Option D: Human Physiology Flashcards

Question

What is anorexia

Answer 1

Lack of appetite

Answer 2

eating disorder characterized by food restriction and irrational fear of weight gain. many patients suffering don’t lose their appetites but have a very limited intake of food. often accompanied by unrealistic body self-perception. can lead to excessive weight loss. leads to electrolyte imbalance, skeletal and heart muscle reduction, reduced blood pressure, and a slower heart rate. body might become covered in fine growth of thin hair. can lead to reduced or absent menstrual cycles. can lead to death if extreme.

Answer 3

- Vitamin C AKA L-ascorbic acid can’t be synthesized by humans and some animals. it’s needed for the production of collagen, a protein found in skin, connective tissues, tendons, and blood vessels. can’t be synthesized by some animals cuz they have a mutation in the GLO gene that codes for an enzyme needed for the last step in the synthesis of L-Ascorbic acid - vitamin C is: - vitamin soluble - found in many fruits, sour taste - used for collagen (skin, blood vessels, muscles, etc.) - supports many immune functions

Answer 4

- vitamin C deficiency causes scurvy, disease common amongst sailors in past centuries because of a lack of citrus fruits in their diets. citrus fruits are a good source of vitamin C. - all primates and some smaller monkeys need vitamin C in their diet or get scurvy. - main symptoms of scurvy: - bleeding gyms, gingivitis, or loose teeth. vitamin c is necessary for synthesis of collagen which builds and maintains tissue - lack of energy. loss of weight and extreme fatigue - mood swings or depression - chronic joint pain caused by bleeding in the joints - suppressed immune system causing frequent diseases - slow wound healing and easy bruising.

Answer 5

- guinea pigs (can’t make vitamin C) were fed diets with different levels of vitamin C, while all other conditions were controlled - Group 0 doesn’t get any foods with vitamin C - groups 1-10 get increasing levels of a daily supplement of vitamin C in their diet - group 0 starts developing symptoms of scurvy - groups 1-2 might also show some symptoms - data collected can be used to calculate amount of vitamin C required by a human

Answer 6

- the metabolic pathway to synthesize vitamin C requires GLO (L-gulonolactone oxidaze) enzyme. this is required for the last step of vitamin C synthesis - many mutations have occured preventing the enzyme from being produced - loss of the ability to synthesize vitamin C, meaning it’s required in diet - many mammals can make vitamin C, most primates can not

Answer 7

- PKU - genetic disease - gene coding for phenylalanine hydroxylase, which is the enzyme that catalyses the hydroxylation of phenylalanine to tyrosine, is mutated, resulting in inability to convert phenylalanine into tyrosine - PKU is inherited as an autosomal recessive trait - enzyme can no longer catalyse the last and rate limiting step, so phenylalanine accumulates in the body

Answer 8

- consequences: - intellectual disability - reduced growth of the head - lack of skin and hair pigmentation - seizures

Answer 9

- needs to be detected and diagnosed within 24 hours of birth - Guthrie test is used to detect PKU - until 24 hours, the phenylalanine and tyrosine levels in the baby are normal as a result of the normal metabolism of the mother - PKU patients need a diet low in phenylalanine

Answer 10

Vitamin D (Calciferol) is needed for absorption of calcium in the digestive system most important roles of vitamin D: maintaining skeletal calcium balance by promoting calcium absorption in the intestines, maintaining calcium and phosphate levels for bone formation

Answer 11

- calcium is needed to build healthy bones, so a deficiency of calciferol can lead to softening or malformation of the bones - in adults, this is called osteomalacia (milder). in children it’s called rickets (serious) - in breastfeeding mothers with low vitamin D intake, there can be problems with the bone mineralisation of their infants

Answer 12

- exposing skin to UV light with wavelength between 290-310 nm triggers synthesis of vitamin D in the skin - Vitamin D can be made in the body, so doesn’t really fit the definition of a vitamin - if skin is exposed for a short time in the open air it is enough to get a daily dose of vitamin D

Answer 13

a certain amount of vitamin D, which is fat soluble, can be stored in the liver for when we are unable to synthesize it

Answer 14

Vitamin D is found in foods such as oily fish, particularly salmon, herring and tuna; egg yolk; liver; and dairy products including milk, cheese and butter.

Answer 15

- Cholesterol is the precursor of bile acids, vitamin D, and steroid hormones like progesterone and oestrogen - cholesterol protects the membrane integrity of animal cells, and enables the cell to change shape and move about - total cholesterol is the sum of the very low density lipoprotein, low density lipoprotein, and high density lipoprotein

Answer 16

Cholesterol in the blood is an indicator of the risk of coronary heart disease. Only cholesterol in LDL is associated with an increased risk of developing CHD.

