Electrophysiology I and II Flashcards
concentrations of potassium, sodium, and chloride, and calcium for generic cell
K+ = intracellular is 120, extracellular is 5 Na+= intracellular is 15, extracellular is 145 Cl-= intracellular is 20, extracellular is 116 Ca++= intracellular 10^-4, extracellular is 2
What is the refractory period in a voltage gated channel? (think heart pace-maker cells)
Let’s say at -70 mv, a channel is closed. At -50 mv, the channel would be open, and ions would rush into the cell. At +30, the gating mechanism INACTIVATES the channel, so although it is above its threshold, no ions can move across. The membrane can then repolarize, and the channel can go back to “closed” after going above -50 mv again.
What are ionotropic receptors?
Extracellular ligand-gated ion channels
what are mechanosensitive receptors?
stress-activated, which equals stretch-activated. Open or close when cells change shape, such as in shrinking or swelling.
what are nicotinic acetylcholine receptors?
bind extracellular ach and nicotine, resulting in opening of non-specific cation channels
What are cyclic nucleotide gated channels?
they bind intracellular AMP or GMP, and then open or close depending on their function
what happens when KATP channels (Kir) bind intracellular ATP?
It closes the normally open channel. The cell depolarizes, and insulin is released from the cell.
What does transiency mean with channels?
It means that overexposure of a channel to a ligand causes desensitization, so it won’t stay constantly activated
What is different about ion concentrations in red blood cells?
intracellular chloride is high, though extracellular chloride is still higher
What is different about ion permeabilities in a muscle cell?
chloride permeability is much higher
what is different about permeabilities in red blood cells?
sodium and potassium permeabilities are slightly higher.
action potentials happen in what cells?
neurons, skeletal muscle, cardiac muscle, and SOME smooth muscle
What are resting K+ channels?
They are leaky channels that are open at resting membrane potential.
what prolongs action potentials in myocardiocytes?
The influx of Ca++
How are action potentials induced in pacemaker cells? include channels, potentials, etc.
no external stimuli, they are spontaneous at a certain frequency.
Na+-HCN hyperpolarizing gated sodium channel… they open at a hyperpolarized state. these are the funny channels
closing the K-Kach channel, which is an ach sensitive potassium channel
opening the T type calcium channel, which depolarizes the cell.
Once you reach -40 mv, the voltage gated sodium channels then open, and you get the all or none action potential. resting was -60 mv
How do calcium channel blockers treat hypertension and angina?
decrease in intracellular calcium in cardiac cells reduces force of contraction as well as oxygen, reducing symptoms of angina. It also relaxes smooth muscle, dilating vessels, lowering blood pressure.
Inhibiting KATP channels treats what?
type II diabetes. It essentially increases intracellular Ca, allowing insulin to leave.
