Flashcards
Synapses
Cards in this deck (18)
- 1What is a synapse?Synapses are where neurons pass on signals to other neurons or to muscle cells
- 2Pre vs Post - synaptic?Pre-synaptic: neuron that sends message
Post-synaptic: neuron that receives message - 3What the post-synaptic electrical response known as?The postsynaptic potential (PSP)
- 4What is an example of a model synapse?Frog neuromuscular junction
- 5Overview of synaptic transmission?1. Pre-terminal contains many vesicles filled with NEUROTRANSMITTERS e.g. Acetylcholine
2. Neurotransmitter released when presynaptic terminal is excited
3. Vesicles fuse with PRESYNAPTIC MEMBRANE
4. Neurotransmitters diffuse across synaptic cleft
5. Some bind to receptors on surface of postsynaptic neuron
6. Cause ion channels to open
7. Ions diffuse, pushed by electrochemical gradient - 6Differences btwn spikes and pspsAP: caused by VG channels
PSP: caused by chemically G channels
AP: Each spike 1/10 V
PSP: few mV
AP: Discrete+fixed amplitude
PSP: adds with other psps
AP: travel by propagation
PSP: Can't travel far - 7What are the types of synapse and which is most common?Chemical synapses are most common
Also electrical synapses - 8How do we know if a synapse is chemical?-Applying a particular chemical to a postsynaptic site causes an electrical response
-The same chemical can be found in vesicles in the presynaptic terminal
-EG Acetylcholine at frog neuromuscular synapse - 9What happens in the release of neurotransmitter?1.Excitation opens voltage-gated Ca++ channels in pre-synaptic terminal (these are similar to V.G. Na+ channels in rising phase of spike)
2. Ca++ enters terminal (v. strong electrochemical gradient)
3. Increase in Ca++ triggers vesicles to fuse with presynaptic membrane and release neurotransmitter - 10How do we know how transmitter release is controlled?By poisoning the channels that control the spikes:
-Using TTX to block v.g. Na+ channels
Using TEA to block v.g. K+ channels - 11Evidence that Ca++ enters presynaptic terminal?Adding AEQUORIN (from jellyfish)
Becomes fluorescent in the presence of Ca++ - 12Non-spiking neurons?Some neurons operate without spikes:
Slow changes in membrane voltage regulate the opening and closing of Ca++ channels and thus neurotransmitter release
E.G. RETINAS contain many non-spiking neurons - 13Cause for synaptic delay?Most of delay in transmission is due to the time taken for Ca++ channels to open
- 14Neurotransmitters opening ion channelsSome neurotransmitter molecules bind to receptors on surface of postsynaptic neuron
Causes associated ion channels to open - 15Example of neurotransmitter opening ion channels?Frog neuromuscular synapse:
1. post synaptic membrane contains ACh-gated channels that allow both Na+ and K+ to pass through
2. When ACh binds to the receptor site it opens the channel.
3. Na+ moves into the cell (and some K+ moves out) driven by electrochemical gr.
4. Muscle cell is depolarised
5.Acetylcholinesterase breaks up the acetylcholine so channel closes again - 16How do we know that neurotransmitters open ion channels?Patch clamping;
Directly measuring the current flow through a single post-synaptic channel
NEHER and SAKMANN - 17How do we know what channels look like?From studying the electric ray
- 18Why do synapses matter?-Frog nmj and squid giant synapse are specialised relays
- Usually, psps are small voltage signals,smaller than spike threshold: a neuron combines the different psps it receives
-Enables nervous system to make decisions - integration
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- 2nd Year Biology (Animal Physiology) Flashcards on Synapses, created by Phoebe Stockton on 20/08/2016.
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