Lecture 7 Flashcards
What is osmosis
Osmosis is the movement of water across a
membrane to equalize solute concentration
What is tonicity
Terms used to describe weather water will move in or out of the cell
Describe what is meant by the term ‘Isotonic’
When the ECF and ICF are in balance
Describe what is meant by the term ‘Hypotonic’
When water loss from the ECF decreases in volume. This makes the solution hypertonic with respect to the ICF.
Describe what is meant by the term ‘Hypertonic’
When the solution moves from the ECF into the ICF
What will happen when a the balance between ICF and ECF becomes hypertonic?
An osmotic water shift from the ICF into the ECF restores osmotic equilibrium but decreases the ICF volume
If a cell has intracellular and extracellular fluids
that are equally matched in water and solute
concentrations, what term describers their
osmotic state?
Isotonic
What is a chemical gradient?
An uneven distribution of molecules across the membrane.
What are the relative concentrations of Na+ and K+ in the Intracellular Fluid?
In the ICF: Low Na+ high K+ (and vice versa)
Explain why chemical gradients allow rapid signaling excitable cells
Ions are highly driven to move down their conc. Gradient but they cant as the semi-permeable membranes wont allow them through. Because of this they require a channel. The moment a pathway opens, the ions will rush in/out along their gradient. The bigger the gradient, the faster and stronger the signal
What do passive ion channels do?
They allow the movement of ions down their chemical/electrical gradients
What does the sodium-potassium exchange pump do?
It maintains the electrical gradients across the cell membrane
How many potassium ions are brought in and sodium ions brought out of the cell for every ATP used by the Sodium-potassium exchange pump
For every 1ATP used, the Sodium-potassium pump brings in 2 K+ and takes out 3Na+
What is the Resting membrane potential?
At rest, the Intracellular space has a more negative charge in comparison to the Extracellular space. This creates an electrical gradient
What is the measure of the nerve resting potential
-70mv (millivolts)
What is depolarization?
When cations are rushed into the cell thus making the electron gradient less polar
What is repolarization?
When the sodium potassium pump moves the positive Na+ cations back out of the cell. This makes it more negative and returns it to its more polar state
