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Year 1 Semester 2 Metabolism, Endocrinology & Haematology > S6) Introduction to the Endocrine System & Endocrine Control of the Appetite > Flashcards

S6) Introduction to the Endocrine System & Endocrine Control of the Appetite Flashcards

1
Q

What is homeostasis?

A

Homeostasis is the maintenance / regulation of a stable condition in an internal environment

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2
Q

Homeostatic mechanisms act to counteract changes in the internal environment. These mechanisms exist on all levels.

Identify some

A
  • Cell e.g. regulation of [Ca2+]i
  • Tissue e.g. balance between cell proliferation and cell death
  • Organ e.g. kidney regulates water and ion concentrations in blood
  • Organism e.g. constant body temperature
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3
Q

What are the different components of a control system?

A
  • Stimulus
  • Receptor
  • Control centre
  • Effector
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4
Q

Illustrate how the different components of a control system act to ensure homeostasis

A
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5
Q

What is a biological rhythm?

A

A biological rhythm is any cyclic change in the level of a bodily chemical or function

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6
Q

What is a circadian rhythm and how is it controlled?

A
  • A circadian rhythm is a biological rhythm which follows a 24 hour cycle
  • It is regulated by a small group of neurones in suprachiasmatic nucleus (biological clock) and varies according to the environment (light, temperature, social interaction, exercise, eating/drinking pattern)
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7
Q

How does jet lag arise?

A

Jet lag occurs due to long haul flights crossing time zones resulting in mismatch between environmental cues and the biological clock

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8
Q

Which hormone is involved in setting the biological clock?

A

Melatonin, from pineal gland

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9
Q

Compare and contrast negative and positive feedback, providing an example for each

A
  • Negative feedback: a response which reverses the direction of change e.g. baroreceptors in blood pressure control
  • Positive feedback: a response which reinforces the direction of change e.g. hormones in ovulation
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10
Q

Body water homeostasis is an example of a feedback system.

In light of this, describe the body water distribution in a 70 kg adult male

A
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11
Q

Distinguish between osmolarity and osmolality

A
  • Osmolarity is the number of osmoles per litre of solution
  • Osmolality is the number os osmoles per kilogram of solution
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12
Q

What monitors the osmotic pressure of blood plasma?

A

Osmotic pressure of blood plasma monitored by osmoreceptors in hypothalamus

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13
Q

Serum osmolality useful when investigating hyponatraemia.

What is the normal range for this?

A

275 - 295 mOsmol/kg

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14
Q

Illustrate the control system set up as ADH regulates serum osmolality in body fluid homeostasis

A
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15
Q

Illustrate the control system set up by the homeostatic regulation of plasma glucose levels by insulin and glucagon

A
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16
Q

What is the endocrine system?

A

The endocrine system is a collection of glands located throughout the body

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17
Q

What are hormones and what do they do?

A

Hormones are chemical signals produced in endocrine glands/tissues that travel in the bloodstream to cause an effect on other tissues

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18
Q

Identify the ten major endocrine glands in the human body

A
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19
Q

There are four different mechanisms of communication via hormones.

Identify and describe them

A
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20
Q

The endocrine and nervous systems have several features in common.

Describe five of these similarities

A
  • Both neurons and endocrine cells are capable of secreting
  • Both neurons and endocrine cells can be depolarised
  • Some molecules acts as both neurotransmitter and hormone
  • The mechanism of action requires interaction with specific receptors in the target cells
  • Both systems work in parallel to control homeostasis
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21
Q

Compare and contrast the endocrine and nervous systems in terms of the following:

  • Signal
  • Nature
  • Conveyance
  • Mediators
  • Speed
A
22
Q

Identify the four different types of hormones and describe their relative solubility

A
  • Peptide / polypeptide – water soluble
  • Amino acid derivatives (amines) – catecholamines are water soluble, thyroid hormones are lipid soluble
  • Glycoproteins – water soluble
  • Steroids – lipid soluble
23
Q

Provide three examples of peptide hormones

A
  • Insulin
  • Glucagon
  • Growth hormone
24
Q

Provide three examples of glycoprotein hormones

A
  • Luteinizing hormone
  • Follicle stimulating hormone
  • Thyroid stimulating hormone
25
Q

Provide three examples of amine hormones

A
  • Noradrenaline (& adrenaline)
  • Melatonin
  • Thyroid hormone
26
Q

Provide three examples of steroid hormones

A
  • Cortisol
  • Aldosterone
  • Testosterone
27
Q

How are hormones transported?

