Module 3 - Exchange and Transport Flashcards

Question

Why do larger cells/organisms have a smaller SA:V ratio?

Answer 1

Volume increases faster than surface area in larger cells

Answer 2

1. Cells in the centre of the organism would not receive any materials if multicellular organs survived on diffusion across an organism's surface alone 2. The high metabolic rate means there is a need to exchange lots of materials quickly

Answer 3

1. Intestinal tissue of the digestive tract may form a ruffled structure (villi) to increase the surface area of the inner lining 2. Alveoli within the lungs which function to increase the total membrane space

Answer 4

- For a cube - 6 x (length x width) - e.g. a cube has 6 sides, each with a measurement of 10μm - 6 x (10 x 10) = 600μm²

Answer 5

- Length x width x height - e.g. a cube has 6 sides, each with a measurement of 10μm - 10 x 10 x 10 = 1000μm³

Answer 6

- SA/V | - e.g. 600/1000 = 0.6

Answer 7

- Volume = length x width x height | - SA = (4 x length x height) + (2 x height x width)

Answer 8

- Area of a circle = πr² - Circumference = 2πr - Volume = πr² x height - Surface area = (2πr x height) + 2πr²

Answer 9

- Volume = 4/3 πr³ | - SA = 4πr²

Answer 10

- A common, chronic inflammation of the airways to the lungs (i.e. bronchi and bronchioles) - Inflammation leads to swelling and mucus production, resulting in reduced airflow and bronchospasm, meaning it is much harder to ventilate

Answer 11

A number of variable and recurring environmental conditions, such as: allergens, smoke, cold air, certain medications, and arthropods (dust mites)

Answer 12

A term used to describe breathing, where air is constantly moving in and out of the lungs

Answer 13

- A ventilation system is needed to maintain a concentration gradient in alveoli, continually cycling fresh air into the alveoli from the atmosphere - This means O₂ levels stay high in alveoli (and diffuse into the blood) and CO₂ levels stay low (and diffuse from the blood)

Answer 14

- The active movement of respiratory muscles that enables the passage of air into and out of the lungs - The contraction of respiratory muscles changes the volume of the thoracic cavity (i.e. the chest)

Answer 15

- Boyle's Law - Pressure (P) ∝ 1/Volume (V) - As volume increases, pressure decreases, and vice versa * Assuming constant temperature and closed environment

Answer 16

It decreases, according to Boyle's Law

Answer 17

- Also known as "inhalation", occurs when air pressure in the atmosphere is greater than that of the lungs; forcing air into the alveoli

Answer 18

- Also known as "exhalation", occurs when air pressure in the lungs is greater than that in the atmosphere; forcing air out of the alveoli - Can be considered passive - Elastic recoil of tissues aids expiration

Answer 19

Contraction

Answer 20

Core muscles: 1. External intercostals (contracts to elevate ribs) 2. Diaphragm (contracts to expand thoracic cavity)

Answer 21

Core muscles: 1. Internal intercostals (contracts to pull ribs down) 2. Diaphragm (relaxes to reduce thoracic cavity)

Answer 22

- Sternocleidomastoid | - Pectoralis minor

Answer 23

- Quadratas lumborum

Answer 24

The exchange of oxygen and carbon dioxide between the alveoli and bloodstream (via passive diffusion)

Answer 25

The release of energy (ATP) from organic molecules - it is enhanced by the presence of oxygen (aerobic)

Answer 26

1. Using a peak flow meter 2. Using vitalographs 3. Using a spirometer

Answer 27

The volume of air that moves into and out of the lungs with each resting breath. It is around 500cm³ in most adults at rest, which uses about 15% of the vital capacity of the lungs

Answer 28

The volume of air that can be exhaled when the deepest possible intake of breath is followed by the strongest possible exhalation

