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Healthy Body 2 > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

How does body temperature fluctuate naturally?

A

With a circadian rhythm - drops at night, increases in the day.
During menstrual cycle - increases due to progesterone.

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2
Q

Describe the dynamic equilibrium between heat input and output?

A

The body has heat input both from the environment and from internal production of heat through muscle contraction and metabolism - 60% energy released from metabolism of organic molecules is heat energy.
Heat from the body is lost to the environment via radiation, conduction, convection and evaporation.

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3
Q

Whats the thermoneutral zone?

A

TMZ is the range of environmental temperature over which the heat from basal metabolism is sufficient to maintain core body temperature.

  • Above TNZ there is net gain of heat
  • Below TNZ there is net loss of heat.
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4
Q

Whats the thermoregulatory centre?

A

The hypothalamus - it integrates sensory input from thermoreceptors located in the core and periphery.
- Increased blood temperature is detected in the anterior hypothalamus.
- Decreased blood temperature is detected in the posterior hypothalamus.
The input temperature is compared with the desired set point and an appropriate regulatory response is produced.

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5
Q

What do the different types of thermoreceptors do?

A

Peripheral thermoreceptors feedback changes in environmental temperature to the hypothalamus.
Central thermoreceptors detect changes in the core body temperature and feedback to the hypothalamus.

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6
Q

Whats the response to increased temperature?

A

Sympathetic cholinergic neurons send signals to:

  • Sweat glands to secrete sweat so heat is lost through evaporative cooling.
  • Cutaneous blood vessels vasodilate so that heat is lost to the environment.
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7
Q

Whats the response to decreased temperature?

A

Sympathetic adrenergic neurons send signals to:
- Cutaneous blood vessels vasoconstrict to conserve heat.
- Brown fat - non shivering thermogenesis causing metabolic heat production.
Somatic motor neuronsalso send signals to:
- Skeletal muscles that start shivering thermogenesis metabolically producing heat.

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8
Q

Sweating is a highly effective mechanism for heat loss - what does the effectiveness depend on?

A

Low environmental humidity and free access to water and sodium.

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9
Q

Whats non shivering thermogenesis?

A

Hormone induced uncoupling of mitochondrial oxidation from phosphorylation in brown adipose tissue. (Only significant in infants).

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10
Q

Whats a fever?

A

A fever is when your body temperature is greater than 38 due to a chemical resetting of the thermal set point.

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11
Q

What can cause a fever?

A

Release of endogenous pyrogens in response to infection. EP’s are cytokines released into circulation.
Body triggers thermoregulatory responses, increasing heat production and decreasing heat loss hence core body temperature rises.
Body temperature stabilises at new elevated set point - augmentation of immune response - body temperature remains elevated when the fever breaks.

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12
Q

Whats the energy balance within the body?

A

Energy input comes from the diet.

50% of energy output is through heat and 50% through work.

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13
Q

Whats the total body energy?

A

The amount of energy stored plus the energy intake minus the energy output.

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14
Q

What is classified as work for energy output?

A

Active transport of molecules.
Mechanical - movement of muscles.
Chemical - synthesis for growth and developement.

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15
Q

Whats the basal metabolic rate?

A

The minimum level of energy required to sustain vital functions.

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16
Q

How is the basal metabolic rate measured?

A

At rest in a fasted state in a thermoneutral environment. It is measured as the heat produced/oxygen consumed per unit of time. It is expressed as the calories released per kg of body mass.

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17
Q

Whats the total energy expenditure?

A

The BMR plus the dietary unduced thermogenesis plus physical activity. It is estimated from a persons BMR and physical activity level.

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18
Q

What is physical activity level?

A

PAL = a 24 hour index of energy expenditure due to physical activity.

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19
Q

Whats the estimated average expenditure for energy ?

A

EAR = BMR x PAL

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20
Q

What are macronutrients?

A

Nutrients in which tens of grams are required in the diet. This includes - proteins, fats and carbohydrates.

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21
Q

What are micronutrients?

A

Nutrients in which only a small amount is required in the diet. This includes - water soluble vitamins, fat soluble vitamins and minerals.

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22
Q

How can macronutrients be used for energy?

A

All the macronutrients can undergo reactions to acetyl-CoA acting as a source of energy - carbohydrate is the preferred short term energy source though.

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23
Q

Why are proteins required in the diet?

A

Dietary proteins are the source of amino acids. Essential amino acids must be supplied in diet whilst non essential amino acids are synthesised in the body.

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24
Q

Why are amino acids required?

