Transport In Mammals Flashcards
(120 cards)
1
Q
What is the most efficient form of respiration?
A
The most efficient form of respiration which releases the most energy from a given amount of glucose is aerobic respiration and this requires a good supply of oxygen. Sublime oxygen to respond tissues is one of the most important functions of an animal’s transport system. At the same time waste products such as carbon dioxide can be removed.
2
Q
Why do mammals have a greater requirement for oxygen than most other animals?
A
Mammals have greater requirements for oxygen than most other animals because they use respiration to generate heat inside their bodies, to help keep their body temperature constant. Diffusion is not sufficient in mammals and a transport system is required to distribute oxygen quickly to all body cells and to remove waste products.
3
Q
What is the main transport system of animals?
A
The main transport system of animals is the blood system or the circulatory system. The circulatory system is a system that carries fluids around an organism’s body. It is made of the pump-the heart and a system of interconnecting tubes-the blood vessels.
4
Q
Why is the circulatory system called the closed blood system?
A
A circulatory system made up of vessels containing blood is called a closed blood system. The blood always remains within these vessels and so the system is known as the closed blood system.
5
Q
What is double circulation?
A
A circulatory system in which the blood passes through the heart twice on one complete circuit of the body is called a double circulation.
6
Q
What is systemic circulation?
A
The part of the circulatory system that carries blood from the heart to all of the body except the gas exchange surface and then back to the heart is called the systemic circulation. Blood is pumped out of the left ventricle into the aorta and travels from there to all parts of the body except the lungs. It returns to the right side of the heart in the vena cava.
7
Q
What is pulmonary circulation?
A
The part of the circulatory system that carries blood from the heart to the gas exchange surface and then back to the heart is called the pulmonary circulation.
The blood is then pumped out of the right ventricle into the pulmonary arteries which carries it to the lungs. The final part of the journey is along the pulmonary veins, which returns it to the left side of the heart.
8
Q
Define an artery.
A
An artery is a vessel with thick, strong walls that carry high pressure blood away from the heart. Small arteries are called arterials.
9
Q
Define a vein
A
A vein is a vessel with relatively thin walls that carries low pressure blood back to the heart. Small veins are called venules.
10
Q
Define a capillary.
A
A capillary is the smallest blood vessel. Linking arterioles and venules taking blood close to almost every cell in the body are tiny vessels called capillaries.
11
Q
What is the function of arteries?
A
The function of arteries is to transport blood away from the hearts swiftly and at high pressure to the tissues.
When blood pressure is high the lumen will widen, reducing the pressure a little while at lower pressure the arteries recoil to increase the pressure by giving small push and raising the blood pressure a little.
12
Q
Describe the structure of the artery.
A
The artery is made up of three layers.
An inner layer which is made up of a layer of endothelium (lining tissue) consisting of a layer of flat cells (squamous epithelium) fitting together like jigsaw pieces plus a layer of elastic fibers. The endothelium is very smooth minimizing friction with the moving blood.
A middle layer containing smooth muscle collagen and elastic fibers.
An outer layer containing elastic fibers and collagen fibres.
13
Q
What is smooth muscle?
A
Smooth muscle is a type of muscle that can contract steadily over long periods of time to maintain high blood pressure.
14
Q
What is the function of collagen?
A
Collagen provides strength to withstand high blood pressure.
15
Q
What is squamous epithelium?
A
Squamous epithelium is one or more layers of thin, flat cells forming the lining of some hollow structures, for example the blood vessels and alveoli.
16
Q
What is the function of elastic fibers?
A
Elastic fibers are allowed to stretch which reduces the likelihood that they will burst. Elastic Fibers stretch as the high blood pressure surges into them and then recoil inwards as the pressure drops.
17
Q
What is the blood pressure measured in?
A
Blood pressure is still measured in the old units of mmHg (millimeters of mercury) and refers to the distance which a column of mercury is pushed up the arm of a U-tube. KPa is the SI unit.
18
Q
What is the diameter of the artery close to the heart and the wall thickness?
A
Arteries have the thickest walls of any blood vessel. The aorta the largest artery has an overall diameter of 2.5 cm close to the hearts and a wall thickness of about two millimeters.
19
Q
Which layer of arteries contains the largest amount of elastic fibers?
