Topic 4 - Circulatory System In Mammals Flashcards
What is the pulmonary circulation
The circuit going from the heart to the lungs and back
What is systemic circulation
The circuit from the heart to the rest of the body
Why is it a double circulation in the heart
Because there are two circuits, and blood gets pumped out of the heart twice
Where does blood get pumped out of from the heart
The right ventricle to the lungs
The left ventricle to the body
Why does the left ventricle have thicker cardiac muscle than the right ventricle
The blood pumped out of the left ventricle needs to go to the body, and therefore needs a greater amount of pressure
What are the advantages of the two-pressure system in the heart
The low pressure in the pulmonary circulation pushes blood slowly to the lungs allowing more time for gas exchange
The high pressure in the systemic circulation ensures blood is pumped to all the other body organs and allows tissue fluid to form in each organ
What is the only artery that pumps deoxygenated blood, and what is the only vein that pumps oxygenated blood
Pulmonary artery
Pulmonary vein
What is the coronary circulation
The circulation that provides the cardiac muscle in the heart with oxygen and nutrients
What are the 3 main stages during each beat of the heart, and what occurs during each
Atrial systole - atria contract
Ventricular systole - ventricles contract
Diastole - both atria and ventricles are relaxed
What makes the first heartbeat sound
The first heart sound is produced by closure of the atrioventricular valves
What causes the second heartbeat sound
The second, sharper sound is produced by the clapping shut of the semilunar valves
What is the difference between a phonocardiogram and a electrocardiogram
A phonocardiogram shows the sounds of the heart, an electrocardiogram records the electrical activity of the heart
On an electrocardiogram, what does the Wave T, QRS, and Wave P represent
Wave P shows the excitation of the atria
QRS indicates the excitation of the ventricles
Wave T corresponds to diastole
What are the events that occurs during Atrial Systole
Atria contract pushing more blood into the ventricles. This is essentially topping up the ventricles.
What events occur during Ventricular systole (a)
Ventricular pressure increase causes the atrioventricular valves to bulge into the atria increasing pressure there, thought this is not great enough to cause blood to exit the major arteries; the falls of the atrioventricular valves are prevented from turning inside out by the chordae tendinae, aided by contraction of the papillary muscles
What events occur during ventricular systole (b)
Ventricular pressure increases to exceed that in the major arteries, pushing the semilunar valves open and causing the ejection of blood from the heart; blood is returned to the atria from the major veins and so atrial pressure gradually increases
What events occur during Diastole (a)
Ventricular pressure drops to become lower than that in the main arteries, so the semilunar valves are forced shut. Blood continues to the be returned to the atria though it cannot enter the ventricles since the ventricular pressure is still greater than that in the atria, so the atrioventricular valves remain closed
What events occur during diastole (b)
Ventricular pressure drops to a point where it becomes lower than that in the atria. Therefore, the atrioventricular valves are forced open and blood enters the ventricles from the atria
How is the heartbeat myogenic
Contraction originates in the heart itself and does not depend on nervous stimulation
What is the sinoatrial node, and what is its function
It is what the heartbeat starts with, it is a small patch of tissue in the right atrium that acts as a pacemaker
What does excitation of the SA node cause
It causes the atria to contract together
Where is the non-conductive tissue located, and what is its function
Between the atria and ventricles, it prevents the spread of the wave of excitation passing directly from atria to the ventricles
Where must the wave of excitation go to to reach the ventricles
The atrioventricular node
What do excitation of the AV node cause
A short time delay before the waves of excitation pass down to the base of the ventricles
What is the function of the Bundle of His
They transport a wave of excitation down both sides of the septum of the ventricles
What is the function of Purkinje fibres
They conduct the waves of excitation to all parts of the ventricles, causing them to contract from the bottom up
How are arteries adapted to carrying blood under high pressure away from the heart
They have an outer layer of fibrous tissue for protection
They have a thick middle layer containing elastic tissue which allows stretching when blood surges and recoils to continue pushing blood along
They have a thick middle layer containing muscle tissue which may contract to narrow the lumen so reducing blood supply to an organ,or relax to increase supply
They have an endothelium which provides a smooth inner surface which reduces the friction caused by blood flow through the lumen
They have a thin lumen which can be constricted or dilated
What are capillaries adapted for the exchange of material between blood and tissue cells
They contain squamous endothelium which provides a short diffusion distance and facilitates the exchange of substances between the blood and tissue cells
How are veins adapted to carry blood under low pressure back to the heart
They have an outer layer of fibrous tissue for protection
They have a thin middle layer containing some smooth muscle and few elastic fibres as blood is under low pressure
They have an endothelium which provides a smooth inner surface
They have a thin lumen which provides a large space making it easier for blood to enter from the capillaries while friction is reduces as blood flows back to the heart
Why does tissue fluid form at the arterial end of capillaries
Because the blood has a high hydrostatic pressure
What does loss of fluid from capillaries cause
It reduces the hydrostatic pressure of the blood
What are the 3 types of White Blood Cell
Monocytes
Lymphocytes
Polymorphs
What is the structure of Erythrocytes
Small cells lacking a nucleus and organelles, and with a biconcave disc; packed with Haemoglobin
What is the function of Erythrocytes
Adapted to carry oxygen; lack of a nucleus provide more space for Haemoglobin; biconcave disc shape increases surface area for gas exchange. Small size facilitates movement through capillaries
What is the structure of Polymorphs
