Transport In Animals Flashcards
1
Q
What are the three main types of blood vessels?
A
- Arteries
- Veins
- Capillaries
2
Q
What are the three layers of the walls of blood vessels?
A
- Tunica externa
- Tunica media
- Tunica interna
3
Q
Describe the tunica externa
A
- Outermost layer
- Tough
- Made up of thick collagen fibres
4
Q
What is the use of the tunica externa?
A
Collagen fibres in it provide strength and prevent extensive stretching of the vessel
5
Q
Describe the tunica media
A
- Middle layer
- Consists of smooth muscle, collagen and elastic fibres
6
Q
What is the use of the tunica media?
A
- The structural proteins in it allow for stretching during vasodilation and the smooth muscles for distension and constriction of the walls of the blood vessel
7
Q
Describe the tunica interna
A
- Innermost layer
- composed of a single layer of squamous endothelium.
- It is found in all walls of blood vessels.
8
Q
What is an artery?
A
A blood vessel that transports blood away from the heart
- Generally oxygenated blood except the pulmonary artery which transports deoxygenated blood from the heart to the lungs
- The umbilical artery is another exception
9
Q
What is a vein?
A
A blood vessel that transports blood towards the heart
- Generally deoxygenated blood except the pulmonary vein which transports oxygenated blood from the lungs to the heart
- The umbilical vein is another exception
10
Q
Compare arteries and veins
A
- Arteries have thicker walls than veins
- The walls of arteries are more elastic than those of veins
- Arteries have more collagen tissues than veins
- Arteries have a narrower lumen than veins
- Veins have valves while arteries lack valves
- Blood in arteries moves in from of pulses while in veins it flows smoothly without any pulse
- Arteries transport blood from the heart to the body tissues while veins transport blood from the body tissues to the heart
11
Q
What is a pulse?
A
A series of waves of dilation that pass along the arteries caused by the pressure of the blood pumped from the heart through contractions of the left ventricle.
12
Q
Why do arteries have thicker walls than veins?
A
Arteries have thicker walls than veins because blood moves through them a a higher pressure than in veins due to the pumping action of blood by the heart.
Thick walls counteract the pressure with which blood moves through them
13
Q
Why are the walls of the arteries more elastic than those of veins?
A
Pressure of blood in arteries is higher than that of blood in veins.
More eleastic walls in arteries are in order to overcome the pressure by which blood flows through them by rapidly stretching without bursting.
14
Q
Why do arteries have a narrower lumen than veins?
A
Narrow lumen maintains the high pressure of the blood flowing through them which reduces the time taken for blood to reach sites where it is needed. In veins, a wide lumen reduces on resistance to blood flow
15
Q
Why do arteries lack valves but veins have valves?
A
Valves in veins prevent the backflow of blood. However, arteries do not need valves since they transport blood under high pressure, which pressure ensures that blood flows forward.
16
Q
True or false
Veins are located between muscles which helps to push blood forward with muscle contraction
A
True
17
Q
Describe the structure of blood capillaries
A
- Smallest blood vessels
- In close contact with tissues
- Numerous
- Thin and permeable membrane
- Possess capillary sphincter muscles
18
Q
What are the adaptations of capillaries to their function in the body?
A
- Blood capillaries are the smallest blood vessels found in close contact with tissues in form of a dense network which allows a high rate of diffusion of materials during their exchange between the blood circulatory system and the tissues.
- They are numerous in number to provide a large surface area which increases the rate of diffusion and allows rapid exchange of materials between blood and the tissue fluid.
- They have a thin and permeable membrane which is made up of thin flattened pavement cells which allow rapid diffusion and exchange of materials between blood and tissues with minimum resistance.
- They possess the capillary sphincter muscles which contract and relax so as to regulate the amount of blood entering into the capillary network.
- Some capillaries have a bypass arteriovenous shunt vessel which links the arterioles and venules directly so as to regulate the amount of blood which flows through the capillary network e.g. in the capillaries of the feet, hands, stomach e.t.c.
- The capillary network offers maximum resistance to blood flowing through them hence decreasing the speed of blood flow which allows the maximum diffusion and exchange of materials between blood and the tissues.
19
Q
What is the main artery in the body?
A
Aorta
20
Q
What is the main vein in the body?
A
Vena cava
21
Q
What is the importance of a blood circulatory system/ blood?
A
- Tissue respiration
It enhances the formation of energy in the tissues by transporting oxygen and soluble food substances to the tissues to be used as raw materials for respiration. - Hydration
Blood transports water from the gut to all tissues. - Nutrition
Blood transports the soluble well digested foodmaterials from the gut to the body tissues. - Excretion
Blood transports metabolic waste products from the tissues to the excretory organs for their removal from the body e.g. urea from the liver to the kidney in order for removal. - Temperature regulation
Blood distributes heat from the organs where it is mainly generated e.g. the liver and the muscles, uniformly throughout the body. - Maintenance of constant pH
Blood maintains a constant pH through the maintenance of circulation of the plasma proteins manufactured by the liver which act as buffers to maintain the pH of the body fluids constant. This enables enzymes to function efficiently as changes will denature the enzyme. - Growth, development and co-ordination
Blood transport different metabolites such as glucose, amino acids and hormones needed for the growth and development of the body. - Defence
Blood defends the body against diseases through the following ways;
a. By using some white blood cells (leucocytes) which phagocytotically ingest and destroy pathogens that cause diseases.
b. By formation of a blood clot around the wound so as to prevent entry of microbes or pathogens into the body.
c. By use of the immune response mechanism towards infection e.g. by use of the different types of antibodies to destroy the microbes.
22
Q
True or false
The mammalian blood circulation is double circulation
A
True
23
Q
Explain what causes the rise and fall In pressure across arteries
A
- The cardiac muscles are involved
- Peaks coincide with contraction/ systole
- Troughs/falls coincide with relaxation/diastole
24
Q
What causes a drop in blood pressure as it flows from arteries to veins?
