Cardiovascular System
Functions of the Cardiovascular system
Functions of the cardiovascular system applied to performance in physical activities are: transporting of oxygen, carbon dioxide and nutrients; clotting of open wounds; and regulation of body temperature.
Functions of the CV system.pdfStructure of Cardiovascular system
Structure of the CV system.pdfThe cardiovascular system is made up of the heart, three types of blood vessel and the blood itself. The heart generates the pumping action, the vessels provide a circulatory network, and the blood itself acts as a carrier for blood cells, gases and nutrients.
The heart has four chambers with the septum separating the right and left sides. The two top chambers are called atria and their role is to push blood into the bottom two chambers, called the ventricles. The heart has four major valves. The valves open to allow blood to flow through them in one direction but close to stop blood flowing back in the other direction. Therefore all valves prevent the backflow of blood.
Cardiac Cycle
The cardiac cycle includes everything that happens within the heart between two consecutive heartbeats. There are two terms used to describe phases that occur during a cardiac cycle; systole and diastole. Diastole is when the heart is relaxing and the chambers are filling with blood. Systole is when the heart chambers contract and blood is pushed out of them. If heart rate was at 60 beats per minute then 1 cardiac cycle would occur every second. During each cycle both chambers will be in diastole (relaxing) for about 0.7 seconds and it takes approximately 0.3 seconds for the chambers to contract (systole). However, they do not contract at the same time; the atria contract first, followed by the ventricles. Blood being delivered from the body via the superior and inferior vena cava enters the right atrium and blood returning from the lungs arrives through the pulmonary vein into the left atrium. Atrial systole involves both atria contracting, pushing blood into the ventricles. During this phase the ventricles are in diastole (relaxing). Ventricular systole occurs and both ventricles contract. Blood is pushed from the left ventricle into the aorta where it is then distributed around the body by the other major arteries. Blood from the right ventricle is pushed into the pulmonary artery where it is taken to the lungs. During exercise, heart rate increases and the time the heart is relaxing decreases significantly. Systole can occur at a slightly faster rate, however, due to the time it takes for action potential to pass across the heart, the heart to contract, and the cells to repolarise, this is not a significant increase. The chart below in Figure 3.2 shows the amount of cardiac cycles in 5 seconds when the heart is beating at; 60 and 180 bpm.
Blood
Red Blood Cells: Red blood cells contain haemoglobin, a substance that allows oxygen to bind and be carried. As a result, red blood cells are responsible for oxygen transport. They are, therefore, key to all sports and physical activities that require any level of aerobic work, because they ensure that muscles have the oxygen they need to perform effectively. Activities that are most impacted by the work of red blood cells are endurance events like marathons and long-distance cycling.
White Blood Cells: White blood cells are part of the immune system. They travel in blood and fi ght disease and infection. They are, therefore, responsible for keeping athletes healthy, ensuring a sportsperson can train and compete.
Blood Plasma: Plasma is the watery fluid part of blood that makes it a liquid. Without
plasma, blood would not flow, and would, therefore, not be able to travel around the body.
Platelets
Platelets clot blood and scab around the site of an injury to seal open wounds. This is crucial to stop excessive bleeding and to heal the body quickly in order to prevent infection. This is important for a sports performer as it will stop injuries becoming life threatening.
Blood.pdfBlood Vessels
Blood vessels
The vascular system consists of five different types of blood vessel which carry blood from the heart, distribute it round the body and then return it back to the heart. For GCSE PE you need to know three: Arteries, Veins and Capillaries.
Arteries carry blood away from the heart. The heart beat pushes blood through the arteries by surges of pressure and the elastic arterial walls expand with each surge, which can be felt as a pulse in the arteries near the surface of the skin. The arteries then branch off and divide into smaller vessels called arterioles, which in turn divide into microscopic vessels called capillaries. These have a single-cell layer of endothelium cells (its wall) and are only wide enough to allow one red blood cell to pass through at a given time The exchange of substances with the tissues takes place and then blood flows from the capillaries to the venules which increase in size and eventually form veins, which return the blood to the heart
To summarise, the order in which blood flows through the vascular system is as follows:
Heart - Arteries - Arterioles - Capillaries - Venules - Veins - Heart
Structure and function of blood vessels.pdfRedistribution of Blood
In exercise, more oxygen is needed at the working muscles so vasodilation will occur, increasing blood flow and bringing in the much needed oxygen, whereas vasoconstriction will occur in the arterioles supplying non-essential organs such as the intestines and liver. This redirecting of blood flow to the areas where it is most needed is known as shunting or the vascular shunt
Vasodilation: blood vessels DILATE (get wider) to increase blood supply to ACTIVE areas (working muscles). During this process the diameter of the Lumen increases which then increases blood flow.
Vasoconstriction: blood vessels CONSTRICT (get narrower) to reduce blood flow to INACTIVE areas (digestive system). During this process the diameter of the Lumen decreases which then decreases blood flow.
Vascular Shunting.pdfBlood pressure is the force exerted by the blood against the blood vessel wall. Ejection of the blood by the ventricles contracting creates a high pressure pulse of blood, which is systolic pressure. The lower pressure as the ventricles relax is the diastolic pressure.
A typical reading at rest is:
120/80 mmHg (millimetres of mercury)
Where 120mmHg is the systolic pressure and 80mmHg is the diastolic pressure
During exercise, changes in blood pressure occur, but these depend on the type and intensity of the exercise being performed. Systolic pressure increases during aerobic exercise due to an increase in cardiac output (the volume of blood leaving the heart per minute), while diastolic pressure remains constant.