7a. MASS TRANSPORT IN ANIMALS Flashcards
Define partial pressure
The measure of a concentration of a gas
Describe the structure of haemoglobin
A globular quaternary protein. It contains four subunits, each containing a haem binding site.
How many molecules of oxygen can a fully saturated haemoglobin carry?
4 molecule, 8 atoms.
Define oxygen loading/association
The binding of oxygen to haemoglobin
Where does oxygen association occur?
At tissues where there is a high partial pressure of oxygen
Where does oxygen association occur in humans?
The lungs
Define unloading/dissociation
The detaching of oxygen from haemoglobin
Where does oxygen dissociation occur?
At tissues where there is a low partial pressure of oxygen
Where does oxygen dissociation occur in humans?
Respiring tissues
Name the complex that is formed when oxygen associates to haemoglobin
Oxyhaemoglobin
What shape is the oxygen dissociation curve?
S (sigmoid) shaped
Recall the equation to calculate the % saturation of haemoglobin with oxygen
% saturation = (oxygenated haemoglobin / maximum saturation) x 100
State the normal maximum saturation of haemoglobin at atmospheric pressures
97%
Define affinity
The tendancy a haemoglobin has to bind with oxygen
Where is haemoglobin’s affinity for oxygen highest?
Where there is a high partial pressure of oxygen
Where is haemoglobin’s affinity of oxygen lowest?
Where there is a high partial pressure of carbon dioxide (and a low partial pressure of oxygen)
Why does the binding of the first oxygen molecule to haemoglobin make it easier for the second oxygen to bind?
Because the binding of the first oxygen molecule changes the tertiary structure of haemoglobin. This uncovers another haem binding site.
How does increasing carbon dioxide concentration in solution affect the pH of the solution?
It decreases it (makes it more acidic)
Write the equation to show the reaction between carbon dioxide and water
Carbon Dioxide + Water ↔ Carbonic Acid
Where in the body would pH be lowest, and why?
Respiring tissues, because the concentration of carbon dioxide is highest
Why will blood leaving a muscle have a lower pH than blood entering a muscle?
Increased carbon dioxide concentration in the blood creates more carbonic acid, which releases more H+ ions, which reduces the pH of the blood
Define the Bohr Effect
Haemoglobin’s binding affinity is inversely related both to the concentration of carbon dioxide, and acidity
Will haemoglobin have a lower of higher affinity for oxygen at muscles?
Lower
What will happen to the amount of oxygen dissociating at muscles?
Increased oxygen dissociating at muscles
Why is the Bohr Effect advantageous at muscles?
More oxygen is required because of the higher rate of respiration
At an increased ppCO2, will the oxygen dissociation curve shift to the left or the right?
To the right
Where in the human body will the oxygen dissociation curve shift to the right?
Respiring tissues
Why will the oxygen dissociation curve shift to the right at a higher ppCO2?
Haemoglobin’s affinity for oxygen decreases, so more oxygen is unloaded
At an increased ppO2 (decreased ppCO2), will the oxygen dissociation curve shift to the left or the right?
To the left
Where in the human body will the oxygen dissociation curve shift to the left?
Lungs
Why will the oxygen dissociation curve shift to the left at a higher ppO2 (decreased ppCO2)?
Haemoglobin’s affinity for oxygen increases, so more oxygen is loaded
Describe the function of the heart
To produce a pressure gradient to pump blood in one direction
Name the chambers of the heart
Right and left atria, right and left ventricles
Why is blood pressure is highest when blood leaves the ventricles. Why?
Because ventricles produce the strongest contractions.
State why the left ventricle is thicker than the right side
To create enough pressure during contraction to pump blood to the whole body, rather than just to the lungs
Why is the heart called a ‘double-pump’?
Because the right side pumps blood to the lungs, and the left side pumps blood to the body
Name the structure that separates the left and right side of the heart
Septum
Why it is important to prevent mixing of the blood from the two sides of the heart?
To prevent oxygenated and deoxygenated blood from mixing, which would reduce the volume of oxygen reaching respiring tissues
Describe the function of the coronary arteries
To transport oxygen and glucose to the heart muscle to use in respiration to release energy for contraction
How is a unidirectional flow of blood maintained in the cardiovascular system?
