d human physiology

Question 1

the autonomic nervous system is made up of

Answer 1

sympathetic system and parasympathetic system

Question 2

sympathetic system

Answer 2

controls processes involved in responses to danger

Question 3

parasympathetic system

Answer 3

controls homeostasis and processes related to rest and digestion.

Question 4

which system speeds up digestion adn which slows it down

Answer 4

The parasympathetic system speeds up digestion when food is ingested, while the sympathetic slows it down when there is no food available

Question 5

gastrin is produced by

Answer 5

g cells in the stomach, duodenum and pancreas, in response to physical stimulation due to the presence of food, as well as to chemical stimulation by protein

Question 6

When gastrin is released, it

Answer 6

stimulates the production of gastric juice by the parietal cells in the gastric glands.

Question 7

gastric juice contains a mixture of

Answer 7

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.

Question 8

when does production of gastrin stop

Answer 8

when there is 1-1.5l of gastric juice

Question 9

secretin is produced by

Answer 9

special cells in the small intestine in response to the presence of acid fluid. The presence of gastric acid activates prosecretin into secretin.

Question 10

what does secretin do

Answer 10

When released, it stimulates the production of alkali by the pancreas, neutralising the intestinal components. When the pH of the intestine reaches 8, the production of pancreatic juice is stopped by negative feedback. Secretin plays a role in osmoregulation as it regulates water homeostasis throughout the body by acting on the kidney, hypothalamus and pituitary gland.

Question 11

Cholecystokinin (CCK) is also produced

Answer 11

by the small intestine when food is present in this organ.

Question 12

waht does cck do

Answer 12

It controls the release of pancreatic juice from the pancreas and bile from the gall bladder (bile is produced in the liver and stored in the gall bladder). It also acts as a hunger suppressor.

Question 13

somatostatin

Answer 13

an inhibitory hormone secreted by special cells in the stomach, duodenum and pancreas. This hormone travels through blood to directly inhibit acid producing cells. It also acts indirectly by preventing the release of gastrin, CCK and secretin, thus slowing down the digestive process.

Question 14

exocrine glands have ducts that…

Answer 14

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

Question 15

stomach acid is produced

Answer 15

Acid in the stomach is produced by the combination of hydrogen ions (H+) and chloride ions (Cl-) produced by the epithelial cells (known as parietal cells) of the stomach lining. The 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

Question 16

gastric juice contians

Answer 16

HCL and pepsin

Question 17

what is pepsin

Answer 17

a protease that hydrolyses proteins to peptides. Pepsin is found in the stomach in an inactive form as the pro-enzyme pepsinogen.

Question 18

waht releases pepsinogen

Answer 18

he chief cells in the lining of the stomach and is activated into pepsin by the presence of acid.

Question 19

how is pepsinogen turned into pepsin

Answer 19

The hydrochloric acid released by the parietal cells of the stomach removes 44 amino acids from pepsinogen transforming it into pepsin.

Question 20

how are stomach ulcers formed

Answer 20

Acidic conditions help to control pathogens in ingested food. The bacteria present in food cannot survive such acid conditions. 
The mucus cover of the stomach avoids self-damage. In some cases (either because the patient has eaten spicy foods or excess proteins, or is very stressed) the stomach will produce an excess of gastric acid. This can damage the mucus layer, producing gastric problems which might develop into a gastric ulcer. This is when the lining of the stomach is disrupted.

Another cause of gastric ulcers is the presence of the bacterium Helicobacter pylori in the stomach. H. pylori produces toxins that cause continuous gastric inflammation.

Question 21

Ulcers due to H. pylori are treated with a combination of medications:

Answer 21

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 synthesis.
Proton Pump Inhibitor (PPI): inhibits acidification of stomach.

Question 22

how do proton pump inhibtors work

Answer 22

Proton Pump Inhibitors (PPI) block the proton pump (hydrogen-potassium-ATPase pump), responsible for the 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 (Figure 4), making it a suitable treatment of gastric ulcers.

Question 23

polysaccharides to monosaccharides

Answer 23

absorbed by small intestine
destination the villus through the hepatic portal vein to liver

Question 24

proteins to amino acids

Answer 24

absorbed by stomach
destination cells of stomach lining

small intestine to villus through hepatic portal vein to liver

Question 25

lipids to short chain fatty acids

Answer 25

absorbed by small intestine
destination villus through hepatic portal vein to liver

Question 26

lipids to longer chain fatty acids

Answer 26

small intestine to lacteal to lymphatic system

Question 27

wall of the small intestine is lined with

Answer 27

villi that increase the surface area for the absorption of substances. Each villus has a central lacteal whose function is mainly the absorption of fats, and capillaries that carry the rest of the absorbed molecules to other organs. Most capillaries join to form the hepatic portal vein that carries blood to the liver. The structure of cells in the epithelium of the villus is adapted to the absorption of food

Question 28

function of the central lacteal

Answer 28

absorption of fats

Question 29

adaptations of the small intestine

Answer 29

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 do not escape through the membrane, and to maintain a concentration gradient.
Enzymes (peptidases and disaccharidases) bound to epithelial membranes to complete hydrolysis/digestion.

Question 30

mucosa

Answer 30

contains the epithelium formed by enterocytes, goblet cells and endocrine cells. Enterocytes are cells that have microvilli; they digest and absorb substances. Goblet cells produce mucus and endocrine cells secrete hormones.

Question 31

submucosa

Answer 31

contains blood vessels and connective tissue.

Question 32

circulrar muscle layer

Answer 32

smooth muscle arranged in a circular manner

Question 33

longitudinal muscle layer

Answer 33

smooth muscle arranged in a longitudinal manner

Question 34

serosa

Answer 34

single layer of epithelial cells with connective tissue.

Question 35

polysaccharides are mainly

Answer 35

hydrolysed to glucose and absorbed by epithelial cells of the small intestine.

Question 36

how is glucose absorbed

Answer 36

Glucose is co-transported with sodium (Na+) by facilitated diffusion. In order for this to happen, Na+ must first be transported out of the cell by active transport (along the basal membrane). This powers the co-transport of glucose and Na+ into the epithelial cells via 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.

Question 37

how are proteins absorbed

Answer 37

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

Question 38

how are fats or lipids absorbed

Answer 38

Fats (or 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.

Question 39

lipids are digested by lipases to turn them into

Answer 39

fatty acids and glycerol

Question 40

glycerol will be absorbed an used in

Answer 40

carbohydrate metabolism

Question 41

fatty acids will diffuse into

Answer 41

the small itnestien epithelial cells

Question 42

long chain fatty acids will combine with proteins to form

Answer 42

chylomicrons

Question 43

where do chylomicrons travel

Answer 43

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.

Question 44

what does the large intenstine absorb

Answer 44

water, minerals and vitamin K.

Question 45

why i s insoluble fibre not digested

Answer 45

no nutritional value

Question 46

what is fibre

Answer 46

Dietary fibre is the non-digestible carbohydrates, especially cellulose, and lignin that are intrinsic and intact in plants.

Question 47

what materials are not absorbed

Answer 47

cellulose and lignin from plant matter, bile pigments, the remains of intestinal epithelial cells and bacteria.

Question 48

what does cholera do

Answer 48

When cholera toxin is released from the bacteria in the infected intestine, it binds to the intestinal epithelial cells (enterocytes), triggering endocytosis of the toxin.The toxin then becomes an active enzyme which activates ions and water to leave the infected enterocytes, leading to watery diarrhea.

Question 49

what are essential nutrients grouped into

Answer 49

minerals
viamins
amino acids
fatty acids

Question 50

minerals

Answer 50

for example phosphorus, calcium, magnesium, iron.

Question 51

vitamins

Answer 51

for example vitamins A, C, D, K.

Question 52

amino acids

Answer 52

for example histidine, tryptophan and others.
Fatty acids: for example certain omega-3 and omega-6 fatty acids.

