Neuronal physiology: Membrane and Action Potentials and Synapse Flashcards
(29 cards)
What are the two gates in Na++ voltage gated channels?
A fast gate and a slow gate.
What gates are closed during activation?
The fast and the slow gate are open but the slow gate will close after a while.
What happens when the membrane is trying to reach the resting potential?
Hyperpolarization, the membrane goes to negative values even below the resting potential.
When is the absolute refractory period?
From the opening of the fast gate to the closing of the slow.
The values higher than the threshold (-60mV).
Impossible to fire up a new action potential (as the Na++ channels are not closed).
When is harder than normal to fire a new action potential?
During the hyperpolarization (Na+ gates closed and K+ gates opened). Relative Refractory Period.
Where are sodium and potassium channels located in neurons?
In the trigger zone, in the axon hillock.
Which type of muscle presents a longer hill in the action potential because of Ca++?
The Smooth Muscle.
What type of conduction allows myelin?
Saltatory Conduction
Faster.
What property of myelin makes the lenght constant higher?
The increase in the membrane resistance.
Where is in myelinated axons the action potential generated?
No me refiero al axon hillock, que también.
In the Nodes of Ranvier
Parts that are unmyelinated.
Why is better to have an axon with a greater diameter?
Greater diameter means less intermembrane resistance
Myelination reduces or increases Capacitance?
Reduces Capacitance.
This ONLY affects the time constant (is lower).
What type of temperature increases conduction?
High Temperatures
Cold Temperature make the conduction slower.
Which type of synapses are unidirectional?
Chemical Synapses
Which type of synapses have a minimal intracellular space?
Electrical Synapses
Why there are many mitochondria at the end of the axon (the presynaptic boutoun)?
As in these region Ca++ has entered to allow the release of Neurotransmitters through the vesicles. Ca must be expelled through a Na/Ca pump that is energy dependent. (Ca2+-ATPase).
What in the end plate increases the surface in contact with the neurotransmitter?
Junctional folds
Why the Na++/K++ voltage gated channels are not at the end plate?
Safety Mechanism. There is a spontanous release of the Neurotransmitters and we don’t want to be a contraction each time this happens. Need lots of Nt to generate the sufficient voltage too open the Na/K voltage gated channels that are far away.
What potential must be reached in the muscle so there is an action potential?
-60mV
How can Ach enter into the vesicles?
Thanks to a proton/Ach countertranspont active (ATPase).
What type of proteins mediate the Nt vesicle fusion with the membrane?
SNARE proteins
Soluble NSF attachment protein recptors
Which what protein Ca++ makes contact?
Synaptotagmin
Tag, it’s tagged by calcium
Which type of receptors act in distant places?
Metabotropic receptors.
Where are Type II synapses usually located?
At the soma and the dentritic branches.
Usually inhibitory.
