42 Circulation and Gas Exchange Flashcards
(265 cards)
1
Q
What structural adaptation do axolotyls have?
A
They have external gills that are feathered to maximise surface area and thus gas exchange.
2
Q
What are axolotyls classed as?
A
Salamanders
3
Q
How does time taken to diffuse relate to distance and what is the implication of this?
A
The taken is proportional to the square of the distance.
Thus as body size gets larger diffusion is slower, resulting in the need for more sophisticated circulatory systems.
4
Q
What are the basic adaptations to the fact that diffusion is slower over long distances?
A
Either have a body plan where all the cells are near the environment i.e. cnidarians and flatworm gastrovascular cavities.
Alternately large organisms can overcome this with circulatory systems where the products are bought close to the cell.
5
Q
What animals have gastrovascular cavity?
A
Cnidarians like jellyfish, hydras and flatworms.
6
Q
Describe the gastrovascular cavity of jellyfish?
A
There is a “central canal” that has many “radial canals” branching from it
7
Q
Describe the gastrovascular cavity of flatworms?
A
It is highly branched.
8
Q
What are the basic forms of circulatory system?
A
Open circulatory systems and close circulatory systems.
9
Q
What are open circulatory systems?
A
Systems in which the circulatory fluid, known as “hemolymph” can leave the vessels through pores and thus is the interstitial fluid between cells.
The hemolymph is then collected by the heart and re circulated.
10
Q
What is an example of an animal that uses an open circulatory system?
A
Grasshoppers.
11
Q
How does the heart pump the hemolymph?
A
As in other animals by contraction.
As the emptied heart expands it creates a vacuum and thus sucks in some hemolymph.
12
Q
What is an open circulatory system typical of?
A
Most, but not all, invertebrates use it.
13
Q
Describe the heart of a grasshopper.
A
It is a long tube, known as the “sinuses”, that extend down the grasshopper’s “back” and has pores to allow hemolymph to enter and exit.
14
Q
What are the advantages of and open circulatory system?
A
It operates under a lower pressure and thus requires less energy.
15
Q
What can open circulatory systems be used besides transport?
A
Spiders use the hydrostatic pressure of the hemolymph to move their legs.
16
Q
Where does hemolymph get released into the body?
A
In many organism this occurs at the heart.
However some larger animals like lobsters and crabs still use open circulatory systems but have vessels that carry the hemolymph part of the way.
17
Q
What is a close circulatory system?
A
A circulatory system in which the circulating fluid does not leave the vessels and instead only nutrients can leave through diffusion.
18
Q
What are the advantages of an open circulatory system?
A
It avoids mixing oxygenated and deoxygenated fluid as it is directional.
It also allows the control of blood flow to specific organs and regions.
19
Q
What animals have closed circulatory systems?
A
All vertebrates as well as annelids and cephalopods.
20
Q
What are annelids?
A
A phylum of invertebrate animals that includes earthworms and leeches.
21
Q
What are cephalopods?
A
A phylum of invertebrate animals that includes squids and octopuses.
22
Q
What is the closed circulatory system often called?
A
The cardiovascular system.
23
Q
How are capillaries arranged?
A
In networks called capillary beds” that ensure they provide all cels with nutrients.
24
Q
In order, what are the vessel types blood passes through as it leaves the heart?
A
Artery, Arterioles, Capillaries, Venules, Vein
25
What are arterioles and venules?
Small arteries/veins respectively that carry blood to and from the capillaries.
26
What can vertebrate circulation be divided into?
Single circulation and double circulation.
27
In what animals does single circulation occur?
Bony fishes, rays and sharks
28
In what animals does double circulation occur?
All other vertebrates i.e. Amphibians, reptiles, birds and mammals.
29
What is single circulation?
A form of circulation in which there is a single circuit of blood flow that passes through two capillary beds: one in the lungs and one in the body
30
How does single circulation affect blood flow?
It significantly decreases pressure after the first gill capillary beds and thus limits the rate of blood flow in the rest of the body.
31
What is the structure of the heart of an animal that uses single circulation?
It has two chambers (one ventricle and one atrium.)
32
How is the slow movement of blood mitigated in animals that use single circulation?
The contraction of muscles during swimming leads to some increase in blood pressure.
33
What is double circulation?
The form of circulation in which blood that leaves the heart passes through the lung capillaries then returns to the heart where it is pumped through the body.
34
What are the circuits of double circulation named?
The circuit through the body i shamed the 'systemic circuit'.
The other circuit is named the 'pulmonary circuit' if it passes exclusively through the lungs or the 'pulmocutaneous' is is passes through the skin and lungs.
35
What groups of animals have distinct double circulatory systems?
Amphibians, Reptiles and Mammals/Birds
36
Describe the circulatory system of Amphibians?
They have 3 chambered hearts with 2 atria and one ventricle. The ventricle is not separated by a septum but it does have a ridge that stops 90% of the blood from mixing.
They have two circuits: the pulmocutaneous and the systemic circuit.
37
Why do amphibians have a pulmocutaneous circuit as opposed to just a pulmonary circuit?
The capillaries passing through the skin are the sole site of gas exchange when the frog etc. is submerged.
38
Describe the circulatory system of reptiles?
Most i.e. snakes, turtles and lizards have a 3 chambered heart separated by an incomplete septum. In crocodilians like alligators and caimans this septum is complete leading to 4 chambers.
