Haemoglobin and the Bohr Effect

This final page introduces haemoglobin and the Bohr effect, which are crucial concepts in understanding oxygen transport in the blood.

Haemoglobin is described as a protein with a quaternary (4°) structure found in red blood cells. Its primary function is to transport oxygen in the blood.

Vocabulary: Quaternary structure refers to the arrangement of multiple protein subunits in a complex.

The page begins to explain the Bohr effect, which describes how haemoglobin's affinity for oxygen changes under different conditions. However, the full explanation is cut off in the provided transcript.

Highlight: The Bohr effect is a key adaptation that allows efficient oxygen delivery to tissues, especially during exercise or in low-oxygen environments.

This section provides a foundation for understanding the complex relationship between haemoglobin, oxygen, and factors that affect oxygen transport in the blood, which is essential for OCR A Level Biology Module 3 transport in animals topics.

Blood Vessels and Circulatory Systems

This page introduces the structure and function of blood vessels and circulatory systems in animals. It provides detailed information on the three main types of blood vessels: arteries, veins, and capillaries.

Arteries are described as having elastic tissue, a thick layer of muscle, and a narrow lumen. They flow away from the heart and carry blood at high pressure. The elastic tissue and folded endothelium allow arteries to stretch and recoil, maintaining smooth pressure. The thick muscle layer enables vasoconstriction and vasodilation to control blood flow.

Vocabulary: Vasoconstriction is the narrowing of blood vessels, while vasodilation is the widening of blood vessels.

Veins are characterized by a wide lumen, thin muscle layer, and smooth endothelium. They flow towards the heart and contain one-way valves to prevent backflow of blood. The wide lumen and thin muscles are adaptations for low-pressure blood flow.

Capillaries are described as having an endothelium one cell thick, providing a short diffusion distance for efficient exchange of materials with surrounding tissues.

Highlight: The structure of each blood vessel type is directly related to its function in the circulatory system.

The page also introduces single and double circulatory systems, using fish as an example of a single circulatory system and mammals and birds as examples of double circulatory systems.

Example: In a fish's single circulatory system, blood flows from the heart to the gills for oxygenation, then to the body tissues before returning to the heart.

The Human Heart and Control of Heart Rate

This page provides a detailed overview of the human heart's structure and the control of heart rate. It includes a labeled diagram of the heart and explanations of key components and processes.

The heart's chambers and major blood vessels are identified:

• Left and right atria and ventricles
• Aorta (largest artery, carrying blood away from the heart to the body)
• Pulmonary veins (carrying oxygenated blood from lungs to heart)
• Pulmonary arteries (carrying blood from heart to lungs)
• Vena cava (large vein returning blood to the heart from the body)

Vocabulary: The atrioventricular valves are one-way valves between the atria and ventricles, while semilunar valves are found at the exits of the ventricles.

The page also describes the heart's electrical conduction system, including:

• Sinoatrial Node (SAN): initiates heart rate
• Atrioventricular Node (AVN): delays electrical impulse
• Bundle of His and Purkyne fibers: conduct electrical impulses to the ventricles

Highlight: The left ventricle has the thickest walls and contracts with the greatest force, as it pumps blood to the entire body.

The control of heart rate is explained step-by-step, emphasizing the role of each component in coordinating the heart's contractions.

Example: The AVN's delay allows the atria to contract and empty before the ventricles contract, ensuring efficient blood flow through the heart.