Transport in animals- Heart

Question 1

Label a diagram and a photograph of the external structure of the heart.

Answer 1

Find an online labellling website

Practice drawing simplified strucutres

Question 2

Label a diagram and a photograph of the internal structure of the heart.

Answer 2

https://www.purposegames.com/game/label-the-heart-quiz

Pracitce

Question 3

Explain why the heart is called a “double pump”.

Answer 3

1. It consists of two muscular pumps
2. The right side pumps deoxygenated blood to the lungs
3. Left side pumps oxygenated blood to the rest of the body

Question 4

Describe the structure of the heart.

Answer 4

1. The heart is made of cardiac muscle, which contracts and relaxes in a regular rhythm, it doesn’t get fatigued like skeletal muscle
2. The coronary arteries supply the cardiac muscle with the oxygenated blood it needs to keep contracting and relaxing all the time.
3. The heart is surrounded by inelastic pericardial membranes which help prevent the heart form over-distending with blood

Question 5

Draw a diagram showing the flow of blood from the blood through the heart (include the names of the blood vessels adjoining the heart as well as whether the blood is oxygenated or deoxygenated and where the blood has come form or is going to).

Answer 5

1. Deoxygenated blood enters the right atrium of the heart from the upper body and head in the superior vena cava and from lower body in the inferior vena cava
2. The blood passes through the tricuspid valve into the right ventricle
3. This then contracts forcing the deoxygenated blood though the semilunar valves into the pulmonary artery, which takes it to the lungs
4. Then oxygenated blood form the lungs flows through the pulmonary vein into the left atrium
5. The blood passes through the bicuspid valves into the left ventricle.
6. The left ventricle then contracts forcing the oxygenated blood through the semilunar valves into the aorta, it then travels round the whole body.

Question 6

Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.

Answer 6

1. The lungs are relatively close to the heart, and the lungs are much smaller than the rest of the body
2. The right side has to pump blood a relatively shor distance and only has to overcome the resistance of the pulmonary circulation
3. The left side has to produce sufficient force to overcome the resistance of the aorta and arterial systems of the whole body and move blood under pressure to the whole body

Question 7

Explain why the walls of the ventricles are thicker than the walls of the atria.

Answer 7

1. Ventricles have to pump blood out of the heart

2. Atria only need to move blood to the ventricles

Question 8

Describe the function of the valves and tendinous cords (valve cords/tendons) in the heart.

Answer 8

1. The atrioventricular valves link the atria to the ventricles and the semi-lunar valves line the ventricles to the pulmonary artery and aorta
2. The valves only open one way
3. If there is a higher pressure behind a valve it is forced to open, if the force is higher in front, it is forced to shut
4. Means the flow of blood is unidirectional and prevent backflow
5. The tendinous cords make sure the valves are not turned inside out by the pressure exerted when the ventricle contracts

Question 9

State the location and function of the septum in the heart.

Answer 9

1. The septum is the inner dividing wall of the heart.

2. It prevents the mixing of oxygenated and de-oxygenated blood

Question 10

Name the stages in the cardiac cycle and outline what is happening at each stage.

Answer 10

1. Diastole- atria and then ventricles fill with blood
2. Atrial systole- atria contract
3. Ventricular systole- ventricles contract forcing blood out of heart.

Question 11

Describe what happens during diastole

Answer 11

1. The heart relaxes
2. Higher pressure in the pulmonary artery and aorta closes the SL valves to prevent backflow to ventricles
3. Blood moves into atria from veins, this increases the pressure of the atria
4. This means the ventricle pressure falls below that of the atria so the AV valves open.
5. Some blood moves passively into the ventricle

Question 12

Describe what happens during atrial systole

Answer 12

1. The ventricles are relaxed
2. The atria contract decreasing the volume inside the chambers
3. This pushes blood into the ventricles through the AV valves
4. Causes slight increase in ventricular pressure and chamber volume as the ventricles receive the ejected blood from the contracting atria.

Question 13

Describe what happens during ventricular systole

Answer 13

1. The atria relax
2. The ventricles contract- decreasing their volume which increases their pressure
3. The pressure becomes higher in the ventricles than the atria which forces the AV valves shut to prevent backflow to the atria.
4. The pressure in the ventricles is also higher than in the aorta and pulmonary artery, which forces open the SL valves and blood is forced into the arteries.