Question 53

Fatty acids

Answer 53

for example certain omega-3 and omega-6 fatty acids.

Question 54

malnutrition can be cause by

Answer 54

an imbalance
an excess of nutrients

Question 55

what is omega 3 needed for

Answer 55

controlling body functions lik eblood clotting and building cell membranes in the brain

Question 56

what is omega 6 needed for

Answer 56

lower LDL cholesterol (‘bad’), and reduce inflammation and are protective against heart disease

Question 57

alpha linolenic acid (omega 3)

Answer 57

Question 58

linoleic acid (omega 6)

Answer 58

Question 59

whre is omega 3 found

Answer 59

in fatty fish such as salmon, veg oil, soybean, rapeseed, flaxseed and in brussel sprouts, kale, spinach, walnuts

Question 60

where is omega 6 found

Answer 60

salflower, corn, cottonseed, soybean

Question 61

what are the nine essential amino acids humans cannot synthesise

Answer 61

phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.

Question 62

Calcium and phosphorus are necessary for the formation of

Answer 62

bones and teeth

Question 63

Calcium is also necessary

Answer 63

for muscle contraction. Sodium and potassium are involved in the propagation of the nerve impulse.

Question 64

Sodium and potassium are involved in the

Answer 64

propagation of the nerve impulse.

Question 65

retinol

Answer 65

fat soluble
found in Liver, leafy vegetables, carrots, fish, soya milk, milk, eggs.

Question 66

thiamine

Answer 66

water soluble
found in Oatmeal, brown rice, vegetables, potatoes, liver, eggs.

Question 67

cyanocobalamin

Answer 67

water soluble
found in Meat and other animal products.

Question 68

riboflavin

Answer 68

water soluble
in Dairy products, bananas, green beans, asparagus.

Question 69

niacin

Answer 69

water soluble
Meat, fish, eggs, many vegetables, mushrooms, tree nuts.

Question 70

Pantothenic acid

Answer 70

water soluble
Meat, broccoli, avocados.

Question 71

pyridoxine

Answer 71

water soluble
Meat, vegetables, tree nuts, bananas.

Question 72

biotin

Answer 72

water soluble
Raw egg yolk, liver, peanuts, leafy green vegetables.

Question 73

Folic acid

Answer 73

water soluble
Leafy vegetables, pasta, bread, cereal, liver.

Question 74

ascorbic acid

Answer 74

water soluble
Many fruits, especially citrus and vegetables, liver.

Question 75

Cholecalciferol(D3), Ergocalciferol (D2)

Answer 75

fat soluble
Fish, eggs, liver, mushrooms

Question 76

Tocopherols

Answer 76

fat soluble
Many fruits and vegetables, nuts and seeds.

Question 77

Phylloquinone

Answer 77

fat soluble
Leafy green vegetables such as spinach, egg yolks, liver.

Question 78

deficiency

Answer 78

a diet lacking in one or more particular nutrients

Question 79

imbalance

Answer 79

a diet that has an inadequate intake of a particular nutrient

Question 80

excess

Answer 80

a diet that has a disproportionate intake of eg carbohydrates, fats or proteins

Question 81

how is appetite controlled

Answer 81

Appetite is controlled by the appetite control centre in the hypothalamus (ACC). The centre regulates our desire to eat. When the stomach is empty, ghrelin is released, stimulating appetite. When food is ingested, the release of peptide PYY3-36 from the small intestine (along with insulin from the pancreas and leptin from adipose tissue) inhibit appetite.

Question 82

BMI

Answer 82

mass/height sq

Question 83

causes of type 2 diabetes

Answer 83

High levels of fatty acids in the blood as a result of diets high in fat but low in fibre.
Overweight, especially obesity, associated with a lack of exercise.
Genetic makeup that influences fat metabolism.

Question 84

symptoms of type 2 diabetes

Answer 84

Increased (elevated) glucose levels in the blood urine.
Frequent need to urinate (may lead to excessive thirst).
Tiredness and fatigue.
Some loss of weight.

Question 85

what is chd

Answer 85

a disease in which a substance called plaque builds up inside the coronary arteries

Question 86

what is catabolysis

Answer 86

The loss of muscle and adipose tissue mass is caused by the body’s need for caloric intake and to protect the vital systems such as the nervous system and heart muscle. The body breaks down muscles and lipids to generate energy and amino acids.

Question 87

what dos anorexia lead to

Answer 87

electrolyte imbalance, skeletal and heart muscle reduction, reduced blood pressure and a slower heart rate. The body can become covered in a fine growth of thin hair. In female patients it can also lead to reduced or absence of menstrual cycles. Extreme cases can lead to death.
BREAKDOWN OF HEARTMUSCLE

Question 88

what is vitamin c needed for

Answer 88

production of collagen

Question 89

what is collagen found in

Answer 89

skin, connective tissues, tendons and blood vessels

Question 90

why can vitamin c not be synthesised in some animals

Answer 90

because they have a mutation in the GLO gene which codes for an enzyme that is needed for the last step in the synthesis of L-Ascorbic acid.

Question 91

what does vitamin c defiencey cause and how can you fix it

Answer 91

scurvy. vitamin c found in citrus

Question 92

symptoms of scurvy

Answer 92

bleeding gums, loose teeth
lack of energy
mood swings or depression
chronic joint pain
suppressed immune system
slow wound healing and bruising
suppressed immune system

Question 93

how is rda calculated

Answer 93

A control group (group 0) does not receive any foods containing vitamin C.
Other groups (groups 1 to 10) get increasing levels of a daily supplement of vitamin C in their diet, e.g. group 1 gets 10 mg of vitamin C per day, group 2: 20 mg vitamin C per day, etc.
The control group will start to develop symptoms of scurvy.
Perhaps also groups 1 and 2 may show some symptoms, but above a certain daily supplement of vitamin C, e.g. 30 mg per day, the guinea pigs do not show the common symptoms of scurvy.
The data collected this way can be used to calculate the amount of vitamin C required by a human.

Question 94

medical consequences of pku

Answer 94

Intellectual disability
Reduced growth of the head
Lack of skin and hair pigmentation
Seizures

Question 95

what is pku

Answer 95

A gene coding for phenylalanine hydroxylase, an enzyme that catalyses the hydroxylation of phenylalanine to tyrosine, is mutated. This results in the inability to convert phenylalanine into tyrosine. PKU is inherited as an autosomal recessive trait which means that patients with PKU have two recessive (mutated) alleles. As the enzyme can no longer catalyse the last and rate limiting step, phenylalanine accumulates in the body.

Question 96

how is pku diagnosed

Answer 96

within 24 hours fobirth via the guthrie test

Question 97

pku diet

Answer 97

Question 98

why cant pku kids have aspartame

Answer 98

The artificial sweetener aspartame contains phenylalanine, so children with PKU cannot eat chewing gum or drink any soft drink that contains this sweetener.

Question 99

what is vitamin d used for

Answer 99

the absorption of calcium in the digestive system. Calcium is needed to build healthy bones,

to maintain skeletal calcium balance by promoting calcium absorption in the intestines and maintaining calcium and phosphate levels for bone formation.

Question 100

calcium deficiency is

Answer 100

a vitamin D deficiency can lead to softening or malformation of the bones. This condition is known as osteomalacia in adults (milder condition) or rickets in children

Question 101

where is vitamin d found

Answer 101

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

Question 102

what triggers the synthesis of vitamin d

Answer 102

xposing the human skin to UV light with a wavelength between 290-310 nm triggers the synthesis of vitamin D in the skin.

Question 103

what is bile the precursor of

Answer 103

bile, acids, vitamin d and steroid hormones such as progesterone and oestrogen

Question 104

when are you high risk for cholesterol

Answer 104

under 240 in mg dm -3

Question 105

when are you not at risk for cholesterol

Answer 105

under 200

Question 106

The total cholesterol that is mentioned in the table is the sum of

Answer 106

Very Low-Density Lipoprotein (VLDL), Low Density Lipoprotein (LDL) and High Density Lipoprotein (HDL).

