Cardiorespiratory system

• Bronchioles - allow for passage of air into alveoli
• Alveoli - air sacs that allow gaseous exchange to occur. Thin cell walls, huge capillary network
• Capillaries - site for gaseous exchange
• Diaphragm - shaped like a dome. Muscle that separates thoracic and abdominal cavities. Moves up for expiration, down for inspiration
• Intercostal muscles - external intercostals attach to each rib. When they contract, rib cage moves up and out. When they relax, rib cage lowers. Internal intercostals - more active during exercise to pull ribs down more to increase ventilation rate
• Inspiration - higher partial pressure of oxygen in atmosphere compared to in the lungs. External intercostal muscles contract to elevate ribs up and out. Diaphragm then contracts to increase thoracic cavity. Pulmonary air pressure is lower than the atmospheric pressure. Movement of air into the lungs due to concentration gradient
• Expiration - internal intercostals contract and diaphragm relaxes, leading to decrease in thoracic cavity. Pulmonary air pressure becomes higher than the atmospheric pressure and air is therefore expired due to a concentration gradient.
• Residual volume - volume of air left in the lungs after a maximum exhalation (RV)
• Vital capacity - greatest amount of air that can be forcibly exhaled after a maximum inhalation (VC)
• Inspiratory capacity - maximum volume of air inspired after the resting expiratory level to full inhalation (IC)
• Functional residual capacity - volume of air remaining in the lungs at the end of a passive expiration (ERV+RV) (FRC)
• Total lung capacity - VC + RV = total amount of air the lungs can hold (TLC)
• Expiratory reserve volume - difference between a normal and maximal expiration (ERV)
• Inspiratory reserve volume - difference between a normal and maximal inspiration, or amount of extra air inhaled after a forceful inhalation (IRV)
• Tidal volume - amount of air that is inspired/expired normally, usually at rest (TV)
• Partial pressure - individual pressure that a gas exerts when it occurs in a mixture of gases
• Diffusion - movement of molecules from an area of high concentration to an area of low concentration until an equilibrium occurs
• Pressure gradient - difference between the high pressure and low pressure area. The steeper the gradient, the greater the rate of gaseous exchange
• CV system - involves the heart and blood vessels
• Circulatory system - refers to transportation throughout the body
• Pulmonary circuit - carries blood to the lungs from the right ventricle (deoxygenated) at high pressure and oxygenated blood back to the left atrium via pulmonary vein
• Systematic circuit - carries blood around the body from the left ventricle (oxygenated) at high pressure and deoxygenated blood back to the right atrium via vena cava at low pressure
• Venous return - blood returning back to the heart is at a lower pressure, though it is largely dependent on cardiac output (Q). When Q levels rise, blood is pumped rapidly from the veins
• Skeletal muscle pump - when the muscles contract, the valves are forced to open to increase venous return
• Respiration - during inspiration, venous return increases due to reduced pressure in the thoracic cavity, drawing more blood into the right atrium
• Blood volume - an increase in the veins, leads to greater pressure also in the veins. Frank-starling mechanism means the heart will be able to cope with the increased blood volume.
• Respiratory - responsible for taking in O2 and dispelling Co2 from the body. A network of organs and tissue that help the body to breathe
• Myocardia - muscle tissue of the heart
• 1. Right atrium - deoxygenated blood from vena cava
  2. Right ventricle - deoxygenated blood from right atrium
  3. Left atrium - oxygenated blood from pulmonary vein
  4. Left ventricle - oxygenated blood from left atrium
  5. Pulmonary artery - deoxygenated blood -> right ventricle -> lungs -> pick up O2
  6. Pulmonary vein - oxygenated blood in from the lungs -> left atrium
  7. Vena cava - vein bringing deoxygenated blood back to the heat -> lungs
  8. Aorta - artery moving oxygenated blood away -> left ventricle -> working muscles. Thicker wall as blood travels further
• Arteries - carry blood away from the heart under high pressure. They have thick, muscular elastic walls. Blood carried is oxygenated, except the pulmonary artery that carries deoxygenated blood to the lungs. Walls contract/relax, help regulate blood pressure and lumen widens.
• Arterioles - smaller arteries, distribute blood to capillary beds
• Veins - carry blood towards the heart under low pressure. They have a large lumen, with thin walls. Contain valves to stop back flow of blood. Blood carried is usually deoxygenated, except the pulmonary vein
• Venuoles - receive blood from capillary bed and link with veins
• Capillaries - very small and link between arteries and veins, moving blood between the 2. Allow gaseous exchange to occur
• Nervous control - action potential created by the sinoatrial node (SAN) that travels to the atrioventricular node (AVN), where the impulse is delayed, allowing diastole to occur. This is due to build up of pressure in the atria that can cause the AV valves to open.

  The atria then contract (atrial systole) to force blood into the ventricles. This decreases pressure in the atria and AV valves close. The impulse is conducted to the bundle of His, then to the Purkinje fibres. The impulse continues to the apex of the heart and up to the ventricle walls.
• The ventricles then contract (ventricular systole), the semi-lunar valves open and blood is ejected out of the aorta and pulmonary artery
• the order of electrical impulse: 1. sino-atrial node 2. atrioventricular node 3. the bundle of His 4. Purkinje fibres
• Atrial systole -> ventricular diastole -> atrial diastole -> ventricular systole
• Atrial systole - the atria contract, forcing the blood into the ventricles
• Ventricular diastole - passive movement of blood from the atria enters the ventricles (semi-lunar valves stay closed)