Final Review Block 3 Flashcards
which ion has the biggest difference in concentration between inside and out of cell?
Ca
3 characteristics of simple diffusion
selectivity
passivity
competition
(no saturation)
describe a simple diffusion channel
hole in the membrane that provides a hydrophilic path for molecules to move through down their concentration gradient
what is Fick’s Law
j = DA (DC/Dx)
what are the consequences of fick’s law?
larger concentration gradient, more molecules will move
larger molecules = slower movement
larger surface area = more molecules diffuse
what is PTPC?
permeability transition pore complex in mito
closed = mito happy
open = apoptosis
what are the 2 types of RyR receptors?
RyR1 skeletal mm
RyR2 other mm
describe NMDA- type glutamine receptors
ligand gated Ca channels
antagonists: anesthetics, drugs (PCP)
what is the reflection coefficient?
measure of how well a solute can cross a membrane
=1 (highest), solute cannot cross
0-1 = semi-permeable
=0 freely permeable
what is required for a substance to be osmotically active?
cannot freely diffuse across the membrane
what allows for the passage of water across a membrane?
aquaporins
what characterizes facilitated diffusion?
competition, selectivity, saturability
describe GLUT-2
facilitative glucose transporter that is found on pancreatic b-cells, acts as a glucose sensor for release of insulin, always present in the membrane (constitutive)
describe GLUT-4
Facilitative glucose transporter that is found on skeletal and cardiac mm cells/fat cells, insulin binds to receptor yielding a signal for the cell to inset GLUT-4 into membrane (regulated)
what are the Ca ATPases?
PMCA- plasma membrane, pumps Ca out
SERCA- pumps Ca into SER
SPCA- on golgi
H/K ATPase on gastric parietal cells
1H out and 1K in per 1ATP
vesicular ATPase
uses ATP to pump H into vesicles
ABC transporter
uses APT to export xenobiotics, cholesterol and bile from liver
which active transporter is importance re: diarrhea?
Na/glucose cotransporter, will help move water out of gut (target of oral rehydration therapy)
K(ATP channel)
part of SUR, blocking k(ATP) leads to depol, which causes release of insulin
consequence of severe hyponaturemia
brain swelling
consequence of hypokalemia
constipation
digoxin MOA
cardiac glycoside- inhibits Na/K ATPase, thereby decreasing extracellular Na and decreasing “fuel” to pump Ca out of cell (decreases contraction)
CCB MOA
inhibit voltage gated Ca channels, decrease contraction strength - used for angina, arrhythmia and HTN, will decrease BP and decrease myocardial O2 consumption
effect of ischemia on the heart
ischemia will decrease OXPHOS and thereby decreased ATP production, Na will reverse the Na/Ca exchanger and increased Ca will be inside of the cell, leading to arrhythmia, heart failure or CVA
define equilibrium potential
the amount of charge needed to oppose the concentration gradient of the ion
what are the equilibrium potentials for K, Na, Cl and Ca?
K= -92 mV Na = +64 mV Cl= -88 mV Ca = -150 mV
what are the 2 things that govern membrane potential?
concentration gradient of ions
permeability of those ions
what is the main determinant of equilibrium potential in most cells?
K+ because Na and Cl permeabilities are insignificant
what is the consequence of increasing extracellular K?
depolarization
when are channels refractory?
after they are inactivated and before the membrane is repolarized
which type of cell has increased permeability to cl?
skeletal mm
describe leak channels
channels for K, Na, Cl that are voltage gated and are OPEN when the membrane is at resting potential
what is the cause of the “plateau” seen on myocardiocytes?
Ca influx
3 special channels in pacemaker cells
Na-HCN
K-KAch
Ca-t type
describe Na-HCN channels
in cardiac pacemaker cells, also called “funny”, will open when cell is hyper polarized and allow Na in to bring cell back to resting potential
describe K-KACh channes
ACh sensitive K channel- Ach opens channel and K flows out to repolarize, closing these will result in depol
describe Ca T type Ca channels
transient, will open at the beginning of depol and allow cells to reach threshold
sulfonylurea MOA
inhibits K(ATP) channel, leads to depol, depol opens Ca channels, increased Ca triggers release of insulin from b-cells
what maintains resting membrane potential?
Na/K ATPase