Cells with a multilobed nucleus and granular cytoplasm. The most common white blood cell (70%)
What is the function of Polymorphs
These short-lived, but numerous cells can squeeze between endothelial cells of capillaries at sites of infection where they engulf bacteria and other foreign bodies by phagocytosis
What is the structure of Monocytes
Large cells with a kidney shaped-nucleus. The least common white blood cell (5%)
What is the function of Monocytes
These reside in blood for only a few days before moving out into body tissues, where they develop into macrophages, which are long-lived phagocytic cells that engulf bacteria and foreign material
What is the structure of Lymphocytes
Cells with a huge nucleus and little cytoplasm. Present in relatively large numbers (25% of WBC)
What are the 2 types of Lymphocytes and what are there functions
B Lymphocytes are involved in antibody production
T Lymphocytes destroy infected cells and foreign tissue
What is the structure of platelets
Essentially cell fragments too small to be readily visible using a light microscope
What is the function of platelets
Have an important role in initiating blood clotting and in plugging breaks in blood vessels
What does plasma consist of
90% water and 10% of a variety of substances in solution and suspension
What are some substances that are function in Plasma
Plasma proteins including prothrombin and fibrinogen, albumin, enzymes, hormones, glucose, amino acids, fats and fatty acids, urea, vitamins and various ions
What does clotting of blood do
Seals cuts and wounds, preventing the entry of pathogens and stopping blood loss
What is thrombin
Thrombin is an enzyme that converts soluble fibrinogen into insoluble fibrin
What occurs in the final stages of blood clotting
An inactive plasma protein, prothrombin is converted into active thrombin
What does Haemoglobin consist of
Each molecule consists of 4 polypeptides: two a-chains and two b-chains. Each polypeptide has a haem group attached, which contains iron
How do you make Oxyhaemoglobin
Hb + 4O2 = HbO8
What is the amount of oxygen carried by Haemoglobin measured as
The degree to which the blood is saturated
What does 50% saturation in blood mean
On average, each Haemoglobin molecule is carrying 2 oxygen molecules
What is the partial pressure measured as
The amount of oxygen carried by the blood depending on the amount of oxygen available in its surroundings
What is the partial pressure
The proportion of the total air pressure that is contributed in the mixture
What is the graph that shows the partial pressure of Haemoglobin
Oxygen dissociation curve
What does an oxygen dissociation curve indicate
How the percentage saturation of blood with oxygen changes with the partial pressure of oxygen
What is the shape of an oxygen dissociation curve
Sigmoid (S-shaped)
What occurs at high partial pressures of oxygen in the body
Since blood entering the pulmonary circulation is deoxygenated, the Haemoglobin loads with oxygen to become 98% saturated
What occurs in respiring tissues at low partial pressures of oxygen, and how does this differ from resting tissues
Since blood arriving at tissues is highly saturated, Haemoglobin unloads oxygen to the tissues.
In resting tissues, Haemoglobin loads oxygen to them
Why is the oxygen dissociation curve an S-shape
Because of the way the four haem-containing polypeptides interact
What becomes easier once the shape of the Haemoglobin molecule becomes distorted
It becomes easier for the other 3 oxygen molecules to bind with the other haem groups
What effect does the partial pressure of carbon dioxide have on the oxygen dissociation curve of human Haemoglobin
It shows that at lower carbon dioxide pressures, the oxygen dissociation curve moves to the left, The Bohr effect
What does the Bohr effect do
It increases the efficiency of Haemoglobin for oxygen transport
Where is the partial pressure of carbon dioxide high
In tissues that are actively respiring
What occurs at a higher level of carbon dioxide, and what is the advantage of this
The lower the affinity of Haemoglobin for oxygen, and so more oxygen is released to the tissues. This is advantageous because tissues with a high respiration rate require increased amounts of oxygen
Where is partial pressure of Carbon Dioxide low
In the alveoli
What occurs at low levels of Carbon Dioxide, and what is an advantage of this
The affinity of Haemoglobin for oxygen is increased and more oxygen can be loaded. This is advantageous because it allows the blood to become as fully saturated as possible
What is Myoglobin
It consists of one polypeptide with a single haem group and does not, therefore, have a sigmoid dissociation curve
Where is myoglobin found
Red muscle
What is the function of Myoglobin
It acts as an oxygen store within the muscle, and only releases oxygen when the partial pressure of oxygen becomes very low
What does myoglobin do as a result of strenuous exercise, and what does this enable
As a result of strenuous exercise, myoglobin gives up its oxygen. This enables aerobic respiration to continue for longer and delays the onset of anaerobic respiration
How is a Llama adapted to living in higher altitudes
Llama Haemoglobin has a high oxygen affinity so that the blood can become fully saturated with oxygen at lower pO2
What is Atherosclerosis
A disease in which an artery wall thickens so that its lumen in narrowed
What are the sequence of events of Artherosclerosis
- The endothelium lining the artery gets damaged, which results in high blood pressure, putting extra strain on the layers of cells
- Once the endothelium is breached, macrophages leave the blood vessel and move into the artery wall. A deposit builds up in the artery wall, called an atheroma
- Calcium salts and fibrous tissue build up around the cholesterol, resulting in the formation of plaque
- Plaques cause a narrowing of the artery lumen so that it is more difficult for blood flow. This increases blood pressure, and increased risk of further plaques forming
What is Genetic predisposition
Possessing genes that increase an individual’s susceptibility to a certain disease
What is a thrombus
A clot that forms inside a damaged blood vessel
What is thrombosis
The condition of thrombus
What occurs during coronary thrombosis
The heart muscle supplied by coronary arteries does not receive oxygen
What is a Cardiac arrest
The point at which the heart stops beating, due to the blockage of a large artery
What is an Aneursym
The weakening of a section of the artery wall, which due to the pressure of the blood, bulges outward, forming a balloon-like sac in the artery
