Mass Transport 3.3.4.1

• The Heart

  
• Structure of the chambers and their function

  Atria= Thin walled and elastic so can stretch when filled with bloodVentricles= Thick muscular walls so can pump blood after high pressure (left thicker so can pump blood all around body )
• Structure of the vessels and function

  Arteries= thick walls to handle high pressureVeins= thin walls as low pressure (had valves to prevent back flow of blood)
• Why are two pumps (left and right) needed instead of one?

  -To maintain blood pressure around the whole body. -When blood passes through the narrow capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue around the whole body. -Therefore it is returned to the heart to increase the pressure.
• The cardiac cycle

  1. Atrial Systole2. Ventricular Systole3. Diastole
• Atrial Systole


  1. Atria contracts2. Pressure in Atria increases3. Semi-lunar valves in the vena cava and pulmonary vein close4. Tricuspid and bicuspid valves open5. Blood flows into ventricle

  
• Ventricular systole


  1. Ventricles contract2. Pressure inside the ventricles increase3. The tricuspid and bicuspid valves close4. Semi lunar valves in the aorta and the pulmonary arteries open 5. Blood flows out the arteries

  
• Diastole


  1. Pressure in the ventricles decrease2. Semi lunar valves in aorta and pulmonary arteries close3. All heart muscles relax4. Blood flows into the atria from the vena cava and pulmonary vein5. Pressure remains low in the ventricles so blood fills the ventricles

  
• Pressure changes during cardiac cycle

  A- atrioventricular valves closeB- semi lunar valves openC- semi lunar valves closeD- atrioventricular valves open

  
• Cardiac output and pulmonary ventilation

  Cardiac output = heart rate x stroke volumePulmonary Ventilation= tidal volume x breathing rate
• Ventricular volume


  1) atrioventricular valves close2) semi-lunar valves open3) semi-lunar valves close4) atrioventricular valves open

  
• Features of a mass transport system in animals

  -suitable transport medium-closed system in tubes or vessels-mechanism -valves to maintain direction -control flow to suit organism ( eg. Temp changes)-mass flow of water or gases
• Closed & open circulatory system


  open- the blood comes out of the veins and pours over the important organsclosed- the blood stays in the veins and just flows through the organs

  
• Single and double loop circulatory system


  -passes through the heart twice to have enough pressure to get round the whole body after becoming oxygenated at the lungs

  
• Artery structure related to function

  Thick muscle layer= muscle contracts and relaxes so arteries can be constricted and dilated in order to control the flow of bloodThick elastic layer= can stretch to hold high volumes of blood and recoil in order to maintain blood pressureThickness of overall wall= withstands pressure to prevent burstingNo valves= blood is at constant high pressure so cannot have back flow

  
• Vein structure related to function

  Thinner muscle layer= as they carry blood away from tissues so no constriction or dilation is neededThinner elastic layer= because the low pressure of blood will not cause them to burstThinner wall= as the pressure is too low for them to burst, also allows them to flatten easilyValves= at intervals throughout to prevent back flow of blood

  
• Capillary structure related to function

  walls consist mostly of endothelium layer, extremely thin= so diffusion occurs quicklynumerous and highly branched= large surface area for exchangenarrow diameter= permeate tissues so no cell is far away from a capillarynarrow lumen= red blood cells squeezed against wall so short diffusion pathwayspaces between lining=allows white blood cells to escape to deal with infections within tissues

  
• Contraction, constriction, relaxation and dilation

  Contraction of muscle -> constriction of blood vesselRelaxation of muscle-> dilation of blood vessel
• What does it mean that cardiac tissue is myogenic?

  -Contraction initiated within the muscle itself -Instead of due to nervous impulses
• Myogenic contraction mechanism


  1) The heart is myogenic -Sinoatrial node (SAN) in the right atrium produces an electrical impulse across both atria causing them to contract (cardiac tissue/atria is depolarised)2) Layer of non-conductive tissue prevents wave crossing ventricles3) Atrioventricular node picks up the impulse and takes the impulse to the bottom of ventricles by conductive tissue (bundle of His)4) Purkinje fibres spread the electrical impulse over the walls of the ventricles causing them to contract (cardiac tissue/ventricles is depolarised)
• Importance of delay at AV node

  1. So ventricles can fully fill with blood2. Before they contract
• Charge of cardiac tissue during diastole

  During diastole, the tissue is repolarised
• What is an electrocardiogram?

  A physiological measurement technique used to obser ve the electrical stimulation of the heart

  
• Waves

  P waves- atrial systolePR wave- delayPRQ complex- ventricular systoleT wave- diastole
• Graph of pressure, volume and ECG

  
• What is tissue fluid?


  -A fluid containing water and small soluble molecules -Through fenestrations in blood vessels -Similar to blood plasma but without plasma proteins -Contains glucose, amino acids etc
• How is tissue fluid formed?

  1. At the arteriole end, the hydrostatic pressure out is greater than the osmotic pressure in2. Therefore net movement is out, so water and small soluble molecules move out of the blood vessel to form tissue fluid3. At the venule end, the osmotic pressure in is greater than the hydrostatic pressure out4. Therefore net movement is in, so 90% of tissue fluid re-enters the blood vessel5. The excess 10% goes into the lymphatic system

  
• Plasma composition

  
• How does high blood pressure lead to accumulation of tissue fluid?

  1. High blood pressure= high hydrostatic pressure2. Increases outward pressure at ateriole end3. So more tissue fluid formed
• Lymphatic System


  Excess tissue fluid (10%) goes into tissue fluid, helps to get rid of body toxins

  
• Describe the structure of haemoglobin

  -Globular, -Water soluble-Consists of four polypeptide chains, each carrying a haem group (quaternary structure).
• Describe the role of haemoglobin

  -Present in red blood cells-Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues.
• 3 factors which affect oxygen- haemoglobin binding (affinity)


  1. Partial pressure of oxygen2. Partial pressure of carbon dioxide 3. Saturation of haemoglobin with oxygen
• How does partial pressure of oxygen affect oxygen-haemoglobin binding?

  -As partial pressure of oxygen increases, -The affinity of haemoglobin for oxygen also increases, -So oxygen binds tightly to haemoglobin. -When partial pressure is low, oxygen is released from haemoglobin.
• How does partial pressure of carbon dioxide affect oxygen-haemoglobin binding?

  -As partial pressure of carbon dioxide increases, -The conditions become carbonic acidic causing haemoglobin to change shape. -The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin. -This is known as the Bohr effect.

  
• How does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding?


  -It is hard for the first oxygen molecule to bind. -Once it does, it changes the shape to make it easier for the second and third molecules to bind, known as positive cooperativity. -It is then slightly harder for the fourth oxygen molecule to bind because there is a low chance of finding a binding site.
• Oxygen dissociation curve

  
• What shape is the oxygen dissociation curve?

  S-shaped (sigmoidal)
• What is co-operative binding?


  The binding of 1 oxygen molecule increases the affinity of oxygen for haemoglobin
• Left shift= At any given partial pressure, has more oxyhaemoglobin Right shift= At any given partial pressure, has less oxyhaemoglobin