A
- with increasing distance from the heart, blood pressure falls due to decrease in blood volume
- Increased resistance to blood flow
- Less recoil effect
- Increasing volume of arterioles and capillaries
- Branching nature of large blood vessels into smaller vessels
25
Why is it important that by the time blood reaches the capillaries it is at a lower pressure?
- to stop damage to the capillaries as they can’t withstand high-pressure
- Slow flow allows for efficient exchange of materials for example amino acids
- They lack much electricity since they are one cell thick
- They lack collagen and muscles
26
How is blood able to flow through the venous system despite low blood pressure?
- Valves to prevent backflow
- Action of skeletal muscles propels blood in the veins forward by constricting them
- Large lumen of the veins reduces resistance to the flow of blood
- Negative pressure in the thoracic region where the heart is located favors the flow of blood
- Gravity effect from areas above the heart
27
With reference to the functioning of arteries, explain how blood flow to organs such as kidneys is decreased during strenuous exercise.
Because the body needs to get more blood to the muscles, it diverts blood flow from non-exercising tissues, like kidneys and intestine. Muscles need more blood to account for the new oxygen demand. The sympathetic nervous system causes vasoconstriction of vessels taking blood to the organs not needed, and sends more blood to the muscles.
28
How do arteries function?
By contracting and relaxing (vasoconstriction and vasodilation)
29
True or false
Fibrin is the soluble form of fibrinogen
False
Fibrinogen is soluble, fibrin is insoluble (constituent of blood clots)
30
What is the function of erythrocytes in the body?
Transport of oxygen from the lungs to the tissues (in form of oxyhaemoglobin) and carbon dioxide from tissues to the lungs
31
Where are erythrocytes manufactured?
- The bone marrow in adults
- The liver in the foetus.
32
Describe the structure of erythrocytes
- Bi-concave disc shaped
- Contain haemoglobin pigment
- Have a thin permeable membrane
- Have enzyme carbonic anhydrase
- Have a flexible membrane
- (Lack nuclei)
33
What are the adaptations of erythrocytes to their function in the body?
i. They have a bi-concave disc shape; provides a large surface area that enhances maximum diffusion of enough oxygen into them.
ii. They lack a nucleus; to provide enough space for haemoglobin in order to carry a lot of oxygen in form of oxyhaemoglobin.
iii. They have a red pigment called haemoglobin in their cytoplasm which has a high affinity for oxygen and therefore rapidly transports oxygen.
iv. They have a thin and permeable membrane which enables faster diffusion of oxygen and carbon dioxide into them.
v. They have an enzyme known as carbonic anhydrase within their cytoplasm which enables most of the carbon dioxide to be transported in form of bicarbonate ions (HCO3-), by catalyzing the reactions between carbon dioxide and water to from carbonic acid.
vi.They have a pliable membrane (flexible membrane) which can enable them change their original shape and squeeze themselves into the blood capillaries in order to allow the exchange of respiratory gases.
34
What is the use of leucocytes in the body?
Defend the body against infections
35
Describe the structure of white blood cells
- Amoeboid shaped
- Have a nucleus
- Colourless cytoplasm important for defense of the body against infections.
36
Where are white blood cells manufactured?
Bone marrow
37
Where do granulocytes originate? What are the three types?
Bone marrow
Basophils
- Produce heparin (anticoagulant) and histamine (released during allergic reactions)
Eosinophils
- Possess anti-histamine properties (combat the effect of histamine)
Neutrophils/ phagocytes
- Engulf pathogens and digest them actively
38
Where do agranulocytes originate? What are the two types?
Bone marrow and lymph nodes
Monocytes
- Enter tissues and develop into macrophages which carry out phagocytosis to defend the body against pathogens
Lymphocytes
- Produced in the thymus gland and lymph nodes
39
What is the use of blood platelets (thrombocytes) in the body?
Start up the process of blood clotting
40
Describe the structure of blood platelets
- Irregularly shaped
- Membrane bound cell fragments
- Formed from bone marrow cells
- (Lack nuclei)
41
Describe the structure of haemoglobin
- Composed of 4 polypeptide chains
- 2 coil to form an alpha helix and the other 2, beta chains
- Quaternary structure stabilized by many kinds of bonds that maintain the shape of the molecule
- Arranged around 4 haem groups
- It is a conjugated protein with the prosthetic group haem which has a central iron atom
- I haemoglobin molecule carries 4 oxygen molecules (8 oxygen atoms)
- The alpha chains contain 141 amino acids each
- beta chains contain 146 amino acids each
42
What does the oxygen dissociation curve indicate?
- A slight increase in the partial pressure of oxygen leads to a relatively sharp/steep increase in the percentage saturation of haemoglobin with oxygen.
- This indicates that haemoglobin has a high affinity for oxygen in that it readily combines with it and become saturated with it at low partial pressures of oxygen.
43
Why is it easier for haemoglobin to pick up more oxygen after the first oxygen molecule?
Haemoglobin undergoes structural rearrangement exposing other haem groups after the first oxygen molecule combines with it
44
Explain the shape of the oxygen dissociation curve
- At first it is gradual; haem groups in the molecule and not exposed, oxygen combines with difficulty
- Then it is rapid; the molecule shape of haemoglobin is distorted by the first oxygen molecule, haem groups are exposed and oxygen combination is rapid
- It is then gradual; haemoglobin gets more saturated with oxygen
- Finally it is constant; haemoglobin is fully saturated with oxygen
45
What is the effect carbon dioxide on the oxygen dissociation curve?
Increase in carbon dioxide concentration decreases the affinity of haemoglobin for oxygen, by making the pH of the surrounding medium more acidic (low), thereby shifting the oxygen dissociation curve to the right. (Bohr’s effect)
46
Define Bohr’s effect
This may be defined as the lowering of the affinity of blood’s haemoglobin for oxygen due to increased acidity caused by increase in carbon dioxide concentration.
47
What does shifting the oxygen dissociation curve to the left mean?
- Haemoglobin has a higher affinity for oxygen and therefore becomes fully saturated with it at very low partial pressures of oxygen.