Question 107

which type of cholesterol has been associated with an increased risk of developing chd

Answer 107

ldl
low density lipoprotein

Question 108

statins

Answer 108

a class of drugs used to lower cholesterol levels. The drug inhibits the enzyme HMG-CoA reductase, which catalyses the second step in the pathway from Acetyl CoA to cholesterol.

Question 109

in children, the rd is

Answer 109

a) Total calorie intake value (TCV): 120 to 160 kcal/kg of weight.

b) Proteins: 10 to 15% of the total calorie value (TCV), 3g/kg of weight for children.

c) Carbohydrates: 35 to 60% of the TCV.

d) Fats: 35 to 50% of the TCV.

e) Fibre: age in years + 5g (i.e. a four-year-old needs 9g of fibre per day).

Question 110

rda for adults

Answer 110

The accepted values for daily intake (11,300 and 8,800 kJ) for men and women (respectively) between the ages of 31 and 50 are averages. Other factors influence this number such as how active you are, e.g. running three to five times per week, or living a sedentary lifestyle. In the latter case your caloric intake should be less.

Question 111

What does the structure of the heart cells allow for

Answer 111

Propagation of stimuli this rough the heart wall

Question 112

What does heart muscle contain

Answer 112

Thick and thin muscle fibres with myofibrils containing myofilaments similar to those in skeletal muscle

Question 113

What are the heart cells rich in

Answer 113

Mitochondria and glycogen granules that are found adjacent to myofibrils

Question 114

Describe the types of cells in cardic muscle

Answer 114

Numerous short, cyclindrical cells arranged end to end, resulting in long, branched fibres giving a characteristic Y shape.

Question 115

Intercalated disc

Answer 115

the attachment site between cardiac muscle cells. It appears as a linear structure transverse to the muscle fibre.
Transverse cross bands

Question 116

What do intercalated deists allow for

Answer 116

contain adhering junctions between cells that hold cells together and gap junctions, which allows communication between cells.

Question 117

What are gap junctions

Answer 117

Gap junctions are 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.

Question 118

Refractory period

Answer 118

When cells cannot contract. Ensures that the contraction or systole of the heart is separated by a resting period or diastole.

Question 119

acid in the stomach is produced by

Answer 119

by the combination of H+ and CL- produced by the epithelial cells (paritetal cells) of the stomach lining. The 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

Question 120

what does gastric juice contain

Answer 120

hydrochloric acid and pepsin

Question 121

what is pepsin

Answer 121

a protease that hydrolyses proteins to peptides

Question 122

what releases pepsinogen

Answer 122

chief cells in the stomach lining

Question 123

how is pepsinogen converted into pepsin

Answer 123

by the presence of acid

Question 124

the hcl released by the paretial cells of the stomach removes

Answer 124

44 amino acids from pepsinogen transforming it into pepsin

Question 125

where is pepsin found

Answer 125

in the stomach in an inactive form as the pro-enzyme pepsinogen

Question 126

opt pH for pepsin

Answer 126

3

Question 127

acidic condiitons help to

Answer 127

control pathogens in ingested food.

Question 128

what protects the stomach from self damage

Answer 128

a mucus cover

Question 129

when will the stomach produce excess acid

Answer 129

spicy food or excess protein or stress

Question 130

what does excess gastric acid cause

Answer 130

gastric ulcer - stomach pain, heartburn, nausea, blood in stool

Question 131

what can Helicobacter pylori cause and how

Answer 131

gastri culcers as H. pylori produces toxins that cause continuous gastric inflammation. The inflammatory response by the immune system damages the stomach lining.

Question 132

treatment of H.pylori

Answer 132

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 synthesis.
Proton Pump Inhibitor (PPI): inhibits acidification of stomach.

Question 133

how do PPI’s work

Answer 133

block the proton pump (hydrogen-potassium-ATPase pump), responsible for the 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 (Figure 4), making it a suitable treatment of gastric ulcers.

Question 134

lipids (short chain fatty acids) are absorbed by

and their destination is

Answer 134

small intestine

villus through hepatic portal vein

Question 135

lipids (long chain fatty acids) absorbed by

Answer 135

small intestine

Question 136

lipids (long chain fatty acids) destination

Answer 136

lacteal to lymphatic system

Question 137

job of the central lacteal found in each villus

Answer 137

absorption of fats, and capillaries that carry the rest of the absorbed molecules to other organs

Question 138

Most capillaries join to form

Answer 138

hepatic portal vein

Question 139

adaptation fo villi

Answer 139

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 do not escape through the membrane, and to maintain a concentration gradient.
Enzymes (peptidases and disaccharidases) bound to epithelial membranes to complete hydrolysis/digestion.

Question 140

mucosa

Answer 140

contains the epithelium formed by enterocytes, goblet cells and endocrine cells. Enterocytes are cells that have microvilli; they digest and absorb substances. Goblet cells produce mucus and endocrine cells secrete hormones.

Question 141

submucosa

Answer 141

contains blood vessels and connective tissue.

Question 142

circular muscle layer

Answer 142

smooth muscle arranged in a circular manner.

Question 143

longitudinal muscle laeyr

Answer 143

smooth muscle arranged in a longitudinal manner.

Question 144

serosa

Answer 144

single layer of epithelial cells with connective tissue.

Question 145

what are polysaccharides mainly hydrolysed to

Answer 145

glucose and absorbed by epithelial cells of the small intestine

Question 146

Polysaccharides are mainly hydrolysed to ??? and absorbed by epithelial cells of the ???

Answer 146

glucsoe and absorbed by the small intestine

Question 147

pathway of polyscahharides

Answer 147

Glucose is co-transported with sodium (Na+) by facilitated diffusion. In order for this to happen, Na+ must first be transported out of the cell by active transport (along the basal membrane). This powers the co-transport of glucose and Na+ into the epithelial cells via 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.

Question 148

pathway of proteins

Answer 148

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

Question 149

fats or lipids ar emulsified in th eintesitne by

Answer 149

bile

Question 150

fats are emulsified in

Answer 150

in the intestine by bile into smalller droplets

Question 151

the emulsification of lipids allows for

Answer 151

allowing lipases to digest them into fatty acids and glycerol.

Question 152

pathway of fatty acids

Answer 152

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.

Question 153

dietary fibre

Answer 153

the non-digestible carbohydrates, especially cellulose, and lignin that are intrinsic and intact in plants.

Question 154

what materials are not absorbed

Answer 154

celluloe and lignin from plant matter, bile pigments, the remains of intestinal epithelial cells and bacteria

Question 155

what does inflammaiton fothe epithelial cells inside the intestine lead to

Answer 155

This will reduce the absorption of water, causing the feces to be loose or liquid (diarrhoea). If the infection persists for several days it can cause dehydration.

Question 156

what i cholera and how does it work

Answer 156

Cholera is a disease caused by the 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), triggering endocytosis of the toxin.The toxin then becomes an active enzyme which activates ions and water to leave the infected enterocytes, leading to watery diarrhea.

Question 157

signs and symptoms fo dehydration

Answer 157

Increased thirst
Dry mouth
Swelling of brain
Weakness
Dizziness
Palpitations
Seizures
Drop in blood pressure
Fainting
Decreased urine output
Kidney failure
Coma
Death

Question 158

the liver is supplied with oxygenated blood from the heart through the

Answer 158

hepatic artery

Question 159

the blood leaves the liver through the

Answer 159

hepatic vein which carries deoxygenated blood which joins the vena cava, which returns the blood to the heart

Question 160

whre does the liver recive deoxygenated blood from

Answer 160

spleen, stomach, pancreas, gall bladder and instines through the hepatic portal vein

Question 161

what is the hepatic portal vein rich in

Answer 161

amino acids, glucose, vitamins, minerals and other foods.

