Brains, Synapses and Neurotransmitters Psychology 3506

Introduction Well, the book is called Drugs and Behaviour, so, we had better know how the nervous system works Well, the book is called Drugs and Behaviour, so, we had better know how the nervous system works The nervous system is made up, basically, of two types of cells The nervous system is made up, basically, of two types of cells NeuronsNeurons Do the communicating Do the communicating Glial CellsGlial Cells Support functions Support functions

Some key neuron facts One axon, many dendrites One axon, many dendrites Dendrite -> cell body -> axon Dendrite -> cell body -> axon Axons transmit information Axons transmit information Dendrites receive information Dendrites receive information Dendrites can grow and change Dendrites 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 neuron Resting potential Resting 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 potential Action potential Changes in one area lead to changes in anotherChanges in one area lead to changes in another Chemical to electrical, very coolChemical to electrical, very cool

The action potential Resistance and myelin affect transmission rate Resistance and myelin affect transmission rate Less resistance with a big axon Less resistance with a big axon Normally you have a resting potential because a process called Active Transport pump ouf NA+ and pulls K+ in (3:2) so you get a negative charge across the cell membrane Normally you have a resting potential because a process called Active Transport pump ouf NA+ and pulls K+ in (3:2) so you get a negative charge across the cell membrane

The Sodium Potassium Pump Active transport takes energy Active transport takes energy Easier encoding? Easier encoding? Faster reaction? Faster reaction? An Action potential happens when stimulation causes the pump to sort of stop, Na gets in, K goes out An Action potential happens when stimulation causes the pump to sort of stop, Na gets in, K goes out Sort of reversed later Sort of reversed later

Biochemical Activity Otto Loewi did a cool experiment in 1921 Otto Loewi did a cool experiment in 1921 Simulated the vagus nerve is a frog’s heart Simulated the vagus nerve is a frog’s heart Slowed the heart down Slowed the heart down Washed heart with solution, collected solution Washed heart with solution, collected solution Poured solution on a second heart Poured solution on a second heart It slowed!!!! It slowed!!!!

Loewi and his frogs Called the substance vagusstoff Called the substance vagusstoff Acetylcholine Acetylcholine Later stimulated heart rate, similar method Later stimulated heart rate, similar method Ended up with a sped up heart Ended up with a sped up heart Epinephrine Epinephrine

The Synapse Gap between the axon and the dendrite Gap between the axon and the dendrite Neurotransmitters are released across this gap Neurotransmitters are released across this gap Sometimes, if all of the transmitter isn’t absorbed it is taken back up, this is known as reuptake Sometimes, if all of the transmitter isn’t absorbed it is taken back up, this is known as reuptake

There is lots of variation in synapses There is lots of variation in synapses Some are inhibitory Some are inhibitory Some are excitatory Some are excitatory

More about synapses Is the excitatory vs. inhibitory nature of a synapse due to shape? Is the excitatory vs. inhibitory nature of a synapse due to shape? Probably Probably GABA synapses are inhibitory, have less post synaptic thickening GABA synapses are inhibitory, have less post synaptic thickening Glutamate synapses have more thickening, more vesicles Glutamate synapses have more thickening, more vesicles There are 7 types of synapses There are 7 types of synapses

The Seven Steps in Neurotransmission Synthesis Synthesis Storage Storage Release Release Receptor interaction Receptor interaction Inactivation Inactivation Reuptake Reuptake Degradation Degradation

The Neurotransmitters Basically, five conditions must be met before we call something a neurotransmitter Basically, five conditions must be met before we call something a neurotransmitter Present in terminalPresent in terminal Released on firingReleased on firing Placing substance or organ emulates firingPlacing substance or organ emulates firing Uptake for inactivationUptake for inactivation Inactivation blocks stimulationInactivation blocks stimulation

The Neurotransmitters Acetylcholine (Ach) Acetylcholine (Ach) Monoamines Monoamines 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 neurotransmitters Amino Acids Amino Acids Glutamate (universally excitatory)Glutamate (universally excitatory) GABA (universally inhibitory)GABA (universally inhibitory) GlycineGlycine ProlineProline Peptides Peptides Substance PSubstance P

Finally…. Morphine like substances Morphine like substances EndorphinsEndorphins EnkephalinsEnkephalins Other peptides Other peptides InsulinInsulin ProlactinProlactin HGHHGH VasopressinVasopressin

Receptors Transmitters bind to receptors Transmitters bind to receptors Sort of like a lock and a key Sort of like a lock and a key Binding site Binding site Ion channel Ion channel One neuron (usually) has only one type of receptor One neuron (usually) has only one type of receptor Great place for drug interaction Great place for drug interaction

The 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 system Autonomic nervous system