- It also means that haemoglobin has a low rate of dissociation to release oxygen to the tissues but a high rate of combining with oxygen.
48
What is the effect of carbon monoxide on the affinity of haemoglobin for oxygen?
- There’s a loose and reversible reaction between oxygen molecules and iron (II) atoms of haem groups of haemoglobin to from oxyhaemoglobin.
- This means that iron (II) is not oxidized to iron (III) as haemoglobin combines with oxygen.
- In the presence of carbon monoxide and oxygen, haemoglobin combines readily with carbon monoxide to form a permanent compound known as carboxyhaemoglobin rather than combining with oxygen.
- A permanent carboxyhaemoglobin compound is formed because carbon monoxide oxidizes iron (II) to iron (III).
- This reduces the free haemoglobin molecules available to transport oxygen molecules to the tissues, which makes the tissues develop symptoms of anoxia (total lack of oxygen in the tissues)
49
Why is carbon monoxide referred to as a respiratory poison?
It can readily combine with haemoglobin much more than oxygen and the product formed i.e. carboxyhaemoglobin does not dissociate.
50
True or false
Myoglobin is a respiratory pigment which also contains iron containing haem groups
True
51
Where is myoglobin mostly found?
In the muscles
(where it remains fully saturated at partial pressures below that required for haemoglobin to give up its oxygen.)
52
True or false
Myoglobin has a higher affinity for oxygen than haemoglobin
True
(in a way that it combines readily with haemoglobin and it becomes fully saturated with oxygen at a lower partial pressure of oxygen)
53
What is the function of myoglobin in the body?
Myoglobin acts as a store of oxygen in resting muscles in form of oxymyoglobin and only releases the oxygen it stores only when oxyhaemoglobin has been exhausted i.e. many vigorous activities because myoglobin has a higher affinity for oxygen than haemoglobin.
54
True or false
The oxygen dissociation curves for myoglobin lies to the right of that of haemoglobin
False
It lies to the left of that of haemoglobin
55
Where does the oxygen dissociation curve of the lungworm’s haemoglobin lie relative to that of man’s haemoglobin?
On the left of that of man’s haemoglobin
- This indicates that the haemoglobin of the lungworm has a higher affinity for oxygen than that of man.
- This is because the lugworm lives in oxygen deficient mud and so in order to extract enough oxygen from that environment of low oxygen tension, the haemoglobin of the lugworm must have a higher affinity for oxygen than that of man thriving in a well supplied environment with oxygen.
- This makes the lungworm less active than man, who releases much oxygen rapidly to the tissues.
56
True or false
The dissociation curves of smaller animals are on the right of the larger animals
True
- Small animals have higher metabolic rates and so need more oxygen per gram of tissue than larger animals.
- Therefore they have blood that gives up oxygen more readily
57
True or false
The oxygen dissociation curve during exercise is to the left of that when the individual is at rest
False
It is to the right of that when the individual is at rest
- During exercise, the oxyhaemoglobin releases oxygen more readily hence the oxygen dissociation curve during exercise is to the right of that when the individual is at rest
58
Where does the oxygen dissociation curve of foetal haemoglobin lie relative to maternal haemoglobin?
It lies to the left of maternal haemoglobin
- Foetal hemoglobin has a higher affinity for oxygen than that of man.
- This enables the foetal haemoglobin to pick sufficient oxygen from the mother via the placenta and also increases on the oxygen carrying capacity to the tissues, especially when the foetus needs a lot of energy
59
What is the effect of changing altitude on oxygen carriage?
- Volume of oxygen is less at high altitudes than at sea level
- When an organism moves from the sea level to high altitudes, very fast, they tend to develop symptoms of anoxia (lack of oxygen) which include headache, fatigue, nausea, and becoming unconscious.
- However, when an organism moves slowly from sea level to high altitudes like the mountain climbers, such an organism can at first develop symptoms of anoxia but later on such symptoms disappear due to adjustments in the respiratory and circulatory systems in response to insufficient oxygen reaching the tissues from the surrounding.
- The amount of haemoglobin increases
- Red blood cell count increases
- Rate of breathing increases
- Heart beat increases
- More red blood cell formation occurs in the bone marrow under the control of the hormone called erythropoietin secreted by the kidney.
- Increase in the amount of haemoglobin and red blood cells together with increase in the breathing rate and heart beat increases the oxygen carrying capacity of the blood to the tissues which leads to the disappearance of the symptoms of anoxia and which also makes the individual organism to be acclimatized.
60
Define Acclimatization
A condition whereby an organism carries out a series of physiological adjustments in moving from a low altitude area to a high one to avoid symptoms of anoxia so that such an organism can survive in an environment of low oxygen content.
61
What position is the oxygen dissociation curve of mammals that live in regions beyond the sea level relative to that of those at sea level?
It is on the right of those that live at sea level
62
How do mammals that live above sea level solve the problem of lack of enough oxygen in the atmosphere?
By possessing haemoglobin with a higher affinity for oxygen than that of mammals at sea level.
This enables the high altitude mammals to obtain enough oxygen through the oxygen deficient environment
(This explains why the oxygen dissociation curve of the haemoglobin of the llama lies to the left of that of other mammals at sea level )
63
What is the effect of temperature on haemoglobin oxygen dissociation curve?
A rise in temperature lowers the affinity of haemoglobin for oxygen thus causing unloading from the pigment i.e. a rise in temperature increases the rate of dissociation of oxyhaemoglobin to release oxygen to the tissues.
This is useful in the muscles.
Increased tissue respiration which occurs in the skeletal muscles during exercise generates heat. The subsequent rise in temperature causes the release of extra oxygen from the blood to the tissues.
This is so because increase in temperature makes the bonds which combine haemoglobin with oxygen to break, resulting into the dissociation of oxyhaemoglobin.
64
In what form is carbon dioxide mainly transported to the lungs from the body tissues?
In form of bi-carbonate ions (hydrogen carbonate ions) in blood plasma
65
In what ways may carbon dioxide be transported to the lungs from the body tissues?
