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12 Cards in this Set
- Front
- Back
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Electrical synapse
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Mediated by Gap Junctions which contain pores between post syn and presyn cells formed by connexon proteins
No delay in transmission of signal (very speedy) Rapid escape response system Cannot be either inhibitory or excitatory, they are bidirectional and allow synaptic transmission in both directions |
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Connexon
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Composed of ix protein subunits connexins
ConnexINS are IN the pores ConnexONS are ON the surface Much larger than ion channels so big molecules like ATP can pass |
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Chemical Synapses
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Unidirectional
Transmission is much slower than electrical synapse Preserve signal strength better than electrical Synaptic junctions and puncta adherentia junctions synaptic junctions: active zones and post synaptic densities PAJ: mechanical junctions between pre and postsynaptic cells |
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Types of synapses
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Axodendritic: axon to dendrite; dendritic spines are excitatory
axosomatic: axon to cell body; are inhibitory axoaxonic: axon to terminal ending; presynaptic inhibition gray type I: glutamatergic (excitatory), typically contact on spines gray type II: GABA ergic/inhibitory, contact cell body |
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Pre-synaptic Components
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Synaptic vesicles (small, 30-35 nm; non peptide NT; 3 pools= readily releasable, small and quickly exhausted; recycling pool, larger than RR but longer to become mobilized; reserve pool= majority, mobilized by intense stimulation, rarely used)
large dense-core vesicles (70-200nm, growth factors, hormones, not recycled, peptides, distant from active zone, trains of AP to release) endocytic organelles (reuptake from the cleft, clathrin coated, few at rest and abundant after strong stimulation) sER (regulate Ca stores) mitochondria cytoskeletal components Pre synaptic dense grid |
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SNAREs and SNAPs
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Facilitate exocytosis
vSNAREs or tSNAREs v for vesicle and t for target v snares incorporated into membrane of synaptic vesicles t snares located in membrane of presynaptic neuron Ca influx binds to synaptotagmin which promotes fusion of vesicle with membrane resulting in exocytosis |
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Post synaptic compartment
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On dendrite or cell body
Post synaptic density PSd often found in protrusion of dendrite called dendritic spine |
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Dendritic Spines
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Thin, stubby or mushroom
Small: plasticity (potential to get bigger); large: memory correlation between size of spine and strength of synapse Spines length and diameter determines overall effect through post synaptic Ca elevation and NMDA receptor activation small, thin spines more often involved in long term potentiation (plasticity spines) mushroom: more stable, "memory spines" |
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LTD
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Stimulation at a low rate for long periods of time, resulting in consequential lessening of EPSP
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Dendritic Spine Pathology
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Due to spine ultrastructure and spine distribution
Ultrastructure Linked to traumatic lesions, Alzheimer's, Creutzfeldt-Jacob Disease Also distribution linked to abnormalities of developing brain following insults also mental retard (downs, or fragile X) |
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Temporal vs spatial summation
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Temporal: AP experiences increased strength when a synapse fires multiple times in quick succession
Spatial: How close the synapses are physically |
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Reversal Potential
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Potential at which there is no net movement of a particular ion
Important because if reversal potential for a certain ion is so skewed from the actions of other ions it is possible for an otherwise inhibitory action to change to an excitatory action |