A
The middle layer which is by far the thickest part of the wall contains a large amount of elastic fibers. These allow the wall to stretch as pulses of blood surge through at high pressure. Arteries further away from the hearts have fewer elastic fibers in the middle layer but have more muscle fibers.
20
Q
What is an elastic artery?
A
Elastic arteries are relatively large arteries, which have a lot of elastic tissue and little muscle tissue in their walls. The function of an elastic arteries to carry blood from the heart on the first part of its journey towards its final destination. The overall effect is to even out the blood flow. However the arteries are not entirely effective in achieving this. An example of an elastic artery is the aorta.
21
Q
What is a muscular artery?
A
Muscular arteries are those arteries that are closer to the final destination of the blood inside them than elastic arteries, they have more smooth muscle in their walls which is able to contract slowly and steadily to alter the diameter of the artery and therefore control the volume of blood that can flow through it. This allows them to constrict and dilate. The proportion of elastic tissue decreases.
22
Q
What do muscular arteries divide into?
A
Muscular arteries divide to form even smaller vessels called arterioles. These also contain a lot of smooth muscle in their walls. Their narrowness provides resistance to blood flow, causing it to slow down, which provides extra time for exchange of gases and nutrients as the blood flows through the capillaries in the tissues.
23
Q
What is vasoconstriction?
A
The walls of arterioles have a nerve supply. Nerve impulses from the brain can cause their smooth muscle to contract. The narrowing of a muscular artery or arterial caused by the contraction of the smooth muscle in its walls is called vasoconstriction.
24
Q
What is the function of vasoconstriction?
A
Vasoconstriction can be used to reduce blood flow to a particular area and divert it to other tissues.
25
What is vasodilation?
The widening of a muscular artery or arterial, caused by the relaxation of the smooth muscle in its walls is called vasodilation.
26
Apart from vasodilation and vasoconstriction what else do smooth muscle respond to in the blood?
Smooth muscle can also respond to hormones in the blood.
27
What is the function of capillaries?
The function of capillaries is to take blood is closest possible to all cells, allowing rapid transfer of substances between cells and blood.
28
What is a capillary bed?
Cappillaries form a network throughout every tissue in the body except the brain, cornea and cartilage. Such networks are sometimes called capillary beds.
29
What is the size of capillaries and why do they have such a size?
The small size of capillaries is of great importance in allowing them to bring blood as close as possible to each group of cells in the body. The human capillary is approximately 7 micrometers in diameter about the same size as a red blood cell. The walls of capillaries are extremely thin because they are made up of a single layer of endothelial cells.
30
How close are the red blood cells carrying oxygen brought to the cells outside of the capillary?
As red blood cells carrying oxygen squeeze through a capillary, they are brought to within his little as 1 micrometer of the cells outside the capillary that need the oxygen.
31
How is endothelium formed?
In most capillaries, there are tiny gaps between individual cells that form the endothelium. These gaps are important in allowing some components of the blood to see through the spaces between the cells in all the tissues of the blood.
32
What happens as blood leaves a capillary bed?
As blood leaves the capillary bed, the capillaries gradually join with one another, forming large vessels called venules. These join to form veins.
33
What is the function of veins?
The function of veins is to return blood to the heart.
34
Why do veins not have thick walls?
By the time blood enters a vein its pressure has dropped to a very low value. In humans a typical value for venous blood pressure is about 5mmHg or less. This very low pressure means that there is no need for veins to have thick walls. They have the same three layers as arteries but the middle layer is much thinner and has far fewer elastic fibers and muscle fibers.
35
How do veins ensure that blood flows within one direction?
Many veins run within or very close to several leg muscles. Whenever you tense these muscles they squeeze inwards on the veins in your legs, temporarily raising the pressure within them. To keep the blood flowing in the right direction veins contain half moon valves or semilunar valves formed from their endothelium.
36
What is a semilunar valve?
Semilunar valve is a half moon shaped valve, such as the ones in the veins and between the ventricles and arteries. In the veins these valves allow blood to move towards the heart but not away from it. So when you contract you like muscles the blood in the veins is squeezed up through the valves but cannot pass down through them.
37
What happens to the value of blood pressure in the circulatory system?
Blood leaves the heart at high pressure and then gradually loses this pressure as it passes through muscular arteries, arterials, capillaries, venules and veins. This happens in both systems-the systemic and pulmonary system. The pressure of blood leaving the heart is much greater in the systemic system than in the pulmonary system.