Valves stop the backflow of blood, and blood moves down a pressure gradient (created by the heart)
Where are the atrioventricular valves found?
Between each atria and ventricle
Describe the function of the atrioventricular valves
They prevent the backflow of blood from the ventricles to the atria
Where is the tricuspid valve found?
Between the right atria and the right ventricle
When will the tricuspid valve open?
When the pressure in the right atrium is higher than the pressure in the right ventricle
When will the tricuspid valve close?
When the pressure in the right atrium is lower than the pressure in the right ventricle
Where is the bicuspid valve found?
Between the left atria and the left ventricle
When will the bicuspid valve open?
When the pressure in the left atrium is higher than the pressure in the left ventricle
When will the bicuspid valve close?
When the pressure in the left atrium is lower than the pressure in the left ventricle
Name the vessels connected to the four chambers of the heart
Aorta, vena cava, pulmonary artery, pulmonary vein
Describe the function of the vena cava
Transports deoxygenated blood back from the body tissues into the right atrium
Describe the function of the pulmonary artery
Transports deoxygenated blood from the right ventricle to the lungs
Describe the function of the pulmonary vein
Transports oxygenated blood from the lungs into the left atrium
Describe the function of the aorta
Transports oxygenated blood from the left ventricle to the body tissues
Where are the semilunar valves found?
Between the ventricles and the arteries
Describe the function of the semi-lunar valves
Prevent backflow of blood from the arteries to the ventricles
Where is the pulmonary semilunar valve found?
Between the right ventricle and the pulmonary artery
When will the pulmonary semilunar valve valve open?
When the pressure in the right ventricle is higher than the pressure in the pulmonary artery
When will the pulmonary semilunar valve valve close?
When the pressure in the right ventricle is lower than the pressure in the pulmonary artery
Where is the aortic semilunar valve found?
Between the left ventricle and the aorta
When will the aortic semilunar valve valve open?
When the pressure in the left ventricle is higher than the pressure in the aorta
When will the aortic semilunar valve valve close?
When the pressure in the left ventricle is lower than the pressure in the aorta
Name the three stages of the cardiac cycle
Diastole, atrial systole and ventricular systole
What happens during diastole?
All chambers relax, and all chamber passively fill with blood
Which valves are open and closed during diastole
Atrioventricular valves are open and semilunar valves are closed
What happens during atrial systole?
Both atria contract and blood passes into the ventricles down a pressure gradient
Which valves are open and closed during atrial systole?
Atrioventricular valves are open and semilunar valves are closed
What happens during ventricular systole?
Both ventricles contract and blood passes into the arteries down a pressure gradient
Which valves are open and closed during ventricular systole?
Semilunar valves are open, and atrioventricular valves are closed
Name the four structures that control the cardiac cycle
Sinoatrial node (SAN), Atrioventricular valve (AVN), Bundle of His, and Purkinje Fibres
Where are both the SAN and AVN located?
In the right atrium
Where is the Bundle of His located?
In the septum
Where are the Purkjne Fibres located?
In the walls of the ventricles
Why is the SAN considered the pacemaker of the heart?
Because it creates the first impulse
How does the AVN coordinate cardiac contraction?
It controls the speed and direction of the contraction
When the SAN creates the first impulse, where does the impulse travel across, and what does this cause?
The atria. It causes the atria to contract.
Why does the AVN delay the impulse?
To ensure the atria are empty before the ventricles contract
Where does the AVN send the wave of impulse down?
The Bundle of His to the apex of the heart
Why does the impulse travel up the Purkjne fibres from the apex of the heart upwards?
To ensure the ventricles contract from the base upwards
Define heart rate
The number of cardiac cycles per minute
Recall the equation to calculate heart rate
HR = 60 / time for one cardiac cycle (bpm)
Define stroke volume
The volume of blood pumped out of the heart / left ventricle during one cardiac cycle
Define cardiac output
The volume of blood pumped by the heart in one minute
State the equation to calculate cardiac output
CO = stroke volume x heart rate
Recall the five types of blood vessels in order that blood travels through them from the left ventricle
Arteries, arterioles, capillaries, venules and veins
Why can arteries, arterioles, venules and veins be described as organs?