1. In form of bicarbonate ions
2. In solution form. (A very small amount is carried as carbonic acid.)
3. Carbon dioxide may combine with the amino group of haemoglobin to form a neutral compound known as carbamino haemoglobin (HbCO2). (If less oxygen is being carried by haemoglobin molecule, then more carbon dioxide is carried in this way as HbCO2.)
66
Describe the transportation of carbon dioxide inform of hydrogen carbonate ions in blood
- When carbon dioxide is formed during respiration, it diffuses from the tissues into the erythrocytes, via their thin and permeable membrane.
- Inside the erythrocytes, carbon dioxide reacts with water in the presence of carbonic anhydrase enzyme to form carbonic acid
- The formed carbonic acid then dissociates into hydrogen ions and bicarbonate ions
- The formed hydrogen ions decrease the pH in erythrocytes which results into the dissociation of oxyhaemoglobin being carried from the lungs to the tissues into the free haemoglobin molecules as free oxygen molecules.
- The free oxygen molecules diffuse into the tissues to be used in respiration.
- The free haemoglobin molecules buffer the hydrogen ions (H+) inside the red blood cells into a weak acid known as haemoglobinic acid
- In case of excess H+, plasma proteins are used to buffer them into another weak acid called proteinic acid.
- The formed hydrogen carbonate ions within the erythrocytes diffuse out into the plasma along the concentration gradient and combine with sodium to form sodium hydrogen carbonate which is then taken to the lungs.
- The outward movement of bicarbonate ions from the erythrocytes into the plasma results into an imbalance of positively charged and negatively charged ions within the cytoplasm.
- In order to maintain electrochemical neutrality, to remove this imbalance in the red blood cells, chloride ions diffuse from the plasma into the red blood cells, a phenomenon known as the chloride shift
- When the bicarbonate ions reach the lungs, they react with H+ to form carbonic acid which eventually dissociates into carbon dioxide and water
- The carbon dioxide and water formed from the dissociation of carbonic acid in the lung capillaries are then expelled out by the lungs during exhalation so as to maintain the blood pH constant
67
Why do animals require a transport system?
- Surface area of the organism
- Surface area: volume ratio of the organism
- Activity of the organism
- The diffusion distance for the transported substances between the tissues to and from their sources.
68
What are the adaptations of arteries to their functions?
- Collagen for structural support
- Thick walls to withstand high pressure
- Elastic to rapidly stretch without bursting
- Narrow lumen to maintain blood pressure as it flows through the body
69
What are the adaptations of veins to their functions?
- Have valves to prevent backflow of blood
- Have wide lumen to reduce resistance to blood flow back to the heart
- Located between muscles which push blood forward when they contract
70
What is tissue fluid?
This is a fluid that bathes (surrounds) the cells
71
Describe the process of formation of tissue fluid
- At the arterial end of the capillary, pressure is high (there is high hydrostatic pressure) due to the pumping action of the heart and narrowness of the capillaries
- High hydrostatic pressure forces the fluid part of blood along with some small molecules eg glucose, mineral salts, oxygen through the capillary wall
- The fluid surrounds the tissues in the intercellular space by ultrafiltration
- Big molecules eg proteins and blood cells are retained in the blood
- At the venous end of the capillary bed, hydrostatic pressure is low
- Increased osmotic potential of the plasma proteins in blood causes tissue fluid to be drawn back into the capillaries
- Excess tissue fluid is drawn into the lymph vessels
72
Compare blood and tissue fluid
Similarities
- Both have nutrients
- Both have wastes
Differences
Tissue fluid
- In contact with the tissues
- Lack large molecules eg proteins, blood cells
- Colourless
Blood
- Confined to blood vessels
- Have large molecules eg proteins, blood cells
- Red
73
Describe the structure of the mammalian heart
- It is muscular
- Has four chambers
- Myogenic in nature
- Has valves
- Tendinous cords prevent the semi lunar valves from turning inside out
- Linked to four blood vessels
- Left ventricle is more muscular or thicker than the right
- Has coronary vessels
- Has a thick muscular septum
74
True or false
The initiation of contraction of the heart is under the control of the central nervous system
False
Cardiac muscle in the walls of the heart is myogenic (initiation of its contraction is within itself and not under the control of the central nervous system)
75
Of what benefit is the myogenic nature of the heart?
Enables the muscles to contract continuously and rhythmically without fatigue to enable the heart to beat without stopping.
76
What does shifting of the oxygen dissociation curve to the right mean?
- Haemoglobin has a lower affinity for oxygen
- higher rate of dissociation to release oxygen to the tissues rapidly to support tissue respiration
77
Why is the left ventricle thicker than the right ventricle?
- To generate a strong propulsive force to pump blood to far regions of the body
- The lungs are close to the heart thus the right ventricle does not need to generate a strong propulsive force
78
On which side of the heart are the bicuspid and tricuspid valves found?
Tricuspid- Right side
Bicuspid- Left side
79
What is the function of the septum in the heart?
Prevents mixing of oxygenated and deoxygenated blood in the heart
80
What is the role of the coronary blood vessels?
Supply the heart with nutrients and take away wastes
81
What are the adaptations of the heart to its function in the body?
- Has four chambers, atria and ventricles which receive and pump blood respectively
- Has cardiac muscles that don’t get fatigued allowing continuous pumping of the heart
- It’s contractions are myogenic (independent of the central nervous system)
- Thickened left side to generate a strong propulsive force to pump blood to far regions of the body
- Has valves which prevent backflow of blood into respective chambers
- Has coronary vessels that supply nutrients and take away wastes
- Surrounded by fats which are a shock absorber
- Have a muscular septum that prevents mixing of oxygenated and deoxygenated blood
- Found in the thoracic cavity in the rib cage to protect it from mechanical damage
82
Where is the Sino Atrial Node (SAN) located?