38
What is plasma?
Plasma is a pale yellow liquid component of blood in which the blood cells float. it carries a very large range of different substances in solution. These include nutrients such as glucose and waster products such as urea that are being transported from one place to another. Solutes also include plasma protein. Blood plasma also transports heat around the body.
39
What are plasma proteins?
A range of several different proteins dissolved in blood plasma, each with their own function; many of them are made in the liver.
40
What is tissue fluid?
An almost colourless fluid that fills the spaces between body cells. It forms from the plasma that leaks through the gaps between the cells of the tissues. Almost one-sixth of your body consists of spaces between your cells.
Tissue fluid=Plasma-(large plasma proteins+ red blood cells).
41
Compare the composition of tissue fluid to blood plasma.
Tissue fluid is almost identical in composition to blood plasma. However it contains far fewer protein molecules than blood plasma, because they are too large to escape easily through the capillary and endothelium. Red blood cells are much too large to pass through, so tissue fluid do not contain these, but some white blood cells can squeeze through and move freely in tissue fluid.
42
What is the volume of liquid that leaves the capillary to form tissue fluid dependent on?
The volume of fluid that leaves the capillary to form tissue fluid is the result of two opposing forces. At the arterial end of a capillary bed the blood pressure inside the capillary is enough to push fluid out of the tissue. However there is a greater concentration of dissolved proteins in the blood plasma than in tissue fluid. Creating a water potential gradient in the venule end. Overall more fluid flows out of capillaries than into them so there's a net loss of fluid from the blood as it flows through a capillary bed.
43
Explain what happens at the venule end of a capillary bed during loss of fluid from the blood.
At the venule end of a capillary bed The blood pressure inside the capillaries is lower, so there is less tendency for water to be pushed out of the capillaries into the tissue. The water potential gradients caused by the difference in the concentration of dissolved proteins is still similar to that of the arterial end. Now the net movement of water is from the tissue fluid back into the capillaries.
44
What is oedema?
If your blood pressure is too high too much fluid is forced out of capillaries and tissue fluid may accumulate in the tissues. This buildup of fluid is called oedema. One of the roles of arterioles is to reduce the pressure of the blood that enters the capillaries, in order to avoid this.
45
Where does exchange of materials between cells and blood occur?
Tissue fluid forms the environment of each individual body cell. Exchange of materials between cells and the blood occur through the tissue fluid ( as capillaries cannot reach each and every cell).
46
In our body why do many processes take place to maintain the composition of tissue fluid at a constant level?
Within your body many processes take place to maintain the composition of tissue fluid out of constant level. Provide an optimum environment in which cells can work. These processes contribute to the overall process of homeostasis.
47
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment and includes the regulation of glucose concentration, water, pH, metabolic wastes and temperature.
48
How much blood do we have in our body?
You have about 5dm3 of blood in your body with a mass of about 5 kg or 5 litres.
49
How do the properties of water help tissue fluid perform their function?
Waters properties as a solvent make it ideal for the role. Water has a high heat capacity which allows it to absorb a lot of heat energy without altering its temperature very much and thus helps to maintain a relatively constant temperature.
50
Describe the structure and function of platelets
Platelets are fragments of cells with no nucleus and their function is blood clotting. They are involved in wound healing.
51
What is the red colour of red blood cells caused by?
The red colour of red blood cells is caused by the pigment haemoglobin which is a globular protein.
52
Describe the shape of red blood cells.
Red blood cells are shaped like a biconcave disk. The debt in each side of the cell increases the surface area to volume ratio (surface area:volume) of the cell. This large surface area means that oxygen can diffuse quickly into or out of the cell.
53
What is the size of a red blood cell?
Red blood cells are very small. The diameter of a human red blood cell is seven micrometers this small size means that no hemoglobin molecule within the cell is very far from the cell surface membrane and the hemoglobin molecules can therefore quickly exchange oxygen with the fluids outside the cell. It also means that capillaries can be only seven micrometers wide and still allow red blood cells to squeeze through them, so bringing oxygen as close as possible to cells which require it.
54
Why are red blood cells very flexible?