A

Amino acids are required for the synthesis of proteins: both structural (keratin, collagen and elastin…) and functional (enzymes, antibodies, receptors and hormones).

Amino acids are also precursors for other biomolecules:

  • Nucleotides - purines and pyrimidines.
  • Catecholamines - dopamine, norepinephrine.
  • Neurotransmitters - serotonin, melatonin.
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25
Q

Why are carbohydrates required in the diet?

A

Carbohydrates provide monosaccharides for the biosynthesis and modification of macromolecules:

  • Glycoproteins - secreted and integral membrane proteins.
  • Membrane glycolipids - blood group antigens.
  • Glycosaminoglycans
  • Proteoglycans - GAGs linked to a protein core e.g. aggrecan.

Dietary carbohydrate is also a source of fibre - an indigestible structural polysaccharide derived from plants e.g. cellulose and pectin.
Fibre adds bulk and thickens the contents of the GI tract hence slowing digestion and absorption of carbohydrates and fats. This allows the production of beneficial short chain fatty acids by colonic microbiota.

26
Q

Why are fats required in the diet?

A

Fats are the source of essential fatty acids - alpha linoleic acid and linoleic acid.
Dietary fats are required for membrane biosynthesis of phospholipids, glycolipids, sphingolipids and cholesterol.
They act as carriers for fat soluble vitamins.
Theyre required for the biosynthesis of lipid mediators.
Theyre required for the biosynthesis of steroid hormones.
Theyre required for the biosynthesis of proteolipids - glycosylphosphatidylinositol anchored proteins e.g. enzymes receptors and cell adhesion molecules.

27
Q

What are triglycerides?

A

Triglycerides are formed from one glycerol and three fatty acid molecules. They account for 95% of fat in our diets.

28
Q

How is cholesterol involved with fats?

A

Cholesterol is produced in the liver and transported around the body by LDL’s and HDL’s - different fats affect these LDLs and HDLs differently.

29
Q

What are saturated fats?

A

Saturated fats contain no double bonds and are solid at room temperature - they increase levels of LDL in the bloodstream and have been associated with heart disease.

30
Q

what are monounsaturated fats?

A

Monounsaturated fats contain 1 double bond - theyre liquid at room temperature but solidify when chilled. They reduce levels of LDL in bloodstream hence decreasing total cholesterol to HDL ratio - HDL helps take cholesterol back to the liver where it can be disposed of.

31
Q

What are polyunsaturated fats?

A

These contain at least 2 double bonds and are liquid at room temperature - they again lower HDL ratios and decrease ratio.

32
Q

What are trans fats?

A

These contain double bonds in a trans rather than cis position - they are formed artificially through hydrogenation and are found in small amounts in meat and dairy. They rais LDL and are associated with heart disease.

33
Q

How does the body metabolise glucose in the fed state?

A
  • Used immediately for energy through aerobic pathways (glycolysis and citric acid cycle).
  • Used for lipoprotein synthesis in the liver.
  • Stored as glycogen in liver and muscle (glucogenesis)
  • Excess is converted to fat and stored in adipose tissue (lipogenesis).
34
Q

How does the body metabolise carbohydrates in the fasted state?

A

Glycogen polymers broken down (glycogenolysis) to glucose in the liver and kidney or to glucose-6-phosphate for use in glycolysis.

35
Q

How are proteins metabolised in the fed state?

A
  • Most amino acids go to tissues for protein synthesis.
  • If needed for energy amino acids are converted in the liver to intermediates for aerobic metabolism (deamination)
  • Excess is converted to fat and stored in adipose tissue (lipogenesis)
36
Q

How are proteins metabolised in the fasted state?

A

Proteins broken down into amino acids which are deaminated in the liver for ATP production or used to make glucose (gluconeogenesis).

37
Q

How are fats metabolised in the fed state?

A
  • Stored as triglycerides in the liver and adipose tissue (lipogenesis)
  • Cholesterol used for steroid synthesis or as a membrane component.
  • Fatty acids used for lipoprotein and eicosanoid synthesis.
38
Q

How are fat metabolised in the fastest state?

A
  • Triglycerides are broken down into fatty acids and glycerol (lipolysis).
  • Fatty acids used for ATP production through aerobic pathways (B-oxidation)
39
Q

What are micronutrients?

A

Nutrients required in small quantities that can not be synthesized de novo. They are essential for growth, maintenance and repair and required for intermediary metabolism.

40
Q

What are some of the metabolic processes micronutrients are involved in?