In the right atrium
83
Describe the process of initiation of the heartbeat
- The heartbeat is initiated by the Sino Atrial Node found in the right atrium wall
- Membranes of the cells of the SAN are permeable to sodium ions
- Sodium ions enter the cell and depolarize (activate) the cell membranes
- Wave of depolarization is generated which spreads rapidly from the SAN across both atria, causing simultaneous contraction
- Depolarization of the atrio-ventricular node (AVN) is delayed for about 0.1s to allow complete contraction of both atria
- Impulses from the AVN are conducted by bundle of His muscle fibres in the inter-ventricular septum towards the apex of the heart
- Purkinye tissue (Purkinje fibres) conduct impulses throughout the ventricular walls causing contraction of the ventricles and forcing blood into the aorta and pulmonary artery
84
Which valves are found on the base of the aorta and pulmonary artery?
Semilunar valves
85
What is the general name for bicuspid and tricuspid valves?
Atrioventricular valves
86
What causes the first heart sound, lub?
Closing of the artrioventrivular valves during ventricular systole
87
What causes the second heart sound, dub?
Closing of the semilunar valves
88
What causes the pulse in arteries?
Ventricular systole and elastic recoil of the arteries due to high pressure of blood
89
What is the difference between the PCG (phonocardiogram) and ECG (electrocardiogram)?
PCG- recording of the sound the heart makes
ECG- recording of the electrical activity of the heart
90
What is cardiac output?
The volume of blood pumped from each ventricle
91
What is the cardiac cycle?
This is the sequence of events of heart beat by which blood is pumped around the body.
92
Describe the cardiac cycle
- The cardiac cycle begins with the contractions of the atria i.e. atrial systole, which is initiated by SAN
- Atrial systole causes the atrial volume to decrease and the atrial pressure increases.
- As the atria contracts, the ventricles relax i.e. undergo ventricular diastole
- The bicuspid and tricuspid valves close.
- The contraction of the atria due to blood entering the atria forces the bicuspid and tricuspid valves to open so that blood moves from atria into the ventricles.
- (Contraction of atria walls has an effect of sealing off the venacava and pulmonary veins, thereby preventing the back flow of blood into the vessels as the blood pressure rises within the atria. It takes 0.1 seconds.)
- When the ventricles are filled with blood from atria, their walls contract simultaneously i.e. ventricular systole, and the atria relax i.e. atrial diastole.
- Ventricular systole is initiated by impulses from AVnode to the bundle of His, Purkije fibres and rapidly through the ventricle muscles.
- The ventricles’ volume reduces while the pressure increases, forcing the bicuspid and tricuspid valves to close and prevent the back flow of blood into the atria.
- The increased pressure in the ventricles also forces blood to be pumped into the pulmonary artery via the open semi lunar valves from the ventricles.
- This enables the blood to be pumped into the lungs via the pulmonary artery and into the body tissue via the aorta.
- After ventricular systole, there’s a short period of simultaneous atrial and ventricular relaxations.
- Relaxation of the atrial wall and contraction of the ventricle, initiates the refilling of the atria by blood under relatively low pressure i.e. deoxygenated blood in the venacava flows into the right atrium and oxygenated blood from the lungs flows into the left atrium via the pulmonary vein.
93
Why is ventricular systole more powerful than the atrial systole?
The ventricles are more muscular than the atria and therefore generate more pressure.
94
True or false
The rate at which the heart beats to pump blood is under the control of the autonomic (Involuntary) nervous system.
True
95
Describe how the heart beat is controlled
- The heart has sympathetic nerves from the sympathetic autonomic nervous system and the vagus nerve, a branch of a parasympathetic autonomic nervous system.
- The nerves modify the rate at which the pace maker gives waves of electrical excitations hence controlling the speeding up or slowing down of the rate of the rate of heart beat.
- When the rate of heart beat increases beyond the normal rate, the vagus nerve (parasympathetic nerve) is stimulated such that it lowers back to normal the rate of heart beat.
- If however, the rate of the heart beat lowers below the normal rate or if there’s need for higher rate of heart beat the sympathetic nerve is stimulated to bring back or increase to the cardiac frequency usually to the normal rate.
Note:
Cardiac output = Rate of heartbeat x Cardiac frequency
96
True or false
The sympathetic and vagus nerves are antagonistic, functionally.
True
97
True or false
Parasympathetic (vagus) nerve increases heartbeat
False
It decreases heartbeat
98
What internal factors affect the heart beat?
1. Body temperature (homeostatic reasons)
2. Blood pH/ Carbon dioxide concentration(oxygen required)
4. Partial pressure of oxygen (low partial pressure means higher heartbeat)
5. Hormonal balance (homeostatic)
6. Salt balance (homeostatic/ osmoregulatory)
7. Blood pressure
8. Emotional situations
99
Define immunity
The capacity of an organism to recognize the entry of materials foreign to the body and mobilize cells and cell products to remove such foreign materials with greater speed and effectiveness
Or
The capacity of an organism to recognize the entry of materials foreign to the body and fight against infection
100
What are some of the defensive mechanisms of blood?
- Clotting of blood
- Phagocytosis
- Immune response to infection
101
What is the importance of clotting of blood?
- Prevents further blood loss
- Prevents entry of pathogens
102
Describe the process of blood clotting
- When blood platelets and damaged tissues are exposed to air, the platelets disintegrate and release an enzyme called thromboplastin or thrombokinase
- In the presence of plasma proteins and calcium ions thromboplastin/ thrombokinase catalyses the conversion of a plasma protein, Prothrombin into thrombin enzymes.
- Thrombin catalyses the hydrolysis of a plasma protein called fibrinogen into an insoluble protein called fibrin.
- Fibrin forms fibres at the wounded area.
- Within the fibrous network of fibrin blood cells become trapped, thereby forming a fibrin clot or a blood clot.
103
What is the use of heparin?
It is an anticoagulant that inhibits conversion of prothrombin to thrombin thus preventing blood clotting
104
Apart from blood clotting, how else may the entry of microbes into the body be prevented?
- Using impermeable skin and its protective fluid called sebum (oily secretion in the skin)
- Using mucus and cilia to trap the microbes and then remove them
- By using hydrochloric acid in the stomach
- By using lysozyme enzyme in the tears and nasal fluids
- By vomiting and sneezing
- Wax in the ears
105
Why doesn’t blood clot in the vessels?