They have system and pulmonary circuits. They have two aortas. The left systemic aorta carries oxygenated blood to the systemic capillaries while the right systemic aorta carries blood that is mixed due to the incomplete septum to the system circuit.
Crocodilians with 4 chambered hearts still have right aortas but they carry oxygenated blood.
39
What circulatory adaption do crocodilians have besides a complete septum?
The right systemic aorta takes blood from both the left and right ventricle. Therefore when the crocodile dives and circulation to the lung is frivolous. The "foramen of panizza' can constrict the pulmonary vein so that blood of the right ventricle destined for the lungs can be re-routed to the systemic circuit, giving it more blood for its underwater activities.
40
Which type of animal has a circulatory system most like a mammal?
Birds
41
From what side does blood enter the heart and from what side does it leave? How does this differ among double circulating animals?
In all double circulating vertebrates blood enters through in the right side of the heart (drawn on left) and exits through the left side (drawn on right)
42
Describe the path blood takes from when it enters the heart to when it leaves?
Right atrium - right ventricle - pulmonary artery - alveolar capillaries - pulmonary vein - left ATRIUM then left VENTRICLE - aorta.
43
How many are there of each vessel entering and exiting the heart?
There are two vena cava : the inferior vena cava and the superior vena cava. Similarly two pulmonary veins enter the left atrium, with one from each lung.
There is one one each of aorta and pulmonary artery although both branch off after they leave the heart.
44
Where is the heart located?
Behind the sternum (breast bone)
45
Which ventricle is under the greatest pressure? How much more blood does it pump?
The left ventricle is under the greatest pressure as it has to pump blood around the entire body. It therefore has the thickest walls.
However because the human circulatory system is a closed system they both pump the same amount of blood per stroke.
46
How many stages is the cardiac cycle divided into?
3
47
What is stage 1 of the cardiac cycle?
Atrial and ventricular diastole.
48
What is stage 2 of the cardiac cycle?
Atrial systole and ventricular diastole
49
What is stage 3 of the cardiac cycle?
Ventricular systole and atrial diastole
50
What happens during Atrial and ventricular diastole?
Blood flows into the atria and can also moves through the atria into the ventricle.
51
What happens during Atrial systole and ventricular diastole?
Blood flow into the atria shuts off as the atrium constricts to force blood into the ventricle.
52
What happens during Ventricular systole and atrial diastole?
The valves between the atria and ventricle closes. The ventricle then constricts forcing blood out of the aorta/pulmonary artery.
53
How long does the Atrial and ventricular diastole stage of the cardiac cycle take?
0.4 seconds
54
How long does the Atrial systole and ventricular diastole stage of the cardiac cycle take?
0.1 seconds
55
How long does the Ventricular systole and atrial diastole stage of the cardiac cycle take?
0.3 seconds
56
What does diastole refer to?
The phase of the heartbeat (or particular area) where the heart is relaxed.
57
What does systole refer to?
The phase of the heartbeat (or particular area) where the heart is contracted.
58
What is the sum of blood exiting the heart called?
Cardiac output.
59
How is cardiac output calculated?
It is heart rate (beats per minute) multiplied by stroke volume (amount of blood pumped per contraction)
60
What is a typical BPM?
72 beats per minute
61
What is a typical cardiac output?
5L per minute
62
What is typical stroke volume?
Around 70 mL
63
What are the valves of the heart?
The atrioventricular valves (AV) are between the atria and their ventricles. The semi-lunar valves are at the exits of the heart (pulmonary artery and aorta)
64
How are heart valves regulated?
Entirely passively based on the pressure of the blood.
The atrioventricular valves are closed by the high pressure of the contracting ventricles and thus prevent blood form back flowing into the atria.
The semilunar valves are pushed open by the pressure of the contracting ventricles so that blood can leave. However as the contraction stops they close themselves to prevent back flow.
65
What causes a ‘heart murmur’ and what is it?
An unusual sound caused by a defective valve
66
What can lead to heart murmurs?
Damage to the valves i.e. through rheumatic fever.
67
How can heart activity be detected?
An electrocardiagram (EKG from german name) consist of sensors placed on the skin that detect the electrical signals of the heart to diagnose heart attacks etc.
68
Where are the electrical signals that control a heart beat regulated?
In vertebrates it is in the heart. Some arthropods have it in the nervous system.
69
What are the regions of a vertebrate heart involved in regulating the heart?
The sinoatrial (SA) node and the atrioventricular (AV) node
70
What are the steps of heart beat regulation?
Signals generated by the SA node spread through the atria.
These signals reach the AV nodes which delay them for around 0.1 seconds to give the atria time to fill with blood.
The AV nodes then pass on the signals which travels along special muscle fibres called “bundle branches” which carry the signal to the ‘apex’ (bottom) of the heart.
From the apex of the heart the signals travel along another specialised form of muscle fibre: Purkinje fibres. These fibres cary the signal from the bottom of the heart to the top, causing contractions as they travel up the heart.
71
What is the significance of heart signals being carried to the apex of the heart then travelling back up again?
This ensure contractions start at the bottom so blood is forced up and out of the aorta/pulmonary artery
72
What is the primary system regulating heart beat?
The sympathetic and parasympathetic divisions of the nervous system?
