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 4 10 Inferior vena cava 5 Left ventricle

1 Anatomy cont.

Aortic semilunar valve 5 not pictured

6 Left 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 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 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)

= = 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

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. 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

10