Synaptic transmission I Flashcards
Parasympathetic innervation of the heart through the______ what nerve and is mediated via______?
- Vagus
2. ACh
Electrical synapses (Gap Junction)
20 Connexin genes and 3 pannexin gene code for gap junction
Gap junction function
- Allows electrical communication between cells
- Chemical communication between cells (IP3 and Ca2+)
- Metabolic coupling (allows molecules smaller than 1,000 Daltons to pass)
Electrical synapses (Gap Junction) allows
- Very fast
- Bidirectional communication
- useful for breathing and oscillation
Chemical synapses
Electrical signal into chemical signal and back to electrical
chemical synaptic contacts
most common between axon terminal, dendritic, somatic, or axonal domain
what defines Neurotransmitters?
- Substance must be present within the presynaptic neuron
- Must be released due to depolarization to presynaptic response
- Must be Ca2+ dependent
- specific receptors must exist on the postsynaptic cell
Classical Transmitter (small molecules)
- Locally synthesized in presynaptic terminal
- Enzyme comes from nucleus vis Slow Axonal Transport
- Small clear core vesicles
Release of _______ requires high-frequency stimulation
-neuropeptide
important to have high calcium level in presynaptic terminal
The Neuromuscular junction (NMJ
- Large postsynaptic cell
- one axon but about 100 synapses per muscle cell
- high reliability
- only one type of ion channel
Stimulation of the motor fiber generates a?
synaptic potential in post-synaptic muscle cell EPP (END PLATE POTENTIAL)
Even in the absence of stimulation very small potentials occur called?
Miniature End Plate Potentials (MEPPs)
Quantal release theory
EPPs are multiples of MEPPs
- Spontaneous neurotransmitters release occurs in quantal packet (MEPPs)
- AP potentials release of many transmitter quanta (EPP)
Quantal (vesicular) release variables are?
- The number of release sites (N)
- Active zones/synapses
- The probability of a quantal release (p)
- docked vesicles
- The size of the quantal response (q)
- receptor sensitivity
Calcium is required for transmitter release due to?
It influences the probability of release
Calcium
- AP opens volage gated Ca2+ channels
- Ca2+ allows vesicles to fuse with membrane
The active zone is where Ca2+ current is?
10x larger than elsewhere
Synaptotagmin
Calcium sensor
-Binding of 4 Ca2+ ions is needed to trigger release
Calcium Sensor - Synaptotagmin (function)
-Early synaptic vesicle docking via interaction with β-neurexin or
SNAP-25
-Late steps of Ca2+ + evoked synaptic vesicle fusion with the presynaptic membrane.
Ca2+ affects the _____ of release, not the quantal_____.
- Probability
2. Size
