Beyond the classic endocrine glands Flashcards

1
Q

What is the main function of adipocytes?

A

→ Store energy as triglycerides

→ Release them as free fatty acids

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2
Q

How do triglycerides get inside cells?

A

→ As free fatty acids

→ hydrolyzed by lipoprotein lipase

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3
Q

What are free fatty acids bound to?

A

→ Albumin

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4
Q

What is the main source of triglycerides?

A

→ Chylomicrons from digestion

→ VLDL

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5
Q

What happens when free fatty acids are in the cell?

A

→ Become triglycerides again

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6
Q

What happens when the body needs fat for energy?

A

→ HSL (hormone sensitive lipase) breaks down fat stored as triglycerides
→ Adrenaline, glucagon,cortisol and GH stimulate this

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7
Q

What happens when the body has excess fat and needs to store it?

A

→ Insulin stimulates LPL to break down TG into FFA

→ FFA enter the cell

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8
Q

What is glucose usually converted to for storage?

A

→ Glycogen

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9
Q

What is glucose converted to when it can no longer be stored as glycogen?

A

→ converted into fat

→ Stored in larger quantities

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10
Q

Why is adipose tissue needed?

A

→ If fat was allowed to accumulate it would be toxic

→ Lipotoxicity

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11
Q

What does leptin do?

A

→ Signals satiety to the brain

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12
Q

What does adiponectin do?

A

→ Increases insulin sensitivity

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13
Q

What is leptin released from?

A

→ Adipose tissue

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14
Q

What do mutations of leptin cause?

A

→ LEP gene or LEPR (leptin receptor)

→ lead to abnormal eating behavior and morbid obesity

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15
Q

What is obesity associated with?

A

→ Leptin resistance

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16
Q

What is obesity a state of?

A

→ Chronic low level inflammation

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17
Q

What are the signals like in healthy adipose tissue?

A

→ Leptin signals satiety to the brain
→ Adiponectin increases insulin sensitivity
→ Resistin levels low

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18
Q

What are the signals like in obesity?

A

→ Leptin is high but resistance to leptin
→ Adiponectin is low
→ Insulin resistance

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19
Q

What happens as adipose tissue expands?

A

→ as adipose tissue expands
→ cytokines are secreted eg IL6 and TNF alpha
→ They attract more macrophages

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20
Q

What are general disorders of energy metabolism?

A
→ Obesity 
→ Hypertension
→ Hyperglycaemia
→ High triglycerides
→ Insulin resistance
21
Q

What is visceral fat exposed to?

A

→ Portal circulation

22
Q

Why is losing weight when obese difficult?

A

→ The body remembers its highest body weight and defends this as the new normal
→ During weight loss there are appetite regulating hormones increase hunger

23
Q

What does gastrin do?

A

→ Stimulates gastric acid secretion

24
Q

What is gastrin stimulated by?

A

→ Peptides and amino acids in gastric lumen

25
Q

What does CCK do?

A

→ Stimulates secretion of pancreatic enzymes

→ Contraction of the gall bladder and emptying

26
Q

What is CCK stimulated by?

A

→ Presence of fatty acids and amino acids in small intestine

27
Q

What does secretin do?

A

→ Stimulates secretion of water and bicarbonate from the pancreas and bile ducts

28
Q

What is secretin stimulated by?

A

→ Acidic pH in the lumen of the small intestine

29
Q

What does ghrelin do?

A

→ strong stimulant for feeding and appetite

→ Stimulates growth hormone

30
Q

What does GIP do?

A

→ Inhibits gastric secretion and motility

→ potentiates release of insulin from beta cells in response to high blood glucose levels

31
Q

What is GIP stimulated by?

A

→ Presence of fat and glucose in the small intestine

32
Q

What are the three factors for regulation of food intake?

A

→ Hormones from stomach
→ Vagal afferents to NTS
→ Leptin from adipocytes

33
Q

What does GLP do?

A

→ Potentiates insulin secretion in response to rising plasma glucose
→ Reduces appetite

34
Q

What happens if you stimulate the lateral hypothalamus?

A

→ Increased feeding

35
Q

What happens if you stimulate the ventro medial hypothalamus?

A

→ Stops feeding

36
Q

What are other non classical endocrine organs?

A
→ Heart
→ Kidney
→ Bone
→ Tumors
→ Pineal gland
37
Q

What is the pathway for inhibiting food intake?

A

→Leptin, Insulin, PPY, CCK, GLP1 increase
→ POMC/CART neurons in the ventromedial hypothalamus are stimulated
→ Decreases food intake

38
Q

What is the pathway for stimulating food intake?

A

→ Ghrelin increases and leptin decreases
→ AGRP and NPY neurons are stimulates in the lateral hypothalamus
→ Stimulates food

39
Q

What do the kidneys secrete and in response to what?

A

→ EPO

→ low partial pressures of oxygen

40
Q

What does EPO do?

A

→ Stimulates the production of erythrocytes

41
Q

What is recombinant EPO used for?

A

→ Treat anaemia due to renal failure

→ Blood doping agent

42
Q

What are circadian rhythms driven by?

A

→ The biological clock in the suprachiasmatic nucleus

43
Q

Where is the suprachiasmatic nucleus?

A

→ Above the optic chiasm

44
Q

In the absence of sensory cues what does the circadian cycle do?

A

→ Generates its own rhythm of 25 hours

45
Q

What rhythms does the suprachiasmatic nucleus control?

A

→ Melatonin

→ Cortisol

46
Q

What is the pathway from retina to pineal gland?

A
→ Retina
→ SCN
→ Paraventricular nucleus 
→ sympathetic chain
→ Pineal gland
47
Q

What are the steps in the synthesis of melatonin?

A

→L- tryptophan
→ Serotonin
→ Melatonin

48
Q

What stimulates and inhibits melatonin?

A

→ Darkness stimulates production and secretion of melatonin

→ Light inhibits it