Answer 29

The maximum volume of air you can breathe in over and above a normal inhalation

Answer 30

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

Answer 31

The volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly

Answer 32

The sum of the vital capacity and the residual volume

Answer 33

The number of breaths taken per minute

Answer 34

The total volume of air inhaled in one minute

Answer 35

Tidal volume x breathing rate (per minute)

Answer 36

- ventilation rate = tidal volume x breathing rate - 6dm³ = 6000cm³ - 6000 = 500 x breathing rate - breathing rate = 6000/500 = 12 breaths/min

Answer 37

A tough exoskeleton, which allows little to no gas exchange to take place

Answer 38

- Air enters (and leaves) through spiracles - small openings along the insect's abdomen, these can be closed (by sphincters) to minimise water loss - Then air moves by diffusion through the trachea - these are tubes that can be up to 1mm in diameter and their job is to carry air into the body. They're lined with chitin, meaning they're impermeable (and also strong), so little gas exchange happens here - The trachea branch to form narrower tubes of 0.6-0.8μm in diameter called tracheoles. These have no chitin lining, and so are permeable to gases. Due to their small size, they can run in between individual cells, allowing for efficient gas exchange

Answer 39

Tracheal fluid, which is found towards the end of tracheoles

Answer 40

Larger beetles, locusts, grasshoppers, bees, wasps, flies

Answer 41

1. Mechanical ventilation of the tracheal system - air is actively pumped into the system by muscular pumping movements of the thorax and/or abdomen. This changes the volume of the body, which changes the pressure in the trachea and tracheoles; allowing more air to be drawn in to the trachea and tracheoles, or forced out, as pressure changes 2. Collapsible enlarged trachea or air sacs, which act as air reservoirs - used to increase the amount of air moved through the gas exchange system

Answer 42

* Bony fish have an evolved ventilatory system adapted to take oxygen from water - Bony fish maintain a flow of water in one direction over the gills - these are organs of gaseous exchange which have large SA, good blood supply, and thin layers. They are contained in a gill cavity and covered by a protective operculum - The gills have two main components: the gill lamellae (rich blood supply, large SA, main site of gas exchange) and gill filaments (occur in large stacks called gill plates. A constant flow of water keeps them apart, increasing SA for gas exchange)

Answer 43

1. The mouth is opened and the floor of the buccal cavity is lowered. This increases the volume of the buccal cavity 2. The pressure in the cavity drops and water moves into the buccal cavity. The opercular valve is shut and the opercular cavity containing the gills expands. This lowers the pressure in the opercular cavity. 3. The floor of the buccal cavity starts to move up, increasing pressure there so water moves from the buccal cavity over the gills 4. The mouth closes, the operculum opens and the sides of the opercular cavity move inwards. All these actions increase the pressure in the opercular cavity and force water over the gills and out of the operculum 5. The flow of the buccal cavity is steadily moved up, maintaining a flow of water over the gills

Answer 44

1. The tips of adjacent gill filaments overlap - this increases the resistance to the flow of water over the gill surface and slows down the movement of the water, leading for more time for gas exchange to happen 2. The water moving over the gills and the blood in the gill filaments flow in different directions. This ensures a steep concentration gradient is maintained.

Answer 45

- High metabolic demand - SA:V ratio gets smaller as multicellular organisms get larger - Molecules (hormones, enzymes..) may be made in one place but be needed in another - Food will be digested in one organ system, but needs to be transported to every other cell for use in respiration/other aspects of cell metabolism - Waste products of metabolism need to be removed from the cells and transported to excretory organs

Answer 46

- oxygen - carbon dioxide - nutrients - waste products - hormones

Answer 47

- A liquid transport medium that circulates around the system - Vessels that carry the transport medium - A pumping mechanism to move the fluid around the system

Answer 48

A circulatory system with very few vessels to contain the transport medium, and so it is pumped straight from the heart into the body cavity (haemocoel) of the animal, then back to the heart through an open ended vessel (a continuous loop). In the haemocoel, the transport medium is under low pressure, and comes in direct contact with the cells and tissues