- Presence of heparin which is an anticoagulant that prevents blood clotting
- Blood vessels are smooth to the flow of blood, mitigating damage to the endothelium which would cause clotting
106
Which cells mainly carry out phagocytosis to defend the body from pathogens?
Neutrophils and macrophages (obtained from Monocytes)
107
Describe the process of phagocytosis as the body’s first line of defense to infection by bacteria
- The amoeboid cells are attracted to areas where cell and tissue damage has occurred.
- The neutrophils are able to recognize any invading bacterial cells.
- This is enhanced by opsonins(plasma proteins btw) which become attached to the surface of the bacteria and make them easily recognize by the neutrophils.
- The neutrophils bind to the bacteria so as to carryout Phagocytosis.
- After binding themselves to the bacteria, the bacteria are engulfed in an amoeboid fashion and then a phagosome is formed.
- Primary lysosomes within the neutrophils fuse with the phagosome to form a phagolysosome.
- Hydrolytic enzymes are poured into the phagolysosomes from which the lysosomes and the bacteria are digested.
- The soluble materials of bacterial secretion are then absorbed in the surrounding cytoplasm of neutrophils.
108
By what process do neutrophils squeeze themselves through the walls of blood capillaries into the tissue spaces?
Diapedesis
109
What is an antigen?
- This is a foreign material to the body which stimulates the body to produce antibodies
110
What is an antibody?
- This is a protein molecule synthesized in response to the presence of the antigen for which it has high affinity
111
Define opsonization
This is the coating of bacteria with proteins called *opsonins* so that they can be easily destroyed by phagocytic enzymes.
112
Describe the types of antibodies and their types of activities
a) Opsonins
- These are antibodies which get attached onto the surface of the pathogens to enable phagocytic leucocytes to recognize the pathogens, then engulf and destroy them.
b) Agglutinins
- These are antibodies which cause foreign cells in the specific antigen to clump together making them more vulnerable to attack from other types of antibodies.
- This is called agglutination
c) Lysins
- These are antibodies which attach themselves on the antigens (foreign bodies) causing such antigens to burst and rupture into smaller pieces.
- The process is called lysis.
d) Antitoxins
- These are antibodies produced in response to particular bacterial toxins to which they bind and neutralize their harmful effect.
- The process is called neutralization.
e) Precipitin
- This is antibody which combines with its specific soluble antigen to form a precipitate which is more easily ingested by phagocytes.
- This process is called precipitation i.e. a process in which precipitin antibodies binds together soluble antigens into larger units which are easily ingested by the phagocytes.
113
What are the two types of lymphocytes?
T-lymphocytes and B-lymphocytes
114
Where do B-cells originate?
In the bone marrow from stem cells
115
Where do T-cells originate?
In the thymus gland, afterwards they enter the lymph nodes by osmosis
116
True or false
T-lymphocytes produce antibodies
False
117
What do T-lymphocytes do when a particular antigen enters the lymph nodes?
- They divide by mitosis and give rise to different types of T-cells including Killer T-cells, Helper T-cells and suppressor T-cells
Killer T-cells
- These are cells which attach to invading cells and destroy/ kill the invading cells
Helper T-cells
- These are cells that recognize a specific antigen on an antigen-presenting cell, binds to it, and then assists a B-cell binding the same antigen to proliferate into specific antibody secreting cells.
Suppressor T-cells
- These suppress the activity of the killer T-cells and B-cells after the microbes have been cleared out of the body to prevent these cells from attacking and destroying the body cells.
- Suppressor T-cells therefore regulate the immune response and prevents antibodies from being produced by the B-cells.
118
What do the T-helper cells do?
- Activate T-killer cells to kill/destroy germs
- Activate B-lymphocytes
119
What occurs when B-lymphocytes have been activated by T-helper cells?
- They duplicate and multiply by cell division
- Differentiation of cells occurs in which they become specialized into either;
- Plasma cells; these produce antibodies which fight off the germs (short lived)
- Memory cell; retain information about germs. (Long lived)
120
Describe the structure of an antibody
- An antibody is a protein molecule
- It is Y-shaped
- Made up of four polypeptide chains
- Chains are linked together by hydrogen bonds and disulphide bonds.
- Two chains are long and slightly bent at the hinge (heavy chains)
- The two other polypeptide chains are short polypolypeptide chains
- Each polypeptide chain is composed of a constant region and a variable region
- The constant region is the one composed of the same amino acid sequence in all different molecules of antibodies
- In the variable region, the amino acid sequence varies with different molecules of antibodies.
- At one end, the two linked heavy and light chains is an antigen binding site where a specific antigen becomes attached.
121
What are the features/ characteristics of the immune system?
- Specific; a given antibody only attacks a given antigen
- Distinguishes self-antigens eg blood groups from foreign antigens
- Memory; retain information about an antigen
- Self regulating; switches off response in absence of pathogens
122
Describe the different types of immunity
1. Natural passive immunity
- This involves passing antibodies in the body of an organism into the body of another organism of the same species
- e.g. from the mother to the foetus via to the placenta to defend the body against disease and also via the first milk called colostrum to the child.
- This type of immunity is temporary.
2. Acquired passive immunity
- This is the immunity in the body whereby the antibodies in the body of an organism are extracted and injected into the body to offer temporary immunity
- e.g. the antibodies for tetanus.
3. Natural active immunity
- This is the immunity that involves formation of antibodies by the body of an organism in the presence of certain antigens.
- This type of immunity is permanent because during the immune response, memory B-cells are produced which recognize the microbes on reinfection (second infection) and then stimulate the rapid production of large amounts of antibodies to curb down the microbes before causing significant damage. Memory B-cells stay for long in blood.
4. Acquired active immunity
- This involves introducing a small amount of antigens (attenuated/weakened germs) (vaccines) orally or by injection into the body of an organism to provoke and stimulate it to produce corresponding antibodies.
