metabolism / endocrine control / homeostasis (wk 3) Flashcards

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1
Q

Adeno- what does the term mean?

A

means gland, eg Adenohypophysis = alternative name for the anterior pituitary gland

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2
Q

An- what does this term mean?

A

means without, eg anabolism = the process of building up molecules

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3
Q

Catabol- what does this term mean?

A

it means break down, eg catabolism = the breakdown of molecules into simpler ones

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4
Q

-crine, what does this term mean?

A

it means secrete, eg endocrine = secrete within

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5
Q

Endo- what does this term mean?

A

within, eg endocrine gland = gland that secretes hormones into the bloodstream

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6
Q

-genesis, what does this term mean?

A

formation or production, eg gluconeogenesis = the production of glucose from non carbohydrate sources

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7
Q

glyco-, what does this term mean?

A

sugar, carbohydrate, eg glycogen = a polysaccharide that serves as a form of energy storage

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8
Q

-lysis, what does this term mean?

A

break down, eg glycolysis = the breakdown of glucose into pyruvate

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9
Q

meta-, what does this term mean?

A

change or beyond, eg metabolism = all the chemical processes occurring within a living organism

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10
Q

pan- what does this term mean?

A

all, eg pancreas = a gland with both endocrine and exocrine functions

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11
Q

-trophy, what does this term mean?

A

growth, development - eg trophic hormone = one that stimulates production and release of hormones; for example thyroid stimulating hormone is one type of trophic hormone

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12
Q

what process involves the synthesis of complex molecules from simpler ones such as the building of proteins from amino acids, requiring energy?

A

anabolic processes

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13
Q

what process involves the breakdown of complex molecules into simpler ones, releasing energy?

A

catabolic processes

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14
Q

what is a catabolic pathway that breaks down glucose into pyruvate, releasing ATP in the process?

A

glycolysis

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15
Q

the final stage of cellular respiration, involves the transfer of electrons through the electron transport chain, leading to the synthesis of ATP?

A

oxidative phosphorylation

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16
Q

part of the cellular respiration in mitochondria, involves the further breakdown of pyruvate, generating more ATP and releasing carbon dioxide?

A

the TCA (or krebs or citric acid) cycle

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17
Q

what does metabolism refer to?

A

all the chemical reactions that take place within an organism to maintain life (anabolism, catabolism, ATP generation, glycolysis, oxidative phosphorylation…. the list goes on and on)

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18
Q

what do endocrine glands do?

A

produce and release hormones

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19
Q

what are hormones?

A

signalling molecules that regulate numerous physiological processes

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20
Q

what produces hormones that stimulate or inhibit the release of other hormones from the pituitary gland? (the pituitary gland secretes hormones that in turn, regulate other endocrine glands)

A

the hypothalamus

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21
Q

what travels through the bloodstream, binds to specific receptors on target cells or organs which then triggers a cellular response, influencing the function of the target tissue?

A

hormones

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22
Q

endocrine glands, feedback mechanisms, hormones, target cells or organs, pituitary gland, hypothalamus - all part of what system?

A

the endocrine system

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23
Q

what is an integral part of the endocrine system, involving the detection of hormone concentrations in the blood and subsequent adjustments to maintain homeostasis?

A

feedback loops

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24
Q

what is the connection between metabolism and the endocrine system?

A

the endocrine system regulates metabolism by signalling (via hormones) to increase or reduce aspects of metabolism - maintains homeostasis

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25
Q

Venous blood leaving the intestine doesn’t just drain directly into the vena cava – what happens to it?

A

all blood leaving the intestine (venous blood) is gathered into a network of veins called the hepatic portal system - brings all the nutrients to the liver

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26
Q

excess carbohydrate and fat, some vitamins, iron, copper - are they detoxified, stored, or synthesised in the liver?

A

stored

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27
Q

ammonia - is it stored, detoxified or synthesised in the liver?

A

detoxified (that’s toxic)

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28
Q

hepatic proteins, bile acids, clotting factors - synthesised, stored, or detoxified in the liver?

A

synthesised :)

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29
Q

Temperature regulation is an example of which kind of homeostatic feedback mechanism?

A

negative feedback - the controller responds to return the temperature to it’s normal set point

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30
Q

How can heat from the skin transfer to the environment?

A
  • conduction (eg lying on cold floor)
  • convection (eg light breeze over body)
  • radiation (transfer of heat via infraed rays)
  • also evaporation, if sweaty/panting
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31
Q

How do eating, digestion, absorption, and metabolism of nutrients result in heat production?

A

heat is a byproduct of all these reactions

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32
Q

What is the function of the endocrine portion of the pancreas?

A

pancreatic islets synthesise hormones and secrete them directly into blood

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33
Q

insulin is released from beta pancreatic islet cells, in response to what?

A

an increase in blood glucose (eg fed state)

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34
Q

glucagon is released from alpha pancreatic islet cells, in response to what?

