Membrane Potentials Flashcards
Greater charge separation results in what?
greater # of volts
What is potential difference?
Separation of electrical charges across inside and outside of plasma membraneT
There are charged ____ and _____ inside the membarne
particles and proteins
Sodium tries to ____ cell, which is termed ___-
enter, influex
Why dose sodium want to enter the cell?
it wants to go down its concentration and charge gradient
When Na enters the cell, what happens to the potential difference?
potential difference is lessened, i.e. voltage moves towards 0
Sodium entering the cell causes ________
depolarization
Potassium ions try to ______ cell, this is called
leave, efflux
When K leaves the cell, what happens to the potential difference?
potential difference is greater, voltage becomes more - becomes + is leaving, therefore further from 0
Potassium leaving the cell causes
hyperpolarization
What are neurons RMP?
-70
What are the two forces acting on ions contributing to RMP?
charge gradient and concentration gradien
What are the two things that cause RMP?
membrane is differentially permeapse and the sodium-potassium ATPase
Explain what “membrane is differentially permeable” means
membrane is less permeable to Na than K, therefore sodium leaks slower than K, causes a net negative charge in cell
Explain the sodium-potasium ATPase pump
due to leakyness ions have to be returned to OG location
How many Na pumped out for every k pumped in?
2 sodium ions pumped out for every 2K pumped in
Pump can be described as
electrogenic
Describe pump mechanism
ATP binds to receptor, convertsit to ADP&Pi, pump becoems activated with energy, 3Na out and 2k in, ADP and Pi leave
ATP pushes _______ _______ and address _____
against gradient and addresses leakage
Which cells are excitable?
muscles and nerve cells
What are MPs used for?
to send electrical signals for communication
What are the two types of membrane potential changes?
action and graded potential
What are two ways of changing potential?
voltage gates or ligand gated ion channels
Cations in , potential difference ____, cell is _____
lessens, cell is depolarized
cations out, potential difference ____, cell is
increases, cell is hyperpolarized
Graded potentials are ______ to _______ ______
graded potentials are precursors to action potentials
Graded potentials are ______ _____-
short lived
Difference between AP and GP?
Graded potentials are local (donts spread v far), GP can be summated
What type of ion channels are GP
ligand gated ion channels
What brings GP back to RMP?
negative feedback mechanism
What is spatial summation?
GP occurring near each other
What is temporal summation?
GP occurring close enough together in time
Graded potentials are added up if they occur w/in few ____ & ____
ms & mm
Action potentials work via _____ feedback mechanism
positive
Explain the positive feedback mechanism
increase in voltage triggers more increase
Voltage gated sodium channels open when?
once membrane potential reaches threshold
What are the five phases of AP?
resting phase, depolarizing phase, repolarizing phase, hyperpolarizing phase, resting phase
What happens in the resting phase
all channels are closed
What happens in the depolarizing phase?
Stimulation causes voltage to rise, ligand gated sodium channels open, threshold is reached and triggers voltage gated sodium channels to open
What happens in the repolarizing phase?
voltage gated K channels open and sodium channels begin closing
What happens in hyperpolarizing phase?
sodium channels are fully closed, voltage gated K channels are open
which phases are sodium channels open?
depolarizing and repolarizing
When cant you fire an AP?
once an AP has started, once K is rushing out
Define absolute refractory period
start of NA threshold to end of repolarizing
Define the term relative refractory period
can send a message but need strong stimulus
Why is it called RELATIVE refractory period?
bc cell is hyperpolarized and therefore more negative, making it hard to stimulate an AP and need ever more channels to reach a threshold
At what voltage do voltage sensitive sodium channels open?
-50
Describe the negative feedback mechanism of AP
occurs at end to restore potential by opening voltage gated K+ channels and close Na channels
What instrument measures electrical activity in muscles?
electromyography
What does electromyography do?
EMG measures electrical activity in muscles
Define conduction velocity
can be calculated by knowing when nerve is stimulated and when uscle contracts and the physical distance btw them
How do EMGs work?
stimulate nerve using electrical stiulator and observe contraction
Why is incandescent light 60Hz?
so light doesnt appear to flicker
What is tetany
muscle cramp
What is the AC frequency in canada?
110V of AC with frequency of 60Hz
Which muscle is affected in tetany?
skeletal muscles
What causes tetany
stimulation of currents with frequency 40-110 Hz
What is death grip and why does it occur?
can’t let go bc flexors are strong than extensors and there isnt enough time to let go
What does DC do to muscles?
produce a single, large muscle contraction that throws electrocuted person away from source