Question 162

why is it said that the liver has a dual blood supply

Answer 162

s the liver receives oxygenated blood from the hepatic artery and deoxygenated blood from the hepatic portal vein

Question 163

hepatocytes

Answer 163

liver cells

Question 164

macrophages

Answer 164

Kupffer cells

Question 165

the hepatocytes monitor

Answer 165

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.

Question 166

diagram of a lobule in the liver

Answer 166

Question 167

each liver lobe has about

Answer 167

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

Question 168

waht are sinusoids

Answer 168

tubes that resemle capillaries but have a discontinuous endothelium

Question 169

capillaris have small pores whilst sinusoids have

Answer 169

Fenestrated (with pores of approximately 175 nm diameter)

Question 170

why are hepatocytes ruch in mitochondria

Answer 170

Hepatocytes are involved in many metabolic processes, therefore they are rich in mitochondria, Golgi complexes, rER, ribosomes, glycogen granules and lipid droplets.

Question 171

what is liver regeneration

Answer 171

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.

Question 172

hepatocytes

Answer 172

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.

Question 173

where are plasma proteins synthesised and processed

Answer 173

in hepatocytes in the rough endoplasmic reticulum and processed in golgi complexes

Question 174

kupffer cells are

Answer 174

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.

Question 175

in the lobules there are also canals that carry

Answer 175

bile to the bile duct tha tleads to the gall bladder where bile is stored until it is used in the small intestine

Question 176

what in the liver absorbs most of the glucose and stores it as glycogen

Answer 176

hepatocytes

Question 177

what happens to fatty acids in the blood passing through the liver

Answer 177

absorbed by hepatocytes and metabolised to produce energy in the form of ATP.

Question 178

what syntehsises lipds like triglycerides, cholesterol and phospoholipids

Answer 178

hepatocytes 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.

Question 179

amino acids entering the liver are transformed into

Answer 179

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.

Question 180

Endoplasmic reticulum and Golgi apparatus in hepatocytes produce

Answer 180

plasma proteins. These plasma proteins include fibrinogen used in blood clotting, and albumin that transports hormones and maintains the blood pH.

Question 181

when amino acids are no longer necessary, hepotcytes

Answer 181

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.

Question 182

detoxification

Answer 182

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.

Question 183

how is alochol metabolised

Answer 183

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.

Question 184

modifications by rbc or erthyocytes

Answer 184

EDIT 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.

Question 185

life cycle of erythrocyte

Answer 185

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.

Question 186

how do kupffer cells recyle dead erythrocytes

Answer 186

phagocytosis

Question 187

what occurs within kupffer cells

Answer 187

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.

Question 188

what is cholesterol the precursor for

Answer 188

bile salts, steroid hormones, vitamin D

Question 189

what regulates cholesterol synthesis

Answer 189

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)

Question 190

is cholesterol soluble in water

Answer 190

no insolube like lipids

Question 191

why must cholesterol be carrid as plasma lipoproteins

Answer 191

insoluble in water

Question 192

Different combinations of lipids and proteins produce particles of different densities. High-density lipoproteins (HDL) contain more ???, while low-density lipoproteins (LDL) contain more ???.

Answer 192

HDL - protein
LDL - lipids

Question 193

where are LDL and HDL’s produced

Answer 193

plasma and a small amount in the liver

Question 194

function of LDL

Answer 194

transport cholesterol from the liver to other organs

Question 195

function of HDL

Answer 195

to transport cholesterol from tissues to lvier

Question 196

what causes atherosclerosis

Answer 196

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.

Question 197

effect of LDL on blood vessels

Answer 197

Question 198

difference between atherosclerosis and arteriosclerosis

Answer 198

atherosclerosis (narrowing of arteries due to plaque)
arteriosclerosis (hardening of arteries).

Question 199

which cholesterol is considered ‘good’

Answer 199

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.

Question 200

bile salts have a crucial role in deigestion as they

Answer 200

emulsify fats

Question 201

bile salts

Answer 201

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.

Question 202

composition of bile

Answer 202

The composition of bile is mainly water (97%), bile salts, cholesterol and fatty acids, bilirubin (from the breakdown of erythrocytes) and inorganic salts.

Question 203

pathway of bile

Answer 203

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.

Question 204

jandice

Answer 204

a condition where the skin and white of the eyes turn yellow. It is caused by the presence of bilirubin in extracellular fluid.

Question 205

bilirubin

Answer 205

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.

Question 206

when does jaundice occur

Answer 206

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).

Question 207

A high level of bilirubin in the blood is a sign of

Answer 207

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.

Question 208

infants and high bilirubin klevels

Answer 208

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 (Figure 1). 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.

Question 209

cirrhosis

Answer 209

a disease where the damaged liver tissue is replaced by scar tissue, as shown in Figure 2. 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.

Question 210

causes of cirrhosis

Answer 210

Excessive alcohol or drug consumption.
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.

Question 211

Why should alcoholics be entitled to receive a liver transplant?

Answer 211

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.

Question 212

Why should they not receive a liver transplant?

Answer 212

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.

Question 213

cardiac conduction diagram

Answer 213

Question 214

the beat of the heart is initaied in

Answer 214

the sinoatrial node, a group of specialised cardiac muscle cells found where the superior vena cava joins the right atrium. S

Question 215

after the sinoatrial node, the impulse spreads along the atria to the

Answer 215

atrioventricular node

Question 216

after the atrioventricualr node, the impulse spreads to the

Answer 216

ventricle

Question 217

There is a delay between the arrival and passing on of a stimulus at the atrioventricular node. This delay allows time for

Answer 217

atrial systole before the atrioventricular (tricuspid and bicuspid or mitral) valves close. The blood therefore leaves the atria to the ventricles when the atrial systole occurs.

Question 218

why is there a delay in cardiac conduction

Answer 218

Remember the delay between the arrival and passing of a stimulus at the AV node gives time for the atria to contract before the AV valves close.

Question 219

The blood is now in the ventricles and the atrioventricular valves are closed. In the interventricular walls there are specialised fibres grouped to form a bundle called

Answer 219

bundle of his

Question 220

what happens at the bundle of his anatomically

Answer 220

the bundle splits into two branches that go to the left and right ventricles, leading to other specialised cells called Purkinje fibres

Question 221

what do purkinje fibres do

Answer 221

carry the impulse at a very high speed. Conducting fibres ensure coordinated contraction of the entire ventricle wall.

Question 222

systole is

Answer 222

the ventricular contraction

Question 223

what happens after the systole

Answer 223

Blood then flows out of the heart as the semilunar (pulmonary and aortic) valves open and give access to the aorta and pulmonary artery. The heart is now relaxed; this is called the diastole.

Question 224

heart sounds

Answer 224

used by the atrioventricular valves and semilunar valves closing causing changes in blood flow.

Question 225

action potential

Answer 225

an electrical event associated with differetn concentrations of ions across membranes

Question 226

difference in cardiac muscle contraction

Answer 226

The mechanism by which the cardiac muscle contracts is similar to that of the striated skeletal muscle. The membrane action potential leads to an increase in the calcium ions round the myofilaments, activating the myosin-ATPase. This leads to the sliding of the thick and thin filaments. The action potential is much longer (around 300 ms) than in nerve cells (around 2 ms) and skeletal muscle cells (around 4 ms). Do you remember that you studied that cardiac muscle cells have a special disposition forming fibres and have gaps between the cells (gap junctions)? Well, this allows for a more rapid spread of the action potential.

Question 227

role of sodium in cardiac conduction

Answer 227

Sodium ions are positive. When the signal reaches the cell, these ions come in, changing the overall membrane potential to positive. The plateau phase is given due to the balance between the potassium ions leaving the cell and the calcium ions coming in. This phase maintains depolarization for a longer time.