Answer 17

drugs like statin are more effective in lowering blood cholesterol levels than diet control. statins are drugs that inhibit the enzyme HMG-CoA reductase, which catalyses the second step in the pathway from Acetyl CoA to cholesterol

Answer 18

- energy content in food can be measured by burning a known mass of the food to test - burning food is placed under the test tube with water - heat liberated by the burning food is absorbed by a volume of water - rise in temperature is recorded - energy value is calculated as temperature rise * mass of water * specific heat capacity of water

Answer 19

to digest food particles into soluble molecules that can pass through membranes, the exocrine glands of the digestive system secrete enzymes that hydrolyse large molecules into smaller molecules

Answer 20

the presence or smell of food stimulates the digestive system, and thinking about it makes your body secrete saliva and gastric juice to prepare for future intake of food

Answer 21

- nervous control is mainly provided by the autonomic nervous system which is divided into the sympathetic and parasympathetic systems - sympathetic system controls processes involved in responses to danger. slows down the speed of digestion when there’s no food available. - parasympathetic system controls homeostasis and processes related to rest and digestion. it speeds up digestion when food is ingested

Answer 22

having food in the mouth induces the secretion of saliva and the presence of food in the gut will induce the secretion of gastric juice (especially after eating proteins), intestinal juice, pancreatic juice, bile (especially if you have eaten fats)

Answer 23

- gastrin - produced by special cells (G cells) in the stomach, duodenum, and pancreas, in response to physical stimulation due to the presence of food, as well as chemical stimulation by protein - when released, it stimulates the production of gastric juice by the parietal cells in the gastric glands - gastric juice has a mixture of water, hydrochloric acid, and other inorganic ions, enzymes (pepsin, rennin), mucus, various, polypeptides, and intrinsic factor - intrinsic factor is necessary for absorbing vitamin B12 - gastric juice changes the pH of the food content from 6.7 to 2, providing acidic conditions that will enhance digestion - when there’s sufficient gastric juice present (around 1 to 1.5 litres), the production of gastrin will stop and subsequently so will the secretion of gastric juice - secretin - made by special cells in the small intestine in response to the presence of acidic fluid - presence of gastric acid activates prosecretin into secretin. when released, it stimulates the production of alkali by the pancreas, neutralising intestinal components - when pH of intestine reaches 8, the production of pancreatic juice is stopped by negative feedback - secretin plays a role in osmoregulation since it regulates water homeostasis throughout the body by acting on the kidney, hypothalamus, and pituitary gland - cholecystokinin (CCK) - produced by the small intestine when food is present in there - controls release of pancreatic juice from the pancreas and bile from the gall bladder (bile is made in the liver and stored in the gall bladder) - acts as a hunger suppressor

Answer 24

Somatostatin is an inhibitory hormone that suppresses digestion. it’s secreted by special cells in the stomach, duodenum and pancreas. it travels through blood to directly inhibit acid producing cells. also acts indirectly by preventing the release of gastrin, CCK, and secretin, thus slowing down the digestive process

Answer 25

acid secretion is regulated by the nervous system, which causes direct stimulation of parietal cells to secrete acid, and indirect stimulation by decreasing somatostatin secretion

Answer 26

a regulatory feedback mechanism exists whereby the presence of acid in the lumen of the stomach stimulates somatostatin secretion, which in turn slows down acid secretion

Answer 27

exocrine glands have ducts that carry their secretory product to the surface of the body or the lumen of the gut. these include the sweat, sebaceous, and mammary glands and the glands that secrete digestive enzymes

Answer 28

- first studies into digestion in the stomach were performed in 1822 - Alexis st. martin (18 yr old Canadian) was accidentally wounded by discharge of a musket - wound was serious and left a hole in his body but he survived - his doctor William Beaumont was able to extract gastric juice by introducing an elastic tube into the stomach through the wound. then he observed which foods were digested and under which conditions - acid in the stomach is produced by combination of hydrogen (H+) and chloride (Cl-) ions produced by the epithelial cells (known as parietal cells) of the stomach lining - release of hydrogen ions through protein carriers is coupled to the intake of potassium ions (K+) from the lumen of the stomach. this process requires energy in the form of ATP

Answer 29

- gastric juice has hydrochloric acid and pepsin - pepsin is a protease that hydrolyses proteins to peptides - pepsin is found in the stomach in an inactive form as the pro-enzyme pepsinogen - pepsinogen is released by the chief cells in the lining of the stomach and is activated into pepsin by the presence of acid - hydrochloric acid released by the parietal cells of the stomach removes 44 amino acids from pepsinogen, transforming it into pepsin

Answer 30

acid conditions in the stomach favour the hydrolysis reactions by pepsin. the optimum pH for this enzyme is 2. acidic conditions help control pathogens in ingested food. the bacteria present in food can’t survive such acid conditions. the mucus cover of the stomach avoids self-damage

