محاضرات الفسيولوجيا البشرية

Study Notes

Human Physiology Lectures - First Year

Cardiovascular System: The circulatory system (cardiovascular system) pumps blood from the heart to the lungs to get oxygen. The heart sends oxygenated blood through arteries to the rest of the body. Veins carry oxygen-poor blood back to the heart. This process circulates blood, crucial for healthy organs, muscles and tissues.
Circulatory System Function: The circulatory system's primary function is to deliver oxygen, nutrients, and hormones to tissues and organs while removing waste products.
Components of the Circulatory System: The heart and blood vessels make up the circulatory system. Blood vessels include arteries, veins, and capillaries. Blood is made of red and white blood cells, plasma and platelets.
Circulatory System Circuits: The circulatory system has three circuits:
- Pulmonary circuit: Carries oxygen-poor blood from the heart to the lungs, returning oxygenated blood to the heart.
- Systemic circuit: Transports oxygenated blood from the heart to the body, picking up waste products as the body uses it.
- Coronary circuit: Supplies the heart muscle with oxygenated blood.
Types of Blood Vessels:
- Arteries: Carry oxygenated blood away from the heart. The largest artery is the aorta.
- Veins: Return oxygen-poor blood to the heart, having valves to prevent backward flow. The superior and inferior vena cava are the largest.
- Capillaries: Small vessels that connect arterioles and venules, allowing the exchange of oxygen, carbon dioxide, nutrients and waste products between blood and cells.
The Heart: A muscular pump that rhythmically contracts to circulate blood.
- Structure: The heart has four chambers: two atria and two ventricles. It contains valves (tricuspid, pulmonary, mitral, and aortic) that regulate blood flow.
Heart Valves: Valves within the heart prevent backflow of blood facilitating efficient circulation.
- Tricuspid valve: Between the right atrium and right ventricle.
- Pulmonary valve: Between the right ventricle and pulmonary artery.
- Mitral valve: Between the left atrium and left ventricle.
- Aortic valve: Between the left ventricle and aorta.
Cardiac Cycle: The sequence of events from the start of one heartbeat to the beginning of the next, encompassing diastole (relaxation) and systole (contraction).
- Diastole: The filling of the ventricles with blood.
- Systole: Contraction of the ventricles, forcing blood out through the aorta and pulmonary artery.
Cardiac Conduction System: A system of specialized cells that generate and conduct electrical impulses to coordinate heart contractions. Key components are the SA node, the AV node, and Purkinje fibers.
Electrical Activity: An electrocardiogram (ECG) records the electrical activity of the heart. The process is driven by the Sinoatrial node (SA node), a pacemaker setting the rate.
AV Node and Bundles (PR Interval): Crucial and fundamental for the delay necessary for effective blood flow. It's the delay between atrial contraction and ventricular contraction. The bundle of His branches into the left and right bundle branches.
Purkinje Fibers/Ventricular Myocardium (QRS Complex): Electrical impulses from the conduction system arrive at the ventricles, resulting in their contraction, and represented by the QRS complex on the ECG.
Ventricular Repolarization (ST and T Waves): The relaxation of the ventricles, marking the end of the cardiac cycle, displayed as the ST segment and T wave on the ECG.
Heart Sounds: Lub-dub sound created by the opening and closing of heart valves.