youtube live for physiology foreign medical exam

Summaries of exam

1. PHYSIOLOGY PACKAGE as the exam approaches - Dr Vivek Nalgirkar

2. WHICH SYSTEMS SHOULD YOU FOCUS ON? General physiology CVS RS Kidney/excretory system CNS {A run-through of Nerve-Muscle, Endocrines, blood……shall boost the confidence level further}

3. WHICH TOPICS SHOULD YOU REVISE?? Body fluid compartments, transport processes Conducting system, cardiac cycle (events and PV changes), Cardiac output, Blood pressure, Exercise Mechanics of breathing (incl. surfactant, compliance, lung volumes & capacities), V/Q ratio, gas transfer, Gas transport, regulation of breathing, hypoxia Nephron, JG apparatus, GFR, clearance, tubule functions, micturition, acid-base balance

4. Receptor, synapse, NTs , ascending tracts, pain, cerebellum, hypothalamus, sleep & EEG, Learning & memory [Anemia, WBCs and immunity, coagulation, blood groups, pituitary, thyroid, adrenal cortex, insulin; NM junction, EC coupling, sarcomere] [If time permits – Errors of refraction, visual pathway, organ of Corti , testosterone, spermatogenesis, saliva, gastric juice, pancreatic juice, bile]

5. “SHOULD I REVISE THE SUBJECT OR SOLVE MCQs AT THIS STAGE?” Too much MCQ solving, very close to exam, will have “law of diminishing returns”. (When you read an MCQ, you also read wrong options. Sometimes, you may retain wrong option as the answer.) Revise..Revise….Revise……..; with light MCQ solving (with emphasis on explanatory answers)

6. General Physiology [Body fluid compartments] TBW = 60% of body weight [42 L] ICF = 40% of body weight [28 L] ECF = 20% of body weight [14 L] ECF  3/4 th is interstitial fluid [11 L] and 1/4 th is plasma [3 L] Blood = 8% of body weight; [5% is plasma; 3% is cells or hematocrit] Measurement of body fluid compartments: V = I/C; V = [I – A]/C

7. Indicators used for measurement: TBW —> Deuterium, tritium, aminopyrine ECF —> Inulin (best), sucrose, mannitol ICF = [TBW – ECF] Plasma volume —> Radiolabeled albumin

8. General Physio [Homeostasis] ECF ~ Rich in Na + & Cl - ; low K + ICF ~ High K + and phosphate, bicarbonate, proteins; low Na + (The ECF rich in K + is endolymph) Homeostasis is maintained by feedback and feedforward mechanisms. (Examples for each)

9. Transport through cell membrane (Osmosis, diffusion, active transport) Osmosis, osmolality, serum osmolality Diffusion: (1) Simple diffusion:- (a) through lipid bilayer ~ CO 2 , O 2 ; (b) Through channels ~ Na + , K + , Ca ++ , etc (2) Facilitated diffusion:- Glucose transport via GLUTs Active transport:- Primary ~ Na + /K + pump, SERCA Secondary ~ (i) Symport :- SGLT, (ii) antiport :- NCX [Na+/K+ pump – 3 Na+ from inside to outside; 2 K+ from outside to inside]

10. RMP & AP Equilibrium potentials of ions:– Calculated by Nernst equation RMP of nerve = - 70 mV, RMP of skeletal muscle = - 90 mV Greatest contributor ~ Diffusion of K + Diffusion of Na + , K + , Cl - contribute - 86 mV; Na + /K + pump contributes - 4 mV.

11. Action potential Recorded by cathode ray oscilloscope (CRO) Depolarization ~ Na + influx (VGSC); Repolarization ~ K + efflux. Afterdepolarization – K + efflux decreases; afterhyperpolarization – excess K + leaves Propagation:- (a) Through myelinated nerve – Saltatory conduction; (b) through unmyelinated nerve – local circuit.