Question 228

difference with pacemakers

Answer 228

Pacemakers are myogenic, this means the action potential is generated by the pacemaker itself.

Question 229

normal heart rate

Answer 229

50 to 100 bpm

Question 230

factors increaseing heart rate

Answer 230

Gender: women have slightly higher heart rate than men 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 rate than smaller people as blood needs to cover a larger area.
Temperature: vasodilation occurring when it is hot increases beats. If a person is running a fever, the pulse is accelerated.
Altitude: the body requires a greater amount of oxygen, therefore cardiac output must increase.
Posture: when one is standing the heart rate is higher than when lying down. This is related to the effect of gravity, as when standing blood needs to be pumped against this force.
Stress: the body will produce 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 heart 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.

Question 231

factors decreasing heart rae

Answer 231

Age: heart muscles cannot pump as efficiently.
Potassium ions: decrease action potentials.

Question 232

bradcardia

Answer 232

heart beats too fast

Question 233

tachycardia

Answer 233

heart beats too slowly

Question 234

pacemakers

Answer 234

This pacemaker consists of a battery-powered generator (that sends out electrical impulses) and wires with electrodes to connect to the heart muscle. If the pacemaker senses that the heartbeat is above a certain rate, it will stop sending signals to the heart. The pacemaker can also sense when the heartbeat slows down too much. It will automatically turn back on and start pacing the heart again.

A small cut is made on the left side of the chest or abdomen and the generator is placed under the skin at this location. The pacemaker can have one lead leading to the right atrium or two leads, one to the right atrium and another to the right ventricular walls (Figure 1). Another type of pacemaker also includes a lead to the left ventricle.

Question 235

explain ecgs

Answer 235

The signals obtained in the ECG are amplified in the ECG machine and displayed on the screen of an oscilloscope or recorded on a moving paper (Figure 2). This gives a graph of voltage variations in time. The R-R interval between successive beats allows the calculation of the heart rate. The P-wave represents the SA node electrical activity and contraction of the atria. The QRS complex corresponds to the excitation of the ventricles. The T-wave is the relaxation of the ventricles at the end of the contraction.

Question 236

blood pressure reading

Answer 236

EDIT
the pressure of blood on the walls of an artery during a systole (highest value recorded) and a diastole (lowest value). During the heart contraction (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 heart relaxation (diastole) the pressure of the blood on the arteries is at its lowest. Blood pressure is measured with a sphygmomanometer (Figure 1). It consists of an inflatable cuff and a measuring device. This measuring device can be mechanical or digital. The mechanical device measures the pressure in millimetres of mercury, while the digital device makes oscillometric measurements.
In the oscillometric method, the cuff pressure is used to detect the small oscillations in the blood flow caused by the pulse. These oscillations increase in amplitude as the cuff pressure falls between systolic and mean arterial pressure. Therefore the systolic blood pressure corresponds to a specific heartbeat: the beat at which the blood pressure becomes higher than the deflating cuff pressure and the blood is capable of flowing in the brachial artery. The oscillations then decrease in amplitude as cuff pressure falls below mean arterial pressure. The corresponding mean oscillation is calculated to estimate blood pressure.

Question 237

how do you measure blood pressure

Answer 237

The sphygmomanometer cuff is placed on the antecubital fossa of the arm of the patient. The antecubital fossa or elbow pit is the triangular area on the front view of the elbow of a human.
The cuff is inflated. This will stop the flow of blood through the artery.
The air is slowly released until the pressure inside the artery is equal to the pressure exerted by the cuff. At this moment a hissing sound is heard if one places a stethoscope under the cuff, close to the artery.
A pounding sound can be heard as the cuff deflates. This initial sound denotes the systolic pressure.
The sound stops when the pressure of the cuff is smaller than that of the artery. The moment the pounding cannot be heard is the diastolic pressure recording.

Question 238

severe hypertension vs low

Answer 238

Systole Diastole
>180 >110
<90 <50

Question 239

cauess of hyeoroteniosn

Answer 239

Question 240

consequences of hypertension

Answer 240

Stroke
Blindness
Arteriosclerosis
Heart attack and heart failure
Kidney failure.

Question 241

stroke

Answer 241

occurs due to a reduced or interrupted supply of blood to the brain. The brain does not get enough oxygen or nutrients, which causes brain cells to die.

Question 242

blindnesss

Answer 242

can happen because of the ruptured capillaries in the retina or optic nerve or damage to the area of the brain responsible for processing images.

Question 243

waht is atherosclerosis

Answer 243

the hardening of arteries, restricting the flow of oxygen and nutrients to tissues. Atherosclerosis is a special kind of arteriosclerosis. It is caused by the damage of arteries and subsequent formation of scar tissue. A plaque is formed when cholesterol and other lipids build up on this scar tissue. The plaque makes platelets release factors that cause the formation of a clot over the plaque, forming a thrombus. The thrombus blocks the flow of blood to tissues, causing thrombosis. If a thrombus (or clot) occurs in the coronary artery, the supply of blood and oxygen to the areas of the heart muscle is blocked. This causes irregular heartbeats and can lead to coronary heart disease (CHD).

Question 244

epdiemology

Answer 244

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

Question 245

what is ischemic heart disease

Answer 245

another name for chd

Question 246

classical risk fact ors for CHD

Answer 246

smoking
akchol consumption
blood pressure
obesity
cholesterol
diet
genetic predisposition

Question 247

what is ventricular fibrillation

Answer 247

the interruption of the electrical impulses that control heartbeat.

Question 248

causes of ventricular fibrillation

Answer 248

the loss of blood flow to the heart or a heart attack. It often begins with ventricular tachycardia (rapid heart beating) and leads to low blood pressure because the ventricles are not able to pump hard enough.

Question 249

symptoms of ventricualr fibrillation

Answer 249

The symptoms are chest pain, dizziness, nausea, heartburn, fluttering heartbeat, fainting, coma, nerve function loss, changes in mental function and eventually death

Question 250

what is cpr and it sfunction

Answer 250

CPR is a lifesaving technique useful in a heart attack, in which the heartbeat has stopped. CPR can keep oxygenated blood flowing to the brain and other vital organs until more definitive medical treatment can restore a normal heart rhythm. It is quite a simple procedure that can be done by anyone if a doctor is not found in the proximity. To learn CPR properly, you can take an accredited first-aid training course, including CPR and how to use an automated external defibrillator (AED). After calling for emergency medical help, this is what you need to do:

Compress the chest to restore blood circulation.
Clear the airway.
Breathe for the person, blowing into the patient’s mouth.

Question 251

how to carry out cpr

Answer 251

Place the heel of your hand on the breastbone at the centre of the person’s chest. Place your other hand on top of your first hand and interlock your fingers.
Position yourself with your shoulders above your hands.
Using your body weight (not just your arms), press straight down by 5–6cm on their chest.
Repeat this until an ambulance arrives.

If the person has not begun moving after about two minutes of compressions and an automated external defibrillator (AED) is available, apply one shock, then resume compressions for two more minutes before administering a second shock. Continue CPR until there are signs of movement or emergency medical personnel take over.

Question 252

how does a defib help

Answer 252

The electrical impulse of the defibrillator is used to depolarise the heart muscle in order to re-establish the function of the natural pacemaker. The electrode is a metal paddle or an adhesive pad that is placed on the patient’s chest. If a patient is having a dangerous heart arrhythmia or is in cardiac arrest, a series of electrical shocks is delivered through the electrodes and usually the patient is monitored through an ECG.
In some cases, an implantable cardioverter-defibrillator (ICD) is used. This ICD monitors heart rhythms and sends out shocks when necessary to increase or decrease heart rhythm. This is different from an implanted pacemaker machine because a pacemaker constantly fires to maintain a regular rhythm.