73
How does body temperature affect heart rate?
As body temperature increases by 1ºC heart rate increases by 10 bpm.
This explains why heart rate is accelerated during a fever.
74
What do all blood vessels contain?
A core of endothelium tissue
75
What is the structure of a capillary?
It has a one cell thick layer of simple squamous epithelium tissue and the associated “basal lamina” of ECM on the outside.
76
From inside to outside, what is the structure of an artery?
Endothelium, smooth muscle and elasticated connective tissue
77
From inside to outside, what is the structure of a vein?
Endothelium, smooth muscle and connective tissue
78
How do arteries and veins differ and what is the significance of this?
Veins have valves to prevent the back flow of blood under lower pressure.
Veins have thinner walls and thus larger lumens to facilitate carrying blood that is not under pressure.
Arteries have more elasticated connective fibres. This allows them to expand as the heart forces blood into them. As they recoil this provides a force that pushes blood along between heartbeats.
79
Why doesn’t blood speed up as it enters the capillaries?
Traditionally as a fluid enters smaller diameter tube it speeds up. Conversely blood slows down as it enter the capillary. This is due to the fact that the total cross section of all the capillaries is greater than the total cross section of the arteries so the blood slows down.
80
What is the advantage of blood flow slowing through the capillaries?
It allows more time form gas exchange and solute diffusion to occur between the capillaries and the surrounding cells.
(it also mitigates the high pressure that would otherwise damage capillaries)
81
What is blood pressure divided into?
Systolic and diastolic pressure
82
How do systolic and diastolic pressure differ?
Systolic is measured when the ventricles contract whereas diastolic is measures when the ventricles relax.
83
Why is diastolic pressure not 0?
The elastic walls of the arteries recoiling provides some pressure.
84
What is blood pressure typically measured in?
mmHg (millimetres of mercury)
85
What is “pulse"
They rhythmic bulging of the arteries (not to be confused with heart beat).
86
How can blood pressure vary?
Physical and emotional stress trigger the smooth muscles of the arteriole walls to constrict, known as vasoconstriction. This reduces cross section and thus blood pressure.
87
What happens when muscles need more blood and how does this affect blood pressure?
Arterioles leading to them undergo vasodilation so that more blood can flow to them.
As this increases surface area it this would be indicative of causing the blood flow to drop.
In reality the heart adjusts its cardiac outputs so blood pressure remains constant.
88
What is a typical blood pressure reading and how is it interpreted?
120/70 indicating 120 mmHg of systolic blood pressure and 70 mmHg of diastolic blood pressure
89
What is used to measure blood pressured?
A sphygmomanometer
90
How does a sphygmomanometer work?
A cuff is placed around the arm and inflates so that it cuts of arterial blood flow?
As the cuff slowly deflates a stethoscope is used to record the point at which blood can periodically pass through due to the pulse. As this point the pressure of the cuff is the systolic blood pressure.
The cuff continues to deflate until blood can flow freely. This indicates the diastolic blood pressure.
91
How is blood flow maintained through the veins?
As the skeletal muscles contract they push blood back to the heart. This is helped by veins that stop this blood flow flowing back own between contractions.
92
Why is physiologically important that athletes ‘cool down’ after exercise?
The skeletal muscles suddenly stop so less blood returns to there heart. The heart, however, continues pumping at the accelerated rate and thus blood pressure drops.
93
How can blood flow to capillaries be regulated?
Either the arterioles that lead to capillaries undergo vasodilation/vasoconstriction to adjust the blood flow.
Alternately there can be a an arteriole that leads straight from the artery to the vein (this is known as the thoroughfare channel) Smooth muscle sphincters named “precapillary sphincters” can dilate or contract to allow or prevent blood from flowing into the capillaries that branch off the thoroughfare channel.
94
How is the regulation of blood flow to the capillaries related to the response to an injury?
At the injury the chemical histamine is released to INCREASE blood flow to the wound site. This is beneficial as it provides greater access for platelets and white blood cells.
95
How do solutes leave the capillaries?
Mostly by diffusion but some leave by exocytosis.
To facilitate the diffusion of ions and polar macromolecules out of the capillaries many have pores to allow sugars, salts and urea to leave.
96
How is water loss from blood vessels regulated and what is the net direction?
The pores allow the bulk exiting of water and the removal of solutes leads to osmotic pressure to suck the water out of the capillaries. Despite this the proteins of the blood, which are too large to leave via the pores/endothelium, give some osmotic pressure to retain the blood.
The net effect of these factors however is a net loss of fluid.
97
Where is most water lost through blood vessels and why is this beneficial?
Through the arteries as they are under the highest pressure.
This is beneficial as it reduces the volume and thus pressure of the blood and thus aids in reducing the pressure by the time it reaches the capillaries.
98
How is water lost by the blood vessels returned?
As it exits it becomes interstitial fluid. It then diffuses into lymph vessels where the fluid is named as “as lymph"
99
What happens to lymph after it enters the lymph vessels?
It circulates based on the contractions of surrounding skeletal muscles. (lymph vessels have valves)
It passes through lymph vessels before being deposited into a major vein.
100
How can lymph vessels be blocked and what does this cause?
Parasitic worms can block the lymph vessels.
Blocked lymph vessels lead to pooling of vessel which leads to swelling named elephantiasis.
101
Where are lymph nodes concentrated?
