Gap Junctions
- Electrical Synapse
- transmison of info does not involve a chemical messenger
- synaptic gap narrows so different cells can literally kiss for current to go between them
- can only send depolarizing message (exititory)
The Chemical Synapse
Exocytosis
- Calcium channels
- Present at high density at axon terminal
- positively charged
- higher concentration in extracellular fluid
- calcium moves into cell rapidly
- calcium in cell causes vesticles to undock
- undocked vesticles are propelled towards terminal membrane
- they pop once at membrane, spilling contents into synaptic gap
- this is exocytosis
- Synaptic Vesticles made up of double phospholipid layer
- material recycled to make new cesticles
Ionotropic Receptor (Reciving or postsynaptic)
- Channels different than those that operate during an action potential
- Respond to chemical messengers
- also knowm as ligandgated receptors
- very fast
Metabotrioic Receptors
- Slower response syste
- binding and recognition site on different structures
- once first recognizes messenger chemical, it releases another to then open up the channel
- can change gene expression to adapt to busy synapse
Deactivation
type depends on neurochemical
- Some diffuse away, measured by astrocytes. They can enter the CSF and have a long lasting impact on far away systems.
- Some are broken down by enzymes into component parts, taken to releasing cell, synthezize and packed in vesicles
- Some neruochems are recyled through reuptake. Transporterds recapture molecules so they can be repacked in vestiles for later released. Not broken down, saving cell energy. Reuptake inhibitors leave neurochems in synapse
Neural integration
- EPSP
- Way a cell repsonds to multi inputs
- excitatory post synaptic potential
- Results when incoming chemical messengers open sodoum channels. usually on dendrites
- IPSP
- Inhibitory postsynaptic potential
- Opens Chlroide channel or Potassium channel
- Drive recording further from threashhold, making it less likely a cell will fire
- Cell recicves both, which cancel eachother out.
Summation
Spatial
- Integrated at initial segment, action pot. generalted
Temporal
- Build up of excitatory current
IPSP and EPSP last longer than tese