Module 1.3 Flashcards
cell membrane helps cells maintain ___________ -
stable internal balance
homeostasis
the cell membrane maintains homeostasis through balancing the ________ (4) through active and passive transport
pH, temperature, glucose (sugar intake), water balance
if a solution’s pH is unbalanced, it is corrected with a
BUFFER
direction of diffusion
high to low
direction of osmosis
high water to low water
low solute to high solute
When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to _____.
shrivel
When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to _____ and possibly explode.
swell
is a distribution of charge across the cell membrane
membrane potential
Membrane potentials
A. The body as a whole is electrically _____
B. All of the cells of body have an _______ across their membrane (_______) known as the membrane potential
C. Membrane potentials develop because of differing _________ between the inside and outside of the cell
neutral
electrical potential ; Voltage difference
ion concentrations
The exact value measured for the resting membrane
potential varies between cells, but ______ is a commonly reported value
-70 mV
________ is determined by the difference in charge between two points
- membrane potential,
- influence transport
Potential difference
Principals of electricity
- Units of electrical potential are in ______ or for biological system _______
- Voltage is always measured between two points (________)
volts (V) ; millivolts (mV) ; 1 V = 1000mV
Potential difference
flow of electrical charges from one point to another
current
B. Current
- Like charges repel unlike attract
- Ions tend to move from areas of greater concentration to areas of least concentration
- Movement of a positive ion from one side of a membrane to the other implies a _______ is left behind
negative charge
the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperature, remain constant.
Ohm’s Law (I = E / R)
R = resistance
I = current flow
E = electrical potential
C. Current Flow
- Cell - Aqueous solution + good ________ (Ions and water)
- Lipid membrane - A few charged groups can not carry current - high electrical resistance - _________
- ECF and ICF - both have _________
good conductor (ions)
good insulator (lipid membrane)
low electrical resistance (ECF and ICF)
describes the steady state of the cell
Resting Membrane Potential
By convention (Resting MP) - ECF (outside of the cell) is assigned a voltage of
zero
Polarity of the membrane is stated in terms of the sign of the ________ inside of the cell
excess charge inside of the cell
Types of channels (2)
- Leak Channels
- Na+/K+ ATPase Pump
Open all of the time - slow leak of ions, simplest type of ion channel, in that their permeability is more or less constant (neurons)
Leak channels
channel that transports sodium, potassium & chlorine
Accounts for 95% of the resting membrane potential
Leak channels
These channels open and close at random, allowing ions to pass through when they are open.
Leak channels
_______ :
a. Unequal transport of positive ions makes the ICF more _______ than it would be from diffusion alone
b. ________ pump
c. Accounts for 5% of resting membrane potential
Na+K+ATPase Pump;
negative,
Electrogenic
Other types of channels (4)
a. Resting K+ channel
b. Voltage-gated channel
c. Ligand-gated channel
d. Signal-gated channel
- channel that is always open
- are responsible for generating the resting potential across the membrane.
Resting K+ channel
- channel that opens (transiently) in response to change in the membrane potential
- are responsible for propagating action potentials along the axonal membrane
Voltage-gated channel
opens (closes) in response to a specific extracellular neurotransmitter
ligand-gated channel
opens (closes) in response to a specific intracellular molecule
signal-gated channel
Two types of ion channels in dendrites and cell bodies are responsible for generating electric signals in postsynaptic cells
ligand-gated channel and signal-gated channel
What are the complications of high potassium?
Hyperkalemia = too much K+ in the blood
What are the two forms of ion gradients?
Together these form what is known as the __________
- Chemical Concentration Gradient
- Electrical concentration gradient (Charge buildup and charge differential)
electrochemical gradient
Membrane potential: 75% more permeable to ____ (K+/Na+) than ____(K+/Na+) due to leak channel
K+ than Na+
In all cells a potential difference across the membrane exists
a. Inside is ______ (Na+K+ATPase)
b. Membrane potentials usually within ___ to ___ mv
negative because Na+/K+ ATPase;
-40 to -90
A cell with a resting membrane potential is
said to be
polarized
if resting MP, Both the inside and the outside of the cell are
electrically neutral
Factors that determine the resting membrane potential (4)
Selective permeability of the of the plasma membrane
Leak channels
Na+K+ATPase pump
Differences in ion concentrations
Many substances are in the cell but the mobile ions _________ (4) play the most important roles
Na+, K+, Ca++ and Cl-
ECF: ____ helps to balance ____
ICF: _____ balance ____
Cl-, Na+
Proteins (Neg charge), K+
At rest - Slightly permeable to Na+ 75 times more permeable to ___, and freely permeable to ___
K+, Cl-
_________ or ______ at which ion movements in both directions across the membrane are exactly balanced (net movement = zero)
Equilibrium potential or electrochemical potential
At equilibrium point, the ion flux = ____
0 (implies no net ion movement)
Equilibrium potential or also known as
Nernst potential
the value of the equilibrium potential (__________) for any ion depends on the concentration gradient across the membrane for that ion
Nernst potential
