Brains, Synapses and Brains, Synapses and NeurotransmittersNeurotransmitters

Psychology 3506Psychology 3506

IntroductionIntroduction

Well, the book is called Drugs and Well, the book is called Drugs and Behaviour, so, we had better know Behaviour, so, we had better know how the nervous system workshow the nervous system works

The nervous system is made up, The nervous system is made up, basically, of two types of cellsbasically, of two types of cells• NeuronsNeurons

Do the communicatingDo the communicating

• Glial CellsGlial Cells Support functionsSupport functions

Some key neuron factsSome key neuron facts

One axon, many dendritesOne axon, many dendrites Dendrite -> cell body -> axonDendrite -> cell body -> axon Axons transmit informationAxons transmit information Dendrites receive informationDendrites receive information Dendrites can grow and changeDendrites can grow and change

• Make connections to more axonsMake connections to more axons• Might be the basis of learningMight be the basis of learning

Electrical activity of the neuronElectrical activity of the neuron

Resting potentialResting potential• About -70 mVAbout -70 mV• Selectively allowing certain ions inSelectively allowing certain ions in• With stimulation Na+ is allowed inWith stimulation Na+ is allowed in

Action potentialAction potential• Changes in one area lead to changes in Changes in one area lead to changes in

anotheranother• Chemical to electrical, very coolChemical to electrical, very cool

The action potentialThe action potential

Resistance and myelin affect Resistance and myelin affect transmission ratetransmission rate

Less resistance with a big axonLess resistance with a big axon Normally you have a resting potential Normally you have a resting potential

because a process called Active because a process called Active Transport pump ouf NA+ and pulls Transport pump ouf NA+ and pulls K+ in (3:2) so you get a negative K+ in (3:2) so you get a negative charge across the cell membranecharge across the cell membrane

The Sodium Potassium PumpThe Sodium Potassium Pump

Active transport takes Active transport takes energyenergy

Easier encoding?Easier encoding? Faster reaction?Faster reaction? An Action potential An Action potential

happens when happens when stimulation causes the stimulation causes the pump to sort of stop, pump to sort of stop, Na gets in, K goes outNa gets in, K goes out

Sort of reversed laterSort of reversed later

Biochemical ActivityBiochemical Activity

Otto Loewi did a cool experiment in Otto Loewi did a cool experiment in 19211921

Simulated the vagus nerve is a frog’s Simulated the vagus nerve is a frog’s heartheart

Slowed the heart downSlowed the heart down Washed heart with solution, collected Washed heart with solution, collected

solutionsolution Poured solution on a second heartPoured solution on a second heart It slowed!!!!It slowed!!!!

Loewi and his frogsLoewi and his frogs

Called the substance vagusstoffCalled the substance vagusstoff AcetylcholineAcetylcholine Later stimulated heart rate, similar Later stimulated heart rate, similar

methodmethod Ended up with a sped up heartEnded up with a sped up heart EpinephrineEpinephrine

The SynapseThe Synapse

Gap between the axon and the Gap between the axon and the dendritedendrite

Neurotransmitters are released Neurotransmitters are released across this gapacross this gap

Sometimes, if all of the transmitter Sometimes, if all of the transmitter isn’t absorbed it is taken back up, isn’t absorbed it is taken back up, this is known as reuptakethis is known as reuptake

There is lots of variation in synapsesThere is lots of variation in synapses Some are inhibitorySome are inhibitory Some are excitatorySome are excitatory

More about synapsesMore about synapses

Is the excitatory vs. inhibitory nature Is the excitatory vs. inhibitory nature of a synapse due to shape?of a synapse due to shape?

ProbablyProbably GABA synapses are inhibitory, have GABA synapses are inhibitory, have

less post synaptic thickeningless post synaptic thickening Glutamate synapses have more Glutamate synapses have more

thickening, more vesiclesthickening, more vesicles There are 7 types of synapsesThere are 7 types of synapses

The Seven Steps in The Seven Steps in NeurotransmissionNeurotransmission

SynthesisSynthesis StorageStorage ReleaseRelease Receptor interactionReceptor interaction InactivationInactivation ReuptakeReuptake DegradationDegradation

The NeurotransmittersThe Neurotransmitters

Basically, five conditions must be Basically, five conditions must be met before we call something a met before we call something a neurotransmitterneurotransmitter• Present in terminalPresent in terminal• Released on firingReleased on firing• Placing substance or organ emulates Placing substance or organ emulates

firingfiring• Uptake for inactivationUptake for inactivation• Inactivation blocks stimulationInactivation blocks stimulation

The NeurotransmittersThe Neurotransmitters

Acetylcholine (Ach)Acetylcholine (Ach) MonoaminesMonoamines

• CatecholaminesCatecholamines Norepinephrine (NE)Norepinephrine (NE) Epinephrine (E)Epinephrine (E) Dopamine (DA)Dopamine (DA)

• IndoleamineIndoleamine Seretonin (5-Ht)Seretonin (5-Ht)

• OthersOthers Histamine (H)Histamine (H)

More neurotransmittersMore neurotransmitters

Amino AcidsAmino Acids• Glutamate (universally excitatory)Glutamate (universally excitatory)• GABA (universally inhibitory)GABA (universally inhibitory)• GlycineGlycine• ProlineProline

PeptidesPeptides• Substance PSubstance P

Finally….Finally….

Morphine like substancesMorphine like substances• EndorphinsEndorphins• EnkephalinsEnkephalins

Other peptidesOther peptides• InsulinInsulin• ProlactinProlactin• HGHHGH• VasopressinVasopressin

ReceptorsReceptors

Transmitters bind to receptorsTransmitters bind to receptors Sort of like a lock and a keySort of like a lock and a key Binding siteBinding site Ion channelIon channel One neuron (usually) has only one One neuron (usually) has only one

type of receptortype of receptor Great place for drug interactionGreat place for drug interaction

The Nervous systemThe Nervous system

Central Nervous system (CNS)Central Nervous system (CNS)• Brain, spinal column, cerebellumBrain, spinal column, cerebellum• Communication is neuralCommunication is neural

Peripheral Nervous system (PNS)Peripheral Nervous system (PNS)• Nerves that make you move basicallyNerves that make you move basically• Communication is neuralCommunication is neural

Autonomic nervous systemAutonomic nervous system