Question 14

Interpret a graph of aortic pressure

Answer 14

1. Rises when ventricles contract as blood is forced into aorta.
2. Then it gradually falls but never below 12kPa - because of elasticity of walls creates a recoil action- temporary pressure

Question 15

Interpret a graph of atrial pressure

Answer 15

1. Always relatively low
2. Highest when contracting but drops when left AV valve closes and walls relax.
3. Then there is a build up of pressure as they fill with blood.
4. Until a slight drop when AV valve opens

Question 16

Interpret a graph of ventricular pressure

Answer 16

1. Low at first but gradually increases as the ventricles fill with blood as the atria contract.
2. The pressure rises dramatically when the AV valve close as the ventricle contracts
3. As the pressure goes above the aortic pressure blood is forced into the aorta and the semi lunar valves open
4. Pressure falls as the ventricles empty and walls relax
5. Semi-lunar valves shut when the pressure of the ventricle becomes lower than the aorta

Question 17

Interpret a graph of ventricular volume

Answer 17

1. Rises as the atria contract and the ventricles fill with blood.
2. Drops suddenly as blood is forced out into aorta hen semi-lunar valves open
3. Volume increases as ventricles fill with blood again

Question 18

Define the term myogenic

Answer 18

Muscle which has it’s own intrinsic rhythm

Question 19

Define the term sino-atrial node (SAN)

Answer 19

Region of the heart that initiates a wave of excitation that triggers the contraction of the heart

Question 20

Define the term atrio-ventricular node (AVN)

Answer 20

Stimulates the ventricles to contract after imposing a slight delay to ensure atrial contraction is complete

Question 21

Define the term bundle of His

Answer 21

Conducting tissue composed of purkyne fibres that passes through the septum of the heart

Question 22

Define the term purkyne fibres

Answer 22

Tissue that conducts the wave of excitation to the apex of the heart

Question 23

Write a sequence of bullet points to describe the sequence of electrical events of the heart beat.

Answer 23

1. A wave of electrical excitation begins in the SAN, causing the atria to contract and so initiating the heartbeat.
2. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles
3. The electrical activity from the SAN is picked up by the AVN .
4. The AVN imposes a slight delay- allowing the atria to stop contracting before the ventricles start- before stimulating the bundle of His (bundle of conducting tissues made of purkyne fibres) which penetrate through the septum between the ventricles
5. The bundle of His splits into two branches and conducts waves of excitation to the apex (bottom) of the heart
6. At the apex the purkyne fibres spread out though the walls of the ventricles on both sides.
7. The wave of excitation triggers the contraction of the ventricles starting at the apex
8. Contraction at the apex allows more efficient emptying of the ventricles

Question 24

Define the term electrocardiogram

Answer 24

A technique for measuring tiny changes in the electrical conductivity of the skin that result from the electrical activity of the heart. This produces a trace which can be used to analyse the health of the heart.

Question 25

Define the term tachycardia

Answer 25

A fast heart rhythm of over 100 beats per minute at rest

Question 26

Define the term bradycardia

Answer 26

A slow heart rhythm of below 60 beats per minute

Question 27

Define the term ectopic hearbeat

Answer 27

Extra heartbeats that are out of the normal rhythm

Question 28

Define the term atrial fibrilation

Answer 28

An abnormal rhythm of the heart when the atria beat very fast and incompletely

Question 29

Define the term arrhythmia

Answer 29

An abnormal rhythm of the heart

Question 30

Outline how an ECG is recorded.

Answer 30

1. the heart muscles depolarises- loses electrical charge when it contracts and repolarises when it relaxes
2. An electrocardiograph records these changes in electrical charge using electrodes placed on the chest

Question 31

Draw and label an ECG with the names of the sections.

Answer 31

1. Look at a graph
2. The P wave- small one at start- is caused by contraction of the atria
3. QRS complex- main peak of heartbeat with the dips either sided- is caused by contraction of the ventricles
4. T wave- smaller wave at the end- due to relaxation of the ventricles
5. Height of the wave- indicated how much electrical charge is passing through the heart- bigger means stronger contraction

Question 32

Explain how to calculate heart rate from an ECG.

Answer 32

1. Heart rate (bpm) = 60 / time taken for one heart beat (s)

2. Work out time between one wave and the next

Question 33

Explain how to identify normal heart action, bradycardia, tachycardia, an ectopic heartbeat and atrial fibrillation from an ECG.

Answer 33

1. Tachycardia- waves are closer together
2. Bradycardia- waves are further away from each other
3. Ectopic heartbeat- extra heartbeats out of the normal rhythm- random wave
4. Atrial fibrillation- A lot of mini waves

Question 34

Describe the structure of haemoglobin.

Answer 34

1. Large, globular, conjugated protein made up of four polypeptide chains
2. Each chain contains an iron-containing haem prosthetic group

Question 35

Write a reversible equation to show how haemoglobin carries oxygen.

Answer 35

Hb + 4O2 ⇌ Hb(O2)4

Haemoglobin + oxygen ⇌ oxyhaemoglobin

Question 36

Describe the route oxygen takes from the air in the alveoli to haemoglobin and explain how the concentration gradient is maintained.

Answer 36

1. When erythrocytes enter the capillaries in the lungs oxygen levels in the cells are relatively low- makes steep concentration gradient between the inside of the erythrocytes and the air in the alveoli
2. Oxygen moves into the erythrocyte and binds with the haemoglobin
3. The arrangement of the haemoglobin molecule means once one oxygen molecule binds to a haem group the molecule changes shape, making it easier for the next oxygen molecules to bind to it- positive cooperativity
4. Because oxygen is bound to the haemoglobin, the free oxygen concentration in the erythrocyte stays low- steep diffusion gradient is maintained until all of the haemoglobin is saturated with oxygen.

