• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Structure and function of the vascular system

Extracts from this document...

Introduction

Structure and function of the vascular system The blood vessels are part of the cardiovascular system and form the body's transport network. It is essential that a sports performer has an efficient vascular system, to deliver oxygen and food supplies to the working muscles and to remove waste products such as carbon dioxide. The blood carries all the vital ingredients needed for the muscles to work and the blood vessels form a closed circulatory network, allowing distribution of blood to all cells. During exercise there is a dramatic change in the distribution of blood around the body, with up to 85% of cardiac output going to the working muscles. The heart, vascular and respiratory systems all work together to coordinate the increase in oxygen delivery needed to cope with the increased demand for energy. Blood vessels Five different types of blood vessels in the body link together to form the vascular system. All blood vessels are basically a muscular wall surrounding a central opening called a lumen. The walls of the blood vessels (except the capillaries) comprise three layers: 1. The tunica interna forms the inner lining of the vessel. It contains endothelial cells and collagen. 2. The tunica media forms the middle layer and is made up of smooth muscle and elastin fibres. The smooth muscle is stimulated by the sympathetic nerves of the autonomic nervous system. ...read more.

Middle

Blood vessels receive a continual low frequency impulse that is known as the vasomotor tone. The vasomotor centre controls this stimulus by: 1. Increasing vasomotor tone, causing vasoconstriction (the lumen decreases in size, resulting in an increase in blood pressure and a reduction in blood flow). 2. Decreasing vasomotor tone, causing vasodilation (the lumen increases in size, resulting in a decrease in blood pressure and an increase in blood flow). As the arteries have a relatively thick tunica media they are responsible for most of the changes in blood flow and blood pressure. There is also a degree of local control of blood distribution, called autoregulation. The arterioles in some areas of the body react directly to chemical changes in the tissues that they supply. An increased demand by the tissue for oxygen seems to trigger the response of vasodilation of the surrounding arterioles, so do increases in carbon dioxide and lactic acid. The vascular shunt - During exercise the demand for oxygen from the skeletal muscles increases dramatically and more oxygenated blood must flow to them to meet this demand. The increase in stroke volume and heart rate helps to increase the overall cardiac output and therefore increases oxygen supply, but this in itself is not enough. Blood must also be redistributed so that more goes to the skeletal muscles and less to the other organs. ...read more.

Conclusion

Effects of exercise on blood pressure and blood volume Systolic blood pressure tends to increase during exercise. The vasodilation that occurs in skeletal muscle causes a drop in blood pressure because of the decrease in resistance, but the cardiac output increases significantly and negates the effect of this vasodilation. During exercise there is very little change in diastolic pressure, which only increases during isometric work because of the resistance to blood flow caused by the contracting muscle. After a period of exercise it is much better to perform a series of cool-down activities than to stop abruptly. If you stop suddenly the blood 'pools' in the working muscles, and as during heavy exercise, up to 85% of the cardiac output is distributed to them, the venous return will instantly drop. The knock-on effect is that less blood enters the heart during diastole which means that the stroke volume will be much lower, leading to a drastic reduction in blood pressure causing sickness and dizziness. Blood volume can change during exercise, but whether it increases or decreases depends on the type of activity and the fitness of the individual. A decrease in volume is mostly caused by plasma moving out of the capillaries into the surrounding tissues. This increases the viscosity of the blood and therefore increases the peripheral resistance. After a period of aerobic training the usual trend is an increase in blood volume. This is of great benefit to performers as it increases their capacity to carry oxygen. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Humans as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Humans as Organisms essays

  1. Marked by a teacher

    Artificial Cardiac Pacemakers

    5 star(s)

    It cannot regulate a heart rate that is irregular. A pacemaker can do this however, as well as treat Bradycardia. A pacemaker is a reliable device and provides the patient with much more control over their heart rate. "Demand pacemakers" can increase heart rate when necessary, for example during physical activity, when oxygen demands are higher.

  2. Marked by a teacher

    Investigate the effect of altitude training on the density of blood.

    4 star(s)

    During the process of aerobic respiration, coupled oxidation-reduction reactions and electron carriers are part of the electron transport chain, a series of electron carriers that eventually transfers electrons from NADH and FADH2 to oxygen. The last electron carrier in the electron transport chain transfers the electrons to the terminal electron acceptor, oxygen.

  1. The Structure and Function Of Arteries, Veins and Capillaries.

    Veins Veins and venules are similar in structure to arteries and arterioles, however veins have a wider inner diameter, which means that they can hold a larger volume of blood.

  2. List the effects of exercise on the cardiovascular system, including the cardiac cycle and ...

    blood flow through the circulatory system and it is determined by two main factors, they are:- Cardiac Output - the volume of blood flowing into the system from the left ventricle. Resistance to flow - the opposition offered by the blood vessels to the blood flow.

  1. The cardiovascular system is made up of the heart and the blood vessels, such ...

    Hence, these cells are responsible for providing oxygen to tissues and partly for recovering carbon dioxide produced as waste. Plasma Plasma is a clear liquid protein and salt solution which carries the red cells, white cells, and platelets about 55% of the total blood volume is made up of plasma,

  2. Effects of Exercise on Cardiac Output.

    Although skeletal muscle contraction is a main feature of exercise, many other systems in the body are activated to support this process. Such as the heart, which pumps increased volumes of blood to supply oxygen and nutrients and remove carbon dioxide and metabolic wastes.

  1. Blood - moving around our bodies via the circulatory system, consisting of the arteries, ...

    cell debris (often left behind by the granulocytes and lymphocytes), invading bacteria, and other foreign particles. In addition to this, monocytes remove dead red blood cells. They usually constitute for between 4% and 8% of all white blood cells, whereas lymphocytes ordinarily number 20 to 35%.

  2. Does cloning benefit or endanger society?

    There isn't a general consensus about when a human's life starts and therefore pro-cloners cannot disregard the idea that an embryo is life. In therapeutic cloning, all of the embryos used are destroyed, whether the process works or not; if it works, it will become a tissue, if it doesn't work, it will be disposed of.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work