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NARAYANA MEDICAL COLLEGE — II Internal Physiology Practical

Complete Answers for All Sections

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I. SPOTTERS — Amphibian Graphs (20M)

1. Simple Muscle Twitch

• A single stimulus → single contraction cycle
• Phases:
  • Latent period (~0.01 sec): time between stimulus and onset of contraction (excitation-contraction coupling)
  • Contraction period (~0.04 sec): cross-bridge cycling, Ca²⁺ released from SR
  • Relaxation period (~0.05 sec): Ca²⁺ reuptake, myosin detaches
• Graph shows a bell-shaped curve

2. Summation (Incomplete Tetanus)

• Two stimuli delivered in quick succession before relaxation completes
• Second contraction adds to the first → taller peak
• Summation occurs because Ca²⁺ hasn't fully returned to SR; second stimulus produces additional Ca²⁺ release

3. Tetanus (Complete Tetanus)

• Rapid, repeated stimuli → smooth, sustained maximal contraction
• No relaxation between twitches
• Fusion frequency: stimulus rate at which individual twitches can no longer be distinguished
• Graph shows a flat plateau at maximum tension

4. Staircase (Treppe) Phenomenon

• With identical stimuli at regular intervals, each successive twitch is slightly stronger
• Due to gradual increase in intracellular Ca²⁺ and temperature

5. Effect of Load on Muscle (Length-Tension Curve)

• Optimal sarcomere length ~2.0–2.2 µm gives maximum tension
• Overstretched or overly compressed → reduced tension
• Basis of Frank-Starling law in cardiac muscle

6. Fatigue Curve

• Successive contractions show progressively decreasing amplitude
• Due to: ATP depletion, lactic acid accumulation, reduced Ca²⁺ release

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II. HAEMATOLOGY (20M)

A. Major Experiments (10M each)

1. RBC Count (Erythrocyte Count)

• Principle: Dilute blood in isotonic fluid, count in haemocytometer (Neubauer chamber)
• Diluting fluid: Hayem's fluid (isotonic, preserves RBC shape; NaCl + Na₂SO₄ + HgCl₂)
• Dilution: 1:200 (20 µL blood + 4 mL diluent)
• Counting area: 5 central small squares (each 1/400 mm² area, depth 0.1 mm = volume 1/4000 mm³)
• Formula:

  RBC/mm³ = (Count in 5 squares × 10,000 × 200) / 5 = Count × 10,000

• Normal values:
  • Male: 4.5–5.5 million/mm³
  • Female: 3.8–4.8 million/mm³

2. Total Leucocyte Count (TLC)

• Diluting fluid: Turk's fluid (acetic acid lyses RBCs; gentian violet stains WBC nuclei)
• Dilution: 1:20
• Counting area: All 4 corner squares (W area) = 4 mm², depth 0.1 mm
• Formula:

  TLC/mm³ = (Count × 20 × 10) / 4 = Count × 50

• Normal: 4,000–11,000/mm³

3. Differential Leucocyte Count (DLC)

• Method: Leishman stained peripheral blood smear, count 100 cells
• Normal differential (BNMLE):

  Cell	Normal %
  Neutrophils	40–75%
  Eosinophils	1–6%
  Basophils	0–1%
  Monocytes	2–10%
  Lymphocytes	20–45%

• Report as percentage and absolute count
• Look for: shift to left (immature neutrophils), toxic granules, eosinophilia

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B. Minor Experiments (5M each)

1. Haemoglobin (Hb) Estimation — Sahli's Method

• Principle: HCl converts Hb → acid haematin (brown); diluted to match standard
• Steps: Add blood to acid, wait 10 min, dilute with distilled water until colour matches standard
• Normal: Male: 13–17 g/dL; Female: 12–15 g/dL
• Alternative: Cyanmethaemoglobin method (more accurate)

2. Bleeding Time (BT)

• Duke's method: Prick ear lobe/fingertip with lancet, blot every 30 sec until bleeding stops
• Normal: 2–5 minutes
• Prolonged in: Thrombocytopenia, platelet dysfunction, von Willebrand disease
• Tests primary haemostasis (platelet plug formation)

