Arteries - Have thick walls and a smaller internal diameter to withstand the pressure of the blood that has just been pumped from the heart - they carry blood away from the heart. They usually carry oxygen-rich blood away from the heart to the rest of the body, with the exception of the pulmonary artery which carries oxygen-poor blood to the lungs from the right ventricle of the heart.
Arterioles - Arteries divide into arterioles as they get further away from the heart.
Capillaries - Arterioles further divide into capillaries. Capillaries are microscopic blood vessels that enable the exchange of oxygen, carbon dioxide, nutrients and waste products to and from the tissues they are supplying, eg muscles.
Venuoles - The oxygen-poor blood returns to the heart from the capillaries via the venoules (sub divisions of the veins), to the veins, and ultimately the vena cava, before reaching the right atrium of the heart.
Veins - Carry oxygen-poor blood towards the heart. They have thinner walls than arteries but a wider internal diameter, and contain valves to ensure the blood flows in the correct direction.
Functions of the Blood
The functions of the blood include transport, protection, temperature regulation and clotting.
White blood cells fight disease in the body, both bacterial infections and viruses. Types of white blood cells include:
Differences between red blood cells and white blood cells
3. Temperature Regulation
Heat is transferred from the warmer areas of our body, such as muscles, and evenly distributed around the body. Temperature is controlled via vasodilation and vasoconstriction.
A complicated mechanism involving blood platelets (thrombocytes - no nucleus, 2 week lifespan) that prevents the body from losing too much blood when injured. Blood clots are prevented from forming in undamaged blood vessels by enzymes, so avoiding a thrombosis.
Factors Affecting Heart Rate
(The bigger the animal, the lower the heart rate, on average)
Hypertension - high blood pressure
Blood pressure is the pressure on the wall ot the artery where the blood pressure is measured. The systolic pressure (or peak) is measured when the heart beats, the diastolic is measure inbetween beats. It is measured in mmHG (mm of mercury) and is given as systolic/diastolic. A typical reading would be 120/70. A raised blood pressure would be in the region of 145/90.
Factors Affecting Blood Pressure
1. Cardiac Output - The amount of blood pumped in one minute (volume/min)
Stroke Volume - The amount of blood pumped per heartbeat (volume/beat)
Heart Rate - (beat/min)
Cardiac Output = Stroke Volume x Heart Rate
(Look at the units - volume/min = volume/beat x beat/min).
An increased heart rate leads to an increase in blood pressure and vice versa.
2. Blood volume - approximately 5l. Increased or decreased blood volume will lead to increased / decreased blood pressure.
3. Peripheral Resistance - resistance to blood flow by friction between blood and blood vessel wall.
4. Postural Hypotension - caused by disorders that cause damage to the nerve supply to blood vessels, such as diabetic neuropathy.
The Effects of Exercise on the Cardio Respiratory System