Cell Physiology Flashcards
Soft cells
Have a cuboidal shape, mostly H2O, sac of ions
Makes epithelial cells that line the GI tarct and airway
Concentration gradient
Water requires a concentration gradient
Solute goes from an area of high conc. to an area of low conc. with the concentration gradient
The equalised concentration is attainted through a process of diffusion
Ionic conc. Gradient
Ions in body go from area of high conc. to area of low through diffusion down conc. gradient
How do ions diffuse?
Through semi-permeable membrane, it is similar to a cellular membrane.
It has Osmotic pressure that provides structure and shape
Why can’t big molecules pass through?
Becasue semi permeable mem can’t pass through large molecules
What does Osmosis and osmotic potential do?
Give the cells shape and tonicity (determines the appearance of the cell)
Buildup of male and female cells
FEMALE
*50% H20
*27% ICF (Intercellular fluid)
*18% ECF (Interstital fluid)
Solids (organic +inorganic) 50%
Plasma 4.5
Other fluids «1%
MALE
*60% H20
*33% ICF (Intercellular fluid)
*21.5% ECF (Interstital fluid)
Solids (organic +inorganic) 40%
Plasma 4.5
Other fluids «1%
Journey of H20
*Water absorbed by the GI tract - 2200 mL
*Water los by breathing and vapour - 1150
*feces - 150
*sweat glands
*Urine - 1200
Solutes and ions are also found in ICF and RCF
Isotonic
*When there a balance between the ions of H20 and solute
*The ICF and ECF have letters. The volume of ICF would be larger has the insides needs to host more H20 in case of emergency.
Hypertonic (change in ECF induced)
When the ECF loses water content resulting in a higher solute to water ration, causing the ECF to become hypertonic in relation to ICF. As conc. of solute is large per volume, the osmotic conc./ osmolarity has increased.
Hypertonic (response of the cell)
In response, water molecules from the cell go down the conc. gradient from an area of high conc. of H2O (low in solute) to low conc. of water in order to restore osmotic equilibrium. In the process the cell loses volume resulting in it to shrivel. If the extra reserve of H2O starts to deplete, it shrivels even more eg changes in total blood volume cause cells are loosing water
Hypotonic solution
Concentration of H2O is too much in the ECF, so water moves down the conc. gradient to maintain the osmotic equilibrium, to enter the cells, causing the cells to swell. Eg is brain swelling when theres too much h2o and kidneys cannot flush H2O very in a short period of time, too much h2o results in hyponatriemia.
How is ion concentration in the bodily fluids maintained?
Ion absorbtion, ion reserves and ion excretion
Ion absorption
From intestines
Ion reserves
1º from skeletal system
Ion secretion
Through 1º i.e the kidneys and 2º i.e sweat glands etc
What are excitable cells?
Those that have a membrane potential and rely on a balance of Na+, K+, Ca2+ and Cl- ions. eg are neurons and muscle cells
Epithelial cells have a membrane potential but they are not excitable
How can ions move across into the cell to maintain ionic equilibrium?
*The phospho bilayer is an insulator and doesn’t allow ions to just flow through.
So to maintain the ionic balance, ions must travel through ion channels or through active transport
Resting membrane potential
Na+ inside the cell is less compared to the outside while K+ is more tha the outside. K+ is a lot bigger than Na+, meaning that more Na+ fits in the cell than K+.
There is a small charge when cell is at rest because of the difference in ions. This is resting mem potential at around -70mV inside the cell
Passive channels
Na goes from out to in
K goes from in to out
Through the channels, regulated by sodium-potas exchange pump to maintain the chemical gradient at a charge of -70mV
sodium-potas exchange pump
Is ATP operated, takes out 3 Na in exchange for two K+ into the inside, ATP –> ADP
Active system, overall energy expenditure in system
Na+ electrochem gradient
positive Na chem grad + a positive Na electrical gradient = very large inwards Na electrochemical gradient
K+ electrochem gradient
outward K+ chem grad and inwards K+ electro grad = a smaller outwards K+ electrochem grad
Difference between chem and elec gradients
Chemical gradient: Forms due to the difference in concentrations on opposite sides of a membrane. Electrical gradients: Forms due to difference in charge on opposite sides of a membrane.