Answer 31

- in come cases (either because the patient has eaten spicy foods, excess proteins, or is very stressed) the stomach will produce an excess gastric acid. this can damage the mucus layer, producing gastric problems which might develop into a gastric ulcer - gastric ulcer — lining of the stomach are disrupted. main symptoms are stomach pain, heartburn, nausea, and in some cases presence of blood in the stools * - another case of gastric ulcers is the presence of the bacterium *Helicobacter pylori* in the stomach. *H. pylori* produces toxins that cause continuous gastric inflammation. the inflammatory response by the immune system damages the stomach lining - ulcers due to *H. pylori* are treated with a combination of medications: - amoxicillin — antibiotic that directly inhibits the synthesis of bacterial cell walls - clarithromycin — antibiotic that prevents bacteria from growing by inhibiting the translation of peptides in the ribosome, thus inhibiting their protein - proton pump inhibitor (PPI) — inhibits acidification of stomach - block the proton pump (hydrogen-potassium-ATPase pump), responsible for secretion of hydrogen ions (H+) in the stomach - the decrease of H+ into the lumen of the stomach reduces the amount of hydrochloric acid (HCl) produced, which makes the stomach less acidic and a suitable treatment of gastric ulcers

Answer 32

If absorption in the small intestine: - once digested, food products are absorbed by the digestive system into the blood or lymphatic system and carried to different organs, where they are metabolised into other molecules Polysaccharides: Digested to monosaccharides. Absorbed by small intestine. Go to Villus through hepatic portal vein to liver Proteins: Digested to amino acids. Can be absorbed by stomach or small intestine. If absorbed by stomach, they go to the cells of the stomach lining. If absorbed by small intestine, they go to the villus through the hepatic portal vein to the liver. Lipids: Digested to short chain fatty acids, absorbed by small intestine, then go to villus through hepatic portal vein to liver. Can also be digested to longer chain fatty acids, absorbed by small intestine, then reach the lacteal to symphatic system.

Answer 33

In the small intestine

Answer 34

- increased surface area due to presence of villi and microvilli - many mitochondria to provide energy for active transport - presence of capillaries in villi for absorption of digested foods presence of lacteal for absorption of absorbed lipids - presence of pinocytotic vesicles aid the uptake of fluids - presence of tight junctions to ensure molecules don’t escape through the membrane, and to maintain a concentration gradient - enzymes (peptidases and disaccharidases) being bound to epithelial membranes to complete hydrolysis/digestion

Answer 35

- mucosa — has epithelium formed by enterocytes, goblet cells, and endocrine cells. enterocytes are cells that have microvilli. they digest and absorb substances. goblet cells make mucus and endocrine cells secrete hormones - submucosa — contains blood vessels and connective tissue - circular muscle layer — smooth muscle arranged in a circular manner - longitudinal muscle layer — smooth muscle arranged in a longitudinal manner - serosa — single layer of epithelial cells with connective tissue

Answer 36

polysaccharides are mainly hydrolysed to glucose and absorbed by epithelial cells of the small intestine. glucose is co-transported with sodium (Na+) by facilitated diffusion. for this to happen sodium must first be transported out of the cell by active transport (along the basal membrane). this powers the co-transport of glucose and sodium into the epithelial cells through the apical membrane. the glucose is then carried along the epithelial cell to a sugar transporter protein that allows its transport into the capillaries, which will carry it to the hepatic portal vein

Answer 37

proteins are digested by proteases into amino acids, which are transported by co-transport with sodium into epithelial cells. amino acid carrier proteins then carry them by facilitated diffusion into the capillaries

Answer 38

fats/lipids are emulsified in the intestines by bile. this transforms them into smaller droplets, allowing lipases to digest them into fatty acids and glycerol. the glycerol will be absorbed and used in carbohydrate metabolism and the fatty acids will diffuse into the small intestine epithelial cells. long chain fatty acids will combine with proteins to form chylomicrons. the chylomicrons travel to the border of the cell in the smooth endoplasmic reticulum and are expelled by exocytosis to later enter the lacteal, thus entering the lymphatic system

Answer 39

exocytosis is a form of active transport. active transport requires energy, therefore villi epithelial cells are rich in mitochondria, as a lot of ATP is required

Answer 40

large intestine is in charge of absorption of water and minerals and vitamin K

Answer 41

- insoluble fibre is not digested so it has no nutritional value. but fibre is still important since it increases faecal mass, stimulating peristaltic movements - dietary fibre aka insoluble fibre — non-digestible carbohydrates, especially cellulose and lignin, that are intrinsic and intact in plants

Answer 42

materials that aren’t absorbed are cellulose and lignin from plant matter, bile pigments, the remains of intestinal epithelial cells, and bacteria

Answer 43

Positive correlation

Answer 44

constipation is unsatisfactory defecation, characterised by infrequent bowel movement, difficult stool passage, or both

Answer 45

an infection of the intestines due to a virus, bacterium, or parasite, will cause inflammation of the epithelial cells lining the intestine. this reduces the absorption of water, causing the feces to be loose or liquid (diarrhoea). if the infection stays for several days it can cause dehydration.

