E.4 presentation

E.4 Neurotransmitters and Synapses

Narisa and Pauline

Synaptic transmission

*note that neurotransmitters is received by a receptor but does not enter the postsynaptic neuron

Neurotransmitters (NT)

Inhibitory Excitatory

•Increase permeability of postsynaptic membrane to (+) ions

•(+) ions to move out of the postsynaptic cell

•Depresses postsynaptic cell harder to excite

Excitatory neurotransmitters

• Ex: Achetylcholine (Ach)• Generates action

potential• Increase permeability of

postsynaptic membrane to (+) ions

• Influx of Na+

• Depolarization • Action potential

Inhibitory neurotransmitters• Ex: Gamma-aminobutryic

acid (GABA)• Hyperpolarization• Postsynaptic neuron more

(-) • Cl- in or K+ out• Difficult to generate action

potential

Decision-making in the CNS • axons (many neurons) feed into the dendrite of the

postsynaptic neuron• Each contribute to the mV of the postsynaptic neuron• excitatory/inhibitory• Summative effect (added up at the axon hillock)• If summative effect of the inputs reaches threshold, an

AP is generated

Psychoactive drugs

Brain Personality ACETYLCHOLINE

NORADRENALINE

Cholinergic synapses • Ex of NT: acetylcholine (Ach)

Released by motor neurons Activates skeletal muscle

• Remaining Ach in synapse Fire indefinitely

• Acetylcholinesterase Breaks down Ach

• Parasympathetic nervous system (E.5) Causes relaxation

Cholinergic synapses (continued)• Cholinergic synapses are synapses that use

Ach• Ex: Nicotine

Stimulates transmission in cholinergic synapses Calming effect

Adrenergic synapses • Ex of NT: noradrenaline

Depolarizes postsynaptic neuron

Sympathetic system ‘fight or flight’

• Synapses using noradrenaline are adrenergic synapses

• Ex: Cocaine&amphetamines Alertness, energy, euphoria

Cholinergic Adrenergic

Neurotransmitter

Nervous system

Effect on mood

Drug(s)

Acetylcholine Noradrenaline

Parasympathetic Sympathetic

calming Increase energy and alertness, euphoria

Nicotine Cocaine, amphetamines

Drugs on synaptic transmission *drugs have structures similar to neurotransmitters *same chemical structure = same effect*not broken down = stays longer = effect stronger

http://i-biology.net/options/option-e-neurobiology-and-behaviour/e4-neurotransmitters-and-synapses/

Excitatory DrugsNicotine- Tobacco products- Stimulant- Mimics Acetylcholine (Ach)

*Cholinergic Synapses (Body & Brain)

*Calming Effect

ADDICTION

Nicotine

• Ach Case: Ach received by receptors Broken down by acetylcholinesterase

• Nicotine Case: Nicotine received by receptors Nicotine molecules remains on the

receptors

*Excites postsynaptic neuron *release a molecule called dopamine

• Dopamine: feeling of pleasure• ‘reward pathway’ of your brain

Cocaine- Adrenergic Synapse- Cocoa plants- Alertness + Euphoria - Dopamine Release

Excitatory Drugs

Blocks removal of Dopamine from the synapse Build up of Dopamine

Overstimulation of the postsynaptic neuron

‘reward pathway’ Euphoria

ADDICTION

http://www.thirteen.org/closetohome/animation/coca-anim-main.html

Excitatory DrugsAmphetamine- Adrenergic synapses- increased energy + alertness

*Directly into nerve cells which carry dopamine + noradrenaline

*Moves into vesicle of presynaptic neuron

*triggers increase in release of neurotransmitters: more action potentials

*Amphetamine interfere with breakdown

Amphetamine• High concentrations of dopamine euphoria• High concentrations of noradrenaline alertness• Amphetamines high energy

DopamineNeurotransmitter for CNSRole:

way the brain controls movement, memory, decision making

More dopamine means: causes neuron to fire more often resulting in a euphoric feeling

ExcessContribute to psychotic illnesses (schizophrenia)

UnderproductionMovement disorder (Parkinson’s)

Excitatory Drugs

http://outreach.mcb.harvard.edu/animations/synapse.swfhttp://www.psych.ualberta.ca/~ITL/flash/stimulants_draft.swf

Inhibitory Drugs Benzodiazepine • Reduces anxiety• Used against epileptic seizures