Red blood cells are very flexible. Some capillaries are even narrower than the diameter of a red blood cell. The cells are able to be squashed so that they can pass through these vessels. This is possible because cells have specialized cytoskeleton made up of mesh-like networks of protein fibers. This allows them to be squashed into different shapes but then spring back to produce the normal biconcave shape.
55
Which organelles does the red blood cell lack and why?
Red blood cells have no nucleus, no mitochondria and no endoplasmic reticulum. The lack of these organelles means that there is no more room for hemoglobin, so maximizing the amount of oxygen which can be carried by each red blood cell.
56
What is the lifespan of red blood cells?
Red blood cells do not live very long (approximately 90-100 days). Old ones are broken down in the liver (they leave the capillaries) a new ones are constantly made in the bone marrow.
57
Where are white blood cells made?
White blood cells like red blood cells are made in the bone marrow.
58
How can you distinguish red blood cells and white blood cells in a micrograph?
White blood cells all have a nucleus, although the shape of this varies in different types of white blood cells.
Most white blood cells are larger than red blood cells although one type of lymphocytes may be slightly smaller.
White blood cells are either spherical or irregular in shape, not a bioncave disk.
59
What are the two main groups a white blood cell can be divided into?
There are many different kinds of white blood cells with a wide variety of functions although all are concerned with fighting disease. They can be divided into two main groups: phagocytes and lymphocytes.
60
What is a phagocyte?
Phagocytes are cells that destroy invading microorganisms by phagocytosis.
61
What is a neutrophil?
The commonest type of phagocyte is called a neutrophil. It has a lobed nucleus and granular cytoplasm.
62
What is a monocyte?
A monocyte is the largest type of white blood cell; it has a bean shaped nucleus; monocytes can leave the blood and develop into a type of phagocytec cell called a macrophage.
63
What is a macrophage?
A macrophage is a phagocytic cell found in tissues throughout the body; they act as antigen presenting cells (APCs).
64
Compare the size of lymphocytes and phagocytes.
Lymphocytes are smaller than most phagocytes and they have a large round nucleus and only a small amount of cytoplasm.
65
What is a lymphocyte?
Lymphocytes destroy microorganisms. Some of them secrete chemicals antibodies which attach to and destroy the invading cell. Lymphocytes are a type of white blood cell with a nucleus that almost fills the cell, which responds to antigens and helps to destroy the antigens or the structure that is carrying them.
66
In which form is oxygen transported from the gas exchange surfaces of the alveoli in the lungs to tissue all over the body?
Oxygen is transported around the body inside red blood cells in combination with the protein haemoglobin. Each haemoglobin molecule is made up of four polypeptides each containing one haem group. Each haem group can combine with one oxygen molecule, O2. Overall then, each hemoglobin molecule can combine with four oxygen molecules (eight oxygen atoms).
67
What happens to a haemoglobin molecule when an oxygen molecule combines with it?
Iron atoms combine with the haem groups of a haemoglobin molecule. Each haemoglobin molecule has four haem group. When an oxygen molecule combines with one haem group, the whole haemoglobin molecule is slightly distorted (its 3D shape changes). The shape change makes it easier for a second oxygen molecule to combine with a second haem group. This is turn makes it even easier for the third oxygen molecule to combine with a third haem group. It is then even easier for the fourth and final oxygen molecule to combine.
68
Explain the shape of the haemoglobin disassociation curve?
The S-shaped curve of the hameoglobin disassociation curve can be explained the behavior of a haemoglobin molecule as it combines with or loses oxygen molecules.
Haemoglobin exhibits cooperative bonding/ allosteric effects, as oxygen binding increases the affinity of hemoglobin for more oxygen.
As it becomes successively easier for the second and third oxygen molecule to combine, so the curve rises very steeply. Over this part of the curve, a small change in the partial pressure of oxygen causes a very large change in the amount of oxygen which is carried by the haemoglobin.
69
What is a dissociation curve?
A graph showing the percentage saturation of a pigment (such as haemoglobin) with oxygen, plotted against the partial pressure of oxygen.
70
What is a saturated oxygen?
The maximum amount of oxygen with which a sample can possibly combine is given a value of 100%. A sample of oxygen which has combined with this maximum amount of oxygen is said to be saturated.
71
What is percentage saturation?
The degree to which haemoglobin in the blood is combined with oxygen, calculated as a percentage of the maximum amount with which it can combine.