Answer 46

- cholera is a disease caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. when cholera toxin is released from the bacteria in the infected intestine, it binds to the intestinal epithelial cells (enterocytes), and triggers endocytosis of the toxin. the toxin becomes an active enzyme which activates ions and water to leave the infected enterocytes, leading to watery diarrhea - there are 4 million patients with cholera every year internationally. - symptoms of cholera: - vomiting - muscle cramps - profuse diarrhea

Answer 47

- sings and symptoms of dehydration: - increased thirst - dry mouth - swelling of brain - weakness - dizziness - palpitations - seizures - drop in blood pressure - fainting - decreased urine output - kidney failure - coma - death - treatment of dehydration includes use of antibiotics to kill the bacteria and oral or intravenous rehydration

Answer 48

found under the diaphragm in the upper right part of the abdomen

Answer 49

* Production of bile, enzymes, hormones, cholesterol, triglycerides * Removal of toxins from blood, drugs * Maintenance of blood temperature and pressure * Breakdown of red blood cells * Regulation of blood clotting * Conversion of ammonia to urea * Storage of glycogen, vitamin A B12 D and K, minerals such as iron and copper * Synthesis of amino acids and proteins

Answer 50

- liver is supplied with oxygenated blood from the heart through the hepatic artery - hepatic artery is a branch of the aorta - blood then leaves the liver through the hepatic vein, which carries deoxygenated blood. the vein joins the vena cava, which returns the blood to the heart - liver also receives deoxygenated blood coming from the spleen, stomach, pancreas, gall bladder, and intestines through the hepatic portal vein. this vein carries foods absorbed mainly in the small intestine. it’s rich in amino acids, glucose, vitamins, minerals, and other foods. blood supplied by this vessel represents majority of the blood received by the liver (75%) - as the liver receives oxygenated blood from hepatic artery and deoxygenated blood from the hepatic portal vein, we say that the liver has a dual blood supply - Because the blood from these two sources is mixed before entering the liver, its cells never receive fully oxygenated blood. - In the liver, blood from the hepatic artery and the hepatic portal vein supply the sinusoids that bathe the hepatocytes and Kupffer cells. As blood passes through the liver, the hepatocytes monitor the contents of the blood and remove many toxic substances such as alcohol and drugs before they can reach the rest of the body. Enzymes metabolise these toxins to render them harmless

Answer 51

Many metabolic reactions take place in the liver. These reactions liberate heat, therefore when blood passes through the liver it is warmed up. This helps to maintain the body temperature in warm-blooded organisms.

Answer 52

The liver is a triangular shaped organ of approximately 1,500 to 2,000 g consisting of four lobes. The internal structure of each lobe has around 100,000 lobules, each consisting of a central venule coming from the hepatic vein surrounded by six venules coming from the hepatic portal vein and six arterioles from the hepatic artery. These blood vessels are connected by sinusoids

Answer 53

Pores: Capillaries have very small pores called intracellular clefts. Sinusoids are fenestrated with pores of approximately 175 nm diameter Membrane: Capillaries have a continuous basement membrane. Sinusoids have a discontinuous basement membrane Shape: Capillaries have a cylindrical shape. Sinusoids have no definite shape Size: Capillaries have smaller size. Sinusoids have a larger size. Intracellular space: Capillaries have little intracellular space, sinusoids have large intracellular space Passage: In capillaries only small molecules can pass. Sinusoids are leaky.

Answer 54

The lobules have mainly two types of cells, hepatocytes and Kupffer cells (as shown in **Figure 1**). **Hepatocytes** perform most of the liver functions, especially storage and metabolism. These cells are large (around 25 μm) and constitute around 80% of the total liver cells. Their nucleus is round and found in the centre of the cell. These cells are capable of regenerating when exposed to toxic substances. Liver regeneration involves the replication of hepatocytes followed by the replication of other liver cells. Once cell proliferation is completed, the newly divided cells undergo restructuring and reformation of the extracellular matrix to complete the process. During regeneration, liver function is only partially affected. Because human liver cells regenerate it has become possible to use partial livers from living donors for transplantation, thereby increasing the number of organs that are available for transplantation. Hepatocytes are involved in many metabolic processes, therefore they are rich in mitochondria, Golgi complexes, rER, ribosomes, glycogen granules and lipid droplets.

Answer 55

**Plasma proteins** are synthesised in hepatocytes mainly in the rough endoplasmic reticulum (rER) and processed in Golgi complexes. As we have mentioned before, hepatocytes are also involved in the degradation of toxins, such as detoxification of alcohol. Many of the detoxification reactions occur in the smooth endoplasmic reticulum (sER). Hepatocytes also have an exocrine function in the secretion of bile. Hepatocytes can have up to 1000 mitochondria and 50 Golgi complexes per cell.

