Human Biology: Cardiovascular System Quiz

Cardiovascular System Overview

• The cardiovascular system works with the majority of the body systems to maintain homeostasis.
• It's composed of the heart and blood vessels.
• The heart pumps blood through blood vessels, transporting oxygen and nutrients to the cells and removing wastes.
• Exchange of substances occurs through interstitial fluid surrounding tissues.
• The lymphatic system collects excess tissue fluid (lymph) and returns it to the bloodstream.

Blood

• Function: Transports oxygen, nutrients, wastes, carbon dioxide, and hormones. Defends against pathogens (white blood cells and antibodies). Protects against fluid loss by clotting. Regulates body temperature by transferring heat. Maintains osmotic pressure. Buffers regulate pH (7.4).
• Composition: Liquid connective tissue with formed elements (cells and fragments) suspended in plasma.
• Formed elements are produced in the red bone marrow.
• Red blood cells (erythrocytes, RBCs)
• White blood cells (leukocytes, WBCs): various types (granular and agranular).
• Platelets (thrombocytes)

Blood Composition Continued

• Percentage by Volume and Weight: Plasma (55% by volume) is mostly water, with proteins (albumins, globulins, fibrinogen), other solutes (ions, nutrients, wastes, gases, hormones, vitamins). Formed elements (45% by volume) are cells and fragments. Water accounts for 91% by weight.

Blood Cells

• Red Blood Cells (Erythrocytes): Biconcave shape, lacking nucleus and mitochondria. Contain hemoglobin (Hb) with four subunits, each with a heme group containing iron (Fe) that binds oxygen. Oxygenated Hb is red; deoxygenated Hb is blue.
• White Blood Cells (Leukocytes): Several types, larger than RBCs, with nuclei. Produced in red bone marrow, with production regulated by colony-stimulating factor. Important for fighting infection (part of the immune system). Some live for only days, others for months or years. Granular leukocytes (neutrophils, eosinophils, basophils) have granules and lobed nuclei, while agranular leukocytes (lymphocytes, monocytes) lack granules and have non-lobular nuclei.
• Platelets (Thrombocytes): Fragments of megakaryocytes, crucial for blood clotting (hemostasis).

Plasma

• Solutes: Mostly water (91%), and organic molecules (9%), including plasma proteins.
• Plasma Proteins: Albumins, globulins, fibrinogen are the most abundant, providing osmotic pressure, transporting molecules, and forming blood clots.

Red Blood Cell Production

• Occurs in red bone marrow.
• As RBCs are produced, they lose their nucleus and most organelles.
• Without a nucleus, they can't make proteins for cell repair.
• Old, worn-out cells are removed from circulation by macrophages in the liver and spleen.
• The biconcave disc shape maximizes surface area for gas diffusion.

Erythropoietin (EPO)

• Hormone produced by kidneys when blood oxygen levels are low.
• Stimulates bone marrow to produce more red blood cells.
• Blood doping (illegally injecting EPO) increases RBC count for athletic performance, but can be dangerous.

White Blood Cells (Leukocytes) Further Details

• Neutrophils: Most abundant WBC, roughly 50-70% of all WBCs, multi-lobed nuclei, "first responders" to bacterial infections. Engulf pathogens via phagocytosis. Can leave bloodstream.
• Eosinophils: Have bilobed nuclei, and involved in parasitic infections and allergic reactions.
• Basophils: Rarest of WBCs, involved in allergic reactions and inflammation

Lymphocytes

• About 25-35% of all WBCs (second most common).
• Two types:
  • B cells: Produce antibodies to mark pathogens for destruction.
  • T cells: Various types, some directly destroying pathogens (cell-mediated immunity).

Monocytes

• Largest of WBCs.
• A type of macrophage, which engulfs pathogens, old cells, and debris.

Platelets (Thrombocytes)

• Fragments of large cells called megakaryocytes.
• About 200 billion platelets are made per day.
• Function in blood clotting (coagulation).
• Hemostasis: clotting forms clots. Involves 13 clotting factors, calcium, and enzymes.
• Vitamin K is essential for these factors.

Blood Clotting

• Prevents plasma and cells from leaking out of broken vessels.
• Platelets and injured tissues release a clotting factor called prothrombin activator.
• Prothrombin converts to thrombin, which converts fibrinogen to fibrin. This forms a framework for clot formation. Calcium ions are required.
• An enzyme called plasmin eventually dissolves the fibrin network, allowing tissue repair.
• Serum: Liquid remaining after clotting (basically plasma without Fibrinogen and Prothrombin)

Blood Type Determination

• Determined by glycoproteins (antigens) on the surface of RBCs.
• ABO blood groups: A, B, AB, and O.
• Blood transfusions require compatibility to prevent agglutination (clumping).

