Appetite Flashcards Preview

Fundamentals > Appetite > Flashcards

Flashcards in Appetite Deck (107):
1

Define appetite

Desire to eat a specific food or nutrient

2

Define satiation

Having eaten enough

3

Define satiety

Preventing the start of the next meal

4

What does hunger trigger?

Food intake

5

What does satiation do?(2)

End food intake
Determines the size of meals

6

What does satiety do?

Determines the length before another meal is wanted

7

What part of the brain regulates energy balance

Hypothalamus

8

What organs does the hypothalamus interact with?(4)

Adipose tissue
Liver
Pancreas
GI tract

9

What system regulates food intake and energy?

Endocrine

10

How does the endocrine system regulate food intake?

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

11

What are hormones classes based on?

Chemical structure

12

What are the classes of hormones?(3)

Proteins
Steroids
AA derivatives

13

Define endocrine

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

14

Define paracrine

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

15

Define autocrine

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

16

What are the two types of hormone receptors?

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

17

How do hormones elicit biological responses?

By binding to specific receptors

18

What are receptors?(2)

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

19

Define agonist

Hormones which bind to receptors and trigger a biological response

20

Define antagonist(2)

Hormones which bind to receptors
But dampens or block agonist mediated biological responses

21

Receptors have high affinity to ____ levels of circulating ______

Low
Hormones

22

Receptors have great _______

Specificity

23

Where are cell membrane receptors located?

Located within phospholipid bilayer of cell membrane

24

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

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

25

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

G-protein coupled receptors
Receptor protein tyrosine kinases

26

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

Intergins
Toll-like receptors

27

Define hunger

Desire to eat

28

Components of energy intake (2)

Food intake
Alcohol

29

Components of energy expenditure (3)

BMR
PA
Thermogenesis

30

Time of positive energy balance (3)

Growth in children
Pregnancy
Fattening

31

Times of negative energy balance (5)

Wasting
Starvation
Under feeding
Hypermetabolism
Dieting

32

Example of a steroid hormone

Cortisol

33

Example of AA derivative hormone

Adrenaline

34

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

7

35

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

Adenylate cyclase
Phospholipase C

36

What activates and inhibits adenylate cyclase?

G alpha s activates
G alpha i inhibits

37

What activates phospholipase C?

G alpha q

38

What are the 2 primary signalling cascades?(2)

Cyclic 3'5'-adenosine monophosphate (cAMP) pathway
Phosphatidylinositol (PIP) pathway

39

cAMP pathway (7)

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

40

PIP pathway (9)

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

41

Characteristics of receptor protein tyrosine kinases (2)

Single transmembrane proteins
Have intrinsic enzymatic activity

42

How does receptor protein tyrosine kinases work?(4)

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

43

What are the 2 general groups of intracellular receptors?

Nuclear (in nucleus)
Cytoplasmic (in cytoplasm)

44

Characteristics of intracellular receptors (3)

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

Nuclear receptors (4)

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

Cytoplasmic receptors (4)

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

Role of hippocampus in appetite

Implicated to be involved in inducing pleasure of eating

48

Role of brainstem in appetite

Involved in neural regulation of appetite signals from the gut

49

2 main nuclei of hypothalamus in relation to appetite regulation

Arcuate nucleus
Paraventricular nucleus (PVN)

50

Arcuate nucleus characteristics (2)

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

51

Paraventricular nucleus (2)

Integrating centre of many neuronal pathways
Crucial site for the actions of many peptides

52

Ventromedial nucleus (VMN) (4)

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

53

Lateral hypothalamic area (LHA) (2)

Described as classical hunger centre
Contain dense population of nuclei

54

4 most important hormones in appetite regulation

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

55

Neuropeptide Y characteristics (4)

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

56

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

Increased food intake within 10-15 mins
Reduced thermogenesis

57

Where do NPY neurones project to?(3)

PVN, DMN, LHA

58

When is NPY unregulated?(2)

During fasting
During leptin deficiency

59

What makes the melanocortin system unique?

Has both endogenous agonist and antagonists

60

What are the melanocortin peptides produced from?

The enzymatic cleavage of the POMC protein

61

Expression site of POMC (3)

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

62

Agonist of melanocortin system

Alpha-MSH

63

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

Decreases

64

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

Antagonist
Increases

65

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

MCR3 and MCR4 receptors
Located in the PVN

66

CART _______ food intake

Reduces

67

PVN second order neuropeptides (5)

CCK
TRH
CRH
Neuromedin U
CGRP

68

LHA second order neuropeptides (2)

MCH
Orexins

69

VMN second order neuropeptide

BDNF

70

Arcuate nucleus second order neuropeptides (2)

Galanin-like peptide
GHRH

71

What are second order neuropeptides?(2)

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

72

MCH characteristics (6)

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

TRH characteristics (4)

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

74

Effects of TSH (3)

Alters T3/T4
Which affects metabolism
And growth and development

75

GHRH characteristics (3)

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

76

Characteristics of insulin (3)

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

77

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

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

78

What receptor does leptin bind to?

Leptin receptor (ObR)

79

Effects peripheral or central leptin administration (2)

Acutely decreases food intake
Induces weight loss (no effect on lean body mass)

80

Leptin and insulin similarities (4)

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

81

Insulin mechanism as weight increases (2)

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

82

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

Formation of hormone receptor complex
Which initiates a cascade of intracellular events

83

What are GPCRs coupled to?

Heterotrimetric guanine-binding proteins

84

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

PVN

85

Leptin body fat dissociation (2)

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

86

Orexigenic first order neurones (2)

NPY
AgRP

87

First order anorexigenic neurones (2)

POMC
CART

88

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

Inhibits orexigenic neurones
Stimulates anorexigenic
Decreasing food intake

89

What causes positive feedback - increasing food intake (3)

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

90

What causes negative feedback - decrease food intake

Satiation and satiety

91

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

Cephalic
Gastric
Intestinal

92

Cephalic phase (5)

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

Secretory events during cephalic phase (6)

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

94

Motor events during cephalic phase (4)

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

95

Gastric phase (consumption stage) (4)

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

96

Intestinal phase - induction of satiety (2)

Release of gut peptides secreted from enteroendocrine cells
Feeding stops

97

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

Blood tissue nutrient response
pH
Heat production
Signals from vagaries nerve

98

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

Ghrelin

99

Where are GI peptide receptors located?(2)

Brain
GI tract

100

Where do GI tract peptides primarily act?

Brain

101

CCK (4)

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

102

GLP-1 (3)

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

103

Peptide YY (2)

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

104

Ghrelin (3)

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

105

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

Dopamine
Serotonin
Endocannbinoids

106

Why do diets fail?(2)

Body will defend against potential weight loss
Therefore increases appetite

107

Adipose tissue hormone examples (6)

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