What electrical signal happens at a synapse?
Small graded potential
Excitatory Synapse
membrane potential of a postsynaptic neuron is brought closer to threshold
Inhibitory Synapse
membrane potential of a postsynaptic neuron is driven further from threshold or stablized at its resting membrane potential
Electrical Synapse characteristics
-direct cell to cell contact
-contains gap junctions which allow ion and other small solutes to pass through
-conducts electrical signals very quickly
Chemical Synapse characteristics
-synaptic vesicles in presynaptic neuro
-slower than electrical synapse
Steps of NT release
- AP goes down the axon to the terminal
- Volate gated calcium channels open
- calcium enters the axon terminals
- calcium induces the exocyptosos of NTs and they are released and diffuse into the cleft
- NTs bind to postsynaptic receptors
- NTs removed from cleft
Excitatory NT steps
- NT binds to the receptor
- Ligand gated ionotropic receptor channel opens
- Net cation iflux of mainly sodium or calcium into postsynaptic cell
- The net effect is depolarization
Inhibitory NT steps
- NT binds to the receptor
- Ligand gated ionotropic channels open
- either potassium flows out, chloride flows in or no net flux of cl-
- Net effect is either hyperpolarization or prevents depolarization
What happens to NTs in the cleft?
- NTs can diffuse away unbounded
- Can be destroyed by enzymes and turn inactive
- NTs are taken back into the presynaptic terminals or transported into nearby glial cells
Synaptotgamin
senses incoming calcium and induces wrapping of the protein. The protein twists together and draws vesicle to the membrane. Exocytosis of NTs occur when vesicle binds to the membrane
NTs can bind to two different kinds of receptors?
Ionotropic and meatbotropic
Ionotropic Receptors
Ligand gated/chemical
Contain and ion chennal
Membrane potential changes immediatly
Metabotropic Receptors
Do not contain ion channels and many are coupled to G protein transducters
-g protein transduction activate second messenger signaling cascades which may open or close ion channels
Temporal summation
one input is repeadtly releasing and adding together
Spatial summation
2 different inputs fired close in time can sumate in space
Presynaptic Faciilation
makes EPSP or IPSP stronger
- increases depolaization and NT release by increasing calcium flux
Presynaptic Inhibition
makes EPSP or IPSP weaker
- decreases depolarization and NT release by decreasing calcium influx, decrease the amount of NT from Queen onto minions
Autoregulation
negative feedback mechanism, Queen’s NT self regulates
Antagoist
blocks receptors on postsynaptic membranes
Agonist
mimics a NT
What binds to ionotropic receptors to elicit EPSPs or IPSPs
NT
What binds to metabotropic recpetors
Neuromodulators
Facts about Neuromodulators:
- they can be released with NTs from a presynaptic axon terminal
- Involved in slower evets such as learning and development
How to metabotropic recpetors work
- NM binds to receptor
- Gs protein becomes activated by the binding of NM to receptor
- Adenylyl cyclose is activated by the G protein activation and converts ATP to cAMP
- Aninactive cAMP dependent protein kinase is activated by cAMP and phosphrylated protei
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Homeostasis Lecture21
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Cell Physiology and Membrane Transport10
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Cell Structure8
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Movement of Solutes and Water Across Cell Membranes23
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Neurophysiology: intro to the NS and cells of NS19
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Neurophysiology: structure and function of the NS14
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SPINAL CORD7
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Membrane Potentials8
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Membrane Potentials Part 220
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Synapse28
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Sensory Receptors11
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Primary Sensory Coding18
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Afferent Divison of the PNS18
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Efferent Divison of the PNS20
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Athletic Movement8
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EXTRA- just was important15
