2. Awatif B. Al-Backer Function of the nerve innervations in the heart (Sympathetic or Parasympathetic): Alteration of the basic rhythm of the heart

3. Conduction in heart

4. Heart Properties Heart Properties “Heart muscle is syncitium”   Contractility   Automaticity   Rhythmicity   Conductivity   Excitability

5. Conduction of impulses in the heart Heart conduction Heart conduction

6. ANS supply of heart SympatheticParasympathetic Receptorb1M2 TransmitterAdrenalineAch Synthetic agonistIsoprenalineMethacholine Effect +ve inotropic, +ve chronotropic -ve inotropic & -ve chronotropic MOA + Gs protein→ + adenylyl cyclase→↑ cAMP→↑ calcium →contraction + Gi protein→ - adenylyl cyclase→↓cAMP→↑K & ↓calcium →hyperpolarization Blocker Propranolol “non-selective” Esmolol, Atenolol “selective” Atropine N.B. -Isoprenaline is more potent than adrenaline on the isolated heart -Atropine can cause bradycardia followed by tachycardia

7. Other agents that influence the heart function 1. Histamine: Receptor: H2 MOA: ↑ cAMP →↑calcium → contraction Antagonist : Ranitidine & Cimitidine Action: + ve inotropic & + ve chronotropic Note: H2R in the stomach & the heart while H1R present all over the body.

8. Continue 2. Methylxanthines: Examples: Theophylline, Caffeine & Theobromine MOA: 1- Phosphodiesterase enz. Inhibitors. 2- Inhibition of adenosine receptors Action: + ve inotropic & + ve chronotropic

9. 3. Serotonin:- Receptors: 5HT2 Example: Serotonin MOA: Bind to 5HT2 leading to increase cAMP & increase Ca. Blocker: Ketanserine Action: + ve inotropic & + ve chronotropic Continue

10. Direct acting drug Direct acting stimulant: E.g. calcium chloride (Cacl2) Direct acting depressant: E.g. potassium chloride (Kcl)

11. Experiment N Isoprenaline Propranolol Isoprenaline N Dil. nicotine Conc.nicotine Dil. nicotine N Ach Atropine Ach N Cacl 2 N Kcl Color key: Agonist Antagonist Normal N

12. CONCLUSION The receptors on the heart are: 1. Stimulatory: B1, H1, & 5HT2 2. Inhibitory: M2, & Nn

13. Determination of heart rate Example: * Speed= 1square/sec, * Number of beat/sq=6 beats/square Calculate the HR (beat per minute)? 6 beats 1 sec. x 60 sec x = 60*6 = 360 BPM