Neck, armpits and groin.
102
What are blood components divided into? (what is the relative concentration)
Plasma (55%) and Cellular Elements (45%)
103
What are the basic constituents of plasma?
Water, Ions ("blood electrolytes"), "Plasma proteins" and Transported Substances
104
What is the function of water in the plasma?
Its a solvent for carrying other substances and also reduces the viscosity.
105
What are the "blood electrolytes" found in plasma?
Sodium, Potassium, Calcium, Magnesium, Chloride and Bicarbonate ions
106
What is the function of blood electrolytes in plasma?
They maintain osmotic balance (prevent excess water loss from blood vessels), act as pH buffers, and regulate membrane permeability.
107
What are the “plasma proteins"
Albumin, Fibrinogen and Immunoglobulins
108
What is the function of albumin as a ”plasma protein”?
Osmotic balance and pH buffering
109
What is the function of Fibrinogen as a ”plasma protein”?
Clotting
110
What is the function of immunoglobulins as a ”plasma protein”?
They are antibodies so have in the immune response
111
What products are transported by the plasma?
Nutrients (glucose, fatty acids, vitamins etc.), Waste products (i.e. urea), hormones and some O2/CO2
112
What are the “cellular elements” of blood?
In order of prevalence: Erythrocytes, Platelets and Leukocytes.
113
What are Erythrocytes and what is their function?
Red blood cells - carry O2 and some CO2
114
What are the forms of Leukocytes found in blood?
Basophils, Lymphocytes, Eosinophils, Neutrophiles and Monocytes
115
What function do all plasma proteins play a role in?
Increasing the viscosity of the blood so it can be pumped more effectively.
116
What are leucocytes?
White blood cells.
117
The concentration of what component is significantly different between plasma and interstitial fluid?
Plasma proteins as unlike the ions-blood electrolytes etc. the proteins can not easily leave the capillary.
118
What is the most numerous cellular component of blood?
Erythrocytes (even more than platelets)
119
What is the shape of red-blood cells and what is the advantage of this?
They are biconcave meaning they are thick at the edges then taper to become thin at the centre.
This maximises surface area.
120
What special adaptions do red-blood cells have?
They lack nuclei and mitochondria to maximise space for transportation.
121
What is the consequence of red-blood cells not having mitochondria?
They must perform anaerobic respiration in the cytoplasm.
122
With what is oxygen carried in red-blood cells?
Hemoglobin, an iron containing protein.
123
What disease if formed by abnormal haemoglobin?
Sickle-cells disease
124
How do red-blood cells appear in those will sickle cell disease and why is this?
The haemoglobin aggregates in the red-blood cells causing them to elongate into a curved sickle shape.
125
What are the consequence of sickle cell disease?
The sickle-red-blood cells often get caught in arterioles and capillaries leading to swelling and pain. This also prevents them from delivering their oxygen and collecting wastes.
The sickle cells are prone to rupturing and thus must be constantly replaced. Often they are lost quicker than they are replaced leading to anaemia.
126
What is the typical lifespan of a sickle-cell and of a normal red-blood cell?
Sickle Cell: 20 days
| Red-blood cell: 120 days
127
What is the abnormal form of haemoglobin seen in sickle cell disease?
Hb^s (as in Hb and a little superscripted s)
128
What cellular component of blood is found outside the blood?
Leukocytes which patrol interstitial fluid and lymph
129
What are the stops that lead to the formation of a blood clot?
A break in a blood vessel wall exposes proteins that attract platelets and initiate coagulation (conversion of liquid blood products to solid).
The coagulant circulates in an inactive form called fibrinogen. In response to a wound, platelets release clotting factors that trigger the formation of the enzyme thrombin which converts fibrinogen to fibrin. Fibrin then aggregates to form the clot
Thrombin also activates a factor that catalyses the formation of more thrombin, accelerating clotting through positive feedback.
130
What region produces cellular blood component and form what cells are they derived?
Multipotent stem cells in the marrow differentiate into blood cellular components.
131
What is the specific path form stem cell to blood cell?
Stem cells in the bone marrow differentiate into Lymphoid stem cells and Myeloid stem cells.
The lymphoid stem cells can then differentiate into B Cells and T Cell, which are both lymphocytes.
The myeloid stem cells can differentiate into Red-blood cells, neutrophils, basophils, monocytes, eosinophils and platelets.
132
What regulates red-blood cell production?
Cells with low oxygen secrete eryrthoprotein (EPO) to stimulate red-blood cell production
133
What is the primary cause for heart attacks?
Atherosclerosis in which plaques form in the coronary arteries causing them to become blocked and thus heart muscle becomes oxygen deprived.
134
What is the technical term for a clot (blood clot or atherosclerotic)?
Thrombus
135
What are the main forms of cholesterol? What are they composed of?
Low-density lipoprotein (LDL) and High-density lipoprotein (HDL)
These are the two main forms of cholesterol found in the blood. They are composed of many cholesterols and other lipids bound to a protein.
136
What are the stages of atherosclerosis?
Lipoproteins such as LDL enter the lining of the artery and aggregate. These lipoproteins are engulfed by macrophages leading to the generation of lipid-rich "foam cells".
Secretion of extracellular matrix components increases lipoprotein aggregation. T lymphocytes enter the “plaque", inflammation. Smooth muscle cells from the lining of the artery also enter the plaque.