A

low blood glucose, eg in fasting state (glucose gone = glucagon)

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35
Q

produced by neural tissue, secreted into a capillary network in the pituitary stalk - is it a releasing hormone or trophic hormone?

A

releasing hormone

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36
Q

produced by an epithelial gland, secreted from the anterior pituitary - it it a releasing hormone or a trophic hormone?

A

trophic hormone

37
Q

hormones are diluted in general circulation, stimulate target glands to produce hormones or stimulate growth - trophic hormones or releasing hormones?

A

trophic hormones

38
Q

what is a trophic hormone?

A

controls the activity of endocrine glands, ensuring balance and coordination of hormone production in the body - stimulates growth, development and function of specific target glands or organs

39
Q

which of these are NOT examples of trophic hormones - growth hormone, cortisol, insulin, thyroid-stimulating hormone (TSH), luteinising hormone (LH), follicle stimulating hormone (FSH), adrenocorticotrophic hormone (ACTH)?

A

cortisol and insulin aren’t

40
Q

where are the adrenal glands found?

A

the paired adrenal glands lie against the roof of the abdomen, usually close to the cranial pole of the kidney

41
Q

mineralocorticoids, glucocorticoids, androgens - are these synthesised by the adrenal cortex or adrenal medulla?

A

adrenal cortex

42
Q

noradrenaline (norepinephrine), adrenaline (epinephrine) - are these synthesised by the adrenal cortex or adrenal medulla?

A

adrenal medulla

43
Q

have important roles in reproductive function, secretion is stimulated by ACTH (adrenocorticotrophic hormone) - which steroid family?

A

androgens

44
Q

influences how the kidney handles sodium and potassium, secretion is stimulated by plasma electrolytes and other hormones - which steroid family?

A

mineralocorticoids

45
Q

involved in glucose and protein metabolism, secretion is stimulated by ATCH (adrenocorticotrophic hormone) - which steroid family?

A

glucocorticoids

46
Q

which of these hormones are glucocorticoids - aldosterone, corticosterone, cortisol, glucagon?

A

cortisol and corticosterone - these are the main two glucocorticoids (amounts differ between species, eg dogs secrete equal amounts of both vs cats predominantly cortisol)

47
Q

would blood concentrations of glucose and fatty acids increase or decrease from adrenal medulla hormones?

A

increased, along with other fight or flight responses (adrenaline is adrenal medulla)

48
Q

What is the major energy-yielding pathway in the body - i.e. the “furnace”?

A

the TCA cycle - pathway through which all body fuels are eventually “burned”. carbon compounds from the various body fuels are oxidised to carbon dioxide and water.

49
Q

What is the substrate for oxidation in the TCA cycle and how is it sourced?

A

acetyl CoA is the substrate of the TCA cycle, and glucose and fatty acids are the two sources of acetyl CoA - selecting between these sources is a major function of fuel homeostasis.

50
Q

Fuel homeostasis is the coordinated process by which the major metabolic fuels are stored, mobilised, and interconverted to ensure a continuous supply of energy for the body - what are the main metabolic fuels?

A

glucose, amino acids, ketone bodies, fatty acids

51
Q

Is the conversion of glucose to pyruvate a reversible process?

A

yes - any pathway that leads to the production of pyruvate can also lead to the creation of glucose

52
Q

Is the conversion of pyruvate to oxaloacetate a reversible process?

A

yes - this means that any pathway leading to the creation of oxaloacetate or pyruvate can lead to the synthesis of glucose. creation of glucose in this manner is called gluconeogenesis, which occurs in the liver and occasionally kidneys

53
Q

most amino acids can be converted to glucose when necessary - true or false?

A

true (they’re substrates for gluconeogenesis)

54
Q

can fatty acids be converted to glucose?

A

no - however, they can be converted to ketone bodies

55
Q

can ketone bodies cross the blood-brain barrier?

A

yes - can be partially used as energy for the CNS, along with some glucose (except for in ruminants)

56
Q

what are the main regulating mechanisms of fuel homeostasis?

A
  • the insulin/glucagon axis
  • the hypothalamic/pituitary axis
  • the central nervous system
57
Q

what part of the pancreas are insulin and glucagon produced?

A

the endocrine pancreas

58
Q

what are the main effects of insulin?

A

to prevent large increases in the concentrations of glucose and amino acids in the blood during the absorptive phase (insulin increases all the anabolic processes in the body and increases glucose stores)

59
Q

what are the target cells for insulin?

A

hepatocytes, muscle cells, and adipocytes (fat cells)

60
Q

what are the main effects of glucagon?

A

to slow down the drop in glucose concentration in blood when glucose is no longer absorbed from the intestine. glucagon is catabolic and mobilises glucose, fatty acids and amino acids from body stores

61
Q

target cells of glucagon?

A

hepatocytes and adipocytes (fat cells)

62
Q

Where are glucocorticoid hormones produced and what stimulates their secretion?