At high partial pressures of oxygen, the percentage saturation of haemoglobin is very high.
72
What is partial pressure?
A measure of the concentration of a gas.
73
What is the amount of oxygen that haemoglobin carries affected by?
The amount of oxygen that haemoglobin carries is affected by not only the partial pressure of oxygen but also by the partial pressure of carbon dioxide.
74
How is carbon dioxide produced and how does it reaches blood?
Carbon dioxide is continually produced by respiring cells. It diffuses from the cells into blood plasma, from where some of it diffuses into the red blood cells.
75
Where is the partial pressure of oxygen the highest and lowest?
Highest at Capillaries in the lungs. Lowest at respiring tissues.
76
What happens to the percentage saturation of haemoglobin when blood travels from the lungs to respiring tissue?
Small decrease in partial pressure of oxygen leads to a large decrease in % saturation.
This allows for more oxygen to be released/disassociate with Hb.
Affinity of a haemoglobin to oxygen decreases at low partial pressure of oxygen.
77
What are the factors which affect the affinity of Hb to O2?
pO2: High pO2 increases affinity of Hb to O2.
pCO2: High partial pressures, decrease affinity of Hb to O2. This results in Bohr shift where curve shifts to the right.
78
What is the Bohr shift?
High partial pressure of carbon dioxide decreases affinity of Hb to O2. Therefore a higher partial pressure of oxygen is needed to meet the same percentage saturation. The curve shifts to the right.
Bohr shift increases disassociation of oxyhemoglobin in actively respiring tissue.
79
How does high partial pressure of carbon dioxide decrease the affinity of haemoglobin to oxygen?
1.CO2 diffuses from respiring tissue →blood plasma →RBC.
2. Carbonic anhydrase in cytoplasm of RBC converts CO2 to carbonic acid. → this maintains a steep concentration gradient for diffusion of CO2 from tissues to blood.
3. Carbonic acid disassociates into hydrogen carbonate ions and hydrogen ions. →causes decrease in pH.
4. Hydrogen carbonate ion diffuses from the RBC to the blood plasma. Cl- moves into RBC to balance out negative charge (chloride shift).
5. H+ ion combines with haemoglobin to form haemoglobinic acid (HHb)
→Hb has higher affinity for H+ than oxygen.
→H+ lowers affinity of Hb for oxygen
→HHb also prevents pH from decreasing/acting as a buffer.
6. Hb releases oxygen.
O2 diffuses from RBC →Blood plasma →respiring cells.
80
Define the chloride shift.
The movement of chloride ions into the red blood cells from blood plasma, to balance the movement of hydrogen carbonate ions into the plasma from red blood cells.
81
Define carbaminohaemoglobin.
A compound formed when carbon dioxide binds with haemoglobin.
82
What are the three ways blood transports carbon dioxide?
About 85% of carbon dioxide is transported by the blood as hydrogen carbonate ions in the blood plasma.
About 5% of the total carbon dioxide is carried as dissolved carbon dioxide molecules in the blood plasma.
About 10% of carbon dioxide is carried as carbaminohaemoglobin.
83
How is CO2 transported from respiring tissues as hydrogen carbonate ions?
Carbonic anhydrase in the cytoplasm of red blood cell converts CO2 to carbonic acid. Carbonic acid disassociated.
HCO3- diffuse from RBC into plasma.
84
How is CO2 transported from respiring tissues as dissolved carbon dioxide molecules in blood plasma?
Some carbon dioxide molecules remain as CO2 molecules and some of these simply dissolve in the blood plasma.
85
How is CO2 transported from respiring tissues as carbaminohaemoglobin?
Some carbon dioxide molecules diffuse into the red blood cells but do not undergo the reaction catalysed by carbonic anhydrase. Instead they combine directly with the terminal amine group (-NH2) of some of the haemoglobin molecules. The compound formed is called carbaminohaemoglobin.
86
How is CO2 transported into the lungs?
Low pCO2, high O2 in the alveoli.
Processes are reversed.
HHb releases its H+ ion and binds with O2. \
→Forms oxyhemoglobin.
1. Hydrogen carbonate ions diffuses back into the RBC.
→Binds with H+ ions and converted back into carbonic acid.
→Carbonic acid converted back to CO2 + H20.
→Diffuse into alveoli.