Answer 49

They're mainly found in invertebrates (insects and some molluscs)

Answer 50

It's called haemolymph and it doesn't carry oxygen or carbon dioxide, as insects have a separate gaseous exchange system for that

Answer 51

- Food - Nitrogenous waste products - Cells involved in immunity/defence against diseases

Answer 52

In this type of circulatory system, blood is enclosed in blood vessels (veins, arteries and capillaries), and therefore does not come into direct contact with the cells of the body

Answer 53

Diffusion (through the walls of the blood vessels)

Answer 54

Haemoglobin

Answer 55

Found in many different animal phyla, including echinoderms (sea urchins, starfish..), cephalopod molluscs (octopuses, squid), annelid worms (e.g. common earthworm), and all the vertebrate groups, including mammals

Answer 56

Fish, annelid worms, etc...

Answer 57

- In these circulatory systems, blood flows through the heart and is pumped out to travel all around the body before returning to the heart - Simplified, this means that the blood travels only once through the heart for each complete circulation of the body

Answer 58

Most land mammals, including birds (because they maintain their own body temperature)

Answer 59

An efficient transport system that includes two separate circulations: - Blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide, and then returns to the heart - Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again

Answer 60

- Single = low blood pressure, so blood returns to the heart slowly. This is due to the blood passing through two sets of capillaries before it returns to the heart - Double = high blood pressure, so blood returns to the heart quickly. This is due to the blood passing through only one set of capillaries

Answer 61

1. Elastic fibres - composed of elastin, can stretch and recoil, allows blood vessels to be flexible 2. Smooth muscle - contracts or relaxes (this changes size of the lumen) 3. Collagen - provides structural support to maintain the shape and volume of the vessel

Answer 62

These are blood vessels which carry blood away from the heart to the tissues of the body; and they all carry oxygenated blood except from the pulmonary artery, which carries deoxygenated blood away from the heart and to the lungs (as well as the umbilical artery, carrying deoxygenated blood from the fetus to the placenta)

Answer 63

- Artery walls contain elastic fibres to help them withstand the force of the blood being pumped from the heart, and they stretch to take in a larger volume of blood - The lining of arteries (endothelium) is smooth so the blood flows easily over it - Artery walls also contain smooth muscle and collagen - Small lumen - Structures called arterioles link the arteries and capillaries together - these have more smooth muscle and less elastin in their walls than arteries, due to them having little pulse surge, but still can constrict and dilate to control the flow of blood into individual organs

Answer 64

When the smooth muscle in the arteriole contracts it constricts the vessel and prevents blood flowing into a capillary bed

Answer 65

When the smooth muscle in the wall of an arteriole relaxes, blood flows into the capillary bed

Answer 66

- A huge bulge or weakness in a blood vessel, most commonly found in the aorta and arteries of the brain - One factor that increases risk of aneurysms is high blood pressure - Scientists might have discovered a link between aneurysms and the changes in proportion of collagen to elastin in aortic walls

Answer 67

Microscopic blood vessels that link arterioles with venules. They form an extensive network through all the tissues of the body

Answer 68

- They have small lumens (7.5-8μm in diameter) | - Substances are exchanged through the capillary walls between the tissue cells and the blood

Answer 69

- They provide a very large SA for the diffusion of substances into and out of the blood - The total cross-sectional area of the capillaries is always greater than the arteriole supplying them so the rate of blood flow falls. The relatively slow movement of blood through capillaries gives more time for the exchange of materials by diffusion between the blood and the cells - The walls are a single endothelial cell thick, giving a very thin layer for diffusion

Answer 70

These are blood vessels which carry blood away from the cells of the body and towards the heart. They mostly carry deoxygenated blood, however in the pulmonary vein, oxygenated blood is carried instead (also in the umbilical vein, oxygenated blood is carried from the placenta to the fetus)

Answer 71

These are smaller veins which connect the capillaries and the larger veins together