Smooth muscle cells in the plaque form a fibrous cap separating the plaque from the blood. Foam cells in the plaque die, releasing cellular debris and cholesterol. If the plaque ruptures, a blood clot can form within the artery. If the plaque continues to grow but does not rupture, the artery becomes increasingly obstructed.
137
What is a heart attack formally known as?
Myocardial infarction
138
What is a heart attack?
The damage of heart tissue due to a lack of oxygen because of blood flow restricted by atherosclerosis.
139
What is a stroke?
The death of nervous tissue in the brain due to a lack of O2.
140
What can lead to strokes?
The blockage of vessels (ischemic) and them rupturing (hemorrhagic)
141
How can a blocked coronary artery be rectified?
By inserting a “stent” which is a metal mesh tube to hold it open or transplanting arteries from other areas of the body.
142
How do LDL and HDL differ?
LDL (low-density lipoproteins) are “bad” in excess as they deliver lipids for membrane formation but also for atherosclerosis.
HDL (high-density lipoproteins) are good as they scavenge excess cholesterol and return it to the liver
143
Interms of cholesterol, how can a person risk of atherosclerosis be accessed?
By deterring their LDL/HDL ratio
144
How can the LDL/HDL ration be improved?
By exercise or the drug "statin".
145
What factors lead to atherosclerosis?
Collecting cholesterol and the inflammation this causes.
146
What can increase the LDL/HDL ratio?
Smoking and consumption of certain processed vegetable oils called trans fats
147
What chemical is released in RESPONSE TO inflammation?
C-reactive protein (CRP) by the liver.
148
How does high-blood pressure lead to atherosclerosis?
It damages the walls of the arteries making them more prone to clot formation.
149
What happens to old red-blood cells?
They are consumed by phagocytic cells of the liver and spleen which recycle their contents, such as the iron in the haemoglobin.
150
What dictates the direction of movement of gases through diffusion?
Their partial pressure.
151
What is partial pressure?
In a mixture of gases, each gas contributes to the total pressure of the mixture. This contribution of each component is that component’s partial pressure.
152
How is partial pressure calculated?
Pressure exerted by the gas mixture multiplied the concentration of that gas: for example the partial pressure of oxygen in air is 0.21 x 760.
153
What does mmHg refer to?
It is a unit of pressure based on how high a cylinder of mercury would have to be to exert that same pressure?
154
What is the pressure of air and thus the partial pressures of O2 and CO2?
Air: 760 mmHg
Partial pressure O2: 160 mmHg
Partial pressure of CO2: 0.29 mmHg
155
What is the partial pressure of oxygen in water?
It is at equilibrium with the oxygen of the atmosphere as there is no net diffusion. Therefore oxygen at the surface of water has a partial pressure of 170 mmHg , just like oxygen in the air.
156
What is the formal definition of partial pressure?
The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.
157
How is parietal pressure denoted?
Po2 etc. i.e. capital P then the specific gas in subscript.
158
Why can breathing underwater be so difficult?
There is only 4-8 mL of dissolved oxygen per litter of water.
159
What aquatic animals demonstrate specific respiratory surfaces?
Marine worms, crustacea and sea stars.
160
Describe the respiratory surface of marine worms?
On each of their many body segments, marine worms have a pair flattened appendages called “parapodia”. By sticking out they increase gas exchange and thus function as gills. They are also used for swimming and crawling.
161
Describe the respiratory surface of crustacea?
They have long feathery gills INSIDE their exoskeletons. Specialised body appendages drive water over these gills
162
Describe the respiratory surface of sea stars?
They have many fine projections of the main body cavity (the coelom). Each of these fine projections act as gills and thus perform gas exchange, along with the fish’s tube feet. Fluid that circulates in the coelom carries these gases
163
What is the formal name for marine worms?
Polychaetes
164
What is the movement of gases over the respiratory surfaces called?
Ventilation.
165
Why is ventilation important?
It provides more gases to the lungs etc. and also maintains the partial pressures.
166
How do animals with gills perform gas exchange?
Some have specialised appendages whereas others just simple use their movement through the water.
167
How do octopuses ventilate their lungs?
By taking in then ejecting water (hence how they have jet propulsion for locomotion)
168
How do fish allow water to pass their gills?
By opening their mouths.
169
Why would gills not work on terrestrial animals?
The large surface area of wet membrane would dry to fast.
The filaments that support the lungs would snap without the buoyancy provided by water.
170
What special phenomena do fish gills exploit and how are they adapted to do this?
Blood flows through the gills from the rear end of lamella to the front (posterior to anterior)
This allows them to make use of countercurrent exchange.
171
What is the respiratory system of insects called?
The “tracheal system"
172
How does the “tracheal system” of insects work?
Throughout the body is a matrix of air tubes. The larger air tubes called trachea branch into tracheoles that where oxygen can diffuse out directly into cells, without the involvement of hemolymph.
Near major organs are large air sacs that ensure the cells of that organ are close enough to O2 and CO2 that it can diffuse in and out of these cells
173
How is the “tracheal system” ventilated?
In most small insects ventilation is not nescecary. In larger more active insects gases are moved around the tracheal system due to contraction and relaxation of the flight muscles.
174
How do lungs differ form the tracheal system?
