Question 1

What is the difference between the pulmonary and systemic circuits?

Accepted Answer

The pulmonary circuit carries deoxygenated blood from the right ventricle to the lungs, where carbon dioxide is exchanged for oxygen, and then returns oxygenated blood to the left atrium. The systemic circuit carries oxygenated blood from the left ventricle to the rest of the body, delivering oxygen and nutrients, and returns deoxygenated blood to the right atrium. The pulmonary circuit is shorter and at lower pressure, while the systemic circuit is longer and requires higher pressure from the left ventricle.

Question 2

How does the heart structure help it pump blood efficiently?

Accepted Answer

The heart has four chambers that separate oxygenated and deoxygenated blood, preventing mixing. The left ventricle has a thicker muscular wall to generate high pressure for systemic circulation. Valves (tricuspid, bicuspid, semilunar) prevent backflow, ensuring blood flows in one direction. The septum divides the heart into two sides, maintaining separation. The cardiac muscle is myogenic (contracts without nerve stimulation) and has its own blood supply via coronary arteries.

Question 3

Why does heart rate increase during exercise?

Accepted Answer

During exercise, working muscles require more oxygen and produce more carbon dioxide. The nervous system (sympathetic) and hormones (adrenaline) stimulate the sinoatrial node (SA node) to increase heart rate. This raises cardiac output, delivering more oxygenated blood to muscles and removing waste products faster. Heart rate increases proportionally to exercise intensity until near maximal levels.

Question 4

What is the difference between an artery and a vein?

Accepted Answer

Arteries carry blood away from the heart (usually oxygenated) under high pressure, so they have thick, muscular, elastic walls. Veins carry blood towards the heart (usually deoxygenated) under low pressure, so they have thinner walls, a wider lumen, and contain valves to prevent backflow. The exception is the pulmonary artery (deoxygenated) and pulmonary vein (oxygenated).

Question 5

How does vascular shunting work during exercise?

Accepted Answer

Vascular shunting is the redistribution of blood flow to meet the demands of exercise. Arterioles supplying working muscles dilate (vasodilation), increasing blood flow, while arterioles supplying non-essential organs (e.g., digestive system) constrict (vasoconstriction), reducing blood flow. This is controlled by the sympathetic nervous system and local chemical factors (e.g., low oxygen, high carbon dioxide).

Question 6

What is cardiac output and how is it calculated?

Accepted Answer

Cardiac output (Q) is the volume of blood pumped by the heart per minute. It is calculated using the formula: Q = Stroke Volume (SV) × Heart Rate (HR). Stroke volume is the amount of blood ejected per beat (usually 70-80 ml at rest), and heart rate is beats per minute. For example, at rest with SV=70 ml and HR=70 bpm, Q = 70 × 70 = 4900 ml/min (4.9 l/min). During exercise, both SV and HR increase, raising Q to meet oxygen demand.

Structure and function of the cardiovascular system

Topic Overview

Key Concepts

What You Need to Demonstrate

Marking Points

Examiner Tips

Common Mistakes

Frequently Asked Questions

Before You Start

Likely Command Words

Ready to test yourself?

Related Topics in OCR GCSE Physical Education

Aerobic and anaerobic exercise

Applied anatomy and physiology

Applying the principles of training

Characteristics of skilful movement

How to Revise Structure and function of the cardiovascular system — OCR GCSE Physical Education

Examiner Tips for Structure and function of the cardiovascular system

Key Marking Points