A
  • Some hormones travel in blood in simple solution e.g. peptides, NA
  • Most hormones must bind to specific proteins
28
Q

In terms of hormone transport, describe three roles of transport proteins

A
  • Increase solubility of hormone in plasma
  • Increase half-life
  • Readily accessible reserve
29
Q

3 factors determine hormone levels in the body.

Identify and describe them

A
  • Rate of production – synthesis and secretion
  • Rate of delivery – dependent on rate blood flow to a particular organ
  • Rate of degradation – hormones are metabolised and excreted from the body
30
Q

How do hormones exert their effects?

A

Hormones exert their effects by binding to specific receptors

31
Q

How do water soluble hormones exert their effects?

A

Water soluble hormones bind to cell surface receptors on target cells

32
Q

In 6 steps, outline the effects of catecholamines like noradrenaline binding to a cell surface receptor on its target cell

A

⇒ Dissociation of G protein a subunit

⇒ Activation of adenylyl cyclase

⇒ Formation of cAMP

⇒ Activation of PKA

⇒ Phosphorylation of target proteins

⇒ Cellular response

33
Q

In 6 steps, outline the effects of peptide hormones like insulin binding to a cell surface receptor on its target cell

A

⇒ Dimerisation (insulin receptor is already dimerised)

⇒ Autophosphorylation of specific tyrosines

⇒ Recruitment of adapter proteins and signalling complex

⇒ Activation of protein kinase e.g. PKB

⇒ Phosphorylation of target proteins

⇒ Cellular response

34
Q

How do lipid soluble molecules exert their effects?

A

Lipid soluble molecules bind to intracellular receptors on target cells

35
Q

In 4 steps, outline the effects of lipid soluble hormones like aldosterone binding to a intracellular receptor on its target cell

A
36
Q

Where is the appetite control centre located?

A
  • The satiety centre is located in the hypothalamus
  • The arcuate nucleus plays a central role in controlling appetite
37
Q

Neuronal, nutrient & hormonal signals are processed by primary neurones in the arcuate nucleus

Identify the two types of primary neurone and explain what they do

A
  • Stimulatory neurones contain neuropeptide Y (NPY) and agouti-related peptide (AgRP) → these promote hunger
  • Inhibitory neurones contain POMC which yields several neurotransmitters including α-MSH and β-endorphin → these promote satiety
38
Q

How do primary neurons transmit signals for appetite control?

A

Primary neurons synapse with secondary neurones in other regions of hypothalamus and the signals integrated to alter feeding behaviour

39
Q

Hormonal signals from the gut to the hypothalamus also have a role in appetite control.

Identify the two hormones involved

A
  • Ghrelin
  • PYY
40
Q

What is the role of ghrelin in appetite control?

A

Ghrelin stimulates the excitatory primary neurones in arcuate nucleus, thus stimulates appetite

41
Q

Describe the release and inhibition of ghrelin

A
  • Released from stomach wall when empty
  • Inhibited when stomach begins to fill with contents
42
Q

What is the role of PYY in appetite control?

A

PYY inhibits the excitatory primary neurones of the arcuate nucleus and stimulates the inhibitory neurones, hence suppresses appetite

43
Q

Describe the release of PYY

A

PYY is released by cells in the ileum and colon in response to feeding

44
Q

Hormonal signals from the body to the hypothalamus are also involved in appetite control.

Identify the three hormones involved

A
  • Leptin
  • Insulin
  • Amylin
45
Q

What is the role of leptin in appetite control?

A

Suppress appetite:

  • Stimulates the inhibitory (POMC) neurones
  • Inhibits the excitatory (AgRP/NPY) neurones
46
Q

Describe the release of leptin

A

Peptide hormone released into blood by adipocytes

47
Q

Explain the cellular mechanism by which leptin exerts its effects

A
  • Leptin induces expression of uncoupling proteins in mitochondria
  • Energy therefore dissipated as heat
48
Q

Describe the release of amylin as well as its role in appetite control

A
  • Peptide hormone secreted by β cells in pancreas
  • Suppresses appetite, decrease glucagon secretion and slow gastric emptying
49
Q

Describe the role of insulin in appetite control

A

Suppresses appetite by similar mechanism as leptin

50
Q

Illustrate the relationship between various hormonal signals in appetite control

A

Year 1 Semester 2 Metabolism, Endocrinology & Haematology (20 decks)

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