In tracheal systems the gases are delivered directly to the cells that need them. In lungs gas exchange occurs in one centralised place with the absorbed gases being transported in blood.
175
What organisms have lungs?
All vertebrates as well as some animals with open circulation systems such as spiders and land snails.
176
What form of respiratory surface do amphibians have?
Some have small lungs and instead depend mostly on diffusion of gases through the skin/
177
What form of respiratory system do reptiles have?
All reptiles have lungs which they depend on entirely for gas exchange.
The only exception is turtles which have lungs but can also perform gas exchange through their skin.
178
What form of respiratory surface so fish have?
All have gills but a select few have lungs such as the “lung fish” which uses them when a pond it is in dries up.
179
What happens to air that passes through the nasal cavity?
It is warmed, moistened and sampled for odours.
180
What is the pharynx?
The intersection where gases are directed down the trachea and food down the oesophagus.
181
What is the larynx?
The upper part of the respiratory tract. During swelling it moves upwards and tips the epiglottis over the glottis to close the trachea. When not eating it returns to allow air down the trachea.
182
What path does air take after the larynx?
Esophagus - trachea - bronchus - bronchiole
183
How is the respiratory system protected from debris?
Nose hairs and mucus prevent some from entering the trachea. Those that do are trapped by the mucus secreted by the epithelium of the trachea/bronchi etc,. The epithelium has cilia which sweep the particle rich mucus out of the way.
184
What does the “mucus elevator" refer to?
The system of cilia sweeping mucus out of the lungs.
185
Where does gas exchange actually occur?
At the end of the bronchioles are air sacs named alveoli that are surrounded by capillaries.
186
How does cigarette smoke damage the lungs?
By traveling to the alveoli and depositing particulates.
187
What disease is typical of coal miners and howls it caused?
Silicosis, in which coal dust gets trapped in the alveoli.
188
Why are alveoli susceptible to damage? How is this mitigated?
They are small and lack cilia or significant air currents to dislodge particles
This is mitigated by white blood cells that patrol and engulf foreign particles (even if not pathogens)
189
What happens to old red-blood cells?
They are consumed by phagocytic cells of the liver and spleen which recycle their contents, such as the iron in the haemoglobin.
190
What dictates the direction of movement of gases through diffusion?
Their partial pressure.
191
What is partial pressure?
In a mixture of gases, each gas contributes to the total pressure of the mixture. This contribution of each component is that component’s partial pressure.
192
How is partial pressure calculated?
Pressure exerted by the gas mixture multiplied the concentration of that gas: for example the partial pressure of oxygen in air is 0.21 x 760.
193
What does mmHg refer to?
It is a unit of pressure based on how high a cylinder of mercury would have to be to exert that same pressure?
194
What is the pressure of air and thus the partial pressures of O2 and CO2?
Air: 760 mmHg
Partial pressure O2: 160 mmHg
Partial pressure of CO2: 0.29 mmHg
195
What is the partial pressure of oxygen in water?
It is at equilibrium with the oxygen of the atmosphere as there is no net diffusion. Therefore oxygen at the surface of water has a partial pressure of 170 mmHg , just like oxygen in the air.
196
What is the formal definition of partial pressure?
The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.
197
How is parietal pressure denoted?
Po2 etc. i.e. capital P then the specific gas in subscript.
198
Why can breathing underwater be so difficult?
There is only 4-8 mL of dissolved oxygen per litter of water.
199
What aquatic animals demonstrate specific respiratory surfaces?
Marine worms, crustacea and sea stars.
200
Describe the respiratory surface of marine worms?
On each of their many body segments, marine worms have a pair flattened appendages called “parapodia”. By sticking out they increase gas exchange and thus function as gills. They are also used for swimming and crawling.
201
Describe the respiratory surface of crustacea?
They have long feathery gills INSIDE their exoskeletons. Specialised body appendages drive water over these gills
202
Describe the respiratory surface of sea stars?
They have many fine projections of the main body cavity (the coelom). Each of these fine projections act as gills and thus perform gas exchange, along with the fish’s tube feet. Fluid that circulates in the coelom carries these gases
203
What is the formal name for marine worms?
Polychaetes
204
What is the movement of gases over the respiratory surfaces called?
Ventilation.
205
Why is ventilation important?
It provides more gases to the lungs etc. and also maintains the partial pressures.
206
How do animals with gills perform gas exchange?
Some have specialised appendages whereas others just simple use their movement through the water.
207
How do octopuses ventilate their lungs?
By taking in then ejecting water (hence how they have jet propulsion for locomotion)
208
How do fish allow water to pass their gills?
By opening their mouths.
209
Why would gills not work on terrestrial animals?
The large surface area of wet membrane would dry to fast.
The filaments that support the lungs would snap without the buoyancy provided by water.
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What special phenomena do fish gills exploit and how are they adapted to do this?
Blood flows through the gills from the rear end of lamella to the front (posterior to anterior)
This allows them to make use of countercurrent exchange.
211
What is the respiratory system of insects called?
The “tracheal system"
212
How does the “tracheal system” of insects work?
Throughout the body is a matrix of air tubes. The larger air tubes called trachea branch into tracheoles that where oxygen can diffuse out directly into cells, without the involvement of hemolymph.
Near major organs are large air sacs that ensure the cells of that organ are close enough to O2 and CO2 that it can diffuse in and out of these cells
213
How is the “tracheal system” ventilated?
