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25 Cards in this Set
- Front
- Back
- 3rd side (hint)
How Electrical synapses are connected
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intracellular specialiaztion known as
gap junctions. these form bridges |
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Chemical synapses
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Mechanism: Action potentials cause calcium channels calcium ions stimulate vesicles causing neurotransmitters to be released
Size: 20 - 40 nm |
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Electrical synapses
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connected through gap junctions
size: 3,5 nm therefore: cleft has immediate regulation |
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Benifit of electrical synapses over Chemical synapses
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They are faster due to direct connection
As postynaptic and presnaptic fire nearly at identical times, it can synchronize activity good when neurons need to fire at same time also as intracellular signals such as ATP and second messengers cna pass through introcellular mechanisms are coordinated |
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Structure of Gap Junctions
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six presynaptic connexons (hexameric complexes) and six postsynaptic connections connect to form a pore
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Characteristics of connexon pore
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larger than voltage-gated ion channels
i.e. less selctive allows ATP and other metabolites to pass can open and close in response to: voltage, pH, or other signals |
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What composes connexons
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ion channel protein known as connexins
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Directionality of Electrical synapses
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can be bidirectional
however, can be normally directional or reverse direction/ rectifying |
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Chemical synapse mechanism
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1. action potential invades terminal of presynaptic neuron
2. change in membrane potentail activates voltage gated calcium channels to open 3. large amont of calicum outside cell to inside causes calcium to flood into cell 4. calcium influx causes synaptic vesicles to fuse to presynaptic membrane releasing neurotransmitter into synaptic cleft 5. neurotransmitters bind to post-synaptic receptors, increasing or decreasing ion flow |
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What does neurotranssmiter induce current flow alter
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1. the conductance (ease at which particles can slow through a medium)
2. usually membrane potential Futhermore what does this do |
increase or decrease probability of action potnetial fireing
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How do neurotansmitters stop
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Ruptake
uptake to glial cells enzymatic degredation |
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acetylcholine on heart
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decrease heartrate
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Types of Ionic Receptors
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Ionotropic receptor
Metabotropic receptor Note about neurotransmitters |
Do not enter into postynaptic membrane
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Ionotropic receptor Characteristics
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Binds to ligantd gated ion channels
increase probability ion channel will open |
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Metabotropic receptor characteristics
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g protein coupeld receptors
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types of neurotransmitters
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Small molecule neurotransmitters - mediate rapid synaptic responses
neuropeptide = mediate slower more ongoing responses |
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End Plate
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where presynaptic spinal motor neurons synapse on postsynaptic muslcle cells
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EPP or End Plate Potential
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Change in membrane potential on postsynaptic muscle cell, if threshold is exceeded cause postynaptic action potential
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EPP and MEPP relatinoship
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minuature end plate potentials the excitatory post synaptic potentail produced from one vesicle release of neurotransmitter, EPP are caused by multiple MEPP's
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Tetradioxin
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poisin - blocks voltage gated sodium channels
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Curear
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blocks acetylcholine receptors
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What is the difference in release between neuropeptides and small neurostransmitters
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neuropeptides are thought to be spatially farther way and require higher frequency of calicum stimulation to cause its release.
i.e. neuropeptides take longer to release than small neurotransmitters |
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synaptic vesicle reserve pool structure
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vesicles are held together by synapsin proteins which are bound to cytoskeleton actin
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Metabotropic receptors
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movement of ions through channel depends on multiple steps
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G potrein oupled receptor mechanism
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neurotransmitter binds to G-protein receptor
This activates G protein which detaches and either activates effector portein or ion channel |
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