Synapses 3 Flashcards
synaptic transmission
information transfer from one neuron to another
presynaptic neuron
information coming from this area (usually axon terminal)
postsynaptic neuron
information going to this area (usually dendrite or cell body)
electrical synapse
electrical signal from the direct flow of ions between neurons allow ions (not neurotransmitters) to move directly from one neuron to the next at specialized sites called = gap junctions
chemical synapse
chemical signal from the flow of neurotransmitters between neurons
gap junction structure
contains proteins called connexin
two connexons (one from each cell) form the gap junction channel
channel allows passive flow of ions from the cytoplasm of one cell to the cytoplasm of another (flow can go in either direction = bidirectional)
Distance between presynaptic and postsynaptic neurons about 3.5 nm
Pores are larger than voltage–gated ion channels
connexion
six connexin subunits make up a channel = connexon
electrical synapse function
Transmission super fast and used in communication between sensory & motor neurons.
Allows activity between neurons to be highly synchronized bc the signal is almost instantaneous.
Signal in postsynaptic neuron will be same sign and same strength as or smaller than that of the presynaptic neuron, only leads to simple behaviors and less modifiable.
electrical synapses etc
Rare in PNS but can be found in CNS – neocortex, hippocampus, thalamic reticular nucleus, olfactory bulb, retina, spinal cord.
Interconnect many non-neuronal cells like glia, smooth and cardiac muscle cells, epithelial cells, liver & glandular cells
Important in early brain development
- allows neighboring cells to share electrical and chemical signals that coordinate their growth and maturation
chemical synapse more
Most synapses
Presynaptic & Postsynaptic membranes separated by synaptic cleft
Cleft 20-50 nm wide
(10X width of gap junction)
Cleft filled with matrix of fibrous extracellular proteins for adhesion
(ECM = extracellular matrix)
on presynaptic neuron electrical
Axon terminal has synaptic vesicles full of neurotransmitters (NTs)
Also has larger vesicles called secretory granules (dense-core vesicles) filled with larger proteins
Active zones
active zones
sites where neurotransmitters are released from vesicles
postsynaptic density
Neurotransmitter receptors on surface
on postsynaptic neuron electrical
neurotransmitter receptors on surface = postsynaptic density
Receptors types:
Transmitter-gated ion channels
G-protein coupled receptors
on presynaptic neuron chemical
Axon terminal has vesicles full of neurotransmitters
Also has larger vesicles for larger proteins = secretory granules
Active zones = sites of vesicle release