Question 253

major endocrine glands

Answer 253

pituitary, pineal, thymus, thyroid, adrenal glands, pancreas

Question 254

development of endocrine glands

Answer 254

Question 255

what is target tissue

Answer 255

consists of cells that have recpetor sites for a given hormone. in some cases it is found on a single gland or organ. in some cases, the target tissues is scattered throughout the body so that many areas are affected

Question 256

hormone def

Answer 256

chemical messengers secreted by cells or glands of the endocrine system that control and regulate the activity of other cells or glands in other parts of the body.

Question 257

hormones are classified as

Answer 257

proteins or steroids

Question 258

epinephrine - PROTEIN
Site of production
Target organs
Main function

Answer 258

Adrenal medulla
Heart, muscles, skin, etc.
Fight-or-flight response.

Question 259

thyroxin PROTEIN
Site of production
Target organs
Main function

Answer 259

Thyroid gland
Most organs
Accelerate metabolism, growth, development and heart rate.

Question 260

insulin PROTEIN
Site of production
Target organs
Main function

Answer 260

Pancreas
Muscle cells and fat cells
Promote absorption of glucose.

Question 261

glucagon PROTEIN
Site of production
Target organs
Main function

Answer 261

Pancreas
Liver
Convert stored glycogen to glucose.

Question 262

oxytocin PROTEIN
Site of production
Target organs
Main function

Answer 262

Hypothalamus
Uterus, mammary glands
Birth and lactation.

Question 263

prolactin PROTEIN
Site of production
Target organs
Main function

Answer 263

Pituitary
Mammary glands
Milk production, metabolism.

Question 264

growth hormone (somatotropin) PROTEIN
Site of production
Target organs
Main function

Answer 264

Anterior pituitary gland
Muscle, liver, bones
Growth.

Question 265

ADH (vasopressin) PROTEIN
Site of production
Target organs
Main function

Answer 265

Hypothalamus
Kidney
Water reabsorption, homeostasis.

Question 266

thyroid stiumulating homrone PROTEIN
Site of production
Target organs
Main function

Answer 266

Anterior pituitary gland
Thyroid
Stimulate production of thyroxin.

Question 267

follicle-stimulating hormone PROTEIN
Site of production
Target organs
Main function

Answer 267

Pituitary gland
Ovary/testes
Maturation of follicle/sperm production.

Question 268

cortisol STEROID
Site of production
Target organs
Main function

Answer 268

Adrenal cortex
Many organs
Increase blood sugar, suppress the immune system, aid in metabolism; decrease bone formation.

Question 269

oestrogen STEROID
Site of production
Target organs
Main function

Answer 269

Ovary, placenta, liver, muscle and brain, as well as the fat cells
Many organs
Secondary sexual characteristics, accelerate metabolism, and increase uterine growth and endometrium.

Question 270

progesterone STEROID
Site of production
Target organs
Main function

Answer 270

Ovary
Uterus
Maintain endometrium.

Question 271

tesosterone STEROID
Site of production
Target organs
Main function

Answer 271

Testes, ovary and adrenal cortex
Many organs
Secondary sexual characteristics, anabolic effect.

Question 272

negative feedback

Answer 272

Negative feedback is seen when the output of a pathway inhibits inputs to the pathway.

Question 273

how can the concentration of hormones be controlled

Answer 273

Synthesis: the rate of production can be regulated by positive or negative feedback.
Delivery: in endocrine glands, this is regulated by blood flow.
Elimination: hormones are metabolised and excreted once their half-life is over.

Question 274

steroid hormones are generally synthesised from

Answer 274

cholesterol in the ovaries or testes and in the adrenal glands

Question 275

steroid hormones are what soluble

Answer 275

fat soluble

Question 276

what do steroid hormones do

Answer 276

they can pass through the phospholipids of the cell membrane. Once inside the cell, some steroid hormones bind to a receptor in the cytoplasm and others to a receptor in the nucleus. When the steroid hormone joins a receptor in the cytoplasm, two receptor subunits join together to form one functional DNA-binding unit that can enter the cell nucleus. Once in the nucleus, the receptor-hormone complex binds to specific DNA sequences and regulates transcription of its target genes.

When the steroid hormone binds to the receptor inside the nucleus, the receptor undergoes a conformational change that renders it activated to recognise and bind to specific nucleotide sequences. When the receptor-hormone complex interacts with DNA it alters the transcriptional level (responses can be either activating or repressing) of the associated gene.


The RNA produced is translated into new proteins, for example, enzymes involved in different metabolic processes. This method of action is relatively slow as it involves synthesis of proteins (Figure 2).

Question 277

what do peptide hormones do

Answer 277

Peptide hormones bind to receptors in the plasma membrane of the target cell. They cannot enter the cell as they can’t pass through the cell membrane. Binding of hormones to membrane receptors activates a cascade mediated by a second messenger inside the cell. 
The sequence of events that results in hormone action is relatively rapid.

Question 278

describe the action of epinephrine

Answer 278

Epinephrine is a peptide hormone produced by the adrenal glands in response to stress and during exercise. Epinephrine attaches to receptors on the membrane of the heart cell called adrenergic receptors. These receptors are coupled to a G-protein. When the epinephrine joins the adrenergic receptor, the G-protein sends a message to the enzyme adenylyl cyclase. This in turn leads to the activation of the secondary messenger, cyclic adenosine monophosphate (cAMP), which induces smooth muscle relaxation, producing vasodilation and increased contraction of the cardiac tissue.

Question 279

what is HGH

Answer 279

an anbolic steroid hormone. increases body cell mass and sprint capacity when administered together with testosterone.

Question 280

HGH consequences

Answer 280

Increase in size of testes and ovaries, impaired spermatogenesis, growth of breasts in males.
Psychiatric disturbance.
Toxic to the liver.
Dyslipidemia (raised LDL and triglycerides and reduced HDL).
Hypertension.
Increased coagulation and platelet aggregation.
Exaggerated left ventricle growth.

Question 281

Functions of the hypothalamus

Answer 281

Control of the release of eight major hormones by the pituitary gland.
Temperature regulation.
Control of food and water intake.
Control of daily cycles in physiological state and behavior (biological clock).
Sexual behavior and reproduction.
Control of emotional responses.

Question 282

Diagram of the hypothalamus and pituitary gland

Answer 282

Question 283

Cells in the hypothalamus also secrete

Answer 283

ADH
oxytocin

Question 284

Pathway of ADH and oxytocin

Answer 284

ADH and oxytocin are transported down the axons from cells in hypothalamus to the posterior pituitary (neurohypophysis), where they are released into the bloodstream.

Question 285

What is neurohypophysis

Answer 285

ADH and oxytocin are transported down the axons from cells in hypothalamus to the posterior pituitary (neurohypophysis), where they are released into the bloodstream.

Question 286

adenohypophysis

Answer 286

The hypothalamus contains many of the neurons that control the endocrine functions of the anterior pituitary. These neurons do not directly release hormones from their endings but rather secrete releasing or release-inhibiting factors (also termed releasing hormones) that regulate release of hormones by the anterior pituitary. Hormones under control of this system include: growth hormone, ACTH, thyrotropin, the gonadotropins (FSH and LH), and prolactin.

Question 287

Effect of oxytocin

Answer 287

acts on the uterus, increasing contraction during childbirth, and breasts, inducing milk discharge in lactation.

Question 288

What does the anterior pituitary gland release

Answer 288

Prolactin, fsh, lh, gosh, thyroxin ACTH, cortisol, GH

Question 289

Prolactin

Answer 289

Milk production

Question 290

FSH and LH

Answer 290

Involved in growth of follicles and ovulation, respectively in ovaries in females, and in sperm formation in testes in males

Question 291

Thyroid stimulating hormone

Answer 291

hormone that induces the thyroid gland to produce thyroxin and other thyroid hormones.

Question 292

ACTH

Answer 292

Stimulates production of steroid hormones like cortisol on adrenal glands

Question 293

Why do breast increase in size in pregnancy

Answer 293

due to an increase in lobules and alveoli. The release of oestrogen and progesterone from the placenta and prolactin from the anterior pituitary causes this breast development.

