exam 1 lecture 3 + 4 Flashcards
plasma membranes are ___ permeable
selectively
there is more sodium in the ICF or the ECF?
ECF =145
ICF=15
Does the cell have more or less potassium inside or outside?
inside
ICF=140
ECF=4
cation is positive or negative ion?
positive
anions are positive or negative?
negative
___ is the potential inside a membrane relative to the outside
membrane potential Vm
the membrane potential when a cell is at rest
resting potential
Depolarization
•a positive change in the membrane potential
cations in (positive in) or anions out (negative ions out)
a negative change in the membrane potential; cations out or anions in
hyper-polarization and repolarization
resting potential of a cell is usually what?
-70
___ is when membrane potential goes below resting potential
hyperpolarization
there is more calcium on the inside or outside of the cell?
outside
ICF= less than 0.001
ECF 1.8
•Membrane potentials describe the ____ inside the cell relative to the outside
electrical charge
Two factors are critical in determining resting membrane potential are ___ and ___
Ion concentration gradients
Membrane permeability to these ions
can membrane permeability be increased?
yes
get more channels/ opening or closing channels
in a hypothetical cell if anions and cations inside and outside a cell are equal what is the electrical force?
0 = no membrane potential
if there is more K inside a cell than outside a cell, and a channel opened. Which way would K go?
outside of cell
diffusion down chemical concentration gradient
electrical force across a cell mebrane is the direction in which which ion wants to move?
cation (positive ion)
cell wants to be zero. if more negative inside, then cations from the outside will want to come into cell. this creates a electrical force into the cell
explain equilibrium potential of an ion across the plasma membrane
when chemical force and electrical force are equal
no more net movement into or out of a cell for a specific ion
when a cell have Na and K channels open why does the inside of the cell become more negative?
more potassium(+) leaves then sodium(+) enters
cell is 25% more permeable to potassium then to sodium
why does K and Na want to go back into the cell
the inside of the cell is negative. This causes a electrical force to force all cations into the cell.
Does not matter if different cations or chemical force, just looking at the charge of the ion
sodium potassium ATPase pump
- Critical for maintaining Vm at rest
- Exchanges 3 Na+ (out) for 2 K+ (in) resulting in a net negative intracellular charge
- Energy (ATP) dependent
sodium potassium ATPase pump move __ into the cell and __ out of the cell
2 potassium in
3 sodium out
how does sodium potassium ATPase pump maintain resting potential
3 sodium out, 2 potassium in creates a net negative charge inside
also maintains chemical gradients of more sodium on outside of cell (15 ICF, 145 ECF) and more potassium on inside of cell (140 ICF, 4 ECF)
___ channels are key to repolarization after an action potential
potassium
(more potassium inside of cell, potassium will leave and charge in cell will decrease back to resting potential -70)
potassium channels can be ___ gated or ___activated
- Voltage-gated (Kv)
- Calcium-activated (Kca)
If the membrane potential is not at equilibrium for an ion then the electrochemical force on that ion is ___
not 0
•The strength of the net force ___ the farther away the membrane potential is from the equilibrium potential of an ion
increases
rubber band example- if you really stretch the stronger the snap back
a ion wants to be at its personal charge (sodium wants to be +60), the farther from the charge the faster/stronger the ions will move across the membrane to create their equal
The net force acts to move the ion across the membrane in the direction that ___its being at equilibrium
favors
•Resting potential = –70 mV•EK = –94 mV
i.e. the Vm is 24 mV less negative (or more positive) than EK .
What is the direction of the electrical force of the K ions?
K wants to go into the cell.
K is +, cell is negative. Will pull potassium into the cell
•Resting potential = –70 mV•EK = –94 mV
i.e. the Vm is 24 mV less negative (or more positive) than EK .
What is the direction of the chemical force?
outside of the cell.
There is more K in the cell, wants to move down the concentration gradient to equal out, wants to move outside of the cell
•Resting potential = –70 mV•EK = –94 mV
i.e. the Vm is 24 mV less negative (or more positive) than EK .
What is the direction of the Net flow?
electrical force wants to pull K into cell
chemical force wants to push K out of cell
the net flow is K leaving the cell, wants to reach -94mV. Cell is currently at -70 wants to be more negative. Potassium is positive will leave cell to make more negative.
