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Fundamentals > Appetite > Flashcards

Appetite Flashcards

1
Q

Define appetite

A

Desire to eat a specific food or nutrient

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2
Q

Define satiation

A

Having eaten enough

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3
Q

Define satiety

A

Preventing the start of the next meal

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4
Q

What does hunger trigger?

A

Food intake

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5
Q

What does satiation do?(2)

A

End food intake

Determines the size of meals

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6
Q

What does satiety do?

A

Determines the length before another meal is wanted

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7
Q

What part of the brain regulates energy balance

A

Hypothalamus

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8
Q

What organs does the hypothalamus interact with?(4)

A

Adipose tissue
Liver
Pancreas
GI tract

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9
Q

What system regulates food intake and energy?

A

Endocrine

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10
Q

How does the endocrine system regulate food intake?

A

Chemicals (hormones) are released from organs and enter the hypothalamus

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11
Q

What are hormones classes based on?

A

Chemical structure

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12
Q

What are the classes of hormones?(3)

A

Proteins
Steroids
AA derivatives

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13
Q

Define endocrine

A

A hormone produced by one organ/cell that is released into circulation to produce an effect on a distant cell/organ

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14
Q

Define paracrine

A

A hormone produced by a cell/organ that is released to produce an effect on a neighbouring cell/organ

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15
Q

Define autocrine

A

A hormone that is produced by a cell/organ that is released to produce an effect on the same cell/organ

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16
Q

What are the two types of hormone receptors?

A

Cell membrane for proteins/catecholamines (cannot cross membrane)
Intracellular receptors for steroid hormones (cross lipid bilayer)

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17
Q

How do hormones elicit biological responses?

A

By binding to specific receptors

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18
Q

What are receptors?(2)

A

Protein molecules embedded in the plasma membrane or cytoplasm of cell
To which molecule can bind to to elicit a biological response

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19
Q

Define agonist

A

Hormones which bind to receptors and trigger a biological response

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20
Q

Define antagonist(2)

A

Hormones which bind to receptors

But dampens or block agonist mediated biological responses

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21
Q

Receptors have high affinity to ____ levels of circulating ______

A

Low

Hormones

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22
Q

Receptors have great _______

A

Specificity

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23
Q

Where are cell membrane receptors located?

A

Located within phospholipid bilayer of cell membrane

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24
Q

What are the types of cell membrane receptors?(5)

A 
Ligand-gated ion channels
G-protein coupled receptors 
Receptor protein tyrosine kinases
Intergins
Toll-like receptors
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25
Q

Which types of cell membrane receptors regulate the activity of intracellular proteins?(2)most important to appetite regulation

A

G-protein coupled receptors

Receptor protein tyrosine kinases

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26
Q

Which type of receptors regulate cellular process and immunity?(2)

A

Intergins

Toll-like receptors

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27
Q

Define hunger

A

Desire to eat

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28
Q

Components of energy intake (2)

A

Food intake

Alcohol

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29
Q

Components of energy expenditure (3)

A

BMR
PA
Thermogenesis

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30
Q

Time of positive energy balance (3)

A

Growth in children
Pregnancy
Fattening

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31
Q

Times of negative energy balance (5)

A 
Wasting
Starvation
Under feeding 
Hypermetabolism
Dieting
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32
Q

Example of a steroid hormone

A

Cortisol

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33
Q

Example of AA derivative hormone

A

Adrenaline

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34
Q

How many transmembrane domains does G-protein coupled receptors have?

A

7

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35
Q

What are the 2 main enzymes that interact with G proteins?(2)

A

Adenylate cyclase

Phospholipase C

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36
Q

What activates and inhibits adenylate cyclase?

A

G alpha s activates

G alpha i inhibits

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37
Q

What activates phospholipase C?

A

G alpha q

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38
Q

What are the 2 primary signalling cascades?(2)

A

Cyclic 3’5’-adenosine monophosphate (cAMP) pathway

Phosphatidylinositol (PIP) pathway

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39
Q

cAMP pathway (7)

A 
Ligand binds to receptor
Alpha subunits changes GDP to GTP
alpha subunits disassociate
Ga synthesis binds adenylate cyclase 
cAMP is released into the cell
cAMP dephosphorylates PKA 
Leads to cellular activity
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40
Q

PIP pathway (9)

A

Ligand binds to G protein coupled receptor
GDP converted to GTP
Subunits disassociate
Phospholipase C is activated
This causes hydrolysis of PIP2 into DAG and IP3
IP3 binds to calcium gated channels channel on ER
Causes release of Ca2+ into cytosol
Ca2+ binds to (calcium channels) calmodulin
This activates cellular activity

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41
Q

Characteristics of receptor protein tyrosine kinases (2)

A

Single transmembrane proteins

Have intrinsic enzymatic activity

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42
Q

How does receptor protein tyrosine kinases work?(4)

A

Hormones bind to the receptor
Which activates their intracellular kinase activity
Leading to dimerisation and phosphorylation of the tyrosine molecules
This results in cellular activation

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43
Q

What are the 2 general groups of intracellular receptors?

