Cardiovascular Physiology Overview

Cardiovascular Physiology Overview

• Cardiovascular physiology studies the heart, blood vessels, and blood, focusing on how these systems maintain homeostasis.
• The cardiovascular system transports oxygen, nutrients, hormones, and waste throughout the body.
• This involves the heart's pumping, blood vessel elasticity, and blood characteristics working together.

Cardiac Cycle

• The cardiac cycle describes the heart's rhythmic contraction and relaxation.
• It has two phases: systole (contraction) and diastole (relaxation).
• Ventricular systole forces blood out of the heart into arteries.
• Ventricular diastole allows the ventricles to fill with blood from the atria.
• Heart rate and stroke volume determine cardiac output.

Heart Rate

• Heart rate is the number of heartbeats per minute.
• It's influenced by autonomic nervous system activity, hormones, and physical activity.
• The sympathetic nervous system increases heart rate; the parasympathetic nervous system decreases it.

Stroke Volume

• Stroke volume is the blood ejected by each ventricle per contraction.
• It depends on preload (venous return), afterload (ejection resistance), and contractility.
• Preload is the heart muscle fiber stretch before contraction; increased preload increases stroke volume (Frank-Starling Law).
• Afterload is resistance to blood ejection; increased afterload reduces stroke volume.
• Contractility is the heart muscle's inherent ability to contract. Factors like hormones (adrenaline, thyroxine) and calcium affect it. Positive ionotropes increase contractility; negative ionotropes decrease it.

Blood Vessel Structure and Function

• Blood vessels include arteries, veins, and capillaries.
• Arteries carry blood away from the heart, with thick walls for high pressure.
• Veins carry blood toward the heart, with thin walls and valves to prevent backflow.
• Capillaries have thin walls for gas, nutrient, and waste exchange with tissues.

Blood Pressure

• Blood pressure is the force blood exerts on vessel walls.
• It's expressed as systolic (contraction) over diastolic (relaxation) pressure.
• Blood pressure is regulated by cardiac output, blood volume, and peripheral resistance.

Regulation of Blood Pressure

• Blood pressure is regulated to maintain tissue perfusion.
• Mechanisms include sympathetic nervous system (vasoconstriction/vasodilation), the renin-angiotensin-aldosterone system, and atrial natriuretic peptide.
• The renin-angiotensin-aldosterone system regulates blood volume and pressure.
• Kidneys regulate blood pressure by influencing blood volume (filtration and sodium excretion).

Cardiovascular Disease

• Cardiovascular diseases impair heart function or damage blood vessels.
• Examples include hypertension, atherosclerosis, coronary artery disease, heart failure, and stroke.
• Contributing factors are lifestyle (diet, exercise, smoking), genetics, and age.

Blood Composition

• Blood is plasma (liquid) and formed elements (cells).
• Plasma is mostly water, proteins, electrolytes, and dissolved substances.
• Formed elements are red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

Hemodynamics

• Hemodynamics is blood flow within the circulatory system.
• Factors impacting blood flow include pressure gradients, blood viscosity, and vessel diameter.
• Blood viscosity and vessel diameter influence peripheral resistance, affecting flow.

Oxygen Transport

• Red blood cells (erythrocytes) carry oxygen in the blood.
• Oxygen binds to hemoglobin in red blood cells for transport.
• Oxygen delivery to tissues is crucial for cellular respiration.