3. Clotting Time (CT)

• Lee-White method: 1 mL venous blood in glass tube, tilt every 30 sec until it doesn't flow
• Normal: 5–11 minutes
• Prolonged in: Haemophilia A/B, deficiency of factors VIII/IX/XII, heparin therapy
• Tests secondary haemostasis (coagulation cascade)

4. Blood Groups (ABO & Rh)

• Principle: Agglutination reaction between antigens (on RBCs) and antibodies (in serum)
• Reagents: Anti-A serum (blue), Anti-B serum (yellow), Anti-D serum
• ABO system:

  Group	Antigen	Antibody	Agglutination
  A	A	Anti-B	Anti-A only
  B	B	Anti-A	Anti-B only
  AB	A+B	None	Both
  O	None	Anti-A + Anti-B	Neither

• Rh: Agglutination with Anti-D = Rh+ (85% population)
• Universal donor: O negative; Universal recipient: AB positive

5. Packed Cell Volume (PCV) / Haematocrit

• Method: Anticoagulated blood in Wintrobe/microhaematocrit tube, centrifuge at 3000 rpm for 30 min
• Formula: PCV = (Height of RBC column / Total height) × 100
• Normal: Male: 40–50%; Female: 36–46%
• Increased: Polycythaemia, dehydration
• Decreased: Anaemia, overhydration

6. ESR (Erythrocyte Sedimentation Rate)

• Method: Westergren method — 200 mm tube, read fall of RBCs at 1 hour
• Normal:
  • Male: 0–15 mm/hr (Westergren); Wintrobe: 0–9 mm/hr
  • Female: 0–20 mm/hr (Westergren); Wintrobe: 0–20 mm/hr
• Increased in: Infections, inflammation, anaemia, pregnancy, multiple myeloma (rouleaux formation)
• Decreased in: Polycythaemia, sickle cell disease
• Mechanism: Rouleaux formation → faster sedimentation

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C. Problems (5M each)

1. MCV (Mean Corpuscular Volume)

MCV = (PCV × 10) / RBC count (millions/mm³)

• Normal: 80–100 fL
• <80 = microcytic (iron deficiency, thalassaemia)

• 100 = macrocytic (B12/folate deficiency)

2. MCH (Mean Corpuscular Haemoglobin)

MCH = (Hb g/dL × 10) / RBC count (millions/mm³)

• Normal: 27–33 pg
• Low = hypochromic; High = hyperchromic

3. MCHC (Mean Corpuscular Haemoglobin Concentration)

MCHC = (Hb g/dL × 100) / PCV

• Normal: 32–36 g/dL
• Most reliable index (not affected by cell size)

4. Cardiac Output by Fick's Principle

CO = O₂ consumption / (Arterial O₂ content − Venous O₂ content)

• O₂ consumption = 250 mL/min
• Arterial O₂ = 0.20 mL/mL blood
• Venous O₂ = 0.15 mL/mL blood
• CO = 250 / (0.20 − 0.15) = 250 / 0.05 = 5000 mL/min = 5 L/min

5. Cardiac Output by Dye Dilution (Stewart-Hamilton Method)

CO = Amount of dye injected / (Mean dye concentration × Duration of first pass)

• Indicator (e.g., Indocyanine green / Evans blue) injected IV
• Concentration measured at downstream site
• Area under concentration-time curve calculated
• CO = D / (C × t) where D = dose, C = mean concentration, t = time
• Avoids recirculation artifact by extrapolating exponential decline

6. Cardiac Index (CI)

CI = CO / BSA (Body Surface Area)

• Normal: 2.5–3.5 L/min/m²
• BSA calculated by Du Bois formula
• Accounts for body size differences

7. Ejection Fraction (EF)

EF = (Stroke Volume / End-Diastolic Volume) × 100

• Normal: 55–70%
• SV = EDV − ESV (End-Systolic Volume)
• Normal EDV ≈ 120 mL; Normal ESV ≈ 50 mL → EF = 70/120 = 58%
• Reduced EF (<40%): Heart failure with reduced ejection fraction (HFrEF)