Answer 72

- Thin layers of smooth muscle and elastin, with a much larger lumen than arteries - The walls have lots of collagen, which provides structural support - The endothelium is smooth (and thin), allowing blood to flow easily - Are able to hold a large reservoir of blood - up to 60% of your blood volume is in your veins at any one time

Answer 73

Low, especially when compared to arteries

Answer 74

Valves to prevent the backflow of blood

Answer 75

- Very thin walls, with little smooth muscle and elastic fibres - Contain collagen - Several link to form a vein

Answer 76

1. A majority of the body's veins have one-way valves at intervals - these are flaps or infoldings of the inner lining of the vein, and they prevent the backflow of blood 2. Many of the larger veins run between the big, active muscles in the body (e.g. arms and legs) - this means that when the muscles contract they squeeze the veins, which forces blood towards the heart. Valves prevent backflow when these muscles relax 3. The breathing movements of the chest act as a pump - the pressure changes and the squeezing actions move blood in the veins of the chest and abdomen towards the heart * In combination, these adaptations assist in the return of deoxygenated blood to the heart

Answer 77

- Plasma = a yellow liquid which carries a wide variety of other components (e.g. dissolved glucose, amino acids, mineral ions, hormones, and the large plasma proteins including albumin, fibrinogen and globulins). Plasma also transports red blood cells, many types of white blood cells, and platelets - these are fragments of large cells (megakaryocytes) found in red bone marrow and are involved in the clotting mechanism of the blood * Plasma only makes up 55% of the blood by volume - and most of that volume is water

Answer 78

1. Oxygen to, and carbon dioxide from, the respiring cells 2. Digested food from the small intestine 3. Nitrogenous waste products from the cells to the excretory organs 4. Chemical messages via hormones 5. Food molecules from storage compounds to the cells that need them 6. Platelets to damaged areas 7. Cells and antibodies involved in the immune response

Answer 79

1. Contributes to maintenance of a steady body temperature (thermoregulation) 2. Acts as a buffer, minimising pH changes 3. Defence

Answer 80

Extracellular fluid which bathes the cells of most tissues, arriving via blood capillaries and being removed via the lymphatic vessels

Answer 81

- ~55% plasma - <1% buffy coat (platelets, wbc) - ~45 red blood cells

Answer 82

Centrifugation

Answer 83

They're responsible for transporting oxygen as it is bound to haemoglobin at the lungs and released from the RBCs at respiring tissues

Answer 84

Involved in the body's immune response, detects and eliminates infections

Answer 85

- About 8% of blood plasma consists of plasma proteins, of which about half may be albumins - These are a group of small proteins involved in the transport of other substances (e.g. fatty acids, hormones) and which help regulate the osmotic pressure of blood - The balance between the hydrostatic pressure of blood (‘blood pressure’) and the osmotic pressure of blood is important in the formation of tissue fluid * Plasma proteins e.g. albumin cannot pass through capillaries. These give blood a high solute potential (lowering the water potential) compared to surrounding fluid

Answer 86

- As blood arrives at the arteriole end of the capillary it is under pressure from the surge of blood from the heart. - Hydrostatic pressure forces fluid out of the capillaries (Pressure: approx.. 4.3-4.6kPa) - This is higher than oncotic pressure causing water top move in. - Net flow out - the fluid flowing out fills the space between the cells (tissue fluid - same composition as plasma except cells and plasma proteins, diffusion occurs here) - As the blood reaches the venous of the capillary, hydrostatic pressure falls to 2.3kPa and pulse lost. - The oncotic pressure is -3.3kPa and is greater than hydrostatic pressure. Water moves back into the capillaries by osmosis. - As the blood enters the veins, 90% of the tissue fluid is back in blood vessels. - Net flow in

