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ESA2 > MEH - Endocrine & Control of Appetite > Flashcards

MEH - Endocrine & Control of Appetite Flashcards

1
Q

What is homeostasis and what does it do?

A

Dynamic equilibrium of the internal environment. Acts to counteract changes in the internal environment.

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2
Q

What 5 characteristics must a homeostatic control system have?

A 
Stimulus
Receptor
Control Centre
Effector 
Negative feedback loop
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3
Q

What three things does a control centre do?

A

Determines set point
Analyses afferent input
Decides efferent output

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4
Q

What examples of efferent pathways from control centre –> effector are there?

A

Neural

Hormonal

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5
Q

What happens to the set point in a circadian rhythm? Where in the brain is this determined? Give some examples of hormones/homeostatic effects that are in a circadian rhythm

A

Set point varies - nocturnal-diurnal
In the suprachiasmatic nucleus
Temperature, exercise, eating/drinking pattern, social interaction

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6
Q

What is a zeitgeber?

A

An environment cue that synchronises a body’s biological rhythms

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7
Q

What does melatonin do and where is it released from?

A

It is a hormone that is involved in setting the biological clock - released from pineal gland

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8
Q

Negative feedback is more common that positive - give 2 examples where positive feedback is used in the body

A
  • Blood clotting

- Ovulation

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9
Q

How many L of fluid are there in the body:
Intracellularly
Extracellularly (Interstitial + Plasma)

A

Total: 42L
IC- 28L
EC - 14
(Interstitial 11 Plasma 3)

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10
Q

How is osmotic pressure of blood plasma controlled, and where in the brain are these found?

A

By osmoreceptors in the hypothalamus

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11
Q

What is osmolarity vs osmolality the measure of? What are electrolytes measured in - e.g. for hyponatraemia? What is the normal range for serum Na+?

A

Osmolarity - number of osmoles/L solution (volume)
Osmolality - number of osmoles per Kg solution (mass)

Electrolytes - measured by serum osmolality - 275-295mOsmol/kg

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12
Q

What do osmoreceptor efferents lead to (2)?

A

Increased Thirst - if osmolality high to reduce it
Increased or decreased ADH from post pituitary (increased leads to increased H2O reabsorbed in kidney collecting ducts - to reduce osmolality)

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13
Q

What is the endocrine system? What are hormones? How are they transported and in what concentrations?

A

A collection of glands throughout the body that secrete hormones into the blood to act on target organs. Hormones are chemicals that are released into the blood to act on target organs (usually determined by their concentration). They can be attached to plasma proteins and normally in conc around 10-10 to 10-9.

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14
Q

Name the 10 major endocrine glands

A 
Pineal
Pituitary
Hypothalamus 
Testis
Ovaries 
Thyroid
Parathyroid 
Pancreas
Adrenal
Thymus
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15
Q

What other tissues/organs secrete hormones that aren’t endocrine glands (6)?

A 
Heart - ANP BNP
Placenta - Inhibin
Liver - IGF1
Stomach - Gastrin
Adipose - Leptin
Kidney - Epo
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16
Q

Can endocrine cells be depolarised like neural cells?

A

Yes

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17
Q

Can some molecules act as a neurotransmitter and a hormone?

A

Yes

18
Q

What 4 groups of chemical are hormones classified into? Say if they are water or lipid soluble.

A

Glycoprotein - water soluble
Polypeptides - water soluble
Amines - lipid soluble
Steroids - lipid soluble

19
Q

What kind of hormones are LH, FSH and TSH?

A

Glycoprotein

20
Q

What kind of hormone are Insulin, Glucagon, Growth hormone?

A

Peptide

21
Q

Which type of hormones travel UNBOUND to plasma proteins?

A
  • Peptides

- Adrenaline

22
Q

What is Thyroxine-binding globulin?

A

The specific plasma protein that binds Thyroid hormones in the blood.