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III. CLINICAL PHYSIOLOGY (20M)

A. Major Experiments (10M)

1. Recording of BP & Effect of Mild-to-Moderate Isotonic Exercise on BP

• Patient seated, arm at heart level, no caffeine/exercise for 30 min
• Cuff wrapped 2.5 cm above antecubital fossa
• Inflate to ~30 mmHg above disappearance of radial pulse
• Deflate slowly (~2 mmHg/sec), auscultate with stethoscope over brachial artery
• Korotkoff Sounds:

  Phase	Sound	Significance
  I	Sharp tapping	= Systolic BP
  II	Swishing/murmur	Turbulent flow
  III	Louder tapping	—
  IV	Muffled	—
  V	Silence	= Diastolic BP

• Systolic BP: Rises significantly (up to 160–200 mmHg) — increased CO
• Diastolic BP: Remains same or slightly decreases — due to vasodilation in exercising muscles
• Pulse pressure: Widens
• Heart rate: Increases (sympathetic activation)
• Mechanism: Increased CO + peripheral vasodilation in skeletal muscles + decreased TPR

2. Clinical Examination of CVS

• Precordial bulge, visible pulsations (apex beat, parasternal, epigastric)

• Apex beat: Normally 5th ICS, midclavicular line — reflects LV
  • Heaving: LVH (aortic stenosis, hypertension)
  • Tapping: MS (palpable S1)
  • Displaced: cardiomegaly, mediastinal shift
• Thrills (palpable murmurs), parasternal heave (RVH)

• 4 areas (see below)
• Heart sounds S1, S2; extra sounds S3, S4; murmurs

3. Clinical Examination of Sensory System

1. Touch: Cotton wisp — both sides, compare
2. Pain: Pinprick with pin
3. Temperature: Test tubes of hot/cold water
4. Vibration: 128 Hz tuning fork over bony prominences (medial malleolus, tibial tuberosity)
5. Proprioception (Joint position sense): Move big toe up/down, patient identifies direction with eyes closed
6. Two-point discrimination: Compass-like instrument; fingertip = 2–3 mm; back = 40–60 mm
7. Stereognosis: Identify objects by touch (parietal lobe)
8. Graphesthesia: Identify numbers written on palm

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B. Minor Experiments (5M)

1. Auscultatory Areas

• S1 (Lub): Closure of mitral + tricuspid valves at beginning of systole; loudest at mitral area
• S2 (Dub): Closure of aortic + pulmonary valves at end of systole; loudest at base
• S3: Rapid ventricular filling (normal in children; LV failure in adults)
• S4: Atrial contraction against stiff ventricle (LVH, diastolic dysfunction)

2. Examination for PICCPE

• Grade 1: Softening of nail bed
• Grade 2: Loss of lovibond angle (>180°)
• Grade 3: Drumstick appearance
• Grade 4: Hypertrophic pulmonary osteoarthropathy

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IV. SKILL EVALUATION (20M)

a) BP Apparatus (Sphygmomanometer)

• Manometer: Mercury column or aneroid gauge calibrated in mmHg
• Inflatable cuff: Standard adult = 12 × 23 cm (bladder); child, obese, thigh cuffs available
• Inflation bulb & valve
• Connecting tubing

• Cuff too narrow → falsely HIGH reading
• Cuff too wide → falsely LOW reading
• Arm below heart level → falsely HIGH
• Deflating too fast → underestimation of systolic, overestimation of diastolic

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b) Stethoscope

• Chest piece: Bell (low frequency: S3, S4, mitral murmurs) + Diaphragm (high frequency: S1, S2, breath sounds)
• Tubing: 25–35 cm, flexible, airtight
• Earpieces: Angled anteriorly to fit ear canal

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c) Myocardial Infarction — Case History

• 55-year-old male smoker, diabetic
• Sudden severe crushing/squeezing chest pain, radiating to left arm/jaw
• Duration >30 min, not relieved by nitrates
• Sweating, nausea, breathlessness