A

Nuclear (in nucleus)

Cytoplasmic (in cytoplasm)

44
Q

Characteristics of intracellular receptors (3)

A

Located inside the cell rather cell membrane

Receptors are transcription factors that having binding sites for hormone and DNA

Binding of ligand to receptor leads to activation or repression of gene transcription

45
Q

Nuclear receptors (4)

A

Unoccupied receptor is bound to DNA
This represses DNA transcription
Binding of hormone causes gene transcription
Receptors are usually dimers and may act with other transcription factors

46
Q

Cytoplasmic receptors (4)

A

Steroid receptor does not bind DNA in absence of ligand
Hormone binding causes dissociation of receptor associated chaperone proteins
The complex then translocates into the nucleus
Then complex binds to DNA to allow gene transcription

47
Q

Role of hippocampus in appetite

A

Implicated to be involved in inducing pleasure of eating

48
Q

Role of brainstem in appetite

A

Involved in neural regulation of appetite signals from the gut

49
Q

2 main nuclei of hypothalamus in relation to appetite regulation

A 
Arcuate nucleus 
Paraventricular nucleus (PVN)
50
Q

Arcuate nucleus characteristics (2)

A

Contains a dense population of orexigenic and anorexigenic peptides
When activated they signal to PVN

51
Q

Paraventricular nucleus (2)

A

Integrating centre of many neuronal pathways

Crucial site for the actions of many peptides

52
Q

Ventromedial nucleus (VMN) (4)

A

Largest nuclei in hypothalamus
Considered to be satiety centre
No production of appetite regulating peptides
Possible site of actin for peptides

53
Q

Lateral hypothalamic area (LHA) (2)

A

Described as classical hunger centre

Contain dense population of nuclei

54
Q

4 most important hormones in appetite regulation

A

Agouti gene related peptides (AgRP)
Alpha melanocyte stimulating hormone (AMSH)
Neuropeptide Y (NPY)
Cocaine amphetamine regulated transcript (CART)

55
Q

Neuropeptide Y characteristics (4)

A

36 AA peptide
Found mainly in arcuate nucleus
Co expressed with AgRP
Increases food intake

56
Q

What happens when Neuropeptide Y is injected into brain?(2)

A

Increased food intake within 10-15 mins

Reduced thermogenesis

57
Q

Where do NPY neurones project to?(3)

A

PVN, DMN, LHA

58
Q

When is NPY unregulated?(2)

A

During fasting

During leptin deficiency

59
Q

What makes the melanocortin system unique?

A

Has both endogenous agonist and antagonists

60
Q

What are the melanocortin peptides produced from?

A

The enzymatic cleavage of the POMC protein

61
Q

Expression site of POMC (3)

A

Primarily expressed in pituitary
Also expressed in arcuate nucleus
In the arcuate nucleus it is co expressed with CART

62
Q

Agonist of melanocortin system

A

Alpha-MSH

63
Q

Alpha-melanocyte stimulating hormone (alpha-MSH) _______ food intake

A

Decreases

64
Q

AgRP is the _______ of the melanocortin system and it ______ food intake

A

Antagonist

Increases

65
Q

What are the major sites of action for a-MSH and AgRP?(2); also where are they located?

A

MCR3 and MCR4 receptors

Located in the PVN

66
Q

CART _______ food intake

A

Reduces

67
Q

PVN second order neuropeptides (5)

A 
CCK
TRH
CRH
Neuromedin U
CGRP
68
Q

LHA second order neuropeptides (2)

A

MCH

Orexins

69
Q

VMN second order neuropeptide

A

BDNF

70
Q

Arcuate nucleus second order neuropeptides (2)

A

Galanin-like peptide

GHRH

71
Q

What are second order neuropeptides?(2)

A

Activation for first order neutrons leads to activation of other nuclei
Peptides in other nuclei are known as second order neuropeptides

72
Q

MCH characteristics (6)

A 
Produced by in the LHA
Primarily receives projections from the arcuate nucleus  
Increases food intake 
Decreases energy expenditure 
Fasting increases expression
Acts downstream of leptin
73
Q

TRH characteristics (4)

A

Produced in the PVN
Processed through proteolysis to give mature TRH molecule
Travels to pituitary gland and stimulates release of TSH

74
Q

Effects of TSH (3)

A

Alters T3/T4
Which affects metabolism
And growth and development

75
Q

GHRH characteristics (3)

A

Released from neurosecretory nerve terminals of the arcuate nucleus
Travels to pituitary gland and stimulates growth hormone secretion
Increases food intake

76
Q

Characteristics of insulin (3)

A

Acts via tyrosine kinase receptors
Administration of insulin to the brain decreases food intake
Insulin antibodies causes an increase in food intake

77
Q

What reduces the transport of insulin into the brain?(3)

A

Fasted animals
Animals maintained on a high fat diet
Genetic and dietary induced obesity

78
Q

What receptor does leptin bind to?

