3.2.8-3.2.12

• What are electrocardiograms?


  used to monitor and investigate activity if the heart. Electrodes that are capable of detecting electric signals are placed on the skin. The electrodes produce an electrocardiogram (ECG)
• ECG of healthy heart -3.2.10

  
• What is point P on the graph? 3.2.10


  P wave - caused by the depolarisation of the atria which results in atrial contraction (systole)

  
• What is the QRS complex?


  Caused by depolarisation of ventricles which results in ventricular contraction (systole)

  
• Why is the QRS complex the largest wave


  This is the largest wave because the ventricles have the largest muscle mass.
• What is point T on the graph?

  T wave - caused by the

  repolarisation of the ventricles which results in ventricular relaxation (diastole)

  
• What is point U on the graph?

  U wave - scientists are still uncertain of the cause of the U wave some think it's caused by the repolasrisation of the Purkyne fibres

  
• What is tachycardia? -3.2.10


  When the heart beat is too fast it's tachycardia. An individual with a resting heart rate over 100 bpm is said to have tachycardia

  
• What is bradycardia ? -3.2.10


  When the heart beats too slow. An individual with a resting heart rate below 60 bpm is said to have bradycardia

  
• What is fibrillation


  An irregular heartbeat will disrupt the rhythm , a severe case can be dangerous and even fatal

  
• What is an ectopic heart beat? -3.2.10


  Caused by an early heartbeat followed by a phase. Common in the population as usually requires no treatment unless very severe

  
• How is tissue fluid formed?

  -high hydrostatic pressure at arterial end

  -pushes water/fluid/soluble molecules out of the blood plasma into the tissue

  -proteins / large molecules remain in blood plasma

  -this lower water potential so creates oncotic pressure

  -at Venus end of capillary water moves back into capillary by osmosis (from high to low)

  -lymph system collects any excess tissue fluid which returns to blood via lymphatic system
• What happens at Venus end


  -water potential not as low in capillary /water potential gradient is reduced/ oncotic pressure reduced

  -less water removed into tissue from capillary at arterial end

  OR

  -less water reabsorbed into capillary at veiled end (water remains in tissues)

  -by osmosis
• What is the cardiac cycle controlled by


  Small patch of myogenic muscle in the walls of the right ventricle (pacemaker cells)
• What are the 2 heart nodes?

  sinoatrial node (SA) and atrioventricular node (AV)
• Where are electrical impulses sent from


  Sent from the SAN to the AVN coordinating heart muscle contractions
• What is the bundle of His


  atrioventricular bundle of tissue that is very conductive
• atrial systole and nodes


  The Sino-atrial node in the upper left wall of

  the right atrium sends a wave a electrical

  activity (depolarisation) throughout the atria

  • This causes the walls of the atria to

  contract almost simultaneously

  • Blood is forced through the bicuspid (mitral)

  and tricuspid valves into the ventricles
• Ventricular systole and nodes


  The Atrio-ventricular Node, picks up the

  wave from the SAN and sends its own

  wave of depolarisation down the bundle

  of hiss, then into the purkyne tissues

  • This causes the ventricular walls to

  contract

  • This forces blood out of the aorta and

  the pulmonary (semi-lunar) valves
• What is an ECG


  series of sensors attached to the skin that test the hearts rhythm and electrical activity
• What is sinus rhythm


  normal heartbeat triggered by the SA node
• Healthy ECG - sinus rhythm

  
• What is atrial fibrillation


  The uncoordinated contraction of the atria
• What are artificial pacemakers


  Electrical devices used to correct irregularities in the heart rate
• What do pacemakers do?


  Monitor the hearts electrical activity and stimulate the ventricles or atria to contract when necessary. Impulses are transmitted down electrodes implanted in the muscular walls.
• Where do heart sounds come from

  Closing of valves

  QRS is the strongest (after atrial systole) then after ventricular systole
• All types of heartbeat on ECG

  
• Order of transmission of electrical activity through the heart P1

  1) The sino- atrial node (SAN) initiates the action potential

  2) the wave of excitation spreads rapidly across the walls of the right and left atrium

  3) the atrial walls contract, increasing the pressure and forcing the atrioventricular valves to open

  4)blood is pumped into the right and left ventricles in atrial systole

  5)the wave passes to the AVN where there is a short delay to allow atrial systole to complete

  6) the wave is conducted down the intraventricular septum on the right and left branches of the Bundle of His to the apex of the heart

  7)the wave is conducted on the purkyne fibres which extend up the walls of the ventricles

  8) the right and left ventricular walls contract, increasing pressure in these chambers which causes the AV valves to close and the semi-lunar valves to open
• Order of transmission of electrical activity through the heart P2


  9)blood is pumped into the pulmonary circulation via the pulmonary artery and into the systemic circulation via the aorta during ventricular systole

  10) all 4 chambers relax during diastole and an elastic recoil causes an increase in volume to allow blood to flow in from the veins
• When do you need a pacemaker

  possibly if SA node fails, always if AV node fails
• What can you see in an ECG of someone with bradycardia


  Fewer number if heart beats than observed in the same time period at sinus rhythm (less peaks and troughs)
• What can you see in an ECG of someone with atrial fibrillation?


  No clear P waves showing that the atria are beating more frequently than the ventricles
• What is atrial fibrillation


  Uncoordinated contraction of the atria
• What can you see in an ECG of someone with tachycardia


  Greater number of heartbeats than observed sin the same time period as the sinus rhythm
• What is haemoglobin? -3.2.11


  Protein that carries oxygen in red blood cells
• What is the structure of haemoglobin? -3.2.11


  Quaternary structure (extra level of polypeptides) made of 4 polypeptides that are linked together to form a spherical molecule
• What is each polypeptide associated with?


  haem group with FE2+ Ion (each FE2+ can combine with a single molecule of O2 so each haemoglobin can carry 4O2 molecules)
• Haemoglobin equation (reversible reaction) -3.2.11


  Hb + 4O2 —> HbO8

  <—
• What is loading / associating? -3.2.11


  Process which haemoglobin binds to O2 in the lungs
• What is unloading/dissociating?


  The process by which haemoglobin releases its oxygen in the tissues