• Hyperacute T waves → ST elevation (convex upward) → Q waves (pathological) → T inversion
• NSTEMI: ST depression / T inversion, no Q waves

• Troponin I/T: Rises 4–6 hr, peaks 12–18 hr, lasts 7–10 days (most specific)
• CK-MB: Rises 4–6 hr, peaks 18–24 hr (returns to normal in 48–72 hr)
• LDH: Late marker (24–72 hr)

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d) WPW Syndrome (Wolff-Parkinson-White)

• Impulse travels: SA node → (1) normal AV node (slowed) AND (2) Bundle of Kent (fast)
• Ventricles activated early (pre-excitation) via accessory pathway → delta wave

• Short PR interval (<0.12 sec) — bypass of AV node delay
• Delta wave — slurred upstroke of QRS (pre-excited ventricular tissue)
• Wide QRS (>0.12 sec)
• May show pseudo-ST changes

• Type A (positive delta in V1): Left-sided pathway
• Type B (negative delta in V1): Right-sided pathway

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e) Heart Blocks — Case History

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f) Calculation of P-R Interval & Heart Rate from ECG

• Small square: 1 mm = 0.04 sec
• Large square (5 mm): = 0.20 sec

Method 1: 300 / number of large squares between R-R interval Method 2: 1500 / number of small squares between R-R interval Method 3 (irregular): Count QRS complexes in 6 seconds × 10

• Tachycardia: >100 bpm
• Bradycardia: <60 bpm

• Measured from start of P wave to start of QRS complex
• Count small squares × 0.04 sec
• Normal: 0.12–0.20 sec (3–5 small squares)

• 0.20 sec = 1st degree heart block

• <0.12 sec = pre-excitation (WPW)

• Normal: 0.06–0.10 sec (<3 small squares)
• Wide QRS (>0.12): Bundle branch block, WPW, ventricular tachycardia

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g) Conducting System of Heart

• Has automaticity (spontaneous depolarization) due to "funny current" (If) — slow Na⁺ inward current
• Phase 4 (pacemaker potential) is unstable → spontaneously depolarizes
• Controlled by ANS: Sympathetic → increases HR; Parasympathetic (vagus) → decreases HR

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h) Cardiac Failure — Case History

• 65-year-old male, IHD/hypertension background
• Presenting: dyspnoea on exertion → orthopnoea → PND
• Pitting pedal oedema, raised JVP, hepatomegaly

1. Frank-Starling: Increased EDV → increased contractility
2. Tachycardia (sympathetic activation)
3. Ventricular hypertrophy (LVH/RVH)
4. Neurohormonal: RAAS, ADH, natriuretic peptides (ANP/BNP)

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i) Hypovolemic Shock — Case History

• Young male, road traffic accident
• Pale, cold clammy skin, tachycardia (HR 120), hypotension (BP 80/50)
• Reduced urine output, altered consciousness

• ↓ Blood volume → ↓ venous return → ↓ CO → ↓ BP
• Compensatory: Sympathetic → tachycardia, vasoconstriction; RAAS → Na⁺/H₂O retention; ADH → water retention

1. Stop haemorrhage (pressure, tourniquet, surgery)
2. IV access × 2 large bore
3. Crystalloids (Normal saline / Ringer's lactate) 1–2L bolus
4. Blood transfusion (Class III/IV)
5. Vasopressors if needed

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V. VIVA VOCE (20M)

Topic 1: Nerve-Muscle Physiology

Resting Membrane Potential (RMP)

• Value: –70 mV (nerve), –90 mV (cardiac)
• Maintained by: K⁺ leak channels (outward K⁺ diffusion), Na⁺-K⁺-ATPase pump (3 Na⁺ out, 2 K⁺ in)
• Nernst equation: E_K = (RT/ZF) × ln([K]o/[K]i)

Action Potential

1. Resting (–70 mV): Na⁺ channels closed, K⁺ leak open
2. Depolarisation: Threshold reached → voltage-gated Na⁺ channels open → rapid Na⁺ influx → membrane reaches +35 mV
3. Repolarisation: Na⁺ channels inactivate; voltage-gated K⁺ channels open → K⁺ efflux
4. Hyperpolarisation (after-potential): Excess K⁺ efflux → brief dip below –70 mV
5. Return to RMP: Na⁺-K⁺ pump restores ion gradients

