Ionic Mechanisms of Synaptic Excitation Synaptic transmission - - PowerPoint PPT Presentation

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Apr 21, 2023 243 likes •487 views

Ionic Mechanisms of Synaptic Excitation Synaptic transmission Synaptic input 1) Communication within the nervous system 2) A site of plasticity for learning and memory 3) A site of action for disease, psychoactive drugs Whimpy axon!

SLIDE 1

Synaptic transmission 1) Communication within the nervous system 2) A site of plasticity for learning and memory 3) A site of action for disease, psychoactive drugs Ionic Mechanisms of Synaptic Excitation

Whimpy axon! Synaptic input

SLIDE 2

Multi-terminal Poly-neuronal Inhibition Often no APs Uni-terminal Uni-neuronal Excitation Only

Neuromuscular Innervation

Mammals Arthropods

Crayfish NMJ as a model for human brain synapses See Synapse Tutorial on class web site for review

SLIDE 3

Crayfish NMJ preparation

SLIDE 4

Example Data

SLIDE 5

Synaptic Integration Map Muscle Innervation Patterns

(Also better distinguish number of axons in nerve 3)

See G-PRIME for example of- Muscle Innervation - Cross Correlation

SLIDE 6

Dendrite Axon Hillock EPSP trying to reach AP threshold Synaptic integration spatial and temporal

SLIDE 7

Space constant important Spatial summation Time constant important Temporal summation

SLIDE 8

Synaptic Inhibition Two flavors: Algebraic Summation Shunting How do they work?

SLIDE 9

Synaptic Inhibition Stimulation of inhibitory nerve blocks AP production

SLIDE 10

Presynaptic inhibition Presynaptic inhibition reduces transmitter release

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Types of Chemical Synaptic Transmission direct, fast indirect, ~slow

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Action Potentials can arise from subthreshold depolarizations if they are not spontaneous

SLIDE 13

Stimulate presynaptic axon

SLIDE 14

Steps in ionotropic chemical synaptic transmission

SLIDE 15

Excitation: Conductance increase (resistance decrease): Channels in membrane open

Membrane potential goes towards Vrev (Equil. Pot)

SLIDE 16

Vrev = Eion Results if EPSP were due to only Na+ or K+

SLIDE 17

Isyn= gACh(Vm-Vrev)

60 mV

(Vm-Vrev)= Driving force Depolarizing because of large Na driving force

SLIDE 18

Conductance change due to multiple ions

SLIDE 19

Inhibition: Conductance increase (resistance decrease):

Membrane potential goes towards Vrev (Equil. Pot)

SLIDE 20

Most common fast transmittters

Proof of Neurotransmitter Identity?? Presence Action Release Pharmacological Congruence Synthetic/packaging machinery

SLIDE 21

Snake Neuromuscular Junction Model Release of Transmitter

SLIDE 22

Freeze-fracture of NMJ EM section of NMJ

SLIDE 23

Ionic Mechanisms of Synaptic Excitation Synaptic transmission - - PowerPoint PPT Presentation

Synaptic transmission 1) Communication within the nervous system 2) A site of plasticity for learning and memory 3) A site of action for disease, psychoactive drugs Ionic Mechanisms of Synaptic Excitation

Whimpy axon! Synaptic input

Multi-terminal Poly-neuronal Inhibition Often no APs Uni-terminal Uni-neuronal Excitation Only

Neuromuscular Innervation

Mammals Arthropods

Crayfish NMJ as a model for human brain synapses See Synapse Tutorial on class web site for review

Crayfish NMJ preparation

Example Data

Synaptic Integration Map Muscle Innervation Patterns

(Also better distinguish number of axons in nerve 3)

See G-PRIME for example of- Muscle Innervation - Cross Correlation

Dendrite Axon Hillock EPSP trying to reach AP threshold Synaptic integration spatial and temporal

Space constant important Spatial summation Time constant important Temporal summation

Synaptic Inhibition Two flavors: Algebraic Summation Shunting How do they work?

Synaptic Inhibition Stimulation of inhibitory nerve blocks AP production

Presynaptic inhibition Presynaptic inhibition reduces transmitter release

Types of Chemical Synaptic Transmission direct, fast indirect, ~slow

Action Potentials can arise from subthreshold depolarizations if they are not spontaneous

Stimulate presynaptic axon

Steps in ionotropic chemical synaptic transmission

Excitation: Conductance increase (resistance decrease): Channels in membrane open

Membrane potential goes towards Vrev (Equil. Pot)

Vrev = Eion Results if EPSP were due to only Na+ or K+

Isyn= gACh(Vm-Vrev)

(Vm-Vrev)= Driving force Depolarizing because of large Na driving force

Conductance change due to multiple ions

Inhibition: Conductance increase (resistance decrease):

Membrane potential goes towards Vrev (Equil. Pot)

Most common fast transmittters

Proof of Neurotransmitter Identity?? Presence Action Release Pharmacological Congruence Synthetic/packaging machinery

Snake Neuromuscular Junction Model Release of Transmitter

Freeze-fracture of NMJ EM section of NMJ

Brain Synapse

Few vesicles at each synaptic site