Our cardiovascular system

After the oxygen is used, a gas called carbon dioxide is produced; the veins carry blood through to the heart. To get to the heart it flows through the vena cava this then goes through to the right atrium, this is when the mitrial valves open and blood goes through to the right ventricle. This then gets pumped to our lungs through the pulmonary artery.

TRAINING

Training affects our cardio vascular system in numerous ways. The heart during training increases in size and contracts constantly and becomes quicker. Capillaries grow around the heart so that more oxygen can be supplied. Our recovery heart rate will go back to normal quicker depending on how fit we are.

RESPIRATORY SYSTEM

The respiratory system, as we breathe our respiratory muscles contract, these muscles include the diaphragm and internal- external intercostals. As we breathe our rib cage moves upwards and outwards, it does this so we can increase the amount of oxygen in our lungs. The oxygen then travels down the wind pipe. The air passage is the split into two sections for both lungs. The oxygen travels through the bronchus; this then goes into the alveoli. After the air particles are branched out in the alveoli gaseous exchange takes place.

When we breathe out the diaphragm and external- inter costals relax. The ribs move inwards and downwards as this decreases the amount of air in the lungs. When we exercise we decide when we breathe, for instance incase we need to breathe faster.

BREATHING CONTROL

Breathing control, this is controlled by the nervous system this is influenced by chemical changes during exercise. When we breathe at normal rate, nerve impulses from the respiratory system are sent out. This controls our bodies' movement and is situated in the middle of our brain. Inspiration then takes place, nerve impulses are sent to the external intercostals and the diaphragm, and this causes contraction.

Expiration then takes place, muscles relax and expiration then follows passively.

BREATHING DURING EXERCISE

Breathing during exercise, this is forced breathing, the respiratory control centre stimulates internal intercostals which causes forced expiration. Ventilation is a function of rate and depth of breathing. Acidity in the blood is increased this is caused by lactic acid and carbon dioxide. This decrease in pH is detected by chemorceptors which relay information to the respiratory centre in the brain. Once blood PH levels drop below a certain level, the respiratory control centre is simulated and voluntary control is lost.

THE STRUCTURE OF AN ARTERY

Blood is received directly from the heart, arteries need to have thick muscular and elastic walls so that they will be able to withstand the very high pressure of the blood as it is forced out of the heart.

Elastic fibres in the arteries are the main structure which provide the strength for the artery to resist the high pressure. The nearer the artery is to the heart, the thicker is the elastic fibres are . The thick elastic walls also help to maintain the high pressure of the blood in the arteries. The high pressure help push the blood along the artery.

Shown below is a diagram of an artery showing the structure of it.

THE STRUCTURE OF VEINS

While veins have the same layers as arteries, i.e. intima, media and adventitia, the organization of each layer is different, reflecting different function. In general veins have to sustain a much lower pressure than arteries, therefore have less need for a thick muscular intima. Veins are the capacitance vessels of the system and must be able to dilate to accept an increased volume.

The large veins have a thin media with smooth muscle, elastin and collagen separated from the intima by an incomplete internal elastic lamina. In many large veins valves are present as specializations of the intima. The adventitia is composed largely of collagen and is thicker than in arteries of comparable size. Perivascular nerves are present in the adventitia but are scarce indicating a low level of control of veins by the nervous system.

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