2. Dissolved CO2 in blood plasma.
→Diffuse into the alveoli.
3. CO2 from carbaminohaemoglobin.
Diffuses into the alveoli.
87
What is the muscle of the heart made up of?
Cardiac muscle is the type of muscle that makes up the heart. it is made up of interconnecting cells with cell surface membranes very tightly joined together. This close contact between the muscle cells allows waves of electrical excitation to pass easily between them.
88
Define the coronary arteries.
Arteries that branch from the aorta and spread over the walls of the heart, supplying the cardiac muscle with nutrients and oxygen.
89
Define the septum.
If the heart is cut open vertically it can be seen to contain four chambers. The two chambers on the left of the heart are completely seperated from those on the right by a layer of tissue/wall of a muscle called the septum.
90
How can blood pass from one side of the heart to the other?
Blood cannot pass through the septum; the only way for blood to get from one side of the heart to the other is for it to leave the heart, circulate around other the lungs or the rest of the body and then return to the other side of the heart.
91
Define the atrium.
The upper chamber on each side of the heart is called an atrium (plural atria). The two atria receive blood from the veins. Blood from the vena cava flows into the right atrium, while blood from the pulmonary veins flows into the left atrium.
92
Define the ventricle.
The lower chambers on each side of the heart are called the ventricle. Blood flows into the ventricle from the atria, and is then squeezed out into the arteries. Blood from the left ventricle flows into the aorta while blood from the right ventricle flows into the pulmonary artery.
93
Define an atrioventricular valve.
A valve between the atria and the ventricle that closes when the ventricles contract and stops back flow of blood into the atria.
94
Define the bicuspid valve.
The atrioventricular valve on the left side of the heart. It is also called the mitral valve.
95
Define the tricuspid valve.
The atrioventricular valve on the right side of the heart.
96
What is the normal heart beat?
Normal heart rate is 75 beats per minute. (bpm) and the average length of one cardiac cycle is 0.8 seconds.
97
Define cardiac cycle.
The sequence of events that takes place during one heart beat.
3 stages in the cardiac cycle:
1. Atrial systole
2. Ventricular systole
3. Ventricular diastole.
98
What does systole mean?
Contaction/Pumping
99
What diastole mean?
Relaxing/Filling
100
Describe atrial systole.
The length is 0.1 seconds.
The atrial contact.
The ventricle relax.
The atrioventricular valves are open.
Blood flows from atria to ventricles.
The semi lunar valves in vena cava, pulmonary vein are closed.
The pressure developed by this contraction is not very great because the muscular walls of the atria are only thin, but it is enough to force the blood in the atria down through the atrioventricular valves into the ventricles.
101
Define ventricular systole.
The length is 0.3 seconds.
The ventricles contract and the atria relax.
The semilunar valves are open.
Blood flows from the ventricles to the aorta and pulmonary artery.
The atrioventricular valves are closed which produces the "lub" sound.
The thick muscular walls of the ventricles squeeze inwards on the blood, increasing its pressure and pushing it out of the heart. As soon as the pressure in the ventricles becomes greater, then the pressure in the atria, the pressure differences push the atrioventricular valves shut, preventing blood from going back into the atria. instead blood rushes upwards into the aorta and the pulmonary artery, pushing open the semilunar valves in these vessels as it does so.
102
Define ventricular systole.
The length is 0.3 seconds.
The ventricles contract and the atria relax.
The semilunar valves are open.
Blood flows from the ventricles to the aorta and pulmonary artery.
The atrioventricular valves are closed which produces the "lub" sound.
The thick muscular walls of the ventricles squeeze inwards on the blood, increasing its pressure and pushing it out of the heart. As soon as the pressure in the ventricles becomes greater, then the pressure in the atria, the pressure differences push the atrioventricular valves shut, preventing blood from going back into the atria. instead blood rushes upwards into the aorta and the pulmonary artery, pushing open the semilunar valves in these vessels as it does so.
103
Describe ventricular diastole.
The length is 0.3/0.4 seconds.
The atria and ventricles relax.
Valves in vena cava, pulmonary veins and atrioventricular valves are open.
Blood flows from vena cava and pulmonary veins.
Blood flows to atria and trickles into ventricles.
Semilunar valves are closed and produces "dub" sound.
104
Describe what happens to pressure during systole.