12. Nerve Muscle Classification of neurons:- Multipolar, bipolar, pseudounipolar , anaxonal Classification of nerve fibers:- A, B, C (sensitivity to pressure, hypoxia, LAs) Myelination of nerve fibers:– Schwann cell, oligodendrocyte

13. Muscle NM junction, EC coupling Nerve ending:- VGCC, ACh vesicles Motor end plate:- Nicotinic AChR (non-specific cation channel) ; EPP = 40 mV —> converts into AP. Myaesthenia gravis EC coupling:- occurs in sarcotubular system (T & L tubules). DHPR = VGCC in T-tutbule ; RyR = L-type Ca++ release channel in L-tubule. [Malignant hyperthermia]

14. Muscle Sarcomere:- Thin : thick = 2:1. {Each thick filament is surrounded by 6 thin filaments} Titin :- Largest protein; dystrophin:- largest gene 1 sarcomere = 1 full A-band + 2 half I-bands H-zone disappears with contraction; I-band shortens Smooth muscle:- Ca++ + Calmodulin; “Latch bridge” – spends less ATPs

15. CVS [Conducting system, cardiac cycle, cardiac output, blood pressure, shock] Properties of cardiac muscle:- Excitability, contractility, autorhythmicity (due to pacemaker potential), long refractory period (due to plateau potential), non-fatiguability, non-tetanizable (due to long refractory period); SYNCYTIUM (gap junctions). Presence of intercalated discs Pacemaker current:- [K+ accumulation inside the membrane —> Na+ funny current —> Ca (T) current.] Depolarization completed by Ca++ (L) current Plateau in Purkinje :- [Slow Ca ++ channels]

16. AV node – Slowest conduction. Blockade of impulse in AV node —> Heart block (3 degrees) Purkinje fiber – Fastest conduction.

17. Cardiac cycle Duration Atrial systole, atrial diastole. Ventricular systole:- Isovolumic contraction, rapid ejection, reduced ejection Ventricular diastole:- Protodiastole , isovolumic relaxation, 1 st rapid filling, diastasis , last rapid filling. 4 sounds are produced; normally, S1 and S2 can be heard clinically over all the 4 areas of auscultation. [S1 better over mitral & tricuspid area; S2 better over aortic & pulmonary area]

18. JVP Recorded over IJV Normal pressure = 0 – 5 cm H 2 O (+/- 5) “a” wave ~ a trial systole “c” wave ~ isovolumic C ontraction of RV (causing ballooning backward of tricuspid valve into RA) “v” wave ~ iso v olumic relaxation of R V (tricuspid valve not opened yet. Filling cannot happen, so v enous blood accumulates in RA) x downslope ~ RV ejection; y downslope ~ RV filling

19. Cardiac output CO = SV X HR = 70 X 72 = 5 L/min Cardiac index = CO/BSA Factors determining CO ~ SV and HR STROKE VOLUME ~ proportional to venous return/end-diastolic volume/preload [Frank Starling law]; sympathetic stimulation, catecholamines, digitalis -> positive inotropic effect -> increases SV SV is inversely related to afterload (aortic pressure/arterial BP) [ Chronotropic , dromotropic , Inotropic, bathmotropic effects] Factors influencing CO:- Physiologic, pathologic

20. Blood pressure [Types, determinants, measurement, regulation] Types ~ systolic, diastolic, pulse, MAP Determinants ~ BP = CO X TPR REGULATION:- Short term ~ Baroreflex , chemoreflex , CNS ischemic response Intermediate-term ~ ADH and thirst, capillary fluid shift, ANP Long term ~ RAAS, kidney body fluids

21. Respiratory system [Mechanics of breathing, lung volumes & capacities, gas transport, regulation of breathing, hypoxia] Intrapleural pressure, intra-alveolar pressure, transpulmonary pressure [alveolar – intrapleural ] Surfactant:- By type II pneumocytes , main constituent is DPPC, absence leads to ARDS COMPLIANCE:- 200 mL/cm H 2 O. Dynamic compliance ~ Greatest at the start of inspiration; increases in emphysema, decreases in pulmonary fibrosis Dead space:- 1 mL/pound of body weight (about 150 mL)

22. Lung volumes and capacities TV – 500 mL IRV – 3000 mL ERV – 1100 mL RV – 1200 mL Insp capacity = TV + IRV FRC = ERV + RV Vital capacity = IRV + TV + ERV TLC = IRV + TV + ERV + RV [RV can not be measured by spirometry; Helium dilution method and nitrogen wash out method ]

23. Respiratory system V/Q ratio = ( avg ) 0.8; due to hydrostatic factor, it is higher at the apex (3.5) and lower at the base (0.5). Diffusing capacity of respiratory membrane ~ CO (O 2 and CO 2 are perfusion limited gases)

24. Oxygen transport 97% with Hb, 3% in plasma Oxygen carrying capacity ~ 1 gm of Hb carries 1.34 mL of O 2 (1 molecule of Hb carries 4 molecules of O2) Oxygen dissociation curve:- “S” shaped. Shift to right (easier dissociation of O2from Hb):- increased H+, CO2 , temperature, 2,3-DPG