Question 37

Define the term “partial pressure” and compare the partial pressure of oxygen in the blood in capillaries in the lungs with blood in the capillaries of respiring tissues.

Answer 37

1. Partial pressure of oxygen pO2 is a measure of oxygen concentration
2. The greater the concentration of dissolved oxygen in cells, the higher the partial pressure
3. In the alveoli there is a high pO2 in the respiring tissue there is a low pO2

Question 38

Draw and annotate an oxygen dissociation curve showing the percentage saturation of haemoglobin when exposed to a range of oxygen partial pressures.

Answer 38

1. a shallow S shape- starts with gradual incline, then is very steep, then begins to plateau
2. Where pO2 is low haemoglobin has a low affinity for oxygen so has a low saturation of oxygen
3. Where pO2 is high, haemoglobin has a high affinity for oxygen, so it has a high saturation of oxygen- maximum is 100% where every haemoglobin molecule is carrying 4 molecules of oxygen.
4. It is 2 shaped because saturation of haemoglobin can affect affinity- when haemoglobin combines with the first O2 molecule, its shape alters making it easier for other molecules to join. As it starts to get saturated it gets harder for more oxygen molecules to combine.

Question 39

Define the term affinity for oxygen

Answer 39

The tendency a molecule has to bind with oxygen

Question 40

Define dissociation

Answer 40

When oxygen leaves haemoglobin it is referred to as dissociation

Question 41

Define the term “Bohr effect” and explain its value in the transport of oxygen.

Answer 41

The effect of carbon dioxide concentration on the uptake and release of oxygen by heamoglobin.

1. The partial pressure of CO2 also affects oxygen unloading.
2. Heamoglobin gives up its oxygen more readily at a higher pCO2 .- gets more oxygen to cells during activity
3. The dissociation curves shifts to the right but is still the same shape

Question 42

Describe how haemoglobin’s affinity for oxygen varies

Answer 42

1. Affinity for oxygen means the tendency a molecule has to bind with oxygen.
2. Haemoglobin’s affinity for oxygen varies depending on the conditions it’s in
3. Has high affinity in alveoli- high pO2 and low affinity in respiring tissue- low pO2

Question 43

Draw and annotate oxygen dissociation curves to show the difference between fetal and adult human haemoglobin.

Answer 43

1. Fetal haemoglobin has a higer affinity for oxygen than adult’s.
2. Important has fetus gets oxygen from its’ mothers blood across the placenta
3. By the time mother’s blood reaches the placenta, its oxygen saturation has decreased beacause some has been used up by the mother’s body.
4. The placenta has a low pO2, so adult haemoglobin will unload its oxygen.
5. The fetus haemoglobin has to have a higher affinity than adult haemoglobin- takes up oxygen in lower pO2 than adult haemoglobin.
6. Fetal haemoglobin graph is to the left of the adult curve.

Question 44

List 3 methods for transporting carbon dioxide in the blood.

Answer 44

1. Small amount is dissolved in plasma
2. medium amount is combined with amino groups in the polypeptide chains of haemoglobin to form carbaminohaemoglobin
3. Large amount is converted into carbonate ions in the cytoplasm of the red blood cells

Question 45

Write a reversible set of equations to show the production of hydrogen carbonate ions.

Answer 45

CO2 ⇌ H2CO3 ⇌ H+ + HCO3-

Question 46

Name, and state the location of, the enzyme that catalyses the production of carbonic acid.

Answer 46

Carbonic anhydrase in the cytoplasm of the red blood cell.

Question 47

Describe the fate of the hydrogen ions produced when carbonic acid dissociates into hydrogen ions and hydrogen carbonate ions, and describe the two positive consequences of this outcome.

Answer 47

1. Cause oxyhaemoglobin to unload so that the haemoglobin can take up H+ ions.
2. Forms haemoglobinic acid
3. Stops the H+ ions from increasing the cell’s acidity

Question 48

Describe the fate of the hydrogen carbonate ions produced when carbonic acid dissociates into hydrogen ions and hydrogen carbonate ions, describe how this is linked to the “chloride shift” and explain its importance.

Answer 48

1. The HCO3- ions diffuse out of the red blood cells and are transported in the blood plasma.
2. To compensate for the loss of HCO3- ions chloride ions diffuse into the red blood cells- chloride shift and it prevents any change in pH that could affect the cells.

Question 49

Describe importance in converting the CO2 to HCO3-

Answer 49

1. It maintains a steep concentration gradient for carbon dioxide to diffuse from the respiring tissues into the erythrocytes.
2. When blood reaches the lung tissue where there is a relatively low level of CO2 the reverse reaction takes place- producing CO2 and water
3. Hydrogen carbonate ions diffuse into the erythrocytes and react with the hydrogen ions to form more carbonic acid.
4. This is broken down by carbonic anhydrase releasing free CO2 which diffuses into the lungs.