Answer 87

- 10% of the liquid that leaves the blood vessels (tissue fluid) drains into a system of blind-ended tubes called lymph capillaries, where it is known as lymph - It has a similar composition to plasma and tissue fluid but has less oxygen and fewer nutrients - It also contains fatty acids, which have been absorbed into the lymph from the villi of the small intestine - The lymph capillaries join up to form larger vessels, where the lymph is transported by the squeezing of the body muscles - There are one-way valves that prevent the backflow of lymph - Eventually lymph will return to the blood, flowing into the right and left subclavian veins (under the clavicle, or collar bone)

Answer 88

Lymphocytes - these are WBCs which produce antibodies to fight of disease

Answer 89

- They intercept bacteria and other debris from the lymph, which are ingested by phagocytes found in the nodes * The lymphatic system plays a major role in the defence mechanisms of the body

Answer 90

- They're a sign that the body is fighting off an invading pathogen - This is why doctors often examine the neck, armpits, stomach, or groin of their patients, as they are major sites of lymph nodes (also referred to as lymph glands) in the body

Answer 91

- They have a biconcave shape, meaning it has an increased SA available for diffusion of gases (than a simple disc or sphere structure, for example). The shape also allows it to pass through narrow capillaries - Mature erythrocytes have no nuclei, maximising the amount of haemoglobin that fits into them

Answer 92

(Very large) globular conjugated protein made up of four polypeptide chains, each with an iron-containing haem prosthetic group

Answer 93

- Haemoglobin + Oxygen ⇌ Oxyhaemoglobin | - Hb + 4O₂ ⇌ Hb(O₂)₄

Answer 94

When the shape of the haemoglobin molecule changes as soon as one oxygen molecule binds to it, which makes it easier for the next oxygen molecule to bind to it (- Once the first oxygen molecule is released by the haemoglobin, the molecule again changes shape and it becomes easier to remove the remaining oxygen molecules)

Answer 95

Because when erythrocytes enter the capillaries in the lungs, the oxygen levels in the cells a relatively low

Answer 96

- The cytoplasm of the body cells | - As a result, oxygen moves out of the erythrocytes down a concentration gradient