A

Leptin receptor (ObR)

79
Q

Effects peripheral or central leptin administration (2)

A

Acutely decreases food intake

Induces weight loss (no effect on lean body mass)

80
Q

Leptin and insulin similarities (4)

A

Act as adiposity signals
Circulate at levels proportional to body fat content
Administration decreases food intake
Also decreases energy expenditure

81
Q

Insulin mechanism as weight increases (2)

A

Greater amounts of insulin is secreted in order to overcome insulin resistance
And maintain glucose homeostasis

82
Q

What happens when hormone binds to cell membrane?(2)

A

Formation of hormone receptor complex

Which initiates a cascade of intracellular events

83
Q

What are GPCRs coupled to?

A

Heterotrimetric guanine-binding proteins

84
Q

Which nuclei in the hypothalamus has extensive and direct connections to other nuclei?

A

PVN

85
Q

Leptin body fat dissociation (2)

A

Fasting lowers leptin plasma levels quicker than changes in adiposity
This tells body to eat more before fat sites become too low

86
Q

Orexigenic first order neurones (2)

A

NPY

AgRP

87
Q

First order anorexigenic neurones (2)

A

POMC

CART

88
Q

Effects of leptin on first order neurones when leptin gets into arcuate nucleus (3)

A

Inhibits orexigenic neurones
Stimulates anorexigenic
Decreasing food intake

89
Q

What causes positive feedback - increasing food intake (3)

A

Hunger and appetite
Sensory properties of food
Social programming - set time of eating

90
Q

What causes negative feedback - decrease food intake

A

Satiation and satiety

91
Q

What are the three phases of response to food ingestion (3)

A

Cephalic
Gastric
Intestinal

92
Q

Cephalic phase (5)

A

Occurs pre digestion
Stretch receptors in stomach detect empty stomach and low blood nutrients
Can be stimulated by body senses
Stimuli increases activation of parasympathetic outflow system
Triggers secretory and motor events in proximal and distal GI tract

93
Q

Secretory events during cephalic phase (6)

A 
Secretion of: 
Salivary acid 
Pepsinogen 
Intrinsic factor
Gastrin
Pancreatic enzymes
Releases of gut peptides
94
Q

Motor events during cephalic phase (4)

A

Relaxation of sphincter
Gallbladder contractions
Relaxation of gastric fundus
Which prepares the stomach to receive food

95
Q

Gastric phase (consumption stage) (4)

A

Distension of stomach
Release of various peptides and neuropeptides
Gut fill effects
Slows down feeding

96
Q

Intestinal phase - induction of satiety (2)

A

Release of gut peptides secreted from enteroendocrine cells

Feeding stops

97
Q

What causes gut peptides to be released from enteroendocrine cells (4)

A

Blood tissue nutrient response
pH
Heat production
Signals from vagaries nerve

98
Q

What is the only peptide that is released from the GI tract the
At increases food intake?

A

Ghrelin

99
Q

Where are GI peptide receptors located?(2)

A

Brain

GI tract

100
Q

Where do GI tract peptides primarily act?

A

Brain

101
Q

CCK (4)

A

Released from small intestine in response to fats and AAs
Causes gallbladder contraction
And secretion of pancreatic enzymes following food intake
Induces satiation

102
Q

GLP-1 (3)

A

Derived from proglucaon gene expressed in intestinal cells
Stimulated in response to orally ingested nutrient
Suppresses appetite

103
Q

Peptide YY (2)

A

Co-secreted with GLP-1 in proportion to calories consumed

Induces satiety

104
Q

Ghrelin (3)

A

Known as the hunger hormones
Acts on GHR
Rises during fasting and before each meal

105
Q

Which compounds are related to hedonic eating behaviour?(3)

A

Dopamine
Serotonin
Endocannbinoids

106
Q

Why do diets fail?(2)

A

Body will defend against potential weight loss

Therefore increases appetite

107
Q

Adipose tissue hormone examples (6)

A 
Testosterone 
IGF-1
TNF-a
IL-6
Resistin
Adiponectin

Fundamentals (17 decks)

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