Cell Physiology Block 1 (Foundations) PDF

Cell Physiology Block 1 (Foundations) KashifAhmad, MD, MSc, MS, PhD WE MAKE DOCTORS  CELL PHYSIOLOGY Recall structure of human cell, cell membrane Differentiate between the forces of diffusion, osmosis, filtrati...

Cell Physiology Block 1 (Foundations) KashifAhmad, MD, MSc, MS, PhD WE MAKE DOCTORS  CELL PHYSIOLOGY Recall structure of human cell, cell membrane Differentiate between the forces of diffusion, osmosis, filtration and convection on water flow. Define ECF and ICF and the major differences in ion concentration Explain the three major states of respectively dehydration and overhydration. Identify at least two major causes of each of these states. Differentiate between the terms osmole, osmolarity, osmolality and tonicity. List the typical value and normal range for plasma osmolality. Define the Donnan equilibrium and list the resulting characteristics. Describe how energy from ATP hydrolysis is used to transport ions such as Na+, K+,Ca2+, and H+ against their electrochemical differences (e.g., via the Na+ pump, sarcoplasmic reticulum Ca2+ pump, and gastric H+ pump). Explain how energy from the Na+ and K+ electrochemical gradients across the plasma membrane can be used to drive the net, uphill, (against a gradient) movement of other solutes (e.g. Na+/glucose co-transport; Na+/Ca2+ exchange or counter-transport). Apply this principle to Describe the role of water channels (aquaporins) in facilitating the movement of water across biological membranes. Describe the mechanisms and role of selective transporters for amino acids, neurotransmitters, nutrients, etc. 2 Remember Cell? 3 THE CELL MEMBRANE Composition mainly of cholesterol, phospholipids and proteins Semi Permeable Selectively Permeable 4 ICF vs ECF 3/4 1/4 60-40-20 rule, 60 (TBW) of which 40 in ICF and 20 in ECF 5 6  Gibbs Donnan Equilibriu Ca+ Na+ m Ca+ Na+ Cl - K+ Cl - HCO3 - HCO3 - K+ Proteins Na+= HCO3 -/ Cl - Mg = phosphates 2+ 7 Types of TRANSPORT Simple diffusion Facilitated diffusion Carrier mediated Cotransport Counter-transport Active transport Primary secondary 8 Fick’s LAW of DIFFUSION J=Pa (C1-C2), where P is permeability and “a” is surface area, you can call “J” FLUX or FLOW” 9 10 OSMOSIS Osmolarity=no. of particles XgxC, where g is “osmotic coefficient” concentration Reflection COEFFICIENT 11 CELL VOLUME REGULATORY MECHANISMS 12 Courtesy NIPS Dept of Cell Physiology TONICITY C=n/V REMEMBER PROTEINS EXERT ONCOTIC/COLLOIDAL OSMOTIC PRESSURE, they attract water they are a pull force, they don’t move much and are negatively charged. They keep fluid inside compartments. If you lose proteins fluid could follow. Also, tonicity is not osmolarity! You could relate effective osmotic pressure to tonicity. Osmotic water flow is the product of osmotic driving force and water 13 permeability which is called hydraulic conductance or filtration coefficient (Kf) Shifts of water between body fluid compartments to maintain osmolarity change 14  BASIC Metabolic Panel Measures electrolytes lab reports critical for diagnosis and treatment Calculating Plasma Osmolarity= 2 x[Na+] + Glucose/18 + BUN/2.8 BUN is Blood Urea Nitrogen 2 x[Na+] + 10 in the ER to speed up the calculation Normal plasma osmolality=285-295 milliosmoles/Liter Measured osmolarity (MO)-Calculated osmolarity, allow up 10, if > than 10 means abnormality, this is referred to as osmolar gap 16 Na balance is the key for fluid balance  Clinical Applications Discuss volume osmolarity graphs in SIADH, DIARRHEA, Sweating, DEHYRDRATION, ADDISON’s DISEASE Plasma EXPANDERS in ER DRUG PERMEABILITY CONDITIONS WHERE OSMOLAR GAP IS INCREASED What WILL HAPPEN In patients where the BODY loses proteins? (Kwashiorkor Disease, NEPHROTIC SYNDROME ETC) DEFECTS IN TRANSPORTERS, Channelopathy FLUID RETENTION AND HYPERTENSION 18 Cellular Communication Endocrine Paracrine Neurocrine Many disease processes related to hormonal issues Think like a clinician! 19 The Na+-glucose Co-transporter 20 CHANNELS Voltage gated channels Ligand gated channels Mechanically gated channels Show selectivity DO you remember the concentration differences? Conductance is determined if channels are open or closed 21 Na/K pump an EXAMPLE of ACTIVE TRANSPORT OTHER PUMPS: SERCA (stores calcium in SR) H/K+ ATPase that produces stomach acid Jens Skou 22 Cardiac Glycosides in CCF 23 ◼ Insulin secretion an excellent example of transport across membranes ◼ Think like a clinician/scientist, various levels of critical thinking 24 CLINICAL APPLICATIONS Sodium Potassium PUMP- BLOCK IN CCF HELPS BUILD CALCIUM by making the Na/Ca exchanger ineffective and makes more calcium available that causes increase in contraction AQUAPORIN CHANNELS –AQP1 (Passive CHANNELS) and AQP2 which respond to ADH or Arginine vasopressin and absorb water in the distal tubule and collecting duct of the nephron in the kidneys Oral Hypoglycemics- drugs such as sulfonylureas and metformin 25 Cell Physiology Block 1 (Foundations) KashifAhmad, MD, MSc, MS, PhD WE MAKE DOCTORS