Answer 97

``` X = partial pressure of oxygen/kPa Y = percentage saturation of haemoglobin with oxygen ```

Answer 98

They show the affinity of haemoglobin for oxygen

Answer 99

When all the haem groups have bound to 4 oxygen molecules, meaning haemoglobin can't take up anymore oxygen

Answer 100

As the partial pressure of carbon dioxide rises (in other words, at high partial pressures of CO₂), haemoglobin gives up oxygen more easily

Answer 101

1. In active tissues with a high partial pressure of carbon dioxide, haemoglobin gives up its oxygen more readily 2. In the lungs where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoglobin molecules easily

Answer 102

Found in fetal blood, it has a higher affinity for oxygen than adult haemoglobin. This is important as if both haemoglobins (fetal and maternal) had the same oxygen affinity, little to no oxygen would be transferred from the maternal blood to the fetal blood. As fetal has a higher affinity, it removes oxygen from the maternal blood as they move past each other (oxygenated blood of the mother runs close to the deoxygentated blood of the fetus in the placenta)

Answer 103

1. About 5% is carried dissolved in the plasma 2. 10-20% is combined with the amino groups in the polypeptide chains of the haemoglobin to form a compound called carbaminohaemoglobin 3. 75-85% is converted into hydrogen carbonate ions (HCO₃⁻) in the cytoplasm of the red blood cells

Answer 104

- Carbonic acid (H₂CO₃⁻) | - It dissociates to form hydrogen ions and hydrogen carbonate ions

Answer 105

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻

Answer 106

It catalyses the reversible reaction between carbon dioxide and water to form carbonic anhydrase (which dissociates to form H⁺ and HCO₃⁻ ions)

Answer 107

The negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma by diffusion down a concentration gradient and negatively charged chloride ions move into the erythrocytes, which maintains the electrical balance of the cell

Answer 108

It prevents changes in pH by accepting free hydrogen ions in a reversible reaction to form haemoglobonic acid

Answer 109

- Cardiac muscle, allowing it to contract and relax in a regular rhythm - Coronary arteries supply the cardiac muscle with the oxygenated blood it needs to keep contracting and relaxing all the time

Answer 110

The septum

Answer 111

Inelastic pericardial membranes, they help prevent the heart from over-distending with blood

Answer 112

Superior/inferior vena cava, right pulmonary artery, right atrium, tricuspid valve (right atrioventricular valve), tendons, right ventricle, aorta (and carotid arteries), left pulmonay artery, pulmonary veins, left atrium, semilunar valves, biscuspid valves (left atrioventricular valves), septum, left ventricle, muscular left ventricular wall

Answer 113

- Right: Superior/inferior vena cava (vein), pulmonary artery - Left: Pulmonary vein, aorta (artery)

Answer 114

1. Deoxygenated blood enters the right atrium from the upper body and head through the superior/inferior vena cava at relatively low pressure 2. As blood flows in, slight pressure builds up until the tricuspid valve opens to let blood pass into the right ventricle 3. When both the atrium and ventricle are filled with blood, the atrium contracts, forcing all the blood into the right ventricle and stretching the ventricle walls. As the right ventricle starts to contract, the tricuspid valve closes to prevent the backflow of blood to the atrium 4. The right ventricle contracts fully and pumps deoxygenated blood through the semi-lunar valves into the pulmonary artery, which transports it to the capillary beds of the lungs. The semi-lunar valves close to prevent backflow of blood into the heart 5. At the same time, oxygenated blood enters the left atrium from the lungs through the pulmonary vein 6. As pressure builds in the left atrium, the bicuspid valve opens between the atrium and the ventricle, filling the ventricle with oxygenated blood 7. When both atrium and ventricle are filled with blood, the atrium contracts, forcing all blood into the left ventricle and stretching the ventricular walls 8. The left ventricle contracts fully and pumps oxygenated blood through the semi-lunar valves into the aorta and around the body. During contraction, the tricuspid valve closes, preventing backflow of blood

Answer 115

The left side of the heart has to pump blood around the whole of the body, and also has to overcome the resistance of the aorta and the arterial systems of the whole body, moving blood under pressure to all the body's extremities. This is compared to the right side, which has to pump the blood a relatively short distance (to the lungs) and only has to overcome the resistance of the pulmonary circulation

Answer 116

In the placenta, not the lungs

Answer 117

The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, dubbed systole

Answer 118

The heart relaxes - the atria and then the ventricles fill with blood. The volume and pressure of the blood in the heart build as the heart fills, but the pressure in the arteries is at a minimum

Answer 119

The atria contract (atrial systole), closely followed by the ventricles (ventricular systole). The pressure inside the heart increases dramatically and blood is forced out of the right side of the heart to the lungs and from the left side to the main body circulation. The volume and pressure of the blood in the heart are low at the end of systole, and the blood pressure in the arteries is at a maximum

Answer 120

Aortic pressure rises when ventricles contract as blood is forced into the aorta. It then gradually falls, but never below around 12kPa, because of the elasticity of its wall, which creates a recoil action - essential if blood is to be constantly delivered to the tissues. The recoil produces a temporary rise in pressure at the start of the relaxation phase