Answer 56

Kupffer cells are white blood cells (macrophages) that break down red blood cells. Therefore they are involved in the recycling of erythrocytes, as you will see later in this subtopic. In the lobules there are also canals (bile canaliculi) that carry bile to the bile duct that leads to the gall bladder where bile is stored until it is used in the small intestine.

Answer 57

Temporary mounts of liver cells can be prepared from fresh liver tissue and observed under light microscope. This can be done by mashing pieces of liver tissue in a mortar together with 10 ml salt solution. Cells can be stained with a drop of methylene blue before placing the coverslip on the slide. Part of the liver of a mouse under the light microscope is shown in Figure 3(a) at a magnification of ×100 and Figure 3(b) at ×400.

Answer 58

The liver is in charge of the processing and storage of many nutrients. As you have seen in the previous section, blood enters the liver through the hepatic portal vein. This vein carries most of the food digested and absorbed in the digestive tract.

Answer 59

Hepatocytes in the liver absorb most of the glucose and store it as glycogen. When the body requires energy, this glycogen is broken down into glucose

Answer 60

Fatty acids in the blood passing through the liver are absorbed by hepatocytes and metabolised to produce energy in the form of ATP. Hepatocytes also synthesise lipids such as triglycerides, cholesterol and phospholipids. These lipids can be bound to proteins forming lipoproteins, which are now soluble in blood plasma and can therefore be transported in blood to all the body. Much of the cholesterol produced by hepatocytes gets excreted from the body as a component of bile.

Answer 61

**Amino acids** entering the liver are transformed into other amino acids or are used in the synthesis of new proteins. Endoplasmic reticulum and Golgi apparatus in hepatocytes produce **plasma proteins**. These plasma proteins include fibrinogen used in blood clotting, and albumin that transports hormones and maintains the blood pH When amino acids are no longer necessary, hepatocytes remove the amine group from the acid group (deamination). The acid group of the amino acid is used to produce energy or new glucose molecules while the amine group is converted into ammonia. As ammonia is toxic, it is transformed into urea, which is then eliminated by the kidneys in urine

Answer 62

A very important function of the liver is detoxification. The liver gets rid of drugs, hormones and other toxins. In some cases it breaks down the substances into harmless compounds. If it cannot break them down, it attaches these substances to other organic groups (such a glycine), which allows the kidneys to recognise them as unwanted waste material and are therefore excreted

Answer 63

The liver is in charge of metabolising alcohol. In Figure 2, it shows the chemical reactions involved in this process. Ethanol is oxidised into acetaldehyde, a toxic substance, by the hepatic enzyme alcohol dehydrogenase. Acetylaldehyde is converted into a less toxic substance, acetate, by aldehyde dehydrogenase. Acetate is then broken down to acetyl-CoA that can enter fatty acid metabolism or be used in the Krebs cycle. If acetaldehyde is not broken down immediately, it can combine with proteins that induce liver injury. Excess of alcohol can damage the liver, causing cirrhosis

Answer 64

Red blood cells or erythrocytes are cells modified to increase their capacity in the transport of oxygen. In order to do this, they have a biconcave shape and have lost their nucleus and organelles. These cells are rich in haemoglobin, a protein that binds oxygen (as HL students will see in section haemoglobin and myoglobin). The biconcave shape increases their surface area:volume ratio, thus increasing the absorption of oxygen. The lack of nucleus increases the amount of hemoglobin in each cell. But at the same time this means that they cannot reproduce, therefore they must be produced in the bone marrow from undifferentiated cells

Answer 65

Erythrocytes are produced in the bone marrow and are liberated into the bloodstream. They die after approximately 120 days circulating in blood. Dead erythrocytes are engulfed by macrophages in the liver, spleen or bone marrow by phagocytosis. In the liver, these macrophages are Kupffer cells

Answer 66

In the Kupffer cells, the hemoglobin is split into globin chains and heme groups. Globin is re-used in protein synthesis. The heme group is transformed into iron and bilirubin. Iron is carried back to the bone marrow where it is used to produce new red blood cells. Bilirubin is secreted into bile that will be used in the emulsification of fats. Figure 1 shows the function of the liver in the recycling of erythrocytes

Answer 67

Cholesterol is one of the most well-known fats. You ingest cholesterol in your diet, but it is not essential, as most cholesterol molecules are synthesised in the liver. As most animal cells require cholesterol for membrane synthesis, a small portion is added to the membranes of hepatocytes, and the rest is exported as lipoproteins or bile salts. Cholesterol is also a precursor for other important molecules: the bile salts, steroid hormones (such as oestrogen and progesterone), and vitamin D. Cholesterol synthesis is regulated according to its concentration in cells. This depends on the amount ingested in diet, and the regulation is performed by the hormones glucagon (inactivating its synthesis) and insulin (activating its synthesis)

Answer 68

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Answer 69

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Answer 70

Cholesterol molecules, like triglycerides and phospholipids are insoluble in water. Therefore, to be carried in blood to other tissues, they need to be carried as plasma lipoproteins. Different combinations of lipids and proteins produce particles of different densities. High-density lipoproteins (HDL) contain more protein, while low-density lipoproteins (LDL) contain more lipids. LDLs and HDLs are both produced in the plasma; however a small amount is synthesised in the liver. The function of LDLs is to transport cholesterol from the liver to other organs. The function of HDLs is to transport cholesterol from tissues to the liver.