Atrial Pressure>Ventricular Pressure
Ventricular pressure is lower than arterial pressure but increasing as blood fill heart.
The pressure in arteries is high but slowly decreasing as blood flows to entire body.
105
Describe the differences in pressure during ventricular systole.
Atrial pressure is much lower than ventricular pressure.
The ventricular pressure is high and increasing rapidly.
The pressure in arteries is high and also rapidly increasing as blood is pumped through aorta.
106
Describe the pressure differences in ventricular diastole.
The atrial pressure is low but increasing as blood fills the heart. The ventricular pressure is low but increasing as blood fills the heart.
The pressure in arteries is greater than the pressure in ventricles. The pressure in arteries is high but slowly decreasing as blood flows to entire body.
107
How do we measure changes in blood in atria, ventricles and arteries?
Blood pressure changes with stage of cardiac cycle.
Usually measure the pressure on the left side of the heart (aorta) due to high pressure and large difference in pressure as compared to right side.
108
Give a general overview on pressure in blood pressure in atria, ventricles and arteries.
Generally atrial pressure is relatively low because it has thinner walls and exerts less force. Atrial pressure increases during atrial systole. Ventricular pressure increases during ventricular systole. Aortic pressure increases during ventricular systole.
109
What is the change in blood pressure caused by?
Pulsates due to ventricular contraction.
Systolic pressure=Maximum blood pressure in the arteries.
Diastolic pressure=Minimum blood pressure in the arteries.
Human Blood pressure is usually between 80-120mmHg.
110
What could happen if the pressure developed in the right ventricle was too high?
For the right ventricle, the force produced must be relatively small, because the blood goes only to the lungs, which are very close to the heart. if the pressure developed too high, lung capillaries would be damaged and tissue fluid would accumulate in the lungs, hampering gas exchange.
111
Why is the thickness of the muscular wall of the left ventricle much greater than that of the right?
For most organs, mot of the time, the high pressures that the left ventricle is capable of producing is too great. So arterials reduce this pressure before blood flows into the capillaries. However during vigorous excercise, the arterials supplying blood to the muscles dilate and increase blood flow to them. The left ventricle must be able to develop enough force to ensure that there is still sufficient blood reaching other organs. For this reason the thickness of the muscular wall of the left ventricle is much greater than that of the right.
112
How do cardiac muscles differ from the rest in the body?
Cardiac muscle differ from the muscle in all other areas of the body in that it is myogenic.
113
Define myogenic.
A word used to describe muscle tissue that contracts and relaxes even when there is no stimulation from a nerve.
114
How is the cardiac cycle initiated and and coordinated?
Wave of excitation/electrical impulses is passed through the:
1. The sinoatrial node (SAN)
2. The atrioventricular node (AVN)
3. Purkyne tissue
115
Why does the heart have its own built-in controlling and coordinating system?
Individual heart muscles cells cannot be allowed to contract at their own natural rhythms. If they did, parts of the heart would contract out of sequence with other parts. The heart has its own built-in controlling and coordinating system which prevents this from happening.
116
Describe the sinoatrial node:
*Determines rhythm of heart
*Also called pacemaker
*Found at the wall of the right atrium
1. SAN/Pacemaker sends out waves of excitation/electrical impulses.
2.Impulses spread out across the atria →Both atria contract simultaneously
→Result in atrial systole
* But non-conducting tissue prevents pulses from reaching the ventricle
→so atria and ventricle do not contract at the same time.
Wave of excitation passed to the AVN.
117
Describe the atrioventricular node.
AVN is found between the atria.
Prevents the atria and ventricles from contacting at the same time.
Acts as a relay station.
3. There is a time delay of 0.1~0.2 seconds.
→allows atria to empty
→and ventricles to fill
4. AVN sends wave of excitation to ventricles
Wave of excitation passed to purkyne tissue.
118
What are purkyne tissue?
Tiny bundles of connecting fibres.
Found at base of ventricles.
5. Purkyne tissue conduct excitation to base of spectum/ventricles.
6. Electrical impulses spread upwards in ventricle walls.
→Ventricle muscles contract from base upwards.
→Ventricles force blood up from base.
→Result in ventricular systole.
119
What is the refractory period?
Period of insensitivity to any stimulation.
~0.4 seconds.
Atrial and ventricular muscles relax.
Diastole.
120
