L3 neurotransmitters & synapses Flashcards
What are neurotransmitters?
Endogenous chemicals that enable signal transmission in brain
Neuron propagate _____ the cell
within
Synapses allow neurons to _________
connect each other
Where do neurons only connect with each other?
In the neuro system
What happens in the soma?
Signal integration & protein synthesis
What is the signal output?
Axon
What is the signal input?
Dendrite
What is in the axon terminal that distinguishes it from axon trunk?
synaptic vesicles, membrane proteins (channels and receptors) & membrane-bounded sphere
What is the antennae of neurons?
Dendrites
What do postsynaptic receptors usually do?
Receives signals from axon terminal
Identify which is/ are electrical /chemical signal. Action potential, presynaptic axon terminal, postsynaptic receptor
- electrical
- chemical
- electrical
How does synaptic transmission work?
Interaction of presynaptic neurotransmitter release upon postsynaptic receptors
What will synaptic transmission dysfunction lead to?
Brain disorders
What does postsynaptic density contain? And what does it do?
Neurotransmitter receptors; convert the chemical signal into an electrical signal in the postsynaptic neuron
Describe the neurotransmitter release process.
Action potential arrives at axon terminal.
Voltage-gated Ca++ channels open
Ca++ enters the presynaptic neuron
Ca++ signals to neurotransmitter vesicles
Vesicles move to the membrane and dock
Neurotransmitters released via exocytosis
Neurotransmitters bind to receptors
Signal initiated in postsynaptic cell
What is the basis of electrical currents in nerve cells?
The movement of electrically charged ions that are dissolved in water
Which chemicals will hyperpolarize the cell?
K+ and Cl-
Which chemicals will depolarize the cell?
Na+ and Ca++
Which chemical is the only one that has higher concentration inside a cell?
K+
Action potential is a ____-lastly event in which the electrical membrane potential ______ rises and falls
short; rapidly
Name the 5 stages of an action potential.
- stimulus (or synaptic input)
- depolarization
- repolarization
- hyperpolarization
- resting state
What is excitatory postsynaptic potential?
Transient (temporary) postsynaptic membrane depolarization caused by presynaptic release of an excitatory neurotransmitter (positively charged ions). Consequently, opening ligand-sensitive channels/ receptors, making the neuron more likely to fire an action potential.
What is glutamine and acetylcholine?
Excitatory neurotransmitter
What is synaptic integration?
The process by which multiple synaptic potentials combine within one postsynaptic neuron.
CNS neurons receive ________ inputs.
thousands of synaptic
What does excitatory postsynaptic potential (EPSP) allow?
Allow for neurons to perform sophisticated computations. EPSPs add together to produce significant postsynaptic depolarization
What does spatial summation mean?
EPSPs generate simultaneously at different sites
What does temporal summation mean?
EPSPs generated at same synapse in rapid succession
IPSP: transient postsynaptic membrane _______ caused by presynaptic release of an _________ transmitter.
hyperpolarization; inhibitory
What are GABA and Glycine?
Inhibitory neurotransmitters
How to hyperpolarize IPSP?
Membrane potential less negative than ~-70mV
What acts as an electrical shunt in shunting inhibition? And what does it do?
Synapses; preventing the current from flowing from the dendrites to the axon
What is action potential?
A transient voltage alteration across an excitable membrane in excitable cells generated by the activity of voltage-gated ion channels.
At electrical synapses, ________ occur between pre and postsynaptic membranes. They contain ____________ that permit current to flow ______ from the presynaptic cell to the postsynaptic cell.
gap junctions; connexon channels; passively
What are the advantages of electrical synapses? (4)
Rapid transmission
Bidirection for electrical synapses vs unidirectional for chemical synapses
Facilitation of synchronized activities (e.g., heartbeat)
Direct mediation of intracellular signalling via second messenger
Why electrical synapses are bidirectional?
When a presynaptic action potential propagates to the postsynaptic cell, the membrane resting potential of the postsynaptic cell simultaneously propagates to the presynaptic cell
Why chemical synapses are unidirectional?
Neurotransmitters cannot be exchanged otherwise
What are receptor antagonists? Give one example.
Inhibitors of neurotransmitter receptors; curare (Acetylcholine (ACh) antagonist)
What are receptor agonists? Give one example.
Mimic actions of naturally occuring neurotransmitters; nicotine (ACh agonist)
What is the root cause of neurological and psychiatric disorders?
Defective neurotransmission
Which is the large molecule? (Amino acids/ amines/ peptides)
Peptides
Peptides are stored in and released from _______.
secretory granules
What are these? Glutamate, glycine, GABA
amino acids.
What are these? Dopamine, acetylcholine, histamine, norepinephrine, serotonin
amines.
What are these? Substance P, Cholecystoskinin, Neuropeptide Y, somatostatin, vasoactive intestinal polypeptides
peptides.
Addictive drugs act on _________ pathway from the ____________ to the ____________
dopaminergic; ventral tegmental area; nucleus accumbens
Chronic overstimulation of this pathway cause a _________, which means ____________
homeostatic response; the dopamine reward system is downregulated
Taking more drugs to get the desired effect is a phenomenon of _________
drug tolerance
What is Acetylcholine receptor (AChR)?
A transmembrane protein, ionotropic receptor
What does AChR do?
Binds 2 ACh molecules
What is the receptor of AChR?
Ligand gated ion channel
What is the result of ACh binding?
A shape change that allows Na+ to pass through the channel
Neurotoxins work by _________
interfering with control of muscle contractions
Neurotoxins cause death because they stop the heart and lungs by __________
the deficit of neural function
Neuromuscular junction is the point where your _______ and __________ meet
muscles; nervous system
Signals sent from your ______ to the NMJ tell _________________
CNS; muscles to move
Acetylcholine is ______
A neurotransmitter used by the synapses at the NMJ
Which substances block acetylcholine receptors?
Cobratoxin, curare
What happens when acetylcholine receptors are blocked?
muscles are paralysed, because the neuronal signals that control your muscles are blocked
If a Indian cobra bite you and you left the wound untreated, you will die in _____
1 hour
Where is curare used?
Indigenous South American tribes for poison darts and poison arrows
Where does curare come from?
Curare plant
Curare was one of the first chemicals used as a ____________ in anaesthesia
muscle relaxant
What are the neurotoxins that one can kill 30 people carried by puffer fish?
Tetrodotoxin, TTX
How does TTX inhibit action potentials?
By blocking voltage-gated sodium channels
Are there antidote for fish toxins?
No
What does tetanospasmin do?
Inhibits the release of y-aminobutyric acid (GABA)
________ is caused by tetanospasmin which comes from a bacterium called ___________
Tetanus; clostridium tetani
Tetanospasmin interfere muscle contractions and the muscles will become ________, and instead of _______, they will go into _______
very sensitive to stimulation; contracting; spasm
What are mamba venoms, neurotoxic cobra venom, scorpion venoms, widow spider venoms?
Synaptic neurotoxins
