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Appetite Flashcards

(107 cards)

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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
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 ```

Fundamentals (17 decks)

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