Blood Compatibility

• During a blood transfusion, antibodies in the recipient's plasma bind to antigens on donated red blood cells, potentially causing agglutination.
• Type A cannot receive Type B or AB blood.
• Type B cannot receive Type A or AB blood.
• Type O can only receive Type O blood.
• Type AB is a universal recipient.

Rh Blood Groups

• The Rh factor is another blood type antigen.
• Rh positive (+) if present.
• Rh negative (-) if not present.
• Anti-Rh antibodies develop only after exposure to Rh factor.
• Hemolytic disease of the newborn can occur if an Rh-negative mother has a subsequent Rh-positive fetus.

Blood Vessels

• Three types: arteries, veins, and capillaries.
• Arteries: Carry blood away from the heart, with 3 layers (inner endothelium, middle smooth muscle, outer connective tissue). Arteries are more muscular to withstand high pressure.
• Arterioles: Small arteries that deliver blood to capillary beds, have smooth muscle for vasoconstriction/vasodilation affecting flow/pressure.
• Capillaries: Microscopic vessels between arterioles and venules, with thin walls for gas exchange, nutrient and waste exchange occurs here. Have precapillary sphincters (smooth muscle) controlling blood flow.
• Venules: Small veins that receive blood from capillaries.
• Veins: Carry blood towards the heart, with thinner walls compared to arteries because pressure is lower. They contain valves to prevent backflow, important for return of blood against gravity.

The Heart

• Location: Between the lungs, slightly twisted to the left.
• Structure: Myocardium (cardiac muscle), muscle fibers branched and connected by intercalated disks containing gap junctions allowing for coordinated contractions. A sac called the pericardium surrounds the heart and secretes pericardial fluid for lubrication. The heart has 4 chambers (2 atria and 2 ventricles)
• Valves:
  • Atrioventricular (AV) valves: Tricuspid (right) and Bicuspid (left). Prevent backflow into the atria.
  • Semilunar valves: Pulmonary (right) and Aortic (left). Prevent blood from flowing back into the ventricles.
• Coronary Circulation: The myocardium needs its own blood supply via coronary arteries branching from the aorta to feed itself first. Coronary veins empty into the right atrium. Coronary artery disease can cause disruptions in this flow leading to heart attack.
• Cardiac cycle: Systole (contraction) and Diastole (relaxation) of atria and ventricles.
• Electrical conduction system: SA (sinoatrial) node (pacemaker in the right atrium) initiates the heartbeat. AV (atrioventricular) node and Purkinje fibers conduct the impulse for ventricular contraction and other pacemaker cells, for the entire heart.
• External Control of Heartbeat: The brainstem controls heart rate (sympathetic nervous system increases rate, parasympathetic decreases, some hormones raise heart rate), based on the body's needs.

Electrocardiogram (ECG or EKG)

• Records electrical activity in the heart muscle during the cardiac cycle.
• P wave: Atrial contraction.
• QRS complex: Ventricular contraction.
• T wave: Ventricular recovery.

Arrhythmias

• Abnormal heart rhythms.
• Many types and causes.
• Ventricular fibrillation: Severe uncoordinated contractions, preventing effective blood pumping and possibly causing tissue death from oxygen starvation.
• Defibrillation: Applying a controlled electrical shock to reset and re-establish normal pacemaker activity.

Blood Pressure

• Pressure exerted by blood against blood vessel walls.
• Highest in aorta, decreasing as it flows through the vessels.
• Determined by the contraction (systole) or relaxing (diastole) state of the ventricles. Typically measured systolic/diastolic as mm Hg, with numbers affected by vascular resistance and volume.
• Measured by a sphygmomanometer (e.g., blood pressure cuff).
• Pulse: Surge of blood with each ventricular contraction detected as a surge in blood pressure, and by palpation of the arteries.
• Average blood pressure for adults is around 120/80 mm Hg.

Blood Flow

• Pulmonary circuit: Blood flows from the heart to the lungs (oxygen-poor blood picks up oxygen, and releases carbon dioxide) and then back to the heart.
• Systemic circuit: Blood flows from the heart to the body's tissues, then back to the heart (oxygenated blood delivers oxygen, picks up CO2).
• Both circuits occur concurrently.
• Hydrostatic pressure (blood pressure) drives movement of fluid from capillaries to tissue. Osmotic pressure drives fluid from tissue into capillaries.
• Venous return is dependent on three additional factors (skeletal muscle contraction, breathing, venous valves).