Because they are made of multiple different types of tissue
Why are capillaries not considered organs?
Because they are only made of endothelial tissue
In which direction do arteries transport blood?
Away from the heart
Which tissue do arteries contain more of than other blood vessels?
Elastic tissue
Why do arteries contain more elastic tissue compared to other blood vessels?
To smooth out blood flow and maintain blood pressure
How do arteries smooth out blood flow and maintain blood pressure?
Because they can stretch when the pressure is high, and recoil when the pressure is low
Why does the aorta have a thick wall?
To withstand the high pressures (because it’s next to the left ventricle)
Why does the aorta contain muscle tissue?
To contract during vasoconstriction
Why does the aorta have a smooth endothelium?
To reduce friction with fast-flowing blood
Which tissue do arteriole contain more of than other blood vessels?
Muscle tissue
Why do arteriole contain more muscle tissue compared to other blood vessels?
To control blood flow to capillaries and to redistribute blood to different organs
Describe how arterioles vasoconstrict
The muscle tissue contracts, narrowing the lumen
Describe how arterioles vasodilate
The muscle tissue relaxes, widening the lumen
Why does the rate of blood flow decrease as blood vessels get smaller?
The diameter of the lumen of the blood vessels decreases. This increases the total area of the endothelium in contact with the blood. Friction increases.
Describe the function of capillaries
Substance exchange between blood and cells
One adaptation of capillaries is that many narrow capillaries create a slow blood flow. Explain why.
This increases time for exchange to occur
One adaptation of capillaries is that they have a narrow lumen. Explain why.
This means a large surface area of blood is in contact with the walls of the capillaries
One adaptation of capillaries is that they have thin walls. Explain why.
To create a short diffusion pathway
One adaptation of capillaries is that their walls are permeable. Explain why.
To allow for substance exchange
What is the smallest diameter of a capillary limited by?
The diameter of a blood cell
In which direction do veins transport blood?
Towards from the heart
Describe the three adaptations of veins
Valves, wide lumen and muscles surrounding the veins
Explain why veins have valves
To prevent backflow of blood
Explain why veins have a wide lumen
To reduce friction and increase the volume of blood transported
Explain why veins are surrounded by muscles
To contract to press the walls of the veins to squeeze the blood along
What is cardiovascular disease?
CVD is a general term for conditions affecting the heart or blood vessels
List the 6 main factors that affect the incidence and severity of CVD
Age, sex, alcohol consumption, exercise, diet and genetics
What is tissue fluid?
An aqueous solution that surrounds the cells in your body
Name six substances contained in tissue fluid
Water, glucose, amino acids, fatty acids, ions and oxygen
Which two systems in the body are involved in tissue fluid formation and transport?
Cardiovascular system and lymphatic system
At which end of a capillary bed is the pressure the highest?
The arteriole end
Why is the blood at the arteriole end of the capillary bed under the highest pressure?
Because this end is closer to the strong contractions of the left ventricle
Why does the high hydrostatic pressure at the arteriole end of a capillary bed cause tissue fluid to be formed?
Because it forces fluid out of the capillaries
Whilst tissue fluid is being formed, what remains inside the capillaries?
Large proteins remain
How will the concentration of small molecules in the tissue fluid be different once exchange has occurred?
It will be lower
What happens to the water potential of the blood remaining inside the capillaries towards the venule end of the capillary beds?
It becomes more negative
Why does the water potential of the blood inside the capillaries become more negative towards the venule end of the capillary bed?
Because water has left the capillary, but proteins remain in the blood
What type of gradient does the return of tissue fluid to the blood occur down?
A water potential gradient
During the return of tissue fluid into the blood, why does the water move from the outside to the inside of the capillary?
Because the water potential of the blood inside the capillary is lower than the tissue fluid
By which type of molecular transport does the water move back into the capillary during the reabsorption of tissue fluid?
Osmosis
Which organ system removes extra tissue fluid and returns it to the blood?
Lymphatic system
