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Make notes from these in short cut to understand Nd mnemonics to remember
Here are your concise notes with mnemonics for Chapter 98: Heart Rate
❤️ CHAPTER 98 - HEART RATE
Quick Notes + Mnemonics
1. BASICS
| Value | |
|---|---|
| Normal HR | 72/min (range: 60-80) |
| Tachycardia | >100/min |
| Bradycardia | <60/min |
2. TACHYCARDIA CAUSES
Physiological: Childhood, Exercise, Pregnancy, High altitude, Emotional/Anxiety
🧠 Mnemonic: "CEPHEd" - Childhood Exercise Pregnancy High altitude Emotional
Pathological: Fever, Anemia, Hypoxia, Hyperthyroidism, Hypersecretion of catecholamines, Cardiomyopathy, Valvular disease, Hemorrhagic shock
🧠 Mnemonic: "FAHHH-CVH" - Fever Anemia Hypoxia Hyperthyroidism Hypersecretion Cardiomyopathy Valvular Hemorrhage
3. BRADYCARDIA CAUSES
Physiological: Sleep, Athletic heart
🧠 "SA" - Sleep, Athletes
Pathological: SA node disease, Hypothermia, Hypothyroidism, Heart attack, Congenital heart disease, Degenerative aging, Obstructive jaundice, Increased ICP, Drugs (beta blockers, digoxin)
🧠 Mnemonic: "SH³ HCOD²" - SA node disease, Hypothermia, Hypothyroidism, Heart attack, Congenital, Obstructive jaundice, Degeneration, Drugs
4. VASOMOTOR CENTER (= CARDIAC CENTER)
- Location: Reticular formation of medulla oblongata + lower pons (bilateral)
- 3 areas: Cardioaccelerator + Cardioinhibitory + Sensory
| Area | Also Called | Location | Function |
|---|---|---|---|
| Cardioaccelerator | Vasoconstrictor / Pressor area | Lateral, floor of IV ventricle | ↑ HR via sympathetic |
| Cardioinhibitory | Vasodilator / Depressor area | Medial, floor of IV ventricle | ↓ HR via vagus |
| Sensory | - | Nucleus tractus solitarius | Receives inputs, controls both above |
🧠 "Lateral = Accelerator, Medial = Inhibitor" (L before M alphabetically = A before I)
5. NERVE SUPPLY TO HEART
Parasympathetic (Cardioinhibitory):
- Origin: Dorsal nucleus of vagus (floor of 4th ventricle, medulla)
- Route: Main trunk → Cardiac branch of vagus → heart
- Right vagus → SA node | Left vagus → AV node
- NT: Acetylcholine → ↓ HR, ↓ force
🧠 "Right = Rate (SA node), Left = Length (AV node)"
Sympathetic (Cardioaccelerator):
- Origin: T1-T4 lateral gray horn of spinal cord
- Route: Superior/Middle/Inferior cervical sympathetic ganglia → Stellate ganglion
- NT: Noradrenaline → ↑ HR, ↑ force
🧠 "Sympathetic starts at T1-T4 = Thoracic accelerator"
6. VAGAL TONE vs SYMPATHETIC TONE
- Vagal tone = cardioinhibitory tone (dominant at rest)
- HR is inversely proportional to vagal tone
- Cutting vagus in dogs → HR increases (proves vagal dominance at rest)
7. VAGAL EFFECTS
| Stimulation | Effect |
|---|---|
| Right vagus (weak) | ↓ HR |
| Right vagus (strong) | Stoppage of heart → then Vagal Escape |
| Left vagus (weak) | Partial heart block (2:1, 3:1, 4:1) |
| Left vagus (strong) | Complete heart block → idioventricular rhythm |
Vagal Escape:
- Ventricles NOT supplied by vagus → escape vagal inhibition
- Ventricular muscle becomes its own pacemaker at 20/min
🧠 "Ventricles Escape Vagus = VEV"
8. FACTORS REGULATING VAGAL TONE (4 main sources)
🧠 Mnemonic: "Higher Respiratory Baro Chemo = HRBC" or "Hungry Rabbits Bark Constantly"
| # | Source | Effect on Vagal Tone | HR |
|---|---|---|---|
| 1 | Higher centers (Cortex/Hypothalamus) | Area 13 cortex → ↑ vagal tone | ↓ HR |
| 2 | Respiratory center | Inspiration → ↓ vagal tone | ↑ HR |
| Expiration → ↑ vagal tone | ↓ HR | ||
| 3 | Baroreceptors (Marey's reflex) | ↑ BP → ↑ vagal tone | ↓ HR |
| 4 | Chemoreceptors | Hypoxia/↑CO₂ → ↓ vagal tone | ↑ HR |
Bainbridge Reflex (bonus):
- ↑ Venous return → stretches right atrium → ↑ HR (cardioaccelerator reflex)
🧠 "Bainbridge = Blood coming IN = Bridges to ↑ HR"
9. KEY REFLEXES SUMMARY
| Reflex | Type | Trigger | Result |
|---|---|---|---|
| Marey's | Cardioinhibitory | ↑ BP → baroreceptors | ↓ HR |
| Bainbridge | Cardioaccelerator | ↑ Venous return → right atrium | ↑ HR |
| Bezold-Jarisch | Pathological | Chemoreceptors in L ventricle wall | Bradycardia + hypotension + apnea |
| RSA | - | Respiratory cycle | ↑ HR on inspiration, ↓ on expiration |
🧠 "Marey Brakes, Bainbridge Boosts" (M = decrease, B = increase)
10. BEZOLD-JARISCH REFLEX
- Also called Coronary Chemoreflex
- Stimulated by alkaloids acting on L ventricle chemoreceptors
- Pathological - does NOT occur normally
- Occurs in: Myocardial infarction, Thrombolytics, Hemorrhage, Aortic stenosis, Syncope
🧠 "MI THAS" - MI, Thrombolytics, Hemorrhage, Aortic stenosis, Syncope
11. HYPOTHALAMUS EFFECTS (Quick Memory)
| Area Stimulated | HR Change |
|---|---|
| Posterior + Lateral hypothalamus | Tachycardia |
| Preoptic + Anterior hypothalamus | Bradycardia |
🧠 "Posterior Pushes rate up, Anterior Arrests rate"
ONE-PAGE MASTER MNEMONIC
"CEPHEd causes TACHY; SA causes BRADY; Lateral Accelerates, Medial Inhibits; Right = Rate, Left = Length; Marey Brakes, Bainbridge Boosts; Hungry Rabbits Bark Constantly"
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