GCSE PE UNIT 1b - the cardiorespiratory system

• The respiratory system is the name given to the process of

  breathing in order to maintain the body with oxygen to function.
• As we breathe, the air follows a specific pathway:

  From the mouth/nose

  To the trachea

  Down to the bronchi

  Into the lungs through to the connecting bronchioles

  Into the alveoli
• Gas exchange takes place by diffusion. As shown in the video, oxygen

  and carbon dioxide are transferred between the capillaries and the

  alveoli.
• Diffusion in the alveoli

  Considered to be a 'passive' process
• Factors determining the diffusion process in the alveoli

  • Large number of very small alveoli, providing a large surface area for exchanging gases
  • Surface area of the alveoli and walls of the blood capillaries are very thin and moist, which help the exchange of gases
  • Distance between the alveoli walls and the blood capillaries is very small as they are touching, meaning there is a short diffusion pathway
  • Large network of blood capillaries surrounding each alveolus, which provides a rich supply of blood for the gases to diffuse in and out
• Inspiration = inhalation of air occurring when we are breathing in

  expiration = exhalation of air when we are breathing out.
• During inspiration, there is an increased volume of air inhaled to our lungs

  as a result of the increase in volume of the chest cavity.

  The pressure in the expanding chest cavity is reduced which allows air to

  be passively drawn from the higher pressure outside of the lungs, into the

  lower pressure inside the lungs.
• During expiration, the volume of air in the lungs is exhaled as the volume

  of the chest cavity is reduced.

  The pressure in the reduced size of the chest cavity is increased which

  causes the air to be expelled from the lungs. Air passes from the high

  pressure of the lungs and into the low pressure of the bronchi and trachea.

  This is known as a ‘passive’ process as it occurs as the muscles simply relax.
• Tidal Volume – the amount of air that enters the lungs during

  normal inspiration at rest.

  Inspiratory Reserve Volume – the amount of extra air inspired

  (above that of the tidal volume) during a deep breath.

  Expiratory Reserve Volume – the amount of extra air expired

  (above that of tidal volume) during a forceful breath out.

  Residual Volume – the amount of air left in the lungs

  following maximal expiration (there is always some air left in

  the lungs following expiration).
• A spirometer trace is a device that measures lung volumes. It consists

  of a chamber filled with oxygen that floats on a tank of water. A

  person breaths from a mouthpiece attached to a cube connected to a

  chamber.

  When breathing in, air is taken away from the chamber, which then

  sinks down. Breathing out then pushes air back into the chamber

  causing it to float again. This allows for lung volumes to be seen and

  measured.
• Arteries carry blood away from the heart.

  They are elastic and maintain the blood pressure

  It is within arteries that blood is at it’s highest pressure.

  Muscular walls of smaller arteries can adjust their diameter to

  increase or restrict blood flow to certain parts of the body.
• Vasoconstriction

  Process of small arteries that contract to decrease their diameter, reducing the

  blood flow through that particular artery.

  Vasodilation

  Process of small arteries that contract to increase their diameter, increasing the

  blood flow through that particular artery to the tissues.

  This occurs during exercise.
• Blood Vessels - capillaries

  They are tiny, thin-walled blood vessels that join arteries and veins.

  They facilitate gas exchange by allowing oxygen to transfer from

  the blood into tissues, and carbon dioxide to pass from tissues into

  the blood.

  Nutrients also diffuse from blood in the capillaries and onto the

  surrounding tissues, and waste products from the tissues into the

  blood.
• Blood Vessels - veins

  They carry blood back to the heart.

  They have much thinner walls than arteries.

  Blood pressure within the veins is much lower than in arteries.

  Veins have a large internal diameter called a lumen.

  They have valves that prevent blood from flowing backwards.
• Human heart


  The most important muscle in the body, about the size of your fist, can beat more than a hundred thousand times a day, pumping about two thousand gallons of blood through a 60,000 mile network of vessels in the body
• Human heart


  • Made up of four major chambers: right atrium, right ventricle, left atrium, and left ventricle
• Blood circulation in the heart

  1. Right side receives low-oxygen blood from veins, pumps it to lungs to become reoxygenated

  2. Left side receives oxygen-rich blood from lungs, pumps it out to the body through arteries, arterioles, and capillaries

  3. Veins return deoxygenated blood to right atrium, cycle begins again
• Heart valves


  One-way doors that keep blood flowing in the same direction, made up of two or three small but strong flaps of tissue called leaflets
• Coronary arteries


  Arteries that provide blood directly to the heart, keep the heart nourished and oxygenated
• Coronary artery disease


  Buildup of cholesterol plaque in the coronary arteries, decreases blood flow to the heart muscle, can cause damage or heart attack
• Heart rhythm


  Regulated by electrical impulses generated by the heart muscle, begin in the sinoatrial node (natural pacemaker)
• Heart rate can change based on external conditions such as diet, exercise, stress, or hormonal factors
• The cardiac cycle refers to the sequence of events that occur

  after the heart beats.

  2 phases of the cardiac cycle:

  1 = diastole (the filling of the chambers)

  2 = systole (the emptying of the chambers).

  During diastole, the heart chambers fill with blood as the

  ventricles relax.

  During systole, the heart chambers empty the blood as the

  ventricles contract, pumping the blood into arteries.

  It is important to note that both phases occur at the same time.

  One cardiac cycle has been completed when the heart fills with blood and is

  then pumped around the body.
• Diastole

  1. Deoxygenated blood arrives into the right atrium from the veins (vena cava)

  2. Relaxed valves allow blood into the right ventricle when the right atrium contracts

  3. Right ventricle contracts, forcing blood into the pulmonary artery towards the lungs

  4. Right atrioventricular valve closes to prevent blood from returning into the heart

  5. Deoxygenated blood flows through the pulmonary artery and arrives in the lungs for gas exchange

  6. Oxygenated blood returns to the heart through the pulmonary veins

  7. Oxygenated blood fills the left atrium
• Systole

  1. Right ventricle contracts, forcing blood into the pulmonary artery towards the lungs

  2. Left atrium empties the blood into the left ventricle

  3. Left ventricle contracts, forcing the atrioventricular valve to close, and the oxygenated blood is pumped into the aorta and pumped around the body
• The term cardiac output = amount of blood pumped per minute

  The cardiac output refer to the amount of oxygenated blood that is

  delivered to the body.

  Cardiac output is influenced by two major factors:

  Heart rate: the number of times the heart beats each minute.

  Stroke volume: the volume of blood that leaves the heart per beat.
• The relationship between cardiac output, heart rate and stroke volume is:

  Cardiac Output (Q) = Heart Rate (HR) x Stroke Volume (SV)
• Your cardiac output is likely to increase shortly before exercise as your heart begins to increase due

  to the expectation of exercise. This is caused by adrenaline.

  This rise in heart rate is known as the anticipatory rise.