CVS

• Pulmonary circuit


  Carries blood to the lungs to pick up oxygen
• Systemic circuit

  • carries blood from heart to the rest of the body
  • exception of the mesenteric artery which supplies blood from the small intestines to the hepatic portal vein for nutrients to be metabolised in the liver
  • the blood then leaves the liver via the hepatic vein
• the mammalian heart

  • the heart is a muscular pump that creates pressure
  • distributes oxygenated blood around the body
  • made up of cardiac muscles - myogenic
• atria

  • storage unit for collecting blood from vasculature
  • thins walls to pump blood to inferior ventricles
  • blood passes through valve separating atria and ventricle once pressure threshold is met
  • left atria receives oxygenated blood from lungs via pulmonary vein
  • right atria receive deoxygenated blood from body via vena cava
• Ventricles

  • Discharging members of the heart
  • Thicker walls to pump blood to external sites
  • Right ventricle pumps to lungs via pulmonary artery
  • Left ventricles pumps to the rest of the body and coronary circulation via aorta
• valves

  • Prevent backflow of blood into previous chambers
  • Atrioventricular valves
  • Semi lunar valves
• atrioventricular valves

  • separates atria and ventricle
  • tricuspid which separates RA and RV
  • bicuspid which separates LA and LV
• Semi lunar valves

  • separates expulsion vasculature and ventricles
  • pulmonary which separates pulmonary artery/trunk and RV
  • aortic which separates aorta and LV
• Blood composition

  • Plasma
  • Thrombocytes
  • Erythrocytes
  • Leukocytes
  • Separated using centrifuge
• plasma

  • straw coloured fluid that contains all the cells within the blood
  • contains plasma proteins, hormones and small molecules and ions
• thrombocytes

  • platelets
  • small disc-shaped erythrocyte fragments that don’t have a nuclei
  • present in large quantities as they’re important for clotting
• erythrocytes

  • differentiated cells without a nucleus or majority of organelles
  • contain haemoglobin which is the protein used for oxygen and carbon dioxide transportation
  • bi-concave shaped
• leukocytes

  • white blood cells involved in immune response
  • neutrophils are involved during the acute inflammatory response to a bacterial infection
  • basophils are involved in the inflammatory and anaphylactic reactions
  • eosinophils are involved in parasitic infections
• cardiac function

  • nutrients required for cell growth/repair
  • oxygen for cellular respiration
  • carbon dioxide for elimination
  • hormones transported to target cells
  • erythrocytes for oxygen transportation
  • leukocytes as part of the immune response
• Regulation of heart rate 1

  • cardiac muscle is the only muscle type that doesn’t require nerve impulses to contract - myogenic
  • Heart muscle contraction is initiated in a specialised patch of cardiac muscle within the right atrium - sinoatrial node (SAN)
  • It is the SAN that maintains regularity in the heartbeat and is known as the pacemaker
• regulation of heart rate 2

  • the SAN generates electrical impulses that spread over the RA and LA surface causing them to depolarise and contract (atrial systole)
  • this electrical impulse cannot pass directly to the ventricles due to a collagen layer between the atria and ventricles that act as an electrical insulator
• regulation of heart rate 3

  • the electrical impulse is instead passed to the atrioventricular node (AVN)
  • after a brief pause, the AVN generates more electrical impulses that are passed along the Bundle Of His
  • the depolarisation of the Bundle of His passes down the septum of the heart and passes into the base of the two ventricles causing ventricular systole
• regulation of heart rate 4

  • the heart then relaxes fully, known as diastole
  • the brief pause between atrial and ventricular systole allows for complete emptying of the atria into the ventricles before contraction
  • contraction from the base of the ventricles upwards allows for complete emptying of the ventricles into the receiving artery
• Heart rate during exercise

  • Heart rate increases during exercise to allow more oxygen to enter the body for aerobic respiration
  • This is regulated by the cardio-regulatory centre found within the medulla
  • This aorta and carotid arteries contain chemoreceptors for detecting pH levels of the blood and pressure receptors for blood pressure
  • The cardio-regulatory centre then responds to these receptor inputs and sends nerve impulses to the SAN to alter the heart rate
• ECGs

  • electrocardiogram can be used to track the electrical impulses within the heart to monitor cardiac activity
  • electrodes are placed onto the skin to detect electrical impulses and produce the ECG
  • produces distinct waves known as PQRST waves
• PQRST waves

  • P wave is caused by atrial depolarisation initiated by the SAN
  • the QRS complex is caused by the ventricular polarisation initiated by the AVN and transmitted along the Bundle of His
  • the T wave is caused by ventricular repolarisation
• pressure changes and blood pressure 1

  • during diastole, the atrial pressure is higher than the ventricular pressure due to the filling of blood
  • in atrial systole, the atrium contracts, emptying its contents into the ventricles before contraction below it
• pressure changes and blood pressure 2

  • ventricular systole causes the pressure of the ventricles to exceed the pressure of the atria and the atrioventricular valves are forced shut
  • the aortic pressure is quickly exceeded forcing the semi-lunar valves open and expelling the blood into the receiving arteries
• Pressure changes and blood pressure 3

  • The ventricles and atria relax after emptying and the aortic pressure becomes higher than the ventricles causing the SL valves to snap shut again
  • Ventricular pressure continue to drop until it becomes lower than the atrial pressure causing the AV valves to open again, refilling the ventricles