In most small insects ventilation is not nescecary. In larger more active insects gases are moved around the tracheal system due to contraction and relaxation of the flight muscles.
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How do lungs differ form the tracheal system?
In tracheal systems the gases are delivered directly to the cells that need them. In lungs gas exchange occurs in one centralised place with the absorbed gases being transported in blood.
215
What organisms have lungs?
All vertebrates as well as some animals with open circulation systems such as spiders and land snails.
216
What form of respiratory surface do amphibians have?
Some have small lungs and instead depend mostly on diffusion of gases through the skin/
217
What form of respiratory system do reptiles have?
All reptiles have lungs which they depend on entirely for gas exchange.
The only exception is turtles which have lungs but can also perform gas exchange through their skin.
218
What form of respiratory surface so fish have?
All have gills but a select few have lungs such as the “lung fish” which uses them when a pond it is in dries up.
219
What happens to air that passes through the nasal cavity?
It is warmed, moistened and sampled for odours.
220
What is the pharynx?
The intersection where gases are directed down the trachea and food down the oesophagus.
221
What is the larynx?
The upper part of the respiratory tract. During swelling it moves upwards and tips the epiglottis over the glottis to close the trachea. When not eating it returns to allow air down the trachea.
222
What path does air take after the larynx?
Esophagus - trachea - bronchus - bronchiole
223
How is the respiratory system protected from debris?
Nose hairs and mucus prevent some from entering the trachea. Those that do are trapped by the mucus secreted by the epithelium of the trachea/bronchi etc,. The epithelium has cilia which sweep the particle rich mucus out of the way.
224
What does the “mucus elevator" refer to?
The system of cilia sweeping mucus out of the lungs.
225
Where does gas exchange actually occur?
At the end of the bronchioles are air sacs named alveoli that are surrounded by capillaries.
226
How does cigarette smoke damage the lungs?
By traveling to the alveoli and depositing particulates.
227
What disease is typical of coal miners and howls it caused?
Silicosis, in which coal dust gets trapped in the alveoli.
228
Why are alveoli susceptible to damage? How is this mitigated?
They are small and lack cilia or significant air currents to dislodge particles
This is mitigated by white blood cells that patrol and engulf foreign particles (even if not pathogens)
229
Which are alveoli susceptible to collapse and how is this mitigated?
They water that covers them exerts significant water tension.
This is mitigated by “surfactants” made of phospholipids and proteins that are secreted by the alveolus to reduce surface tension.
230
How does vertebrates are differing mechanisms of ventilation seen?
Amphibians, birds and mammals.
231
How does an amphibian ventilate its lungs?
By “positive pressure breathing” in which it forces air into the lungs and thus into the blood.
232
How do amphibians perform positive pressure breathing?
Muscles lower the floor of an amphibian’s oral cavity, drawing in air through its nostrils. Next, with the nostrils and mouth closed, the floor of the oral cavity rises, forcing air down the trachea. During exhalation, air is forced back out by the elastic recoil of the lungs and by compression of the muscular body wall.
233
What do amphibians use positive pressure breathing for besides ventilation?
By inhaling multiple times without exhaling they can puff themselves up for courtship etc.
234
How does the respiratory system of a bird work?
Air travels in one direction like a circuit. It first reaches the posterior air sacs. It then passes through the lung.
As it passes through the lung it goes for parabronchi. These are tubes unlike the dead end alveoli seen in mammals etc. The gases go through the anterior air sacs before leaving the body.
235
What special features of the bird’s respiratory system make it particularly efficient?
Air travels in only one direction and thus oxygenated and deoxygenated gasses do no mix.
236
What happens as birds breathe?
It takes two cycles of inhalation and exhalation for air to make one full circuit.
Therefore the steps are:
1 First inhalation: Air fills the posterior air sacs.
2 First exhalation: Posterior air sacs contract, pushing air
into lungs.
3 Second inhalation: Air passes through lungs and fills anterior air sacs.
4 Second exhalation: As anterior air sacs contract, air that entered body at first inhalation is pushed out of body.
237
Where are the air sacs of the bird located?
The posterior air sacs are at the posterior end of the bird i.e. the back whereas the anterior sacs are near the front of the bird i.e. by the head.
238
What method of ventilation do mammals employ and what characterises it as this?
Negative pressure breathing in which air is sucked in by increasing the volume of the lung.
239
How is the lung ventilated in mammals?
During rest the diaphragm is sufficient to provide the pressure to ventilate the lung. However during intense exercise muscles are used to raise and lower the ribcage.
In some mammals, such as kangaroos, locomotion i.e. hopping also helps ventilate the lungs.
240
What is the contracted and relaxed forms of the diaphragm?
As is contracts it flattens down. As it relaxes it domes up.
241
Based on the motion of the diaphragm, what is are the active and passive phases of breathing?
During exhalation the rib muscles and diaphragm relax so this is the passive phase.
242
What is the amount of air inhaled and exhaled per breath called and what is a typical figures?
The “tidal volume”
It is typically 500 mL during rest.
During exercise the peak volume, known as the “vital capacity” is often around 3.4 L for women and 4.8 L for college aged men
243
What is the volume of air that remains after forced exhalation called?
Residual volume.
244
What is the consequence of residual volume?