A 
Endocrine signalling (hormones)
Intermediary metabolism (coenzymes and cofactors)
Many function as antioxidants - scavengers of free radicals.
41
Q

What are the minerals required in the body?

A

Calcium, copper, iodine, iron and magnesium.

42
Q

Why is calcium required?

A

For bone and teeth formation, blood clotting, muscle activity and nerve function.
Calcium deficiency can cause spontaneous action potential generation in neurons and tetany.

43
Q

Why is copper required?

A

Copper is required for haemoglobin and melanin production and the electron transport system. Lack of copper can cause anaemia and energy loss.

44
Q

why is iodine required?

A

Iodine is required for thyroid hormone production and maintenance of metabolic rate. Deficiency can cause goiter and a decrease in metabolism.

45
Q

Why is iron required?

A

Iron is a component of haemoglobin and involved in ATP production in the electron transport system. Deficiency can cause anemia and energy loss.

46
Q

Why is magnesium required?

A

Coenzyme constituent, bone formation, muscle and nerve function. Deficiency can cause increased nervous system irritability vasodilation and arrhythmias.

47
Q

What are the fat soluble vitamins?

A

Vitamin A, Vitamin D, Vitamin E and Vitamin K.

48
Q

Why is Vitamin A required?

A

Vitamin A is from provitamin acrotene found in yellow and green vegetables and preformed in liver, egg yolk, butter and milk. It is required for rhodopsin synthesis (in retina involved with vision), normal health of epithelial cells, and bone and tooth growth.
Vitamin A deficiency can cause rhodopsin deficiency, night blindness, retarded growth, skin disorders and increased infection risk.

49
Q

Why is vitamin D required?

A

Vitamin D is found in fish liver oil, enriched milk and eggs. Provitamin D is converted by light to cholecalciferol in the skin. Vitamin D promotes calcium and phosphorus use, normal growth and bone and tooth formation. a deficiency of vitamin D can cause rickets (poorly developed, weak bones) or osteomalacia (bone reabsorption).

50
Q

Why is vitamin K required?

A

Vitamin K is found in alfalfa, liver, spinach, vegetable oils, cabbage and intestinal bacteria. It is required for synthesis of a number of clotting factors. A vitamin K deficiency can cause excessive bleeding due to retarded blood clotting.

51
Q

Why is vitamin E required?

A

Vitamin E is found in wheat germ, palm and rice oils, liver and lettuce. It prevents oxidation of cell membranes and DNA. A vitamin E deficiency can cause hemolysis of red blood cells.

52
Q

What are water soluble vitamins?

A

Vitamin B1, Vitamin B2, biotin, folate, vitamin C.

53
Q

Why is vitamin B1 required?

A

Thiamine is found in yeast, grains and milk and is involved in carbohydrate and amino acid metabolism - necessary for growth.A deficiency can cause beriberi - muscle weakness, neuritis and paralysis.

54
Q

Why is Vitamin B2 required?

A

Riboflavin is found in green vegetables, liver, milk and eggs - it is a component of flavin adenine involved in the citric acid cycle. A deficiency can cause eye disorders and skin cracking.

55
Q

Why is biotin required?

A

Biotin is found in liver, yeast, eggs and intestinal bacteria. Biotin is required for fatty acid synthesis, nucleic acid synthesis and movement of pyruvic acidinto the citric acid cycle. A deficiency can cause mental and muscle disfunction, fatigue and nausea.

56
Q

Why is folate required?

A

Folate is present in the liver, green leafy vegetables and intestinal bacteria. It is required for nucleic acid synthesis, hematopoiesis and prevents birth defects. A deficiency can cause macrocytic anemia (enlarged red blood cells) and spina bifida.

57
Q

Why is vitamin C required?

A

Vitamin C is found in citrus fruits, tomatoes and green vegetables. It is involved in collagen synthesis and general protein metabolism. A deficiency can cause scurvy - defective bone formation and poor wound healing.

58
Q

What can cause anemia?

A

Iron deficiency can cause microcytic anemai - smaller red blood cells.
Vitamin B12 deficiency can cause macrocytic anemia - enlarged red blood cells.

59
Q

What are the symptoms of anemia?

A

Tachycardia, fatigue, tiredness, headache, breathlessness and angina.

60
Q

What are free sugars?

A

Sugars added to foods and drinks plus sugar naturally present in honey, syrups and fruit juice.

61
Q

Whats a non energy related function of carbohydrates and fats?

A

The post translational modification of proteins and biosynthesis of glycosaminoglycans and proteoglycans.

Healthy Body 2 (9 decks)

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