2 Biochemical Activity Otto Loewi did a cool experiment in 1921 Simulated the vagus nerve is a frog’s heartSlowed the heart downWashed heart with solution, collected solutionPoured solution on a second heartIt slowed!!!!
3 Loewi and his frogs Called the substance vagusstoff Acetylcholine Later stimulated heart rate, similar methodEnded up with a sped up heartEpinephrine
4 The Synapse Gap between the axon and the dendrite Neurotransmitters are released across this gapSometimes, if all of the transmitter isn’t absorbed it is taken back up, this is known as reuptake
5 There is lots of variation in synapses Some are excitatory (Type I)Some are inhibitory (Type II)
6 More about synapsesIs the excitatory vs. inhibitory nature of a synapse due to shape?ProbablyGABA synapses are inhibitory, have less post synaptic thickeningGlutamate synapses have more thickening, more vesiclesThere are 7 types of synapses
7 SEVEN? Yes, Seven Depends on function We usually learn about axodendritic onesEasiest to think about them I guess
8 The Seven Steps in Neurotransmission SynthesisStorageReleaseReceptor interactionInactivationReuptakeDegradation
9 The Neurotransmitters Basically, five conditions must be met before we call something a neurotransmitterPresent in terminalReleased on firingPlacing substance or organ emulates firingUptake for inactivationInactivation blocks stimulation
10 The Neurotransmitters Acetylcholine (Ach)MonoaminesCatecholaminesNorepinephrine (NE)Epinephrine (E)Dopamine (DA)IndoleamineSeretonin (5-Ht)OthersHistamine (H)
11 More neurotransmitters Amino AcidsGlutamate (universally excitatory)GABA (universally inhibitory)GlycineProlinePeptidesSubstance P
12 Finally…. Morphine like substances Other peptides Endorphins EnkephalinsOther peptidesInsulinProlactinHGHVasopressin
13 Receptors Transmitters bind to receptors Sort of like a lock and a key Binding siteIon channelOne neuron (usually) has only one type of receptorGreat place for drug interaction
14 Synapses, neurotransmitters, learning and memory The Hebbian synapseWhen 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 A’s efficiency as one of the cells firing B, is increased
15 HabituationDecrease in the strength of a response after repeated presentation of a discreet stimulusGetting used to it, sort ofNOT sensory adaptation or simply fatigueStimulus specificOrienting responseStartle response
16 The rules Thompson and Spencer (1966) Gradual with time Withhold stimulus and response will reoccurSavingsIntensityOverlearningStimulus generalization
17 Pokin’ aplysisa Kendel et al Gill withdrawal Seonsory -> motor pretty muchLess transmitter released into synapses!Decrease in Ca currentSimilar results in catsBecause of its generality, habituation is often thought of as the universal learning paradigm
18 LTP Long Term potentiation NMDA (a neuromodulator) basically allows LTP to happenBlock NMDA, block LTPBlock LTP, block learning in say a Morris water mazeBut…..Deb Saucier….
19 Barnea and Nottebohm (1994) Chickadees store in the fall and winter, lessen off in the springHP seems to shrink and grow!!
20 In conclusionMuch of the interesting activity in the nervous system takes place at the synapseThis is where the electrical goes chemicalThis is where learning MAY be happeningThere is still much to learnEvery mall in Athens has a store called ‘The Synapse’