(brain disorder)• modulate activity of GABA

(inhibitory NT)Inhibitory NT hyperpolarization

• Increases the binding of GABA to receptorsPostsynaptic neuron more

hyperpolarized

Effect of benzodiazepines at the synapse

Alcohol• Increases the binding of

GABA to the postsynaptic membraneHyperpolarized

• Sedative effect Decrease activity of glutamate

(excitatory NT)Increase the release of

dopamine

Inhibitory Drugs

Inhibitory Drugs• Tetrahydrocannabinol (THC)• Psychoactive chemical in marijuana• Mimics NT anandamide

Binds to the same receptor (cannabinoid receptors)

• Inhibitory neurotransmitterHyperpolarized

• Anandamide – role in memory functionsMarijuana affects short-term memory Anandamide may be involved in

eliminating information that is not needed

MarijuanaRelaxed, MellowLight-headed, HazyTHC Dilate pupils Color PerceptionSenses may be enhancedPanic + Paranoia

THC and Cocaine: Mood, synapse, behavior

SYNAPSE*Cannabinoid receptors LearningCoordinationProblem solvingShort-term Memory

Mechanism*mimics anandamide*inhibits the neurons that anandamide inhibits*No enzyme to break down THC*Stays in the synapse longer = greater effect

THC and Cocaine: Mood, synapse, behavior

Short Term Memory

CoordinationMotor impairment (THC)

CocaineEuphoriaTalkativenessMental AlertnessTemporary decrease in need for food + sleepLarge amounts: erratic/violent behavior

THC and Cocaine: Mood, synapse, behavior

SYNAPSE*ability to sustain dopamine levels in the synapse

*dopamine: ‘reward pathway’Longer it is there, the better you feel

• Alcohol• Tobacco• Psychoactive drugs• Pharmaceuticals (some)

Body: develops a tolerance

Addiction: Chemical dependency on drugs where the drug has ‘rewired’ the brain and has become an essential biochemical in the body

SmokingCauses the brain to be rewired Nicotine mimics acetylcholinePeople who smoke: crave a dopamine spike

Causes of Addiction

AddictionAbused drugs: euphoriaWithdrawal: anxiety, depression,

craving

Alcohol: seizures, delirium tremens (severe shaking)

Continued addiction: harmfulInhaled drugs: damage lungsSharing needles: contract

HIV/Hepatitis B and CKidney disease

Causes of Addiction

*Addiction + GenesGenetic Predisposition

Dopamine ReceptorsDeficiency of dopamine receptors addiction

Case: RatsAlcohol preferring rats 20 % lower levels of dopamine receptorsConsumed: 5g ethanol/kg EVEN when given a choice between ethanol + waterNon-preferring rats: 1g ethanol/kg of body weight

• Some people are genetically more pre-disposed to becoming addicts• Family histories/pedigree charts Susceptibility to addiction• Different allele of a receptor gene, or to carry modified versions of other genes linked to drug metabolism• Risk-taking behavior more likely to experiment with drugs• Explains why some people never try drugs• Why some people who do drugs don’t become addicts

Determine child’s vulnerability to substance abuse

Family addiction Family parenting skills Mental health problems of

family/child

PEER PRESSURE!*affects adolescents more than adults*drugs/alcohol*users teach new users: effects to

expect + what altered state is desirable

Social Factors

British: Opium into ChinaSOCIAL PROBLEM

Heroin USASOCIAL CATASTROPHE

Alcohol at parties:Notion that only with alcohol can there be a party

Saudi Arabia: Alcohol is prohibited by culture+ lawAlcoholism is rare

CHEAP and EASY ACCESS ADDICTION

Social Factors

DOPAMINE:Neurotransmitter activate reward

pathway pleasure/satisfactionCocaine use: dopamine build up

Drug AddictionReceptors are constantly stimulatedOverstimulation decreases the

number of receptors

Less sensitive tolerant

Neuroadaptive change critical for producing addiction

Dopamine Secretion

ResearchKnockout mice – genetically

manipulated mice addicted to cocaine

Neurotransmitter GlutamateGlutamate = oversee learning

and memories which lead to cocaine seeking

Dopamine Secretion

DRUG FUN FACTWhich was the first country in the world, in

2003, to offer medical marijuana?a) Germanyb) Netherlandsc) Canadad) United States

Cocaine is the _______ most commonly used illicit drug in the United States.

a) Firstb) Secondc) Thirdd) Fourth

DRUG FUN FACT

What did the drink Coca-Cola originally contain?

DRUG FUN FACT

COCAINE!!!

Scientist claim that the average smoker will lose _____ years of their life due to smoking.

DRUG FUN FACT

14

Nicotine reaches the brain in _____ seconds.

DRUG FUN FACT

10