Post on 16-Jan-2016
Force – Length Relationship in Heart
Guyton 2011
Chapter 9
Heart as a pump
Cardiac valves
Heart as a pump
Cardiac valves
Semilunar Valves
Av ValvesMitral
Tricuspid Aorta
Pulmonary
Heart as a pump
Cardiac Sounds
• Low frequency
• Loudest and longest
• High frequency
• Shorter duration
• Low intensity
• In children with thin chest wall
and heart failure
• In early diastole
•Atrial contraction
•Occasionally in healthy
individual
S1
S4
S2
S3
Heart as a pump
The Force-length Relationship of Myocardial Fibers
Heart as a pump
The Force-length Relationship of Myocardial Fibers
Heart as a pump
Muscle Length and Force of Contraction
Passive Tension
Total Tension
Active Tension
Heart as a pump
The Volume – Pressure Relationship of Myocardial Fibers
10
Heart as a pump
Ventricular Pressure-Volume Relationship
End -Diastolic Ventricular
Volume(EDV)
End -Systolic Ventricular
Volume(ESV)
Stroke Volume(SV)
Ejection Fraction(EF)
= SV/EDV
11
Heart as a pump
Points
Efficiency of Cardiac Contraction• In normal condition is about 20-25 percent• In heart failure is as low as 5-10 percent
Preload and Afterload
Chemical Energy Required for Cardiac Contraction• 70 to 90 percent derived from oxidative catabolism of fatty
acids• 10 to 30 percent from other nutrients especially lactate
and glucose
12
Heart as a pump
Regulation of Heart Pumping
Intrinsic Regulation
Frank-Starling
Extrinsic Regulation
Nervous Control
13
Heart as a pump
Intrinsic Regulation of Heart Pumping The Frank-Starling
Mechanism
14
Heart as a pump
Intrinsic Regulation of Heart Pumping The Frank-Starling
Mechanism
15
Heart as a pump
Extrinsic Regulation - Nervous
Control
16
Heart as a pump
17
Heart as a pump
Effect of Potassium and Calcium ions on Heart Function
CaK
Arrest in Diastole
Bradycardia
Arrest in Systole
Bradycardia
18
Heart as a pump
Effect of Temperature Heart Function
Tachycardia
Bradycardia
The End