestablish polarity of

membranemembrane

Sodium PumpSodium Pump


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Overview of Lesson

Nervous system


Drug addiction


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There are gaps or junctionsThere are gaps or junctions

between neurons called synapsesbetween neurons called synapses

Based on: Mader, S., InquiryInto Life, McGraw-Hill


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Synapses

Neurotransmitter being released

into synapse and attaching to

receptors on dendriteBased on HarvardMedical School

FamilyHealth Guide


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50 Known Neurotransmitters

Examples include:

Acetylcholine

Dopamine

Serotonin


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Why do we need a

neurotransmitter likedopamine?


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Human behavior is controlled by naturalHuman behavior is controlled by naturalchemical reward systems in the bodychemical reward systems in the body

For example, we like to eat fatty foodsFor example, we like to eat fatty foods

because it make us feel goodbecause it make us feel good

It is the release of dopamine that is theIt is the release of dopamine that is the

chemical reward system responsible for thechemical reward system responsible for the

good feelinggood feeling

Dopamine reinforces behaviors essential toDopamine reinforces behaviors essential to

our survival.our survival.

Importance of DopamineImportance of Dopamine


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After neurotransmitter stimulates theAfter neurotransmitter stimulates the

postsynaptic membrane, it is removedpostsynaptic membrane, it is removed

by an enzyme or transported out ofby an enzyme or transported out ofsynapsesynapse

For example, acetylcholine is removedFor example, acetylcholine is removedfrom synapses by an enzyme calledfrom synapses by an enzyme called

acetylcholinesteraseacetylcholinesterase

Synapses must be cleaned upSynapses must be cleaned up


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Overview of Lesson

Nervous system


Drug addiction


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Cigarettes contribute to death rates fromCigarettes contribute to death rates from

cancer and heart diseasecancer and heart disease

Alcohol is the leading cause of violenceAlcohol is the leading cause of violence

Needles are spreading AIDSNeedles are spreading AIDS

Addiction to drugs, cigarettes and alcoholAddiction to drugs, cigarettes and alcohol

account for a third of all hospital admissions,account for a third of all hospital admissions,

and a majority of all crimesand a majority of all crimes

Drug use costing us excess of 240 billionDrug use costing us excess of 240 billion

dollars annuallydollars annually

Price of Drug Addiction in U.S.Price of Drug Addiction in U.S.


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According to scientists, what isAccording to scientists, what is

the master molecule of addictionthe master molecule of addictionand where is it produced?and where is it produced?


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Dopamine isthought to be the

master molecule of

addiction

It is made in the

brain and affects

primitive parts of

the brainBased on Time, May 5, 1997


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Cocaine blocks the

normal absorption of

dopamine. As a

result, dopamine

accumulates in the

synapse, where is

stimulates the

receiver cell.

Amphetaminesstimulate excess

release of dopamine,

overwhelming the

processes of reuptake

and enzyme

breakdown.

Nicotine stimulatesthe release of

dopamine, while

another substance in

cigarette smoke

blocks the action of

MAO.

How Drug Affect Dopamine LevelsBased on Time, May 5, 1997


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Physiology of AddictionPhysiology of Addiction

Drug enhances amount of dopamine in theDrug enhances amount of dopamine in thesynapsessynapses

Increased dopamine results in increasedIncreased dopamine results in increased

feelings of pleasurefeelings of pleasure Nervous system responds by reducing theNervous system responds by reducing the

number of dopamine receptor sitesnumber of dopamine receptor sites

Addict must take more drug to produceAddict must take more drug to produce

the same highthe same high So while addicts begin by taking drugs toSo while addicts begin by taking drugs to

feel high, they end up taking them in orderfeel high, they end up taking them in ordernot to feel low.not to feel low.


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Nervous System Drugs

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