This air mixes with the new air so it has a slightly lower concentration of oxygen.
245
Why can’t mammals breathe so well at high altitudes?
The residual air mixing with the fresh air reduces the partial pressure of the oxygen, making it even harder for us to breathe at high altitudes.
246
Where is the bird’s respiratory system most advantageous?
At high altitudes as by eliminating residual volume it the partial pressure of oxygen does not drop like in mammals, providing a significant advantage at high altitudes where the partial pressure of oxygen is already low.
247
In what region of the brain is breathing controlled?
In the ‘breathing control centre’ of the ‘medulla oblongata'
248
How does the ‘medulla oblongata’ detect how much berthing is needed?
If the rate of breathing is too low carbon dioxide will form carbonic acid in the blood. This lowers the pH of the blood and in turn the cerebrospinal fluid.
As the pH of the cerebrospinal fluid drops the ‘medulla oblongata’ triggers an increase in the rate of breathing.
249
What is the formula for carbonic acid
H2CO3
250
What is ‘H2CO3’?
Carbonic acid
251
What happens when carbonic acid dissolves i.e. in blood?
It dissociates into an HCO3- (bicarbonate ion) and an H+ ion.
252
How do oxygen levels in the blood regulate the breathing rate?
Generally the primary influence is carbonic acid in the blood, an indirect measure of the oxygen present as the more CO2 released indicates more respiration and thus more oxygen used.
However in high altitude situations where the air is low on oxygen both CO2 and oxygen levels can be low.
Under these circumstances the low blood oxygen levels are detected by sensors in the aorta. These signals are sent to the ‘breathing control centre’ of the medulla oblongata.
253
What enables the directionality of gas exchange at the alveoli i.e. O2 in and CO2 out?
Relative to the air in the alveoli, the CO2 in the blood has a greater ‘partial pressure’ while O2 has a lower partial pressure.
Thus CO2 diffuses down its gradient out of the blood while O2 diffuses out.
254
How specifically does oxygen move form the air in the alveolus into the capillary?
It dissolves in the fluid that coats the alveolar epithelium and diffuses into the blood.
255
How is most oxygen transported in blood?
It is most commonly bound to ‘respiratory pigments'
256
Where are the ‘respiratory pigments’ of the blood found typically?
In specialised cells i.e erythrocytes.
257
What are the respiratory pigments seen commonly in animals?
Arthropods and many molluscs have hemocyanin which is blue as it is bound to a copper atom.
Almost all vertebrates and many invertebrates use haemoglobin whose red colour comes from an iron atom.
258
What is the structure of a haemoglobin molecule?
It has four subunits
Each subunit has a cofactor called a ‘heme group’ which has an iron atom at the centre.
Therefore each haemoglobin can bond to 4 oxygens atoms simultaneously.
259
What factors worm together to increase the efficiency of haemoglobin?
‘Cooperativity’ and the ‘Bohr shift'
260
In terms of haemoglobin, what is ‘cooperativity’?
When O2 binds to one subunit, the others change shape slightly, increasing their affinity for O2.
When four O2 molecules are bound and one subunit unloads its O2, the other three subunits more readily unload O2, as an associated shape change lowers their affinity for O2.
In this way the haemoglobin quickly loads oxygen. Because one oxygen atom leaving triggers the rest this causes all the oxygen atoms to be released where they are most needed i.e. actively repairing tissues.
261
What is the ‘Bohr shift’?
In regions where there are high levels of respiration there is a greater concentration of CO2 and thus a lower pH.
In what is called the ‘Bohr’ shift this reduced pH reduces the affinity of haemoglobin for oxygen and thus releases the oxygen atoms it carries.
Thus oxygen is supplied to where it is needed most - the actively respiring cells.
262
How is CO2 transported by the blood?
- 7% is carried by being dissolved in plasma
- 23% binds to the amino ends of the haemoglobin polypeptide chains.
- 70% is transported in the form of bicarbonate ions (HCO3-)
263
What is the primary way CO2 is transported through the blood?
As bicarbonate (HCO3-) ions
264
How is CO2 carried in the blood as bicarbonate ions?
Carbon dioxide produced by body tissues diffuses into the interstitial fluid and the plasma.
CO2 reacts with water in red blood cells, forming carbonic acid (H2CO3). This is catalyzed by carbonic anhydrase in the red blood cells. This Carbonic acid dissociates into a bicarbonate ion (HCO3–) and a hydrogen ion (H+).
Hemoglobin binds most of the H+ from H2CO3, preventing the H+ from acidifying the blood and thus preventing the Bohr shift. Most of the HCO3– diffuses into the plasma, where it is carried in the bloodstream to the lungs.
In the lungs, HCO3– diffuses from the plasma into red blood cells, combining with H+ released from hemoglobin and forming H2CO3. This causes the Carbonic acid to be converted back to CO2 and water.
CO2 is also unloaded from haemoglobin and diffuses into the alveolar space before being exhaled.
265
What adaption do diving mammals typically have?
They have additional oxygen-storing proteins called ‘myoglobins’ in their muscles to increase the oxygen stored.
Their muscles are also more accustomed to perfuming fermentation.
Typically the blood flow is directed to the brain, spinal cord, eyes, adrenal glands and the placenta (if pregnant) The neutral buoyancy of a seal etc. when diving means that blood flow can be mostly cutoff to the muscles.
