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SGUL - Physiology 1 > Beyond the Classic Endocrine Glands > Flashcards

Beyond the Classic Endocrine Glands Flashcards

1
Q

How is fat considered an endocrine gland?

A

Capable of synthesising several hormones such as:
- Leptin: signals satiety to the brain
- Adiponectin: increases insulin sensitivity
- Resistin
- Cytokines

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2
Q

Describe the relationship between leptin and obesity. PART 1

A
  • Mutations of the leptin (LEP) gene in adipose tissue or the leptin receptor (LEPR) gene lead to development of early-onset morbid obesity.
  • Leptin deficiency has been successfully treated with leptin, resulting in a reduction in fat mass.
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3
Q

Describe the relationship between leptin and obesity. PART 2

A
  • Obesity is associated with leptin resistance (leptin levels are already high in obesity).
  • Multiple interacting pathways control food intake and energy utilisation.
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4
Q

Obesity is regarded as a state of chronic, low-level inflammation.
Expand on this. PART 1

A

In healthy adipose tissue:
- leptin signals satiety to the brain
- adiponectin increases insulin sensitivity
- resistin levels low

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5
Q

Obesity is regarded as a state of chronic, low-level inflammation.
Expand on this. PART 2

A

In obesity:
- leptin secretion is high, but there is resistance to leptin
- adiponectin secretion is low
- insulin resistance, diabetes and metabolic syndrome
- adipose tissue expands, secrete chemokines (eg. chemotactic cytokines); attract macrophages

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6
Q

What is metabolic syndrome?

A

General disorder of energy metabolism associated with obesity, hypertension, hyperglycaemia, high serum triglycerides and insulin resistance

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7
Q

List some differences between visceral or intra-abdominal fat (VS) versus subcutaneous fat (SC).

A
  • VS and SC express different developmental genes
  • Different signalling profiles
  • FFA and adipocytokines released from VS fat drained directly to liver - alter metabolism
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8
Q

Describe how obesity is a chronic disease. PART 1

A
  • Body ‘remembers’ highest body weight and recognises it as its ‘new normal weight’.
  • During weight loss, changes occur in appetite-regulating hormones which increase hunger.
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9
Q

Describe how obesity is a chronic disease. PART 2

A
  • If people with obesity do not eat enough, the hormones trigger the body to conserve energy.
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10
Q

Describe the gut as an endocrine gland.

A

Gastroenteropancreatic tract is the largest endocrine gland in the body.
The incretin hormones:
- GIP (glucose-dependent insulinotropic peptide)
- GLP-1 (glucagon-like peptide 1)

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11
Q

Which three stimuli can signal the hypothalamus regarding regulation of food uptake?

A
  • hormones secreted by the stomach and intestines
  • vagal afferents to the nucleus of the tractus solitarius
  • leptin secreted from adipocytes
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12
Q

In response to different stimuli, describe the appetite inhibitory pathway in the hypothalamus

A
  • With increased food intake/ obesity, increase in leptin, insulin, PPY, oxyntomodulin, GLP-1 and CCK.
  • Stimulate POMC/CART neurones, which stimulates the ventromedial hypothalamus.
  • Results in inhibited food intake (anorexigenic, appetite suppressant).
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13
Q

In response to different stimuli, describe the appetite stimulatory pathway in the hypothalamus

A
  • With fasting/ starvation, there is increased ghrelin and decreased leptin.
  • Stimulates AGRP and NPY neurones, which stimulate the L hypothalamus.
  • Results in increased food intake.
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14
Q

List some other ‘non-classical’ endocrine organs.

A
  • heart
  • kidney
  • bone
  • tumours
  • pineal gland
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15
Q

How does the kidney stimulate the production of RBCs?

A
  • Secretes EPO in response to low partial pressures of oxygen in the circulation.
  • Stimulates the production of RBCs.
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16
Q

Describe biological clocks. PART 1

A
  • Circadian rhythms are driven by the biological clock in the suprachiasmatic nucleus (SCN) above optic chiasm
  • Other rhythms respond to external daily cues.
  • SCN produces a 24-hour cycle spontaneously
17
Q

Describe biological clocks. PART 2

A
  • SCN affects melatonin, cortisol and core-body temperature.
  • Circadian rhythms are not entrained to the light-dark cycle; so the day-night cycle doesn’t cause the rhythm, it simply corresponds to the rhythm.
18
Q

How is the pineal gland thought to measure time?

A
  • Nerves that provide neural input to the pineal gland from the retina.
  • Goes from the retina to SCN) then to paraventricular nucleus (PVN), then to pineal gland (through the superior cervical ganglion).
  • Darkness stimulates pineal gland to secrete melatonin. Light inhibits
19
Q

What is the proof of the different effects of melatonin when dysregulated?

A
  • Epidemiological studies in (for example) shift workers, long-distance flight crews and patients with sleeping disorders
  • Higher prevalence of psychological disorders, metabolic syndrome, and CVS disease.
20
Q

What are the steps in the synthesis of melatonin?

A

→L- tryptophan
→ Serotonin
→ Melatonin

21
Q

What is recombinant EPO used for?

A

→ Treat anaemia due to renal failure
→ Blood doping agent

22
Q

What does GLP do?

A

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

23
Q

What is GIP stimulated by?

A

→ Presence of fat and glucose in the small intestine

24
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

25
Q

What does ghrelin do?

A

→ strong stimulant for feeding and appetite
→ Stimulates growth hormone

26
Q

What is secretin stimulated by?

A

→ Acidic pH in the lumen of the small intestine

27
Q

What does secretin do?

A

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

28
Q

What does CCK do and what is it stimulated by?

A

→ Stimulates secretion of pancreatic enzymes
→ Contraction of the gall bladder and emptying
→ Stimulated by presence of fatty acids and amino acids in small intestine

29
Q

What does gastrin do and what is it stimulated by?

A

→ Stimulates gastric acid secretion
→ Stimulated by peptides and amino acids in gastric lumen

30
Q

What is leptin released from?

A

Adipose tissue

31
Q

Why is adipose tissue needed?

A

→ If fat was allowed to accumulate it would be toxic
→ Lipotoxicity

32
Q

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

A

→ converted into fat
→ Stored in larger quantities

33
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

34
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

35
Q

What happens when free fatty acids are in the cell?

A

→ Become triglycerides again

36
Q

What is the main source of triglycerides?

A

→ Chylomicrons from digestion
→ VLDL

37
Q

What are free fatty acids bound to?

A

Albumin

38
Q

How do triglycerides get inside cells?

A

→ As free fatty acids
→ hydrolyzed by lipoprotein lipase

39
Q

What is the main function of adipocytes?

A

→ Store energy as triglycerides
→ Release them as free fatty acids

SGUL - Physiology 1 (68 decks)

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