Question 294

How is milk released

Answer 294

Prolactin and oxytocin are two major endocrine hormones involved in the initiation and control of lactation. Infant suckling sends messages to the brain, via nerves, that induce the pituitary gland to release prolactin and oxytocin. Prolactin, a protein hormone (Figure 1) produced by the anterior pituitary gland, induces milk production in the breasts. This occurs by binding to mammary epithelial cell receptors, which stimulates synthesis of mRNA of milk proteins.

Question 295

Where is oxytocin produced and released from

Answer 295

Hypothalamus and Posterior pituitary gland

Question 296

What type of hormone is oxytocin

Answer 296

is a peptide hormone formed by nine amino acids, while prolactin is a protein hormone.

Question 297

Where is dopamine produced

Answer 297

Hypothalamus

Question 298

How does dopamine act

Answer 298

produced in the hypothalamus, is secreted into the bloodstream and acts as a hormone. Dopamine inhibits the production of prolactin in the anterior pituitary gland. This is why dopamine is sometimes called prolactin-inhibitor factor.

Question 299

Describe the negative feedback loop relating to dopamine and prolactin

Answer 299

When a baby suckles the breasts, mechanoreceptors send messages to the hypothalamus to inhibit the production of dopamine, thus increasing the production of prolactin. Prolactin itself enhances the secretion of dopamine, so this creates a negative feedback loop

Question 300

Why is iodine necessary

Answer 300

Synthesis of thyroid hormones

Question 301

Sources of iodine

Answer 301

Seafood, seaweed, cows milk, table salt

Question 302

How is TSH produced

Answer 302

the hypothalamus sends a message to the anterior pituitary to produce TSH, which will stimulate the thyroid gland to produce thyroid hormones. Iodine deficiency affects this hormonal control.

Question 303

If there is an iodine deficiency

Answer 303

This will decrease the negative feedback on the pituitary gland, leading to the increased production of thyroid-stimulating hormone (TSH). The accumulation of TSH causes the thyroid gland to enlarge, resulting in a condition called goitre. Cretinism occurs when there is a congenital deficiency of thyroid hormones

Question 304

Symptoms Iodine deficiency diseases

Answer 304

Miscarriages, stillbirth,
Impaired phys dev, int disability, cretinism
Goitre, hypothyroidism, cretinism

Question 305

the cells froming the alverolus are called

Answer 305

pneumocytes

Question 306

type I pneumocytes are

Answer 306

flat witha greater surface area
are involved in the process of gas exchange between the alveoli and blood.

Question 307

type II pneymocytes

Answer 307

have a cubic shape and cover a small fraction of the alveolar surface area (5%). They secrete pulmonary surfactant, a fluid that decreases the surface tension within the alveoli. They are also capable of cellular division, giving rise to more type I pneumocytes when the lung tissue is damaged.

Question 308

pH of blood

Answer 308

regulated to stay in the range of 7.35 to 7.45

Question 309

buffers in teh blood

Answer 309

plasma and tissue fluids, hydrogencarbonate, proteins and ions (such as phosphate) act as buffers to maintain the pH close to neutral (slightly alkaline).

Question 310

hydrogencarbonate buffering

Answer 310

Carbon dioxide combines with water producing carbonic acid that lowers the pH. The carbonic acid dissociates into hydrogencarbonate that is alkaline, so it increases the pH, plus a hydrogen ion that acidifies the medium, decreasing the pH.

Question 311

haemoglobin is composed of

Answer 311

four peptide chains
two alpha and two beta
each with a ring-like heme group containing an iron atom

Question 312

differences in haemoglobin structure in fetal blood

Answer 312

instead of having two alpha and two beta peptides, the fetal hemoglobin has two alpha and two gamma peptides

Question 313

why is fetal blood different

Answer 313

the mother must deliver O2 to the fetus and remove CO2 through the placenta. Mother and fetal blood never mix, so capillaries from both must come in close proximity for exchange to happen. In order to get O2 into fetal blood, the haemoglobin in fetuses is slightly different to the adult haemoglobin.

Question 314

myoglobin

Answer 314

the protein used ot bind oxygen in muscles.
It consists of only one peptide chain and a heme group containing iron (Figure 4). There is no sequence similarity in haemoglobin and myoglobin chains. Myoglobin can only bind one oxygen molecule, but this binding is stronger than that in haemoglobin. Therefore myoglobin can take the oxygen from haemoglobin in respiring muscle cells.

Question 315

wy is the binding of the third and fourth oxygen molecules easier

Answer 315

Once the first heme binds to oxygen, there is a small change in the protein structure of haemoglobin, making the heme of another chain join oxygen more easily. Cooperative oxygen binding by haemoglobin causes conformational changes in an individual peptide that are propagated to the other peptides. The joining of the third and fourth oxygen molecules becomes easier due to this allosteric change in the haemoglobin molecule, leading to an S-shape or sigmoid curve.

Question 316

oxygen dissociation curve

Answer 316

Question 317

partial pressure

Answer 317

the individual pressure exerted independently by a particular gas within a mixture of gases.

Question 318

describe the oxygen dissociation cure

Answer 318

If you look at the graph from right to left, blood cells in the capillaries surrounding the alveoli carry 100% of the haemoglobin (shown in purple) as oxyhaemoglobin (with four molecules of oxygen bound, shown in red). These capillaries lead to the pulmonary vein, which carries blood to the heart. As the blood leaves the heart, the partial pressure of oxygen decreases (to about 40 mmHg in the pulmonary arteries) and the haemoglobin molecule releases one oxygen molecule. This causes an allosteric change in the haemoglobin molecule that makes the further release of the other oxygen molecules easier, as less energy is required. This means that a smaller drop in partial pressure is required to liberate a molecule of oxygen, leading to an S-shape or sigmoid curve. In this way, haemoglobin attaches the largest possible amount of oxygen in the lungs, and delivers all of it where and when it is needed.

Question 319

effect of fetal hemoglobin on oxygen dissocaiton curve

Answer 319

Fetal haemoglobin binds O2 with a greater affinity, therefore extracting it from the mother’s blood in the placenta. This means that at lower partial pressures of O2, the fetal haemoglobin loads O2 easier than adult haemoglobin. This would cause a shift to the left in the oxygen dissociation curve.

Question 320

is there an allosteric effect for myglobin

Answer 320

Myoglobin has a stronger affinity for oxygen than haemoglobin. Because myoglobin is formed by only one peptide, there is no allosteric effect in the molecule

Question 321

carbon dioxide diffuses into ___
some remains dissolved in ____
binds to ___

Answer 321

the blood
plasma
haemoglobin

Question 322

waht happens to carbon dioxide in red blood cells

Answer 322

the carbon dioxide is converted to carbonic acid (H2CO3) by the enzyme carbonic anhydrase. This carbonic acid then dissociates into hydrogen ions (H+) and hydrogencarbonate (bicarbonate) ions (HCO3-). Most of the carbon dioxide is therefore transported as hydrogencarbonate in blood (70-85%).
The H+ joins the haemoglobin molecule to form a weak acid called haemoglobinic acid (HbH). The HCO3- leaves the red blood cells to enter the blood plasma. To balance the electric charge in the red blood cells, chloride ions (Cl-) enter the cells by diffusion. This is called the chloride shift. The opposite occurs in pulmonary capillaries, where the decrease in intracellular HCO3- induces the outward movement of Cl-.

Question 323

the affinity of haemoglobin for oxygen is related to the pH of blood and to the partial pressure (or concentration) of CO2 (pCO2). An increase in blood acidity causes a shift of the oxygen dissociation curve to the ???, and a decrease in acidity (a more alkaline pH) will cause a shift to the ???.