23
Q

Are free or bound forms of hormone active?

A

Only free

24
Q

Why would you have a hormone bound to a plasma protein (3)?

A

Enhances solubility
Creates reserve (as not active)
Increases half-life of hormone

25
Q

What three factors determine hormone levels in the blood? Which is the most tightly regulated?

A
  • Rate of synthesis - most tightly controlled
  • Rate of delivery
  • Rate of degradation
26
Q

Are hormones circulate the blood in low or high concentrations?

A

Low

27
Q

How do you differentiate between a hormone target cell and non target cell?

A

A target cell will have a receptor for that hormone

28
Q

What kind of receptors do adrenaline and insulin bind to? Are these cell surface or nuclear or cytoplasmic? Why?

A

Adrenalin - GPCR
Insulin - Tyrosine Kinase

  • Cell surface - as they are hydrophilic hormones so can’t cross cell membrane
29
Q

How do TK receptors work?

A

Binding of hormone
Dimerisation (except insulin - already dimerised)
Autophophorylation of specific tyrosines
Recruitment of adaptor proteins and signalling complex
Activation of protein kinase (e.g. PKB)
Phosphorylation of target proteins
Cellular response

30
Q

What 2 types of intracellular receptors are there for lipid soluble hormones?

A

1) Cytoplasmic - binds in cytoplasm then enters nucleus to bind to DNA
2) Pre-bound receptor on DNA (Hormone enters nucleus) - binding received repression of gene transcription. Receptor binds to specific DNA sequence called a hormone response element in promotor region of specific genes

31
Q

What BMI is considered obese?

A

30kg/M-2

32
Q

What part of the hypothalamus controls appetite?

A

Arcuate nucleus

33
Q

What two types of neurone are there in the arcuate nucleus and what do they do?

A

Primary - receive input and synapse with secondary neurones
Secondary - modulate feeding behaviour

34
Q

What two types of primary neurones are there and what do they do?

A

Stimulatory - neurones contain neuropeptide Y (NPY and Agouti-related peptide (AgRP). These promote hunger
Inhibitory - neurone contain POMC which yields several neurotransmitters including alpha-MSH and beta-endorphin and promote satiety.

35
Q

Where do primary neurones synapse with secondary neurones?

A

In other regions of the hypothalamus

36
Q

Which two hormonal signals from the gut travel to the hypothalamus and how do they control feeding behaviour? When might you see a blunted PYY response in humans?

A

Grehlin - Peptide hormone released from stomach wall when empty - stimulates excitatory primary neurones in arcuate nucleus therefore stimulating hunger. Are inhibited with filling of stomach

PYY (pepticde tyrosine tyrosine)
Peptide hormone released from ileum and colon in response to feeding - inhibits excitatory primary neurones of arcuate nucleus and stimulates inhibitory primary neurones of arcuate nucleus - suppresses appetite.

Blunted PYY response in obese humans

37
Q

What 5 broad hormones help control appetite? Do they supress or enhance?

A 
Grehlin - enhance
Leptin - suppress
Insulin - suppress 
PYY - suppress
Amylin - suppress
38
Q

How does leptin work? is Insulin similar or different? How does Leptin increase heat?

A

Leptin - peptide hormone released by adipocytes
Suppresses appetite by
1) Stimulates inhibitory primary neurones in arcuate nucleus (POMC)
2) Inhibit excitatory AgRP/NPY primary neurones in arcuate nucleus

Leptin induces expression of uncoupling proteins in mitochondria –> energy lost as heat

Yes insulin similar to leptin

39
Q

How does amylin work?

A

Peptide hormone - released by beta-cells in pancreas. Role not fully understood but suppresses appetite - decreased glucagon secretion and slows gastric emptying.

40
Q

What is pamlintide?

A

An amylin analogue that is used to treat T2 diabetes

41
Q

What does orexigenic mean?

A

Appetite stimulant

ESA2 (37 decks)

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