• All-or-none law
• Refractory period: Absolute (no stimulus works) and relative (only suprathreshold)
• Conduction velocity: Myelinated > unmyelinated; larger diameter > smaller

Neuromuscular Junction (NMJ)

• Presynaptic: Motor neurone terminal bouton, stores ACh in vesicles
• Steps:
  1. AP arrives at terminal
  2. Ca²⁺ influx (VG Ca²⁺ channels)
  3. ACh vesicles fuse with membrane (exocytosis)
  4. ACh binds nicotinic receptors on motor end plate
  5. Na⁺ influx → end plate potential (EPP)
  6. EPP > threshold → muscle AP → contraction
  7. ACh broken down by acetylcholinesterase

• Curare (non-depolarizing block): Competitive antagonist at nicotinic receptor → flaccid paralysis
• Succinylcholine (depolarizing block): Persistent depolarization → fasciculation then paralysis
• Neostigmine: AChE inhibitor → prolongs ACh action (treats myasthenia gravis)

Excitation-Contraction Coupling (Skeletal Muscle)

1. AP travels along sarcolemma → T-tubules
2. T-tubule AP activates DHP receptors (voltage sensor)
3. DHP → activates ryanodine receptors on SR → Ca²⁺ release
4. Ca²⁺ binds troponin C → conformational change in troponin-tropomyosin complex
5. Tropomyosin moves → exposes actin binding sites
6. Myosin head binds actin (cross-bridge formation) → power stroke (ADP+Pi released)
7. New ATP binds myosin → detachment
8. ATP hydrolysis → re-cocking of myosin head
9. Relaxation: Ca²⁺ pumped back into SR by SERCA (ATP-dependent)

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Topic 2: CNS (Central Nervous System)

Motor System

• Role: Coordination, balance, smooth movement, timing
• Disorders → DANISH: Dysdiadochokinesis, Ataxia, Nystagmus, Intention tremor, Slurred speech, Hypotonia

• Caudate, putamen, globus pallidus, STN, substantia nigra
• Function: Initiation and suppression of voluntary movements
• Disorders:
  • Parkinson's disease: Loss of dopaminergic neurons in substantia nigra → bradykinesia, rigidity, tremor (pill-rolling)
  • Huntington's: Loss of striatal neurons → chorea

Sensory Pathways

1. Dorsal column-medial lemniscal: Fine touch, vibration, proprioception → decussates at medulla → thalamus → somatosensory cortex (parietal lobe)
2. Spinothalamic tract: Pain & temperature → decussates at spinal cord level → thalamus → cortex

Reflexes

• Monosynaptic (stretch) reflex: Knee jerk (L3-L4): stimulus → muscle spindle Ia afferent → alpha motor neurone → contraction
• Polysynaptic (flexor withdrawal): Pain → flexion of affected limb + extension of opposite limb
• Reflexes tested: Knee (L3-L4), ankle (S1-S2), biceps (C5-C6), triceps (C7-C8)

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Topic 3: CVS (Cardiovascular System)

Cardiac Cycle

Frank-Starling Law

• Increased preload (EDV) → increased force of contraction → increased SV
• Mechanism: Increased sarcomere stretch → better actin-myosin overlap → increased sensitivity of troponin C to Ca²⁺
• Clinical: In heart failure, this mechanism is exhausted

ECG Interpretation

Arterial Blood Pressure

• BP = CO × TPR (Total Peripheral Resistance)
• CO = HR × SV
• Pulse pressure = Systolic − Diastolic (Normal ~40 mmHg)
• MAP = Diastolic + 1/3 (Pulse pressure) or MAP ≈ DBP + (SBP−DBP)/3

• ↑BP → stretch baroreceptors → ↑afferent impulses → NTS → ↓sympathetic + ↑vagal → ↓HR, ↓CO, vasodilation → ↓BP (negative feedback)

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