Answer 71

Fats can deposit in arteries causing an atheroma or plaque. This is mainly caused by white blood cells (foam cells) and LDL. Molecules of LDL deposit in the blood vessels and can become oxidised. This will cause atherosclerosis of the walls of the arteries (Figure 2)

Answer 72

Do not confuse atherosclerosis (narrowing of arteries due to plaque) with arteriosclerosis (hardening of arteries)

Answer 73

After some time this can cause cardiovascular disease and stroke. If the artery leading to the heart (coronary artery) is clogged, the cells of the heart will not receive enough oxygen and can therefore die. These cells are replaced by fibres causing coronary heart disease (CHD). If the artery leading to the head (carotid artery) is affected, this can lead to a brain stroke.

Answer 74

HDL is considered “good” cholesterol as it removes LDL from blood by transporting it to the liver and helps to maintain the endothelium of the blood vessels, thus avoiding coronary heart problems.

Answer 75

**Bile salts** have a crucial role in digestion as they **emulsify** fats. This means they break fats down into smaller droplets to increase their surface area. This allows enzymes (for example pancreatic lipase) to work better. Bile salts are synthesised by the liver from surplus cholesterol, and may be modified by bacteria in the intestines. Bile salts are reabsorbed from the intestines into the liver, but lots are lost in faeces. Approximately 600 mg of bile salts are synthesised daily to replace bile acids lost in egestion. Bile salts aid in the digestion and absorption of dietary lipids and fat-soluble vitamins. The liver produces about one litre of bile per day. This fluid is carried by the bile canaliculi to the bile duct, which carries it to the gall bladder to be stored. The composition of bile is mainly water (97%), bile salts, cholesterol and fatty acids, bilirubin (from the breakdown of erythrocytes) and inorganic salts.

Answer 76

**Jaundice** is a condition where the skin and white of the eyes turn yellow. It is caused by the presence of **bilirubin** in extracellular fluid. As you have seen before, bilirubin is produced from haemoglobin breakdown in erythrocyte recycling in the liver. The metabolism of haemoglobin accounts for 65% to 80% of the total bilirubin production. Bilirubin in blood binds reversibly to albumin (a plasma protein), forming conjugated bilirubin that travels to the liver, which removes it from the plasma. When the liver is not able to remove the bilirubin from blood, its level may rise (especially in the unconjugated form) and the skin and eyes may begin to appear jaundiced. Jaundice appears under several circumstances - Increased destruction of red blood cells. - Immaturity in the conjugation of bilirubin (greater in premature babies). - Genetic diseases (*e.g.* Gilbert syndrome). - Defects in the secretion of conjugated bilirubin from hepatocytes (in liver damage). - Defects in transit of bilirubin to intestines (*e.g.* with bile duct obstruction).

Answer 77

A high level of bilirubin in the blood is a sign of liver malfunction. Depending on the level of exposure, the effects range from clinically unnoticeable to severe brain damage and even death. Jaundice is usually a symptom of hepatitis or liver cancer. It can also be caused by the use of drugs, genetic factors, malaria or anemia It is common for a baby's bilirubin level to be a bit high after birth as it might take some time for the liver to function properly. Some of the causes are a mismatch between the blood type of the mother and the child, lack of certain enzymes, or excess or abnormal blood cells. Special blue lights are used on infants whose bilirubin levels are very high

Answer 78

Cirrhosis is a disease where the damaged liver tissue is replaced by scar tissue. Not only does this affect the functioning of liver cells, but also interferes with the blood supply to these cells. The symptoms are weakness, fatigue, jaundice and bruising. A liver biopsy will confirm the presence of scars. There is no cure for this disease. A liver transplant can be the solution in extreme cases.

Answer 79

Excessive alcohol or drug consumption may cause liver cirrhosis. Other causes of cirrhosis include chronic viral hepatitis B or C, chronic bile duct obstruction, fatty liver disease, excess of iron, cystic fibrosis and Wilson’s disease The amount of alcohol consumed affects the possibility of liver cirrhosis in a direct manner: the greater the consumption, the greater the chances of dying of liver cirrhosis. The probability of dying of cirrhosis is greater in women than men at lower alcohol consumption, but higher for men at greater alcohol consumption, as shown in Figure 4.

