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Synapses and neurotransmitters Psychology 2606. Biochemical Activity Otto Loewi did a cool experiment in 1921 Otto Loewi did a cool experiment in 1921.

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Presentation on theme: "Synapses and neurotransmitters Psychology 2606. Biochemical Activity Otto Loewi did a cool experiment in 1921 Otto Loewi did a cool experiment in 1921."— Presentation transcript:

1 Synapses and neurotransmitters Psychology 2606

2 Biochemical Activity Otto Loewi did a cool experiment in 1921 Otto Loewi did a cool experiment in 1921 Simulated the vagus nerve is a frogs heart Simulated the vagus nerve is a frogs 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!!!!

3 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

4 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 isnt absorbed it is taken back up, this is known as reuptake Sometimes, if all of the transmitter isnt absorbed it is taken back up, this is known as reuptake

5 There is lots of variation in synapses There is lots of variation in synapses Some are excitatory (Type I) Some are excitatory (Type I) Some are inhibitory (Type II) Some are inhibitory (Type II)

6 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

7 SEVEN? Yes, Seven Yes, Seven Depends on function Depends on function We usually learn about axodendritic ones We usually learn about axodendritic ones Easiest to think about them I guess Easiest to think about them I guess

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

9 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 terminal Present in terminal Released on firing Released on firing Placing substance or organ emulates firing Placing substance or organ emulates firing Uptake for inactivation Uptake for inactivation Inactivation blocks stimulation Inactivation blocks stimulation

10 The Neurotransmitters Acetylcholine (Ach) Acetylcholine (Ach) Monoamines Monoamines Catecholamines Catecholamines Norepinephrine (NE) Norepinephrine (NE) Epinephrine (E) Epinephrine (E) Dopamine (DA) Dopamine (DA) Indoleamine Indoleamine Seretonin (5-Ht) Seretonin (5-Ht) Others Others Histamine (H) Histamine (H)

11 More neurotransmitters Amino Acids Amino Acids Glutamate (universally excitatory) Glutamate (universally excitatory) GABA (universally inhibitory) GABA (universally inhibitory) Glycine Glycine Proline Proline Peptides Peptides Substance P Substance P

12 Finally…. Morphine like substances Morphine like substances Endorphins Endorphins Enkephalins Enkephalins Other peptides Other peptides Insulin Insulin Prolactin Prolactin HGH HGH Vasopressin Vasopressin

13 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

14 Synapses, neurotransmitters, learning and memory The Hebbian synapse The Hebbian synapse When an axon of cell A is near enough to excite cell B and repeatedly or persistenly takes part in firing it, some growth process or metabolic change takes place in one or both cells such that As efficiency as one of the cells firing B, is increased When an axon of cell A is near enough to excite cell B and repeatedly or persistenly takes part in firing it, some growth process or metabolic change takes place in one or both cells such that As efficiency as one of the cells firing B, is increased

15 Habituation Decrease in the strength of a response after repeated presentation of a discreet stimulus Decrease in the strength of a response after repeated presentation of a discreet stimulus Getting used to it, sort of Getting used to it, sort of NOT sensory adaptation or simply fatigue NOT sensory adaptation or simply fatigue Stimulus specific Stimulus specific Orienting response Orienting response Startle response Startle response

16 The rules Thompson and Spencer (1966) Thompson and Spencer (1966) Gradual with time Gradual with time Withhold stimulus and response will reoccur Withhold stimulus and response will reoccur Savings Savings Intensity Intensity Overlearning Overlearning Stimulus generalization Stimulus generalization

17 Pokin aplysisa Kendel et al Kendel et al Gill withdrawal Gill withdrawal Seonsory -> motor pretty much Seonsory -> motor pretty much Less transmitter released into synapses! Less transmitter released into synapses! Decrease in Ca current Decrease in Ca current Similar results in cats Similar results in cats Because of its generality, habituation is often thought of as the universal learning paradigm Because of its generality, habituation is often thought of as the universal learning paradigm

18 LTP Long Term potentiation Long Term potentiation NMDA (a neuromodulator) basically allows LTP to happen NMDA (a neuromodulator) basically allows LTP to happen Block NMDA, block LTP Block NMDA, block LTP Block LTP, block learning in say a Morris water maze Block LTP, block learning in say a Morris water maze But….. But….. Deb Saucier…. Deb Saucier….

19 Barnea and Nottebohm (1994) Chickadees store in the fall and winter, lessen off in the spring Chickadees store in the fall and winter, lessen off in the spring HP seems to shrink and grow!! HP seems to shrink and grow!!

20 In conclusion Much of the interesting activity in the nervous system takes place at the synapse Much of the interesting activity in the nervous system takes place at the synapse This is where the electrical goes chemical This is where the electrical goes chemical This is where learning MAY be happening This is where learning MAY be happening There is still much to learn There is still much to learn Every mall in Athens has a store called The Synapse Every mall in Athens has a store called The Synapse

21 Other neural learning stuff


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