Transport A2

• Basic idea of the heart

  - heart is a pump for both the PULMONARY (to the lungs) and SYSTEMIC (to rest of the body) circulatory systems

  
  

  - DOUBLE PUMPING WORKS SYNCHRONOUSLY TO KEEP OXYGENATED AND DEOXYGENATED BLOOD SEPARATE

  
  

  - CARDIAC MUSCLE - myogenic - it can initiate its own contraction; can contract and relax rhythmically even without being connected to the rest of the body
• The left side of the heart receives oxygenated blood from the lungs and then pumps this out into the systemic circulation which supplies all other parts of the body with oxygen and nutrients.
• The right side of the heart pumps blood to the lungs where it picks up oxygen and gets rid of carbon dioxide. This process is called pulmonary circulation.
• draw the structure of the heart

  Check

  
• when talking about the heart, what should you always talk about?

  - distance

  - resistance

  - pressure (FORCE/AREA)

  - force

  - thickness of chamber wall/muscle
• WHY DO ATRIA HAVE THIN MUSCLE WALLS?

  pump blood a shorter distance (to ventricles) than ventricles, so blood can be pumped at a lower pressure due to less resistance and less force required
• WHY IS THE WALLS OF VENTRICLES THICKER THAN THE WALLS OF ATRIA?

  - ventricles pump blood a longer/further distance (tissues/lungs) than blood leaving the atria

  - blood in ventricles needs to be pumped at a higher pressure with MORE force

  - against more pressure (more resistance)
• why is the muscle wall of the left ventricle 3x thicker than the right?

  - more/thicker muscle provides more force to create higher pressure

  • blood is being pumped/pushed against greater friction/resistance and a longer distance/further around the body (TISSUES)
• Function of coronary arteries

  supply oxygenated blood to cardiac muscle/heart muscle
• why must the heart have a constant supply of oxygen?

  - heart is a working organ that requires ATP

  - need a constant supply of oxygen as heart muscle cells can only respire fatty acids aerobically

  • WITHOUT OXYGEN, HEART MUSCLE CELLS CAN'T AEROBICALLY RESPIRE FATTY ACIDS AND PRODUCE ATP, SO HEART MUSCLE CAN'T PUMP
• HEART VALVES

  ensure blood only flows in one direction in the heart

  • TENDINOUS CHORDS - ensure valves only open in one direction and prevent inversion of valves
  • open and close due to pressure differences on either side of the valve
• TENDINOUS CHORDS

  ensure valves are only open in ONE direction

  prevent inversion of valves
• ATRIO-VENTRICULAR VALVE

  prevents backflow of blood into ATRIA when ventricle wall muscles contract
• SEMI-LUNAR VALVE

  prevents backflow of blood into ventricles when ventricle wall muscles RELAX
• what is SYSTOLE

  period of CONTRACTION of cardiac muscle
• what is DIASTOLE

  period of RELAXATION of cardiac muscle
• What type of muscle is the heart muscle? (two things)

  - CARDIAC MUSCLE

  • MYOGENIC

  can initiate its own contraction - can contract and relax rhythmically without being connected to the rest of the body
• what must the contraction of ventricle and atrial muscle be?

  contraction of atrial and ventricular muscle must be SYNCHRONISED (two ventricle muscles contract at the same time, two atrial muscles contract at the same time) otherwise it would pump inefficiently (FIBRILLATION)
• why must atrial muscle contract first AND finish contracting before ventricle muscle contracts?


  atrial muscle must contract before the ventricle muscle contracts

  • IMPORTANT

  the muscle of atria must finish contraction so that blood flows into the ventricles BEFORE the ventricle muscles contract
• basic idea of CARDIAC CYCLE

  - diastole

  - atrial systole

  - ventricular systole
• CARDIAC CYCLE - Diastole

  all heart muscle relaxed

  • semi-lunar valve shut
  • overall, low pressure in the heart, but pressure slightly higher in atria due to having filled up with blood from vena cava
  • ATRIOVENTRICULAR VALVE OPENS due to atria having filled up with blood making it have slightly higher pressure than ventricles
  • SOME BLOOD MAY FLOW INTO VENTRICLES AS A RESULT OF GRAVITY (NOT FORCED)
• CARDIAC CYCLE - Atrial Systole

  atrial muscle contracts

  • pressure in atria now higher than pressure in ventricles
  • ATRIOVENTRICULAR VALVE remains OPEN
  • semi-lunar valve remains shut
  • BLOOD IS FORCED INTO VENTRICLES BELOW
• CARDIAC CYCLE - Ventricular systole

