Cardiovascular Physiology
Cardiovascular System
¾ Purpose
• Transport O2 to tissues and removal of waste • Transport of nutrients to tissues • Regulation of body temperature
¾ Two Systems: • Pulmonary Circulation 9Blood flow to, within, and from the lungs • Systemic Circulation 9Blood flow to, within & from the remainder of the body
Heart Anatomy
6 Aorta Superior vena cava 1 7 Pulmonary trunk Right coronary artery2 8 Left atrium Right atrium 3 9 Great cardiac vein Right ventricle 4 10 Inferior vena cava 5 Left ventricle
1 Heart Anatomy cont.
Aortic semilunar valve 5 not pictured
6 Left pulmonary artery Right pulmonary artery 1
7 Pulmonary semilunar 2 valve Tricuspid valve 8 Bicuspid (Mitral) valve Chordae tendineae 3
Papillary muscle 4 9 Myocardium
Aorta artery The Heart Pulmonary artery Pulmonary veins Superior vena cava
Aortic valve
Mitral valve
Inferior vena cava Left ventricle
Tricuspid valve Pulmonary Semilunar valve Right ventricle
Bicuspid Pulmonary (Mitral) semilunar valve valve
Aortic semilunar valve Tricuspid valve
Figure 9.5 (1) Figure 9.5 (1) Page 307 Page 307
2 Valve opened
Valve closed; does not open in opposite direction
Figure 9.4 Page 307 Figure 9.4 Page 307
The Circulatory System ¾ Heart • Pumps blood
¾ Arteries and arterioles • Carry blood away from the heart
¾ Capillaries • Exchange of nutrients with tissues
¾ Veins and venules • Carry blood toward the heart
Systemic & Pulmonary Circuits
¾ Systemic circuit ¾ Pulmonary circuit • Left side of the heart • Right side of the heart
• Pumps oxygenated • Pumps deoxygenated blood to the whole blood to the lungs via body via arteries pulmonary arteries
• Returns deoxygenated • Returns oxygenated blood to the right heart blood to the left heart via veins via pulmonary veins
3 Driving Pressures Pulmonary capillaries
Arterioles Venules Pulmonary Pulmonary Pulmonary artery circulation veins
Aorta (major Systemic systemic veins artery)
Systemic circulation
Systemic Smaller arteries capillaries branching off to supply various tissues Venules Arterioles Figure 10.4 Figure 10.4 Page 346 Page 346 Tissues
Figure 9.3 (2) Figure 9.3 (2) Page 306 Page 306
Venae cavae Pulmonary artery Right Right atrium ventricle
Other Systemic Pulmonary systemic Brain Digestive Kidneys Muscles Lungs organs tract circulation circulation
Left Left ventricle atrium Aorta Pulmonary veins
Electrical Conduction System
4 The Myocardium
Electrical Activity of the Heart
¾ Cardiac muscle cells • Contractile (99%) • Autorhythmic 9Pacemaker potential
¾ Impulse is initiated in the right atrium and spreads throughout entire heart
¾ May be recorded on an electrocardiogram (ECG)
= Action potential = After hyperpolarization
Na+ equilibrium potential
Figure 4.6 Figure 4.6 Page 103 Page 103
Threshold potential Resting potential Triggering event K+ equilibrium potential
5 Pacemaker Potential (Autorhythmic Cells)
1. Slow initial depolarization caused by: • Decrease in K+ leaving cell 9 Cardiac cells – membrane decreases in permeability to K+ between AP • Slow, inward leak of Na+ 9 No voltage gated Na+ channels, only leak
2. Membrane gradually becomes less negative •More Na+ coming in than K+ leaving
Pacemaker Potential (Autorhythmic Cells)
3. One of 2 Ca2+ channels open (T) (prior to threshold) • Short acting channel
4. Once threshold is reached, 2nd Ca2+ channels open (L) & membrane depolarized
5. Return is similar to nerve cell • Calcium begin to close •K+ leaves cell
Self-induced action potential
Slow depolarization (pacemaker potential)
Figure 9.10 Page 310 Figure 9.10 Page 310
6 Conduction System of the Heart Interatrial Figure 9.11 pathway Page 311
Atrioventricular (AV) node Sinoatrial (SA) node
Internodal Left pathway branch of bundle of His Right branch of bundle of His Purkinje fibers
Action Potential Discharge
Tissue AP’s per minute
SA node 70 – 80
AV node 40 – 60
Bundle of His & 20 – 40 Purkinje fibers
Cardiac Contractile Cells
1. Explosive increase in Na+ (similar to skeletal)
2. Membrane potential remains positive (despite decrease in Na+ permeability) • Plateau phase: Activation of slow L-type Ca2+ channels Decrease in K+ permeability
3. Falling phase due to inactivation of Ca2+ channels & increase in K+ permeability
7 Figure 9.16 Action potential Figure 9.16 in cardiac Page 316 contractile cell Page 316 Travels down T tubules
Entry of small Release of large amount of amount of Ca2+ Ca2+ from sarcoplasmic from ECF reticulum Induces larger influx Cytosolic 2+ of Ca2+ Ca Troponin-tropomyosin complex in thin filaments pulled aside
Cross-bridge cycling between thick and thin filaments
Thin filaments slide inward between thick filaments
Contraction
AP of Contractile Cardiac Cells
Plateau phase of action potential
Threshold potential
Path of Conduction
Autorhythmic to Contractile
8 Interatrial pathway
Right atrium Left atrium
SA node
AV node Internodal pathway
Purkinje fibers Bundle of His
Figure 9.14 Figure 9.14 Page 314 Page 314 Right ventricle Left ventricle
Electrocardiogram (ECG) (EKG)
¾ Records the electrical activity of the heart •Size • Position •Rate • Condition (healthy/sick)
Electrocardiogram
•P-wave –Atrial depolarization •QRS complex –Ventricular depolarization •T-wave –Ventricular repolarization
9 Relationship Between the ECG and Cardiac Contraction
Figure 9.17 Figure 9.17 Page 317 Action Contractile Page 317 potential response
Refractory period
Diagnostic Use of the ECG
¾ ECG abnormalities may indicate coronary heart disease • ST-segment depression can indicate myocardial ischemia
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