Excitable Cells Flashcards
what is action potential?
a brief flip flop in polarity across the membrane
why is action potential important?
it is how nerves and muscles contract
how does sodium ions enter the cell?
through facilitated diffusion
why does the cell loose positive charge?
potassium moves out the cell, therefore the cell looses the positive charge
what happens during the depolarizing stage
there is a change in sodium; positive charge is entering the cell
what happens during the repolarizing stage
there is a change in potassium; moves out the cell
what is the threshold
-55
what is the resting membrane potential
-70
what is the peak
+30
is action potential graded or not graded
not graded; meaning all the responses are identical once the threshold is met
what channels open during depolarization
voltage-gated ion channels open so the axon keeps gaining positive charge
when does the refractory period take place
beginning of hyperpolarization
do concentration gradients change during an action potential
the overall concentration gradients for Na+ and K+ do not change during an action potential
is action potential required
nerves have to have action potential in order to function properly
what does absolute refractory mean
the cell cant respond at all
what does relative refractory mean
the cell needs a bigger stimulus then usual to reach threshold
are leaky potassium channels always open ?
yes
what kind of stimulus is needed during the refractory period
a larger stimulus because its farther from threshold
what is the purpose of an inactivation gate
prevents the cell from being stimulated again until you are done with action potential
when do the inactivation gates slide into place
at the peak
what does propagate mean
to make more
where do action potentials take place
in the axon
what is the cell membrane mostly made of
phospholipids
what is the axon covered in
mylein
why is mylein covering the axon important
it increases speed, because it insulates the axon
why kind of charge flows under the myelin
positive charge
what occurs when there is a small space where the mylein isnt covering the axon
the sodium channels are open and the membrane reaches peak
what is velocity
how fast the axon conducts information
whats the difference between a myelinated axon and an unmyelinated axon?
a myelinated axon carries information faster with less friction, while covering more area (its thicker)
what kind of diffusion is ion movement
passive diffusion
what happens once threshold is met
sodium enters
which channels open first
sodium channels, then potassium
what is passive diffusion
type of membrane transport that does not require energy to move substances across cell membranes
which ion channels happen on the synaptic knob
voltage-gated calcium channels
what does blood calcium reflect
extracellular calcium
what is the importance of calcium
calcium helps the vesicles migrate to the synaptic cleft; calcium also helps to trigger the neurotransmitters to be released
what does exocytosis mean
to move something out of the cell
what are the steps of exocytosis
the cell manufacturers the neurotransmitters, the neurotransmitters are packaged within the vesicle, the vesicle fuses with the cell membrane and becomes a part of it, the calcium stimulates the vesicles to move to the synaptic cleft and then the neurotransmitter is released from the cell
what happens to the neurotransmitter once exocytosis process is over
once the neurotransmitter binds to the voltage channel, some of the neurotransmitters are removed by an enzyme out of the synaptic cleft while some neurotransmitters are recycled so they will go back by a process called endocytosis
where is electrical synapses found
cardiac muscle and smooth muscle
why are gap junctions important in cardiac muscle and smooth muscle
because they allow for an exchange of cytoplasmic products
