Pearson Edexcel A-Level Biology: Topic 1B Principles of Circulation

Vocabulary flashcards focusing on Topic 1B Principles of Circulation, covering circulatory system types, blood components, hemoglobin transport mechanics, blood vessel anatomy, the cardiac cycle, and related cardiovascular diseases.

Diffusion

The free movement of particles in a liquid or gaseous state down a concentration gradient.

Mass transport system

A system in animals that helps overcome the limitations of diffusion by efficiently distributing fluids, nutrients, and oxygen throughout multicellular organisms.

Open circulatory system

A circulatory system in which blood circulates in open spaces within the body, such as in insects.

Closed circulatory system

A circulatory system in which blood is contained inside vessels or tubes throughout the animal.

Single circulatory system

A circulatory system where blood moves through the heart once per complete cycle, common in fish.

Double circulatory system

A circulatory system found mainly in birds and mammals where blood moves through the heart twice in one complete cycle.

Systemic circulation

The system that carries oxygenated blood from the heart to the cells of the body and returns $CO_2$ back to the blood vessels.

Pulmonary circulation

The system concerned with carrying deoxygenated blood away from the heart to the lungs so the blood can be oxygenated before returning to the heart.

Blood plasma

The liquid component of blood making up over $50\%$ of blood, carrying blood cells, dissolved nutrients, excretory products, hormones, and distributing heat.

Erythrocytes

Red blood cells containing hemoglobin for binding oxygen, characterized by a biconcave shape, lack of a mature nucleus, and a lifespan of about $120\text{ days}$.

Leukocytes

White blood cells made in the bone marrow that contain a nucleus and function to defend the body against infection and carry out inflammatory responses.

Thrombocytes

Cell fragments called platelets, formed in the bone marrow from megakaryocytes, that are involved in the blood clotting process.

Hemoglobin

A large globular protein consisting of four polypeptide chains, each with an iron-containing prosthetic group, capable of binding up to four $O_2$ molecules.

Carbonic anhydrase

An enzyme inside red blood cells that catalyzes the reversible reaction between $CO_2$ and water to form carbonic acid.

Hemoglobinic acid

The compound formed when hemoglobin acts as a buffer by accepting a $H^+$ ion inside red blood cells to prevent blood pH from decreasing.

Bohr effect

The ability of hemoglobin to release oxygen more readily in respiring tissues that have lower partial pressure of oxygen and higher concentrations of $CO_2$.

Fetal hemoglobin

A form of hemoglobin in a fetus that has a higher affinity for oxygen than adult maternal hemoglobin, ensuring effective oxygen transfer across the placenta.

Thromboplastin

An enzyme released from broken platelets that catalyzes the conversion of prothrombin into thrombin in the presence of calcium.

Serotonin

A chemical released by damaged platelets that causes smooth muscles in blood vessels to contract, narrowing the vessel to reduce blood loss.

Arteries

Blood vessels carrying high-pressure blood away from the heart toward organs, featuring thick walls made of elastic fibers and smooth muscle.

Arterioles

Smaller subdivisions of the arterial system located farther from the heart that connect arteries to capillary networks.

Capillaries

Microscopic blood vessels with walls one cell thick that link arterioles to venules, providing a short diffusion distance for exchange of materials.

Veins

Blood vessels carrying low-pressure blood back toward the heart, equipped with valves to prevent the backflow of blood.

Inferior vena cava

The major vein that carries deoxygenated blood from the lower parts of the body back to the right atrium of the heart.

Superior vena cava

The major vein that carries deoxygenated blood from the upper body, including the head and arms, back to the heart.

Cardiac muscle

The specialized, self-contracting muscle tissue that makes up the walls of the heart.

Systole

The stage of the cardiac cycle in which cardiac muscle actively contracts to force blood out of heart chambers.

Atheroma

An accumulation of cholesterol, immune cells, and fatty deposits beneath damaged endothelium within an artery wall.

Aneurysm

A fluid-filled bulge or weakening in an arterial wall resulting from blood collecting behind a blockage caused by plaque.

Angina

A condition causing severe gripping chest pain during exertion due to narrowed coronary arteries forcing heart muscle to undergo anaerobic respiration.