Midterm Exam Flashcards
(125 cards)
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)