Answer 121

Atrial pressure is always relatively low because the thin walls of the atrium cannot create much force. It is highest when they are contracting, but drops when the left atrioventricular valve closes and its walls relax. The atria then fill with blood, which leads to a gradual build-up of pressure until a slight drop when the left atrioventricular valve opens and some blood moves into the ventricle

Answer 122

Ventricular pressure us low at first, but gradually increases as the ventricles fill with blood as the atria contract. The left atrioventricular valves close and pressure rises dramatically as the thick muscular walls of the ventricle contract. As pressure rises above that of the aorta, blood is forced into the aorta past the semi-lunar valves. Pressure falls as the ventricles empty and the walls relax

Answer 123

Ventricular volume rises as the atria contract and the ventricles fill with blood, and then drops suddenly as the blood is forced out into the aorta when the semi-lunar valve opens. Volume increases again as the ventricles fill with blood

Answer 124

- They're made by blood pressure closing the heart valves - Lub = comes when blood is forced against the atrioventricular valves as the ventricles contract - Dub = comes as a backflow of blood closes the semi-lunar valves in the aorta and pulmonary artery as the ventricles relax

Answer 125

It has is own intrinsic rhythm at around 60 bpm, preventing the body wasting resources maintaining the basic heart rate

Answer 126

Exercise, excitement, stress, etc...

Answer 127

- By a wave of electrical excitation (similar to a nerve impulse) - A wave begins in the pacemaker area called the sino-atrial node (SAN), causing the atria to contract and so initiating the heartbeat. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles - The electrical activity from the SAN is picked up by the atrio-ventricular node (AVN). The AVN imposes a slight delay before stimulating the 'bundle of His', a bundle of conducting tissue made up of fibres (Purkyne fibres), which penetrate through the septum between the ventricles - The bundle of His splits into two branches and conducts the wave of excitation to the apex (bottom) of the heart - At the apex the Purkyne fibres spread out through the walls of the ventricles on both sides. The spread of excitation triggers the contraction of the ventricles, starting at the apex. Contraction starting at the apex allows more efficient emptying of the ventricles * The way in which the wave of excitation spreads through the heart from the SAN, with AVN delay, makes sure that the atria have stopped contracting before the ventricles start

Answer 128

You can measure the spread of electrical excitation through the heart as a way of recording what happens as it contracts. This recording of the electrical activity of the heart is called an electrocardiogram (ECG). An ECG doesn't directly measure the electrical activity of your heart. It measures tiny electrical differences in your skin, which result from the electrical activity of the heart. They can be used to diagnose heart problems, such as heart attacks, where reconisable changes take place in the electrical activity of the heart, allowing diagnosis and correct treatment

Answer 129

1. Tachycardia - When the heartbeat is very rapid, over 100 bpm. This is often normal, for instance when you exercise, if you have a fever, if your are frightened or angry. If it is abnormal it may be caused by problems in the electrical control of the heart and many need to be treated by medication or by surgery 2. Bradycardia - When the heart rate slows down below 60 bpm. Many people have bradycardia because they are fit - training makes the heart beat more slowly and efficiently. Severe bradycardia can be serious and many need an artificial pacemaker to keep the heart beating steadily 3. Ectopic heartbeat - Extra heartbeats that are out of the normal rhythm. Most people have at least one a day. They are usually normal but they can be linked to serious conditions when they are very frequent 4. Atrial fibrillation - This is an example of an arrhythmia, which means an abnormal rhythm of the heart. Rapid electrical impulses are generated in the atria. They contract very fast (fibrillate) up to 400 times a minute. However, they don't contract properly and only some of the impulses are passed on to the ventricles, which contract much less often, As a result the heart does not pump blood very efficiently

Answer 130

By using a manual sphygmomanometer - a cuff, which is connected to a mercury manometer (a way of measuring pressure using the height of a column of mercury), is placed around the upper arm. The cuff is then inflated until the blood supply to the low arm is completely cut off. A stethoscope is positioned over the blood vessels at the elbow. Air is slowly let out the cuff. The pressure at which blood sounds first reappear as a slight tapping sound is recorded. The first blood to get through the cuff is that under the highest pressure - in other words, when the left ventricle of the heart is contracting strongly. The height of the mercury at this point gives the systolic blood pressure in mmHg (the height of the mercury column). The blood sounds return to normal at the point when even the lowest pressure during diastole is sufficient to get through the cuff. This gives the diastolic blood pressure. A reading of 120/80 mmHg is regarded as being normal. More recently, a digital sphygmomanometer is often used - but the same principles apply, with the stethoscope being built into the cuff applied around the arm

Module 3 - Exchange and Transport Flashcards

(159 cards)