Answer 80

Why should alcoholics be entitled to receive a liver transplant? - Everybody has the right to live. - They can change their lifestyle and stop drinking. - They might be the only support for a family. - Many people care for them. Why should they not receive a liver transplant? - They caused the liver damage by their own choice of drinking. - They must put up with the consequence of their own reckless attitude. - Other people deserve the transplant more. - They can relapse back into drinking and damage the new liver.

Answer 81

Type of striated muscle found in the wall of the heart

Answer 82

Allow propagation of stimuli through the heart wall

Answer 83

- Has thick and thin muscle fibres with myofibrils containing myofilaments similar to those found in skeletal muscle - Nucleus is in the centre of the cell - Rich in mitochondria and glycogen granules that are found adjacent to the myofibrils - Numerous short, cylindrical cells arranged end-to-end, resulting in long branched fibres, giving a y-shape - “all or none” effect: once a cell is activated, it produces maximum contraction

Answer 84

The attachment site between cardiac muscle cells(not present in skeletal cells). Appears as a linear structure transverse to the muscle fibre. Contain adhering junctions between cells that hold cells together and gap junctions, allowing communication between cells. Allow electrical impulses to pass rapidly from cell to cell, so linked cells contract almost simultaneously.

Answer 85

Arrays of densely packed protein channels that permit intercellular passage of ions and small molecules. Electrical activation of the heart requires cell-cell transfer of current via gap junctions.

Answer 86

Period during which cells cannot contract for a second time, to ensure systole of the heart is separated by a diastole.

Answer 87

1. Initiated in the sinoatrial node 1. Signals from the sinoatrial node that cause contraction cannot pass directly from the atria into the ventricles 2. Impulse spreads along the atria to the atrioventricular node 3. Impulse spreads to the ventricle 1. Note: There’s a delay between the arrival and passing on of a stimulus at the atrioventricular node. This allows time for atrial systole before the atrioventricular (tricuspid and bicuspid) valves close 4. Blood leaves the atria to the ventricles when the atrial systole occurs, and atrioventricular valves close 5. In the interventricular walls, there is the Bundle of His which leads to the Purkinje fibres that carry the impulse at a very high speed 6. Conducting fibres ensure coordinated contraction of the entire ventricle wall. The ventricular contraction is called the systole 7. Blood flows out of the heart as the semilunar (pulmonary and aortic) valves open and give access to the aorta and pulmonary artery 8. The heart relaxes

Answer 88

Group of specialised cardiac muscle cells found where the superior vena cava joins the right atrium.

Answer 89

Specialised fibres grouped to form a bundle in the interventricular walls. Splits into to branches that go to the left and right ventricles, leading to the Purkinje fibres

Answer 90

Specialised cells that carry impulse at a very high speed.

Answer 91

Sounds generated by the beating of the heart and the closing of the heart valves. Lub-dub in a healthy person. Caused by the closing of the atrioventricular valves at the beginning of the ventricular systole (lub) and the closing of the semilunar valves after the ventricular systole and beginning of the diastole (dub).

Answer 92

used to listen to the heart sounds. Acoustic device that has a resonator that is placed on the patient’s chest and two tubes connected to the earpieces.

Answer 93

Factors that increase heart rate: - Gender: Women have slightly higher because they need more energy for metabolism - Physical activity: More blood is required in muscles for oxygen supply - Body size: larger people have higher heart rates since blood needs to cover a larger area - Temperature: Vasodilation occurs when it is hot, increasing heartbeat. If running a fever, pulse is accelerated - Altitude: Body requires a greater amount of oxygen, therefore cardiac output must increase - Posture: When standing, the heart rate is higher than when lying down. Related the the effect of gravity, since when standing, blood needs to be pumped against it. - Stress: Body produces epinephrine, which will accelerate the rate - Eating: More blood needs to be pumped to the stomach and intestines after eating - Sodium and calcium ions in blood: Blood retains more water to dilute the ions, so it needs to pump more. Patients suffering from dehydration will have a higher rate due to increase in concentration of ions in blood. - Drugs: Caffeine and nicotine are both stimulants of the nervous system and of the cardiac centres, causing an increased heart rate. Decrease: - Age: heart muscles can’t be pumped as efficiently - Potassium ions: decrease action potentials

Answer 94

Bradycardia: Heart beating too slowly Tachycardia: Heart beating too quickly Arrhythmia: Heart beating irregularly

Answer 95

Artificial pacemaker: Battery-powered generator that sends out electrical impulses and wires with electrodes to connect to the heart muscle to maintain the heart rate pace. If it senses the heartbeat is too high, it will stop sending signals to the heart. Pacemaker senses when heartbeat is too slow as well, and automatically turn back on and start pacing the heart again. Installation: Small cut is made on the left side of the chest or abdomen, and the generator is placed under the skin. The pacemaker can have one lead leading to the right atrium or two leads, one to the right atrium and one to the right ventricular walls. Another type also includes a lead to the left ventricle.