- This results in rapid immune response towards the living microbes in case of an infection because of production of memory B-cells which cause greater production of many antibodies on second infection.
123
What advantage does active immunity have over passive immunity?
Provides long lasting immunity since the antibodies are synthesized by the body itself
124
What advantage does passive immunity have over active immunity?
Has immediate effects since antibodies are given to the body from outside itself
125
What is a vaccine?
These are toxic chemicals or attenuated (weakened) microbes introduced into the body of an organism to make it produce very many antibodies against a certain pathogen.
126
What are attenuated microbes?
Living microbes which are inactivated and they lack powers to infect the body due to the chemical or temperature treatment given to them.
127
Define blood transfusion
This is the transfer of compatible blood from the donor to the recipient.
128
What antigen is present on the surface of the RBC of a person of blood group A?
What antibody is in the blood plasma of that person?
- Antigen A
- antibody b
129
What antigen is present on the surface of the RBC of a person of blood group B?
What antibody is in the blood plasma of that person?
- Antigen B
- antibody a
130
What antigen is present on the surface of the RBC of a person of blood group AB?
What antibody is in the blood plasma of that person?
- Both antigen A and B
- no antibody in the blood plasma of that person
131
What antigen is present on the surface of the RBC of a person of blood group O?
What antibody is in the blood plasma of that person?
- no antigen
- both antibody a and b
132
True or false
Blood plasma permanently contains antibodies depending on a particular blood group
True
133
Why don’t the antibodies of a particular blood group correspond to their respective antigen?
Agglutination would occur (precipitation of blood).
134
Why are individuals with blood group O called universal donors?
They lack antigens which would react with the corresponding antibodies in the recipient’s blood.
135
Why are individuals with blood group A called universal recipients?
They lack antibodies in their blood plasma which would have reacted with the corresponding antigens in the donor’s blood.
136
People with D-antigens on the surface of their erythrocytes are called?
Rhesus positive (Rh+)
137
People without D-antigens on the surface of their erythrocytes are called?
Rhesus negative (Rh-)
138
How does the Rhesus factor affect pregnant mothers and their unborn children?
- The bodies of individuals do not have already manufactured antibodies against the D-antigens.
- When an expectant mother who is Rh- bears the foetus with which is Rh+, some foetal erythrocytes with D-antigens will cross the placenta and enter into the blood circulation of the Rh- mother towards the end of the pregnancy
- It is also possible for the blood of the foetus to mix with that of the mother during birth so that the mother gets Rh+ by getting the D-antigens from the child.
- The D-antigens that have entered the mother’s blood circulation stimulate the maternal body to manufacture corresponding antibodies (antibody-d or anti-D antibodies) which attack and react with the D-antigens in the mother.
- Some formed antibodies-d can also pass via the placenta and enter the foetal blood circulation where they attack and react with the D-antigens in the foetal blood
- This results into clumping together and bursting of the foetal red blood cells, a condition called erythroblastosis foetalis (Haemolytic disease of the new born).
- This disease results into acute anaemia which can lead to death of the feotus.
139
Why does the first born rarely with regard to the Rhesus factor?
- The time is too short for the mother to produce enough antibodies that can pass to the foetus to cause death
- However subsequent Rh+ foetus can die due to the many antibodies of the mother entering its circulation to cause agglutination.
140
Why are viruses hard to treat?
- They mutate
- HIV in particular is a retrovirus (it uses the individual’s DNA to synthesize its own DNA)
141
How does HIV work?
- HIV enters the T-helper cells
- This renders them non-functional
- HIV multiplied and the cell bursts giving rise to many new HIV particles
- Rise in HIV particles results in decrease of T-helper cells thus lowering the immunity of the infected person
142
How do ARVs work?
- They surround T-helper cells and enclose the HIV particles within them
- T-helper cells remain many without bursting and HIV particles are prevented from multiplying
143
True or false
Sympathetic nerve increases heart beat
True
144
What can be done to prevent haemolytic disease of the newborn?
Pregnant mothers can be given anti-D chemicals 72hours to delivery or within 72 hours after her first born, to render her immune system insensitive towards the D-antigen
- Also the blood of the foetus can be transfused with normal blood to dilute antibody-D so as to save the child.
145
What are the three distinct characteristics of vascular systems in animals?
a. It has a circulating fluid e.g. blood
b. It has a pumping device inform of a
modified blood vessel or a heart.
c. It has tubes through which the fluid can circulate e.g. blood vessels
146
Why do animals require a transport system?
- Surface area of the organism
- Surface area: volume ratio of the organism
- Activity of the organism
- The diffusion distance for the transported substances between the tissues to and from their sources.
147
Define open circulation
Open circulation is the flow of blood through the body cavities called Haemocoel instead of flowing in blood vessels.
This exists in most arthropods, molluscs and tunicates.
148
Describe the mechanism of open circulation in arthropods
- Blood flows through the heart from the posterior end to the anterior end by waves of contractions (systole) which begin from the posterior end and proceed to the anterior end.
- These waves of contractions enable blood to flow through the heart and then enter the perivisceral cavity.
- During systole, the heart ligaments are stretched such that during diastole they pull the heart walls outwards, thereby decreasing the pressure in the heart and increasing its volume.
- This results into sucking of blood into the heart via the ostia from the perivisceral cavity which has a higher pressure than the pericardial cavity.
- The ostia have valves that prevent the back flow of blood.
- During diastole, the alary muscles contract which increases the volume of the heart and reduces the pressure at the same time.
- The drop in pressure leads to movement of blood from the haemocoel through the ostia into the heart.
- Contraction of the alary muscles also has the effect of pulling the pericardial membrane downwards, thereby raising the blood pressure in the perivisceral cavity and decreasing it in the pericardial cavity, hence blood flows into the pericardial cavity.
- The heart chambers are equipped with valves which allow blood to enter, but not to leave, the heart through them.
149
Define a closed vascular system
In a closed vascular system, blood flows in blood vessels or sinuses.
It occurs in all vertebrates, annelids such as earthworms, cephalopods and echinoderms.
150
What is the benefit of a closed vascular system?
