Midterm Exam Flashcards
Why is a cell can depolarize ?
Because the cell receives signal from other cells.
What is the concept that is happening at +40 mV when sodium ions rushing in equals potassium ions rushing out of the cell ?
Equilibrium potential
On which ion those action potentials depends on and why ?
Sodium because at -40 mV, the voltage-gated sodium channels open.
The resting membrane potential is dependent of which ion and why ?
Potassium because at rest, it is only potassium that goes in and out of the cell (the other doors are locked)
What are the two kinds of refractory period and describe them ?
Absolute refractory period: Complete insensitivity to stimuli (no more action potential).
Relative refractory period: A period of reduced sensitivity during which only strong stimulation produces an action potential.
The conduction velocity in the axon varies with what ?
The diameter of the axon and the myelin sheathing
myelination is better than bigger diameter
Where does the action potential is taking place and is regenerated ?
Nodes of Ranvier
How is the phenomena named in which action potential flies through the other node of Ranvier ?
Saltatory conduction
Why does a neuron generated action potentials ?
To communicate with other neurons.
True or false.
At the axon terminal, the chemical signal of the action potential is usually converted into a electrical signal (neurotransmitter).
False.
At the axon terminal, the electrical signal of the action potential is usually converted into a chemical signal (neurotransmitter).
How does the electrical signal is converted into a chemical signal ? (Synaptic Transmission)
When the action potential arrives in the axon terminal, it depolarize the region and then voltage-gated calcium channels open and calcium (Ca2+) rushing in by diffusion (because there are less calcium inside the cell than outside).
Because of the influx of calcium, synaptic vesicles migrates to the presynaptic membrane.
With v-SNAREs that are attached to the vesicle and t-SNAREs attached to the presynaptic membrane, the vesicle docks to the presynaptic membrane promoting exocytosis, the fusion of vesicles with the presynaptic membrane, which releases transmitter into the cleft.
Transmitter molecules cross the cleft to bind to special receptor molecules in the postsynaptic membrane, leading to the opening of ion channels in the postsynaptic membrane.
This ion flow creates a local EPSP or IPSP in the postsynaptic neuron.
Synaptic transmitter is either degraded by enzymes or removed from the synaptic cleft by transports.
Synaptic transmitter may also activate presynaptic autoreceptors, regulating future transmitter release.
What are the two types of release ?
Kiss and run
Full release
What are the two prompt cessation of transmitter ?
Degradation: transmitter is broken down by a special enzyme (acetylcholinesterase)
Reuptake: transmitter is taken up into the presynaptic cell via transport
What is the role of autoreceptors ?
They inform the presynaptic cell about the net concentration of neurotransmitters in the cleft.
The message comes from the neurotransmitters that didn’t cross the cleft.
What are the two types of ligands ?
Endogenous ligand: neurotransmitters or hormones
Exogenous ligand: drugs, toxins from outside the body
When activated by a neurotransmitter, ionotropic receptors may… ?
Change shape
When activated by a neurotransmitter, metabotropic receptors may… ?
Alter chemical reactions in the target cell
What are the two types of postsynaptic potentials ?
Excitatory postsynaptic potential (EPSP)
Inhibitory postsynaptic potential (IPSP)
*work the same but have opposite effects on postsynaptic neurons
In which case a postsynaptic neuron will generate an action potential ?
If the integration of these postsynaptic potentials depolarizes the axon hillock enough.
What are the two types of summation ?
Spatial summation: summing potentials from different locations
Temporal summation: summing potentials across time
What is a chemical substance made within the body ?
Endogenous ligand
What are the six criteria of a substance to be considered a classic neurotransmitter ?
1) The substance exists in presynaptic axon terminals
2) The presynaptic cell contains appropriate enzymes for synthesizing the substance.
3) The substance is released in significant quantities when action potentials reach the terminals
4) Specific receptors that recognize the released substance exist on the postsynaptic membrane
5) Experimental application of the substance produces changes in postsynaptic cells
6) Blocking release of the substance prevents presynaptic activity from affecting the postsynaptic cell
Where does the raw material are produced ?
It is produced in the nuclei and transport by anterograde.
What are the three big families of transmitters
Amino Acids: GABA, glutamate
Amines: Acetylcholine (ACh), norepinephrine, epinephrine, dopamine
Neuropeptides: Oxytocin, nitric oxide (gas)
What is co-release ?
The appearance of ore than one neurotransmitter in a given vesicle.
What are the most abundant neurotransmitters in the brain ?
Amino Acids
True or false.
Glutamate and aspartate are the most prevalent inhibitory neurotransmitters in the brain.
False.
Glutamate and aspartate are the most prevalent EXCITATORY neurotransmitters in the brain.
Glutamate is also associated with which phenomena ?
Excitotoxicity. The property by which neurons die when overstimulated, as with large amount of glutamate.
What glutamatergic transmission employs ?
Ionotropic receptor (AMPA, kainate, NMDA), Fast-acting
Metabotropic receptor (mGluR’s), slow-acting
*the names of these receptor subtypes refer to drugs that activate them
What is making NMDA receptors different from AMPA or kainate receptors ?
Magnesium is blocking the way. So, the postsynaptic cell’s inside needs to depolarize to pop out the Mg2+. The magnesium is popped out by electrostatic repulsion. (Magnesium is a positive ion and the inside of the cell is more positive)
How can a postsynaptic cell can depolarize if channels are closed ?
There are other receptors that can allowed a depolarization.
Which amino acids have an inhibitory effect ?
GABA and glycine
What GABA-ergic transmissions employs ?
Ionotropic receptors: (GABAa, GABAc) Fast-acting
Metabotropic receptors: (GABAb) Slow-acting
Why some receptors are fast-acting and others are slow-acting ?
Because the fast-acting receptors are ionotropic, which means that they allow need a ligand to bind to the receptor and then, the channel will open.
Slow-acting receptors are metabotropic, which means that they work through a second messenger.
What happened when channels are opened by GABA knowing that they have a inhibitory effect ?
Channels let negatively charge ions to go through (chloride). They go through the channel by diffusion because there is a higher concentration of chloride outside the cell than inside.
What are the two types of ACh receptors ?
Nicotinic: mostly ionotropic and excitatory, important in muscle contraction
Muscarinic: metabotropic, ionotropic or excitatory
What are the two main classes of amines ?
Catecholamines: dopamine, norepinephrine and epinephrine
Indoleamines: serotonin and melatonin
True or false.
Dopamine can be a neurotransmitter or an hormone
True.
What is the amino acid that all catecholamines synthesized from ?
Tyrosine
The indoleamine neurotransmitters derived from which amino acid ?
Tryptophan
What are the two main indoleamines neurotransmitters ?
Melatonin and serotonin
What happen if we don’t have the enzyme that synthesized dopamine ?
We don’t have a dopamine and the other neurotransmitters synthesis.
What are the main catecholamine neurotransmitters ?
Dopamine, norepinephrine and epinephrine
What is cholinergic cell ?
Cell that use acetylcholine as their synaptic transmitter.
What is common with both muscarinic and nicotinic cells ?
They both respond to their specific chemical response and acetylcholine
Which dopamine receptors activates the second messenger ?
D1 and D5 receptors.
Which dopamine receptors inhibit the second messenger ?
D2, D3, D4 receptors
When we talk about dopamine, the second messenger is involved. What is the first messenger ?
The first messenger is the neurotransmitter (dopamine)
What are the names of the two pathways that dopaminergic neurons projected ?
Mesolimbocortical pathway
Mesostriatal pathway
Norepinephrine receptors are ionotropic or metabotropic ?
Metabotropic