Answer 323

right
left

Question 324

bohr shift

Answer 324

the oxygen dissociation curve to the right with the increase of H+ or CO2, as the oxygen binding affinity is inversely related to acidity and carbon dioxide concentration.

Question 325

bohr shift on oxygen release

Answer 325

The Bohr shift explains the increased release of oxygen by haemoglobin in respiring tissues. 
As explained before, inside erythrocytes CO2 reacts with H2O forming H2CO3. The H2CO3 breaks down to H+ and HCO3-. The H+ combines with haemoglobin, causing oxyhaemoglobin dissociation and the liberation of O2. The larger the amount of CO2, the greater the amount of H+ produced. Likewise, if the pH of the blood is more acid, there will be a greater availability of H+ to combine with haemoglobin and more oxygen will be released to the tissues.

Question 326

what is the bohr shift

Answer 326

the shift of the oxygen dissociation curve to the right with the increase of H+ or CO2, as the oxygen binding affinity is inversely related to acidity and carbon dioxide concentration.

Question 327

what is the medulla oblongata

Answer 327

the respiratory control centre

Question 328

where the chemorecpetors

Answer 328

aorta and carotid artery

Question 329

what do the chemoreceptros do

Answer 329

detect the levels of carbon dioxide in the blood

Question 330

carotid receptors

Answer 330

detect changes in the pH of blood. During exercise, the rate of ventilation increases in response to the amount of CO2 in the blood.

Question 331

spirometer

Answer 331

ventilation rate can be measured by using this it is attached to a kymograph that measures the volume and speed of air blown out

Question 332

Although the percentage of oxygen in inspired air is constant at different altitudes,

Answer 332

the fall in atmospheric pressure at higher altitude decreases the partial pressure of oxygen (pO2)

Question 333

As pO2 decreases, the percentage saturation of haemoglobin decreases rapidly (Figure 1). Haemoglobin has low affinity for oxygen at low pO2, hence it is not fully saturated as it passes through the lungs. This means that the tissues of the body are supplied with less oxygen.

Answer 333

edit

Question 334

when does moutnain sickeness coccur

Answer 334

when a person travels from low to high altitude. The most common symptoms are headache, nausea and dizziness. High blood pressure in mountain sickness leads to body fluid buildup. After several days (or even weeks), the body becomes acclimatised.

Question 335

acclimatisation

Answer 335

Heart pumps faster.
Blood vessels increase in diameter.
Lung ventilation rate increases.
Muscles produce more myoglobin to store more oxygen.
More capillaries develop in alveoli.
Amount of erythrocytes increases.

Question 336

why is there an increase in the number of erythrocytes

Answer 336

increased production of erythropoietin (EPO)

Question 337

EPO

Answer 337

This peptide hormone is produced in the kidneys and acts in the bone marrow, on precursors of erythrocyte production. EPO levels in blood are usually low, around 10 mU/ml of blood, but can increase to 10,000 mU/ml in cases of lack of oxygen. The greater amount of EPO will increase the amount of erythrocytes. This means that more oxygen is delivered to the muscles, therefore improving endurance capacity.

Question 338

dangerous effects of EPO

Answer 338

Increased viscosity.
Reduced blood flow.
High blood pressure.
Increased risk of coronary heart disease.

Question 339

adv of training in high alt

Answer 339

increased stamina
natural increase in epo
increase in erythrocytes
more oxygen to muscles
more myoglobin in muscles

Question 340

disadv of training in high alt

Answer 340

altitude sickeness
high blood pressure
increased risk of stroke
unfair adv
high blood pressure

Question 341

how does CO affect lung function

Answer 341

Carbon monoxide binds irreversibly to haemoglobin; therefore gaseous exchange is diminished, causing the smoker to get breathless when exercising.

Question 342

how does tar affect lung function

Answer 342

Tar coats lining of alveoli, increasing the risk of emphysema.

Question 343

other symtoms of smoking

Answer 343

Breathing infections are common due to the fact that cilia do not move mucus out of airways.
Cough due to irritation of bronchi and bronchioles.
Chronic bronchitis.
Increased chances of developing lung, throat or mouth cancer.
Cardiovascular disease due to atherosclerosis.
Nicotine increases heart rate and blood pressure.
Nicotine makes blood platelets stickier, increasing the chance of thrombosis.

Question 344

whya re fetuss particularly susceptible to smoking

Answer 344

Although smoking increases the amount of fetal haemoglobin, the human fetus does not have a biological capacity to accommodate to maternal cigarette smoking, and therefore the fetus is particularly susceptible to the adverse effects of cigarettes.

Question 345

emphysema

Answer 345

the condition where the walls of the alveoli break down, so air sacs are fewer and larger.

Question 346

The main symptoms of emphysema are

This condition is detected

Answer 346

cough and shortness of breath.

by measuring lung capacity with a spirometer. Diagnosis is confirmed with a chest X-ray and arterial blood gas analysis.

Question 347

causes of emphysema

Answer 347

Smoking (most important factor).
Congenital (alpha-1 antitrypsin deficiency).
Exposure to passive cigarette smoke.
Air pollution.
Occupational dust (for example in coal mines).
Inhaled chemicals.

Question 348

treatment of emohysema

Answer 348

Treatment consists of the use of bronchodilators that cause dilation of bronchi, corticosteroids to reduce inflammation, oxygen supplementation, and antibiotics if there are signs of infection. This does not halt or cure the damage already done to the alveoli; it just alleviates the symptoms. The most important step is to quit smoking. Surgery or even lung transplant is done in very severe cases. Figure 1 shows the oxygen dissociation curve for a patient with emphysema compared to that of a normal person.

Question 349

where does the cardiac conductions tart

Answer 349

embryonic tissues by specilasie dcels forming the pacemaker

Question 350

pathway of cardiac conduction

Answer 350

sinoatrial node sends sginals along the atria to the atrioventricular node, to a ventricel. This delay allows time for atrial systole before the atrioventricular (tricuspid and bicuspid or mitral) valves close. The blood therefore leaves the atria to the ventricles when the atrial systole occurs. The blood is now in the ventricles and the atrioventricular valves are closed. In the interventricular walls there are specialised fibres grouped to form a bundle called Bundle of His. This bundle splits into two branches that go to the left and right ventricles, leading to other specialised cells called Purkinje fibres. These fibres carry the impulse at a very high speed. Conducting fibres ensure coordinated contraction of the entire ventricle wall. The ventricular contraction is called the systole. Blood then flows out of the heart as the semilunar (pulmonary and aortic) valves open and give access to the aorta and pulmonary artery. The heart is now relaxed; this is called the diast

Question 351

shortneed pathway of cardiac conduction

Answer 351

sa node
av note
ventricle
bundle of his
purkinje fivre

Question 352

heart soudns, waht does the dub and lub mean

Answer 352

The closing of the atrioventricular valves at the beginning of the ventricular contraction (systole) produces the first sound, the club.
the closing of the semilunar valves just after the ventricular systole and beginning of the diastole causes the second sound, the dub sound.

Question 353

action potential

Answer 353

an electrical event associated with different concentrations of ions across membranes.

Question 354

action potentiall difference inc aradiac and striated cells

Answer 354

The action potential is much longer (around 300 ms) than in nerve cells (around 2 ms) and skeletal muscle cells (around 4 ms).

Question 355

why do cardiac muscle cells have a special disposition forming fibres and have gaps between the cells (gap junctions)?

Answer 355

allows for a more rapid spread of the action potential.

Question 356

membrane premeability dyring action potetinal in a cardiac cell

Answer 356

Question 357

what does myogneic mean

Answer 357

actipn potential generated by pacemaker or muscle itself rather than ocmign from neurla origin which wouldne urogenic

Question 358

do pacemakers have gaps in theri action potentials

Answer 358

Pacemaker cells have their own intrinsic rhythms of activity; therefore, as one action potential is completed, immediately another action potential is generated in the membrane, even in the absence of nerve impulse.