Physiology of Cardiovascular System Lecture 2

Cardiovascular System

• A closed system of the heart and blood vessels that delivers oxygen and nutrients, and removes carbon dioxide and waste products.

Heart

• Has a double serous membrane called pericardium, with a visceral and parietal layer.
• Has four chambers: right and left atria (receiving chambers) and right and left ventricles (discharging chambers).
• Right atrium receives deoxygenated blood from the body, while left atrium receives oxygenated blood from the lungs.
• Right ventricle sends blood to the lungs, and left ventricle sends blood to the body through the aorta.

Heart Valves

• Allow blood to flow in only one direction, with four valves: atrioventricular valves (bicuspid and tricuspid) and semilunar valves (pulmonary and aortic).
• Valves open as blood is pumped through and are held in place by chordae tendineae.

Heart Associated Great Vessels

• Aorta leaves the left ventricle, while pulmonary arteries leave the right ventricle.
• Vena cava enters the right atrium, and pulmonary veins enter the left atrium.

Coronary Circulation

• The heart has its own nourishing circulatory system, with coronary arteries and cardiac veins that empty into the right atrium via the coronary sinus.

Heart Conduction System

• Intrinsic conduction system sets the pace, with the sinoatrial node as the pacemaker.
• Contraction is initiated by the sinoatrial node, with sequential stimulation occurring at other autorhythmic cells.

Heart Contractions

• Cardiac output (CO) is the amount of blood pumped by each side of the heart in one minute, calculated as CO = heart rate (HR) x stroke volume (SV).
• Heart rate can be increased or decreased to change cardiac output.

Regulation of Heart Rate

• Increased heart rate is stimulated by the sympathetic nervous system, hormones, and exercise.
• Decreased heart rate is stimulated by the parasympathetic nervous system, high blood pressure, or decreased blood volume.

Blood Vessels

• The vascular system takes blood to the tissues and back, with five types: arteries, arterioles, capillaries, venules, and veins.
• Walls of arteries are the thickest, while lumens of veins are larger.
• Capillary walls are only one cell layer thick, allowing for exchanges between blood and tissue.

Blood Vessel Anatomy

• Three layers (tunics) make up the blood vessel wall: tunic intima, tunic media, and tunic externa.
• Smooth muscle in the tunic media is controlled by the sympathetic nervous system.

Movement of Blood Through Vessels

• Most arterial blood is pumped by the heart, while veins use the milking action of muscles to help move blood.

Capillary Beds

• Capillary beds consist of two types of vessels: vascular shunt and true capillaries.
• True capillaries are exchange vessels where oxygen and nutrients cross to cells, and carbon dioxide and waste products cross into blood.

Capillary Exchange

• Substances are exchanged due to concentration gradients, with oxygen and nutrients leaving the blood and carbon dioxide and waste products leaving the cells.

Blood Pressure

• Measurements are made on the pressure in large arteries, with systolic pressure at the peak of ventricular contraction and diastolic pressure when ventricles relax.
• Blood pressure can be affected by neural factors, renal factors, temperature, chemicals, and diet.

Variations in Blood Pressure

• Normal range is 90-140 mm Hg systolic and 60-90 mm Hg diastolic.
• Hypotension is low systolic pressure (below 90 mm Hg), while hypertension is high systolic pressure (above 140 mm Hg).