Water, Ions, Cell / tissue Fluid And Balance Flashcards
What does it mean for a cell to be hypertonic
The solute concentration inside the cell is lower than outside the cell.
Water moves from low concentration of solutes to restore equilibrium (water leaves the cell).
Water leaves the intracellular fluid and flows to the extracellular fluid.
Volume of intracellular fluid decreases, the cell shrinks
What does it mean for a cell to be isotonic
The Extracellular fluid and Intracellular fluid solute concentrations are the same.
No solute concentration gradient.
No osmotic movement of water.
What does it mean for a cell to be hypotonic
Solute concentration in intracellular fluid is greater than solute concentration in extracellular fluid.
Osmotic water flow from low solute concentration in ECF to high concentration in ICF to restore osmotic equilibrium.
Volume of intracellular fluid has increased and cell swells
How is the concentration of ions in the ICF/ECF regulated
Ion excretion
Ion absorption
Ion storage
What is exitable tissue
Tissues that can alter their membrane potentials in response to stimuli, and generate action potentials
What are examples of excitable tissues
Nervous and muscular tissues are excitable
What are the cations and anions that are involved in maintaining ionic balance/equalibrium
Cations - Na+, K+ Ca2+?
Anions - Cl-
What prevents the free flow of ions into and out of the cell
The lipid bilayer - it acts as an insulator
How do cations and anions move across the membrane to maintain ionic balance/equilibrium
Membrane channels or an active transport mechanism
What is the resting membrane potential and how is it created
The electrical potential difference across the cell membrane in non excited state
Sodium is high and potassium is low in the ECF. Sodium is low and potassium is high in the IFC
This creates average resting membrane potential of -70mV
What are the two electrochemical gradients acting on a cell
The sodium gradient is inwards, with a large electrochemical gradient
The potassium gradient is outwards, with a smaller electrochemical gradient
Overall gradient is inwards
What is depolarisation and Hyperpolerisation
Depolarisation - sodium channels open and sodium is transported into the cell and the membrane potential decreases
Hyperpolarisation - potassium channels open and potassium is transported out of the cell and the membrane potential increases
What is an action potential
A rapid sequence of changes in the voltage across a cell membrane
What triggers a change in membrane potential
Chemical stimulus/neurotransmitters