Answer 96

Function: Checks electrical activity of the heart. Electrodes that detect electrical changes on the skin are placed on the patient’s body. These changes are made from the muscle electrical activity due to cardiac conduction in the heart. Reading: Signals obtained in ECG are amplified in the ECG machine and displayed on the screen of an oscilloscope or recorded on a moving paper, giving a graph of voltage variations in time. The R-R interval between successive beats allows the calculation of the heart rate. P-wave represents the SA node electrical activity and contraction of the atria. QRS complex corresponds to the excitation of the ventricles. T-wave is the relaxation of ventricles following contraction. An abnormal ECG pattern is most likely a sign of heart failure.

Answer 97

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Answer 98

Definition: Pressure of blood on the walls of an artery during systole and diastole. During systole, blood flows out of the heart at a high pressure through arteries, which support the pressure because their walls are elastic and strong. During diastole, the pressure of the blood on the arteries is at its lowest.

Answer 99

Tool to measure blood pressure. Has an inflatable cuff and a measuring device, which can be mechanical or digital. Mechanical measures pressure in millimetres of mercury, while digital makes oscillometric measurements

Answer 100

1. Cuff pressure is used to detect small oscillations in blood flow caused by the pulse 2. Oscillations increase in amplitude as cuff pressure falls between systolic and mean arterial pressure 3. Systolic blood pressure corresponds to a specific heartbeat: the beat at which the pressure becomes higher than the deflating cuff pressure and the blood is capable of flowing in the brachial artery 4. Oscillations decrease in amplitude as cuff pressure falls below mean arterial pressure 5. Corresponding mean oscillation is calculated to estimate blood pressure

Answer 101

1. Sphygmomanometer cuff is placed on the antecubital fossa of the arm of the patient (elbow pit; triangular area on the front view of the elbow of a human) 2. Cuff is inflated to stop the flow of blood through the artery 3. Air is slowly released until the pressure in the artery is equal to the pressure exerted by the cuff. A hissing sound is heart at this moment if one places a stethoscope under the cuff close to the artery 4. A pounding sound can be heart as the cuff deflates, denoting the systolic pressure 5. Sound stops when the pressure of the cuff is smaller than that of the artery. When the pounding can’t be heard anymore, the diastolic pressure is recording.

Answer 102

Causes: - Gender - Obesity - Lack of physical activities - Age - Genetics - Stress/anxiety - Sodium - Alcohol - Smoking - Caffeine Possible Consequences: - Stroke due to a reduced or interrupted supply of blood to the brain, which causes brain cells to die - Blindness due to the ruptured capillaries in the retina or optic nerve or damage to the area of the brain responsible for processing images - Arteriosclerosis: The hardening of arteries, restricting the flow of oxygen and nutrients to tissues. Atherosclerosis is a special kind of arteriosclerosis caused by the damage of arteries and subsequent formation of scar tissue. A plaque is formed when cholesterol and other lipids build up on the scar tissue. The plaque then makes platelets release factors that cause the formation of a clot over the plaque, forming a thrombus, which blocks the flow of blood to the tissues, causing thrombosis. if a thrombus occurs in the coronary artery, the supply of blood and oxygen to the areas of the heart muscle is blocked, causing irregular heartbeats and can lead to CHD. - Heart attack/failure - Kidney failure

Answer 103

Study of all the factors and effects that determine the presence or absence of diseases and disorders in a population.

Answer 104

Decreased blood flow and oxygen to the heart muscle caused by narrowed heart arteries. Also called cardiac ischemia or ischemic heart disease.

Answer 105

- Viral or bacterial infections and nutritional deficiencies (developing countries) - Hypertension, high-fat diets, cigarette smoking, sedentary lifestyles (developed countries) - Genetic predisposition in some ethnic groups can be explained by insulin resistance syndrome and associated chances of diabetes, or elevated triglyceride and HDL cholesterol concentrations

Answer 106

The interruption of the electrical impulses that control the heartbeat. Can be caused by the loss of blood flow to the heart or a heart attack. Often begins with ventricular tachycardia (rapid heart beating) and leads to low blood pressure because the ventricles can’t pump hard enough

Answer 107

Symptoms: - Chest pain - Dizziness - nausea - heaertburn - fluttering heartbeat - fainting - coma - nerve function loss - changes in mental function - death

Answer 108

During ventricular fibrillation, delivering cardiopulmonary resuscitation (CPR) or electric shock to the heart can be vital to survival.

Answer 109

CPR: lifesaving technique useful in a heart attack in which the heartbeat has stopped. Can keep oxygenated blood flowing to the brain and other vital organs until more definitive medical treatment can restore a normal heart rhythm. Compress the chest to restore blood circulation, clear the airway, breathe into the patient’s mouth.