•Resting potential = –100 mV•EK = –94 mV
What is the direction of the Net flow of K?
K would move into cell to get to -94.
make inside of the cell more positive.
•Resting potential = –70 mV•EK = –94 mV
i.e. the Vm is 24 mV less negative (or more positive) than EK .
What is the direction of the Net force?
chemical force = K out of cell
electrical force= K into the cell
the chemical force is stronger then the electrical force until K gets to its happy place at -94
wants to make K leave
Net force vs Net flow
force= pressure put on an ion to move across a membrane
flow= actual movement, which direction does the ion actually go
difference between force and flow is “open doors”/ permeability
considerations impacting the net flow of an ion
permeability, how many doors are open
considerations impacting the net force of an ion across a membrane
chemical force and electrical force
•Resting potential = –70 mV•ENa = +60 mV•
i.e. the Vm is 130 mV more negative than Ena
Describe the direction of the electrical force? chemical force? Net force? and Net flow?
electrical force= into the cell (cell is negative wants to make it more positive)
chemical force= more Na on outside wants to go into cell to even out
Net force= into the cell wants to get to +60
Net flow= into the cell
in a neuron the resting potential is -70 this is closer the the K equilibrium of -94 then the Na equilibrium of +60.
What does this mean if you open a K or a Na gate
Na will move faster than K because it has a stronger force acting on it.
Farther from its happy place (rubber band theory)
nicotinic acetylcholine receptor is an example of active or passive transport?
passive
sodium potassium ATPase pump is an example of active or passive transport of ions?
active= needs ATP
pump 3 Na out and 2 K in
voltage gated ion channel for K
if cell more negative inside, gates are closed
if more positive inside, gates will open and K will leave along electrical potential gradient (+ will move out to make inside and outside charge equal)
example of intracellular ligand gated ion channel
G protein coupled receptor complex will trigger alpha subunit to bind and act as ligand to open up ion channel
where can you find stretch activated channels?
inner ear
open through mechanical force of sound wave that allows K into the cell
example of promiscuous ion channel
acetylcholine receptor
non-specific receptor lets any ion in
ryanodine receptors can be found on the ___ and are an example of intercellular ion channel
sarcoplasmic reticulum (calcium transport)
Graded potentials are ___ changes in the membrane potential
small
In graded potentials the ___ varies depending on the strength of the stimulus
magnitude
stronger stimulus = stronger reaction
Graded potentials are decremental meaning ___
the get smaller with distance and time
what is the axon hillock
where action potential starts
needs a certain amount of stimulus and then causes action potential to go (push on a slide)
What does it mean when graded potentials can be excitatory or inhibitory
can make membrane potential more or less positive. (closer or farther away from threshold)
depending on where the cell is can stop or go a potential
graded potentials have ___ effects and can lead to an action potential
additive
can build on each other to cause action potential
temporal summation for action potential
same signal repeated will build to action potential
spatial summation of action potential
stimulus from different sites will add together to create action potential
___ is a large depolarization wave that travels along the plasma membrane
action potential
does an action potential diminish over time?
no, maintains its strength by the sodium Na channels along the neuron
___ is when an region of the neuron can not respond to another stimulus/ depolarization
absolute refractory state
relative refractory period
when a cell is hyperdepolarized (below resting), could respond to a stimulus and start a new action potential but the stimulus would need to be very large
what cause depolarizing in an action potential
Na channels open- Na floods into cell very quickly - cell becomes more +, opens and closes quickly
at peak: Na channel close and K channels open
voltage gated K channels open slowly cause K to leave- K opens at peak of action potential and closes slowly
what happens at repolarization
Na channels close (less + coming into cell)
K channels are open but taking their time to close so + is leaving cell
Cell becomes more negative
what happens during hyperpolarization?