A

the adrenal cortex - ATCH from the pituitary gland stimulates glucocorticoid secretion (in mammals, the main glucocorticoid being cortisol)

63
Q

Glucocorticoids (cortisol) are not important in energy metabolism in normal conditions, but they become essential for stimulating gluconeogenesis and lipolysis during periods of….

A

stress or exercise

64
Q

what does growth hormone stimulate during periods of stress?

A

Like cortisol, growth hormone stimulates mobilisation of fatty acids during periods of stress.

65
Q

What is the storage form of glucose and where can the storage depots be found?

A

glycogen, in the liver - limited space for this though, only 10% of total weight of liver is available for glycogen storage. skeletal muscle can also store glucose as glycogen, but it can’t be used later to boost blood glucose

66
Q

Which hormone stimulates the conversion and storage process of glucose?

A

insulin - secretions of insulin begin even before glucose is absorbed, triggered by GIP (gastric inhibitory hormone, which is released as soon as food enters the stomach). early insulin secretion ensures the liver is primed and ready for the arrival of glucose from the gut

67
Q

How are fatty acids stored in the body?

A

in adipose tissue in the form of triglycerides (triacylglycerols - consist of three fatty acids and a glycerol molecule)

68
Q

Is the conversion of glucose to fatty acids a reversible process?

A

no - glucose can form fat, but fat cannot form glucose

69
Q

Fatty acids are insoluble in blood. How can they be transported to tissues from the liver?

A

essentially the same mechanism used to transport fatty acids out of enterocytes after absorption in the gut, but with VLDLs instead of chylomicrons - fatty acids are esterified to form triglycerides, then wrapped in a coat of phospholipid, cholesterol and protein (this package is known as a very-low-density-lipoprotien, VLDL) before being moved out of the liver cell. VLDL’s are smaller than chylomicrons, but similar structure

70
Q

Triglyceride fatty acids are transferred from chylomicrons and VLDLs to adipose tissue by the action of what enzyme?

A

lipoprotein lipase, an enzyme that hydrolyzes the triglycerides back into fatty acids and glycerol. Under the influence of insulin, adipose tissue can also make fatty acids directly by taking up glucose and converting it to fatty acids in the same process as the liver.

71
Q

What is glycogenolysis?

A

the breakdown of glycogen stores into glucose

72
Q

what is gluconeogenesis and why is it necessary?

A

the creation of glucose from non-carbohydrate carbon substrates, because liver stores of glycogen are limited and the body needs some form of glucose in prolonged fasting times

73
Q

what can be used to make glucose via gluconeogenesis?

A

amino acids, glycerol and lactate (same molecules that are intermediates in glucose’s oxidative destruction)

74
Q

what does NEFA stand for?

A

non-esterified fatty acids - these are fatty acids released from adipose tissue into the blood, reversibly bound to albumin for transport (they’re not water soluble)

75
Q

During prolonged periods of fasting or energy deficiency, what become the main fuels?

A

ketone bodies (K), fatty acids (FA) and triglycerides (TG) become the major fuels.

76
Q

all the glucose available to ruminants with typical diets comes via gluconeogenesis. Which volatile fatty acid is the most important glucose precursor?

A

propionate

77
Q

What happens during the absorptive phase in response to a meal?

A

Nutrients are absorbed from the gastrointestinal tract.

78
Q

Which hormone is released by the pancreas during the absorptive phase to promote glucose uptake and storage?

A

insulin

79
Q

During the absorptive phase, amino acids absorbed from the gastrointestinal tract are primarily used for:

A

protein synthesis

80
Q

Excess glucose is stored in the form of glycogen primarily in the…..

A

liver and muscles

81
Q

What characterises the transition from the absorptive phase to the post-absorptive phase - a decline in nutrient absorption, or a decrease in blood glucose levels?

A

a decline in nutrient absorption

82
Q

During the post-absorptive phase, the liver breaks down glycogen into glucose through…

A

glycogenolysis

83
Q

In the absence of dietary glucose, the liver synthesises new glucose from non-carbohydrate precursors in a process called…

A

gluconeogenesis

84
Q

What happens to adipose tissue during the post-absorptive phase?

A

it undergoes lipolysis, releasing fatty acids into the bloodstream, which can be used as an energy source by many tissues

85
Q

What are non-esterified fatty acids (NEFAs)?

A

a form of fatty acid that circulates in the bloodstream bound to albumin, a carrier protein. this allows them to be transported to various tissues in the body, even though they’re not water soluble.

86
Q

During prolonged periods of undernutrition, why is it not a good idea to rely on skeletal muscle for energy and glucose production?

A

it would lead to muscle weakness

87
Q

What are the three potential metabolic paths that NEFAs in hepatocytes may follow?

A
  • oxidation for energy production
  • esterification to form triglycerides
  • production of ketone bodies
88
Q

When oxaloacetate concentrations are low, what happens to the excess acetyl-CoA produced during fatty acid oxidation?

A

it is converted to ketone bodies