  - atrial muscles relax and ventricular muscles contract

  • pressure in ventricles now higher than pressure in atria
  • ATRIOVENTRICULAR VALVE SHUTS
  • pressure in ventricles also higher than pressure in arteries
  • SEMI-LUNAR VALVE OPENS
• draw cardiac cycle

  check

  
• Tips for the graph

  - blood moves from a higher to lower pressure

  - when the muscle of a chamber wall contracts, pressure in that chamber increases

  - WHEN LINES ON THE CARDIAC CYCLE CROSS OVER, SOMETHING HAS HAPPENED TO THE VALVE

  • DIVERGE: valve closed
  • PARALLEL: valve opens
• what happens at D (end of graph)

  DIASTOLE: all heart muscle relaxed

  • AV valves already closed before D - atria fills up with blood from vena cava causing pressure to slightly increase
  • pressure in ventricles decrease due to ventricle muscle relaxing
  • PRESSURE IN ATRIA HIGHER THAN PRESSURE IN VENTRICLES
  • AV valve opens
• what happens at D-A? (beginning of graph before A)

  ATRIAL SYSTOLE: atrial muscle contracts

  • pressure in atria higher than pressure in ventricles
  • blood is forced down to ventricles below (due to atrial muscle contraction) through already open AV valve
• what happens at A?

  Ventricle Systole - ventricle muscle contracts

  • pressure in ventricles higher than pressure in atria
  • PRESSURE PUSHES AV VALVE SHUT
  • Tendinous chords prevent inversion of valves
• what happens at B?

  Ventricular systole continues

  • pressure in ventricles increases further so that it is higher than pressure in aorta
  • SEMI-LUNAR VALVES OPEN AT B
• what happens at C?

  DIASTOLE - all heart muscle relaxes (including ventricle muscle)

  • pressure in ventricles start to decrease
  • pressure in aorta now higher than pressure in ventricles
  • THIS CAUSES SEMI-LUNAR VALVE TO CLOSE AT C
• what happens at D-C?

  DIASTOLE CONTINUES - all heart muscle still relaxed

  • AV valve already closed before D, and fills up wit blood from vena cava causing pressure to slightly increase
  • pressure in ventricles decrease due to ventricle muscle relaxing
  • pressure in atria now higher than pressure in ventricles so AV VALVE OPENS
  • some blood (via gravity NOT FORCE) flows into the ventricles below
• What happens at A

  1. Ventricular SYSTOLE

  2. Pressure in Ventricles higher than pressure in atria

  3. Pressure pushes AV valve shut (prevent backflow of blood into atria when Ventricular muscle contracts)

  4. Tendinous chords preventing inversion of valve
• What happens at B

  1. VENTRICLE SYSTOLE

  2. Ventricular continue to contract

  3. Pressure further increases

  4. Pressure is higher in Ventricular than aorta

  5. SEMI LUNAR VALVE OPEN

  6. Blood pushed up and out of heart
• What happens at C

  1. DIASTOLE

  2. All heart muscle relaxes

  3. Pressure in Ventricle decreases

  4. Pressure in Ventricle is lower than the aorta

  5. SEMI LUNAR VALVE CLOSE
• What happens at D

  1. DIASTOLE

  2. Pressure in atria higher than pressure in Ventricle

  3. Atria fill up with blood from vena cava

  4. Pressure slightly increases

  5. AV VALVES OPEN

  6. Blood flows from atria to Ventricle via GRAVITY not FORCE
• Heart sounds

  sounds of heart beat made from valves closing

  • LUB DUB

  FIRST SOUND - AV valve closing and ventricle muscle contracting

  SECOND SOUND - AV valve opening and ventricle muscle relaxing
• what is heart rate and what is it measured in?

  Heart rate is the number of times a person's heart beats per minute.

  Measured in beats per minute (bpm)/(beats min^-1)

  • WAVE OF EXCITATION INITIATED APPROXIMATELY 55-80 TIMES A MINUTES, SO A PERSON'S HEART BEATS APPROXIMATELY 55-80 TIMES A MINUTE
• how to calculate heart rate?

  60/heart rate x length of one cycle
• STROKE VOLUME

  volume of blood pumped out by the left ventricle each time the heart beats

  
  

  dm^3 beat^-1
• CARDIAC OUTPUT

  volume of blood pumped out by the left ventricles in one minute

  
  

  dm^3 min^-1