The distribution of blood in this system is adjustable e.g. blood from the heart is at high pressure and that to the heart is at low pressure.
151
Define single circulation
Single circulation is the flow of blood through the heart once for every complete circulation around the body.
Single circulation occurs in fish and the deoxygenated blood from the body tissues is pumped by the heart to the gills from where it flows back to the body tissues and eventually returns to the heart.
152
What is the problem of single circulation?
Blood tends to move very slowly at the venous side due to the significant drop in pressure before completing the circulation.
153
What causes the drop in pressure in single circulation?
This is as a result of capillaries having a considerable resistance to blood flow i.e. capillaries in the gills and body tissues.
154
How is the sluggishness of blood flow at the venous side in fish solved?
By replacing the veins with large sinuses which offers minimum resistance towards blood flow.
155
Define double circulation
This is the flow of blood through the heart twice for every complete circulation around the body.
156
Which organisms have a four chambered heart?
Reptiles (only crocodiles), birds and mammals
157
Which organisms have a three chambered heart?
The frog and toad experience double circulation although its heart has three chambers namely; one ventricle and the two atria i.e. the left and right atria.
The folding in the walls of the ventricle enhances the separation of deoxygenated blood from oxygenated blood and this separation is also facilitated by the spinal valves in the conus arteriosus.
158
Why is the diameter of the RBC wider than the capillary lumen?
As the RBC squeezes through the narrow capillary lumen, the cell membrane and capillary walls are in close contact thus diffusion distance is reduced and rate of diffusion increases
159
Why is haemoglobin transported in RBCs and not directly in blood?
Haemoglobin being transported in blood would make it more viscous which would reduce blood flow to the tissues, supply of oxygen would not meet demands of the organism
160
What happens to mature RBCs?
Destroyed in the liver to form bile
161
What are the differences between red and white blood cells?
Red
- No nucleus
- Biconcave shaped
- Transports respiratory gases
White
- Nucleus
- Amoeboid shaped
- Defense against infection
162
Describe the structure of agranulocytes
- Spherical or bean shaped nucleus
- No granules
163
Describe the structure of lymphocytes
- Round
- Small quantity of cytoplasm
164
Explain how the substitution of only one amino acid can be dangerous.
- In sickle cell anaemia, the fault occurs at the sixth amino acid in the beta chain. The amino acid should be glutamic acid, however it is replaced by valine.
- This leads to crystallization of haemoglobin, HbS (pg 859 BS)
165
What is the oxygen dissociation curve?
Sigmoid curve obtained when percentage saturation is plotted against oxygen partial pressure
166
What causes anaerobic respiration to occur?
When oxygen supply to respiring tissues is lower than the demand.
167
Why are reptiles more successful or adapted to land compared to amphibians?
- Skin of reptiles is covered by scales while amphibians skin is moist leaving it prone to water loss
- Reptile eggs have shells while those of amphibians lack hard shells
- Reptiles have internal fertilization while amphibians have external fertilization aided by water
- Amphibians use moist skin and poorly developed lungs for gaseous exchange which is not favorable on land while reptiles have well developed lungs
168
How have problems of low blood pressure at the venous side been overcome by organisms?
- Double circulation eg in man
- Branchial hearts eg in octopus
- Enlarged vessels called sinuses to reduce resistance to blood flow
169
Describe the process of clotting in man
- Platelets rupture and break down when exposed to air leading to release of the enzyme thrombokinase
- Thrombokinase in the presence of calcium ions catalyses the activation plasma protein prothrombin to thrombin enzyme
- Thrombin catalyses conversion of fibrinogen a soluble plasma protein to fibrin an insoluble plasma protein
- Fibrin forms a mesh of fibres which traps blood cells forming a clot.
170
What are the characteristics of an efficient immune system?
- Ability to quickly recognize antigens
- Ability to respond and remove antigens quickly
171
What are the types of immune responses?
- Cell mediated immune response (T-lymphocytes)
- Humoral immune response (B-lymphocytes)
172
Give differences between B-lymphocytes and T-lymphocytes
B-lymphocytes:
- Produced and Matures in bone marrow
- Produce antibodies
T-lymphocytes:
- Produced in bone marrow but matures in thymus gland
- Does not produce antibodies
173
What is the process of bone formation called?
Ossification or osteogenesis
174
What happens when one is stung by a bee?
(Inflammatory response)
- Area is wounded or infected
- Surrounding tissue becomes inflamed or swollen
- This is due to escape of chemicals like histamine from damaged tissues
- These chemicals collectively cause local vasodilation of capillaries
- Increases the amount of blood in the area
- Increase in blood raises the local temperature
- Leakiness of the capillaries increases
- This permits escape of plasma and WBCs into surrounding tissues thus causing swelling of the area; this is known as oedema
- The plasma contains antibodies and phagocytes which combat spread of infection
- Fibrinogen may be converted to fibrin for clotting where necessary catalysed by thrombin
175
True or false
Rhesus negative blood usually contains antibodies in plasma
False
It does not usually contain antibodies in plasma.
They are manufactured when rhesus positive blood enters a negative individual
176
True or false
Rhesus negative is dominant over Rhesus positive
False
177
What protection is there for rhesus negative mothers who give birth to rhesus positive children?
- Anti-D injections within 72 hours of her giving birth which prevents production of D-antibodies in the mother (makes her immune system insensitive to D-antigen)
- If the mother is rhesus negative with blood group O and the child is rhesus positive of any blood group except O, haemolytic disease would not occue because a and b antibodies of the mother would destroy fetal cells in maternal circulation before production of anti-rhesus antibodies
178
Explain how a rhesus negative mother of blood group O may give birth to a rhesus positive child without haemolytic disease?
- If the mother is rhesus negative with blood group O and the child is rhesus positive of any blood group except O, haemolytic disease would not occue because a and b antibodies of the mother would destroy fetal cells in maternal circulation before production of anti-rhesus antibodies
179
What are the consequences of overbleeding?
- Reduced blood pressure
- Anaemia
- Unconsciousness