potassium channels close to slowly and cell goes too negative. (refractory period) Eventually the potassium channels fully close and cell will return to resting potential with help of sodium potassium ATPase pump
explain Na channels on neuron during action potential
at resting potential: channel closed, inactivation gate (ball and chain) open
depolarization (threshold met and action potential starts): channel opens and lets Na into the cell
1 msec later: the inactivation gate closes, the channel is still open but Na can’t get through
Once cell returns to resting potential: channel will close and inactivation gate will open - ready for next action potential
___ neuronal action potential initiates depolarization of muscle membrane
synaptic transmission
____ action potential is converted into mechanical energy, and through crossbridge cycling, sarcomeres shorten, resulting in contraction
excitation-contraction coupling
•Skeletal muscle is controlled by ___-motor neurons
somatic
•Neurons integrate excitatory and inhibitory signals and fire an ___ when the activation threshold of voltage-gated Na+ channels is crossed
action potential
at the axon terminal, action potential opens voltage-gated ___channels in presynaptic membrane
calcium
•Ca2+ influx into the axon terminal causes ___ containing vesicle fusion & ___ release into synaptic cleft
acetylcholine (ACh)
ACh
In the NMJ, ACh binds to nicotinic ACh receptors on the ___
motor end plate
what causes depolarization at the motor end plate?
ACh receptors allow ions to flow into the cell causes the cell to become more positive = depolarization
if ACh receptors let both Na and K in and out of the cell why depolarzation?
forces on sodium stronger (resting potential farther from Na happy place) - more sodium floods into the cell (more + = depolarization)
forces on potassium weaker (resting potential closer to K happy place)- less potassium moves out of the cell
On skeletal muscle, depolarization spreads to adjacent membrane and activates voltage-gated ___channels
Na+
allows Na into the cell, makes more + = depolarization
NMJ will lead to action potential that travels along the border of cell(sarcolemma) and down the T tubules
An action potential on a motor neuron is ___ and will lead to an action potential on the skeletal muscle cell, which will always lead to contraction
excitatory
define Excitation-Contraction (E-C) Coupling
•The signal transduction mechanism by which extrinsic stimuli (electric) are translated or encoded into an intracellular response (muscle contraction)
•Contraction and relaxation of a muscle cell is a direct function of the ___ Ca2+ concentration
intracellular
action potentials will increase or decrease the amount of intracellular calcium in a muscle cell?
increase
T-tubules are invaginations of the ___ and allow ___ fluid to permeate through muscle fiber
sarcolemma
extracellular
(T tubules have voltage gated Na channels that allow action potential to move down into the muscle cell)
what is stored in the sarcoplasmic reticulum?
calcium
Triad in skeletal muscle is?
T tubule and the sarcoplasmic reticulum on each side
•In skeletal muscle, the DHP receptor is directly linked to the ____ receptor
ryanodine- calcium release unit
will allow calcium out of the SR and into the intracellular space
In skeletal muscle, action potential triggers opening of ___ receptor, which in turn, opens the ryanodine receptor
DHP
what is the name of the receptor that binds the SR to the T tubules
DHP bound to ryanodine receptor
sliding filament model
thin and thick slide over each other
H and I shorten
A stays the same
Ca2+ binds to ___, causing a shift in tropomyosin, and promotes cross-bridging
troponin
binding sites will be exposed and myosin will bind to actin and cross bridging and power stroke will happen. ATP will bind and myosin lets go, ATP hydrolyzed into ADP and Pi and head is cocked and ready for next cross bridge
In the ___ of ATP, Myosin heads bind to actin
absence
In the ____ of ATP, Myosin/actin bond is weak. Actin stimulates myosin ATPase activity. Myosins move towards the barbed end
presence
In the presence of ATP, which direction will myosin move?
toward the barded end
to cock the head of myosin what has to happen
ATP has to be hydrolyzed- high energy form Pi+ADP
for powerstroke to happen, what needs to happen
calcium binds and binding site is exposed
high energy cocked ADP Pi myosin head binds, Pi(inorganic phosphate) leaves and power stroke happens
for myosin to let go of thin filament what needs to happen
ATP needs to bind to myosin head
explain cross bridge cycle
how if ACh removed from synaptic cleft
acetylcholinesterase
how does acetylcholinesterase work
acetylcholinesterase lives on the motor end plate
breaks ACh into choline, choline taken back into the neuron terminal and recycled back into ACh to be used later
what are SERCA pumps
sarco/endoplasmic reticulum Ca2+-ATPase pump
pull calcium from the sarcoplasm back into the sarcoplasmic reticulum
calcium will then bind to calsequestrin in the SR to keep it there
how does muscle relax
calcium pumped back into the SR by SERCA
calcium pumped out of cell
•Together, these pumps lead to a low Ca2+ concentration inside the sarcoplasm under resting conditions
