EXCHANGE AND TRANSPORT

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How does the wave of excitation during the cardiac cycle result in the ventricles only contracting after they have filled with blood?
The atrioventricular node delays the impulse whilst the ventricles fill with blood, the ventricles then contract due to the impulse transmission through the purkyne fibres.
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How does the wave of excitation during the cardiac cycle result in the contraction of the ventricles starting at the apex of the heart?
The wave of excitation is transmitted through the 'Bundles of His', down the Atrio-ventricular node into the Purkyne Fibres which infiltrate the ventricular walls and cause the ventricles to contract.
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Why does ventricular systole cause a decrease in blood volume in the left ventricle?
The ventricles contract causing a higher pressure in the LV than the aorta; this pressure forces the semi lunar valves open and blood is forced out and so the volume of blood in the LV decreases.
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Describe the pressure story of the Aorta -->>Vena Cava
The pressure is highest in the aorta, the pressure then decreases as the blood is pumped further away from the heart into the capillaries, the pressure is lowest in the capillary at the venule end, and the overall bp is lowest in the Vena Cava
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Describe how tissue fluid is reabsorbed into blood capillaries.
There is a more negative W.P in the capillaries due to plasma proteins in the blood, therefore tissue fluid moves back into the capillaries by osmosis down the W.P gradient.
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State and explain 2 differences between the tissue fluid and the blood.
The blood has more plasma proteins as they are too large to diffuse into the tissue fluid. The blood has erythrocytes leucocytes and platelets- the tissue fluid has some phagocytic white blood cells.
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What is the role of cartilage?
Supports the trachea and bronchi to hold them open. Prevents collapse when air pressure is low during inhalation. Cartilage is flexible and so allows the oesophagus to expand during swallowing and the neck to move without constricting airways.
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What is the role of smooth muscle?
Can contract and constrict airways to make narrower lumen.
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What is the role of elastic fibres?
When smooth muscle relaxes - elastic fibres recoil to their original size and shape - this helps dilate the airway.
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What do goblet cells and glandular tissue do?
Secrete mucus which traps harmful particles from the air to reduce infection.
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Where are goblet cells situated?
Under the epithelium.
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What is the role of ciliated epithelium?
Contains ciliated cells, have cilia which move in a synchronised pattern to waft mucus up the airway to the back of the throat where it can be swallowed and bacteria can be killed by the acidity in the stomach.
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What is tidal volume?
The volume of air moved in and out of the lungs with each breath when you are at rest. It is approx 0.5dm3 and provides the body with enough oxygen for its resting needs whilst removing sufficient carbon dioxide to maintain a safe level.
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What is Inspiratory reserve volume?
How much more air can be inspired over and above the normal tidal volume when you take in a big breath.
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What is vital capacity?
The largest volume of air that can be moved into and out of the lungs in any one breath. It is approx 5dm3 but varies between men and women.
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Suggest how a spirometer trace from a trained athlete would differ from
Larger tidal volume and more breaths per minute.
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What factors affect vital capacity?
Person's size age and gender
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Outline atrial systole.
Ventricles relax - lower pressure in the ventricles than atria above - atria contract and force blood through the atrioventricular valves - closes valves in vena cava and pulmonary vein.
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Outline ventricular systole.
Ventricles contract - raises ventricular pressure - blood forced out the semi-lunar valves due to high BP in the ventricles Blood pushed out of ventricles and into Aorta.
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Why the must the cardiac cycle be controlled?
The myogenic properties of cardiac muscle means that atrial and ventricular muscle have different frequencies, this could cause the chambers to beat out of sync which causes fibrillation, therefore we need a control mechanism.
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What is the sinoatrial node?
The heart's pacemaker. It is a small patch of tissue that sends out waves of electrical excitation at regular intervals to initiate contractions.
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How is tissue fluid formed?
At the aterial end of a capillary there is a strong hydrostatic pressure which pushes blood fluid out of capillary wall - this fluid consists of plasma with dissolved nutrients and oxygen.
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What is the Bohr Shift?
The Bohr shift refers to a change in the shape of the oxyhaemoglobin curve when carbon dioxide is present - this causes the oxyhaemoglobin to release oxygen more readily.
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What is the difference between a foetal and maternal oxygen dissociation curve and why?
The foetal dissociation curve must be above (steeper) than the maternal dissociation curve as the foetus has a higher affinity for oxygen.
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Explain what causes the blood hydrostatic pressure to decrease from one end of the capillary to the other.
Tissue fluid is lost out of the capillary - resistance of capillary walls
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Describe how Carbon Dioxide is formed in bicarbonate ions.
Carbon dioxide diffuses in erythrocyte - carbon dioxide binds with H2O using a carbonic anhydrase enzyme to form carbonic acid - this dissociates to produce H+ and H2CO3 (bicarbonate ions) - Bicarb ions diffuse out of RBC into plasma - CO2 transport
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In the blood during CO2 transport what happens to the H+ ions and what role do they play?
The H+ ions displace the oxygen in the saturated oxyhaemoglobin to form haemoglobinic acid and this causes the oxygen to be released (dissociated) and then the oxygen diffuses into respiring cells.
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Other cards in this set

Card 2

Front

How does the wave of excitation during the cardiac cycle result in the contraction of the ventricles starting at the apex of the heart?

Back

The wave of excitation is transmitted through the 'Bundles of His', down the Atrio-ventricular node into the Purkyne Fibres which infiltrate the ventricular walls and cause the ventricles to contract.

Card 3

Front

Why does ventricular systole cause a decrease in blood volume in the left ventricle?

Back

Preview of the front of card 3

Card 4

Front

Describe the pressure story of the Aorta -->>Vena Cava

Back

Preview of the front of card 4

Card 5

Front

Describe how tissue fluid is reabsorbed into blood capillaries.

Back

Preview of the front of card 5
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