Class Notes (808,761)
Canada (493,382)
Physiology (1,038)
Tom Stavraky (262)

Excitable Cells.doc

2 Pages
Unlock Document

Western University
Physiology 3120
Tom Stavraky

Excitable Cells 42L Total Body Fluid 28L Intracellular (67%) 14L Extracellular (33%) 11L Interstitial 3L Plasma o Membrane Protein Functions: receptors, enzymes, transport, cell recognition, cytoskeleton anchors o Diffusion – Time required for diffusion increases with the square of the distance. Luckily, most cells are less than 25-50um from the capillary. − kT dc Fick’s Law of diffusion: 6πηr • dx • A o Diffusion through channels: Dependent on size (less than 0.8nm), charge (filter, NOT chemical specificity), electrochemical gradient, pressure gradient, hydration energy (larger electronegativity coefficient causes greater hydration shell). o Facilitated Diffusion: Does not require energy, shows chemical specificity, can be competitively inhibited and shows saturation kinetics. o Active Transport: Shows saturation kinetics, chemical specificity, and competitive inhibition. Involves the use of energy to move substances against concentration gradient. o E.g. Na+/K+ pump, 1 ATP, 2 K+, 3 Na+. Functions to increase negativity inside the cell, and net reduction in particles inside the cell. Can be inhibited by ouabain, dinitrophenol, O2 deprivation. o Secondary Active Transport: Powered by concentration gradient, usually an exchange system or co-transport. Osmotic Pressure – pressure needed to stop the net influx of water into a solution. Depends on the number of particles, not the type. Osmosis depends on: the permeability, the concentration gradient, and the pressure gradient. Osmole – number of particles of an undissociated solute. E.g. NaCl makes 2 osmoles. - Osmolality of body fluids is approximately 300 mosmoles per kg water Capillary Hydrostatic Pressure of Plasma – Pc – capillary blood pressure, arterial end about 25 mmHg while venous end is about 10 mmHg. Interstitial Fluid Hydrostatic Pressure – Pif – Interstitial Fluid pressure, depends on tissue, encapsulated organs tend to be (+) and cause reabsorption while others are (-) and cause filtration. Interstitial Osmotic Pressure – πif – Few proteins in interstitium (5 mmHg) Plasma Osmotic Pressure – πp – Proteins in plasma (28 mmHg) Net fluid movement = Kf [ (Pc – Pif) – (πp – πif) ] + is filtration - is reabsorption - lymphatics also play a role! Edema: (1) tissue damage, increases Kf (2) Decreased plasma protein (malnutrition) lower πp (3) Blockage of lymphatic system (4) Blockage of venous return increasing Pc - Potential difference across the plasma membrane is the resting membrane potential - All cell have an RMP but only some are excitable. Nersnt Equation – to calculate the equilibrium potential of an ion. (i) membrane must be permeable to only on ion and (ii) there must be a concentration gradie
More Less

Related notes for Physiology 3120

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.