Synapse Flashcards
(40 cards)
Functional connection between a neuron and 2nd cell
Impulse are transmitted from one nerve cell to another to be able to react
Synapse
Type of Synapse
current flows directly
no synaptic delay
allow conduction in both directions rectification
cells that are joined by gap junctions useful in reflex pathways
Electrical Synapse
Type of Synapse
modify the transmission (plasticity)
terminal buttons
one-way conduction
0.5 second synaptic delay
Chemical Synapse
4 Functional Anatomy of Synapse
Dendrodentritic
Axo-somal
Axodendritic
Axo-axonic
The cell before the synapse/connection
Synaptic vesicles contain the neurotransmitters
Synaptic vesicles and plasma membrane contain several protein interactions
Mitochondria that supply energy to some
processes
Presynaptic Cell
The cell right after the synapse
Dendrites
Postsynaptic Cell
2 Types of Synapses
Electrical Synapse
Chemical Synapse
Current flows directly
No synaptic delay
No need to traverse the extracellular space
Ions that produce AP gets shared with the
postsynaptic cell; gap junctions
Allow conduction in both directions
Cells can share ions
Rectification
Cells that are joined by gap junctions - Connexins, connexons
Useful in reflex pathways
Examples: SA node, pacemaker cells of the heart and of GI
Share ions with cardiac muscle cells through
gap junctions
Electrical Synapse
Most abundant in our bodies
Modify the transmission (plasticity)
Postsynaptic cell can either be excited or inhibited
Dictates whether postsynaptic cell will discharge/fire or not
Involve ligands, neurotransmitters
End up on terminal buttons
One-way conduction
Mediator only on synaptic knobs not on postsynaptic cell
Once transmitted, there is no turning back
0.5 msec synaptic delay
Need to traverse the ECF before reaching the postsynaptic cell
Chemical Synapse
Functional Anatomy:
We name the pathways in the nervous system from its …
origin towards its destination
Originates from a dendrite and goes to another
dendrite
Will not conduct impulses to the postsynaptic
cell
Dendrites do not contain synaptic vesicles at the terminal button
NO synaptic vesicle = NO transmission of impulse
Dendrodentritic
Axon to body
From the axon of the presynaptic to the soma of the postsynaptic neurons
Axo-Somal
From the axon of the pre-synaptic to the
dendrite of the postsynaptic
Majority of synaptic connections are
axodendritic
Endings are commonly located on dendrites
Axodendritic
Axon of the presynaptic to the axon of the
postsynaptic
Presynaptic nerves terminate on the axon of
postsynaptic neurons
Axo-Axonic
One nerve will receive 10k synaptic
inputs (2k on soma; 8k on dendrites)
Dendrites expand surface area up to
90%
Principle of Convergence
In the cerebral cortex
__% on dendrites
__& on cell bodies
98%
2%
Takes time to traverse and be received by the
post synaptic cell
20-40 nm wide synaptic cleft
Highly specific for the neurotransmitters from the presynaptic cell
Proteins act as receptors
Receptor on postsynaptic cell
Proteins create this thickening
Proteins acting as receptors
Thickening on postsynaptic cell
Many mitochondria
Membrane enclosed vesicles (synaptic vesicles)
Presynaptic terminal
3 Kinds of Synaptic Vesicles
Small, clear which contains ACh, glycine, & GABA
Small vesicles with dense core which contains
catecholamines (granulated in appearance)
Large vesicles with dense core which contains neuropeptides
Where small vesicles are located
Darkened portion
Conglomeration/group of small clear synaptic vesicles in the presynaptic cell
Dense bars: conglomeration/group of receptors in the postsynaptic cell for small clear vesicles in
the active zones
Active Zones
When calcium enters, it becomes the key ion of exocytosis
Ca++ is the key for synaptic vesicle fusion
Restores Ca++ level
Calcium does not belong inside; therefore it has to be removed against its gradient in exchange for one sodium ion
Utilizes ATP (priming, anti-port, Na K pump)
Pumps in Ca2+ in exchange of sodium
Ca++ - Na+ antiport
