NB9 Synaptic transmission Flashcards
Which type of synapse doesn’t involve a neurotransmittor?
Where is it found?
e.g.
electrical synapses
cardiace muscle cells and epithelial cells
e.g. gap junctions
What type of synapse is the fastest?
electrical synapse is compared to chemical synapse
Where are chemical synapses found?
neurones
Describe structure and how they function of gap junctions
protein pores made up of 6 connexin ( a protein subunit) that bridge the gap between 2 cells allowing flow of ionic curretn
for a) electrical synapses and b) chemical synapses: give
1) distance between membranes
2) cytoplasmic continuity?
3) structural units
4) transmittor
5) transmission delay
6) transmission direction
1) a) 3.5mm b)20-40mm
2) a) yes b) no
3) a) gap-junction channel b) many (vesicles, docking/fusion proteins , channels and postsynaptic receptors)
4) a) Ionic current b) chemical transmittor
5) a) no B) yes (1-5msec)
6) a) bi-directional b) unidirectional
What must all neurotransmittors do?
1) be manufactured in presynaptic cell adn stored in terminal
2) mechanism for removing substance from presynaptic membrane
3) be released from presynaptic neurone when excited
4) when applied experimentall y mimics normal transmission
5) Drugs that effect tranmssion must effect tranmission of this possible neurotransmitor due to their effects on postsynaptic membrane.
State whether the following
a) excite/ inhibit or both
b) secretion sites in CNS, PNS ,neuromuscular junciton type
for. ..
1) GABA 2)acetyl choline 3) dopamine 4) aspartate
1) a) inhibits b) CNS, invertebrate NMJ
2) a) excitory (to vertrbate skeletal mm. or other) ot inhibitory
b) CNS, PNS, vertebrate NMJ
3) a) usually excitatory b) CNS, PNS
4) a) excitory b) CNS
What are the 2 type of receptors to neurotransmittors?
1) ionotropic: linked to an ion channel
2) metabotropic- linked to G-protein coupled receptor thus use 2nd messenger
Describe the sequence of events that occurs in synaptic transmission:
1) synaptobrevin (the V-snare) binds to vesicles
2) SNAP-25 and syntaxin (the T-snares) are inserted into the membrane and bind to synaptobrevin
3) Fusion of vesicle to membrane is tiggered by opening of voltage-sensitive Ca++ channels which activates synaptotagmin allowing exocytosis to occur.
What 2 things can result from neurotransmission across a synapse?
1) excitatory post-synaptic potential
2) inhibitory post -synaptic potential
what causes a composite postsynaptic potential?
EPSP and IPSP both occurring at the same time.
What to methods are used to reach threshold level? (hint_ summation)
temporal summation: increase in frequency of action potentials
spatial summarion: more then one post-synaptic source
What happens when the neurotransmitter reaches the post-synaptic membrane?
transmittor binds to receptor on membrane of post-synaptic neurone this Na+/K+ channels open
What does descremental mean?
amplitude decreases with distance
Describe
a) effect on voltage (hint _polarisation
b) magnitude
c) conduction properties
d) duration
for. . 1) Action potential
2) EPSP
3) IPSP
A) 1 & 2) depolarisation + _3) hyperpolarisation -
b)1) all or none Vrest to +30
2) Vrest to threshold level
3) Vrest to Ek or Ecl
c) 1) non-decremental _ 2&3) decremental
d) 1) 2-3msec
2&3)15-20msec
