Blood Circulation Pathways 🛣️

Let’s track the blood’s journey through your body:

  • Systemic Circulation:
    • Oxygen-rich blood → Left ventricle → Aorta → Body organs
    • Oxygen-poor blood returns via vena cava → Right atrium
  • Pulmonary Circulation:
    • Oxygen-poor blood → Right ventricle → Pulmonary artery → Lungs
    • Oxygen-rich blood returns via pulmonary veins → Left atrium
  • Special Path: Intestines → Hepatic portal vein → Liver → Heart (toxin filtering!)

Heart’s Electrical System ⚡

Your heart has its own “wiring” that controls beats:

1. Pacemaker (SAN) starts impulse → Atria contract
2. Signal reaches AV node → Brief delay
3. Impulse travels through bundle branches → Ventricles contract
This creates the “lub-dub” sound we hear!

Understanding Blood Pressure 🩺

TermMeaningNormal Value
Systolic PressurePressure when heart contracts (pumps)120 mm Hg
Diastolic PressurePressure when heart relaxes (fills)80 mm Hg

Hypertension = Systolic ≥140 and/or Diastolic ≥90

Heart Failure Explained 💔

Think of it like a tired pump:

  • Left-side failure: Fluid backs up into lungs (coughing, shortness of breath)
  • Right-side failure: Fluid builds up in body (swollen ankles, tiredness)
  • Key difference from heart attack: Slow weakening vs sudden blockage

NEET Practice Corner 📚

Memory Tip: Cardiac Output Formula

Remember this equation for exams: \( \text{Cardiac Output (CO)} = \text{Stroke Volume (SV)} \times \text{Heart Rate (HR)} \)
Example: If SV = 70 mL and HR = 72 bpm, then CO = ? \( 70 \times 72 = 5040 \text{ mL/min} = 5.04 \text{ L/min} \)

Quick Quiz (Answers Below)

  1. What makes the heart “myogenic”?
  2. Which nerve slows heart rate? (Sympathetic/Parasympathetic)
  3. True or False: Angina means permanent heart damage

Answers:

1. Its ability to generate its own electrical impulses
2. Parasympathetic nerves
3. False! It’s temporary oxygen shortage (like a warning light)

Keep these diagrams in mind for NEET:
→ Blood flow path (Fig 15.4)
→ Electrical conduction system
→ Coronary artery blockage sites

Real-World Connection 🌍

Why this matters to you:

  • High BP often has no symptoms – “silent killer”
  • CAD starts young – fatty deposits begin in teen years!
  • Knowing CPR can save lives during cardiac arrest ⚠️

You’re mastering complex topics – celebrate your progress! 🎉 Next we’ll explore blood composition in detail.