The student's statement is largely correct. The structure of arteries is indeed better suited to carrying blood than the structure of veins. This is because the functions of arteries and veins are fundamentally different, and their structures reflect these differences.

Arteries carry blood away from the heart under high pressure. The thick, elastic walls of arteries are essential for withstanding this high pressure and ensuring a continuous, forceful flow of blood. The elasticity allows the arteries to stretch and recoil with each heartbeat, maintaining blood pressure and preventing a significant drop in pressure between heartbeats. The structure of the tunica media, with its abundance of elastic fibres, is crucial for this function.

Veins, on the other hand, carry blood back to the heart under low pressure. The veins do not need to withstand high pressure, so their walls are thinner and less elastic. Instead, veins rely on valves to prevent the backflow of blood, especially in the limbs where blood is fighting against gravity. The thinner walls of veins mean that they are more easily compressed, which helps to propel blood back towards the heart. The valves are a key structural adaptation for this function.

Therefore, the structure of arteries, with their thick, elastic walls, is specifically adapted for carrying blood under high pressure, while the structure of veins, with their thinner walls and valves, is adapted for carrying blood under low pressure and preventing backflow. The statement accurately reflects this functional relationship between structure and function.

When physical activity increases, the body responds to meet the increased oxygen and energy demands of the muscles. This involves coordinated changes in the nervous and hormonal systems, which directly impact pulse rate.

Nervous System Response: The sympathetic nervous system is activated. This system releases neurotransmitters like noradrenaline (norepinephrine), which bind to receptors on the heart. This increases the rate of firing of the sinoatrial (SA) node, the heart's natural pacemaker, leading to a faster heart rate (increased pulse rate). The nervous system also causes vasodilation (widening of blood vessels) in the working muscles, increasing blood flow to those areas.

Hormonal System Response: The adrenal glands are stimulated to release adrenaline (epinephrine). Adrenaline further increases heart rate and stroke volume (the amount of blood pumped with each beat). It also helps to prepare the body for 'fight or flight' by increasing blood flow to the muscles and diverting blood away from non-essential organs.

Relationship to Pulse Rate: The combined effect of these nervous and hormonal responses is a significant increase in heart rate. The heart beats faster to deliver more oxygenated blood to the working muscles, ensuring they have the energy they need to continue contracting. The increased stroke volume also contributes to a higher cardiac output, further enhancing oxygen delivery.

Arteries: Arteries are blood vessels that carry blood away from the heart. They have thick, elastic walls. The wall consists of three layers:

• Tunica intima: A thin inner layer of endothelium (smooth lining) that reduces friction.
• Tunica media: A thick middle layer of smooth muscle and elastic fibres. The abundance of elastic fibres allows the artery to stretch and recoil with each heartbeat, maintaining blood pressure and ensuring a continuous flow of blood.
• Tunica adventitia: The outer layer of connective tissue that anchors the artery to surrounding tissues.

The thick walls of arteries are necessary to withstand the high pressure of blood pumped from the heart. The elasticity allows them to accommodate the pulsatile flow of blood. Arteries carrying oxygenated blood (except the pulmonary artery) are typically bright red.

Veins: Veins carry blood back to the heart. They have thinner walls than arteries and are less elastic. The wall also has three layers:

• Tunica intima: Similar to arteries, it has a thin layer of endothelium.
• Tunica media: The middle layer is thinner and contains less smooth muscle and elastic fibres than arteries.
• Tunica adventitia: The outer layer is thick and contains more connective tissue.

Veins have valves inside them to prevent the backflow of blood, especially in the limbs where blood is fighting against gravity. Veins carrying deoxygenated blood (except the pulmonary vein) are typically a darker shade of red.

Capillaries: Capillaries are the smallest blood vessels and connect arteries and veins. They have very thin walls, only one cell thick (the endothelium). This single layer of endothelium allows for the efficient exchange of substances between the blood and the surrounding tissues.

The thin walls also allow for a slow blood flow, which is essential for the exchange of oxygen, carbon dioxide, nutrients, and waste products. Capillaries are found throughout the body, supplying oxygen and nutrients to all cells and removing waste products.