Appetite Flashcards
(141 cards)
1
Q
What are the 3 main triggers of the control of thirst?
A
- body fluid osmolality
- reduced blood volume
- reduced blood pressure
2
Q
What is the most potent stimulus for thirst control?
A
Plasma osmolality
3
Q
What change in plasma osmolality is required to induce thirst?
A
2-3%
4
Q
What change in blood volume/arterial pressure is required to induce thirst?
A
10-15%
5
Q
How does the body regulate osmolality?
A
Anti-diuretic hormone (ADH)/vasopressin
6
Q
Where does ADH act?
A
- on the kidneys to regulate the volume and osmolality of urine
- collecting duct, aquaporin 2 channel
7
Q
What happens when ADH is low?
A
large volumes of urine is excreted (water diuresis)
8
Q
What happens when ADH is high?
A
small volumes of urine are excreted (anti-diuresis)
9
Q
Where is ADH stored?
A
in the posterior pituitary gland
10
Q
How does the body measure osmolality?
A
via osmoreceptors in the hypothalamus
11
Q
What are osmoreceptors?
A
- sensory receptors
- involved in osmoregulation
- found in the hypothalamus
12
Q
Where are osmoreceptors in the hypothalamus?
A
- Organum vasculosum of the lamina terminalis (OVLT)
- Subfornical Organ (SFO)
13
Q
How is ADH release regulated in a dehydrated condition?
A
- cells shrink when plasma is more concentrated
- the proportion of cation channels increases, and the membrane depolarizes
- sends signals to ADH producing cells to increase ADH
- fluid retention, invokes drinking
14
Q
How is ADH release regulated in a hydrated condition?
A
- cells expand when plasma is less concentrated
- cation channels are inhibited, the membrane is hyperpolarised
- inhibits signals
- excretion of fluid
15
Q
What causes a decrease in thirst?
A
drinking
16
Q
What detects that drinking has occured in order to stop thirst?
A
receptors in the mouth, pharynx and oesophagus
17
Q
When is thirst completely satisfied?
A
when plasma osmolality is decreased or blood volume/arterial pressure is corrected
18
Q
What type of relief is provided by mouth/pharynx/oesophagus receptors?
A
temporary
19
Q
What else can prompt thirst?
A
- habit
- cravings
- desire
20
Q
What are the negatives of excessive fluid consumption?
A
- energy wastage
- ## interference with nutrient absorption (dependent/driven by sodium)
21
Q
What system responds to changes in blood pressure/volume?
A
the renin-angiotensin-aldosterone system
22
Q
What happens when blood pressure drops?
A
juxtaglomerular apparatus secretes renin
23
Q
Where is the juxtaglomerular apparatus?
A
the renal afferent arterioles
24
Q
What happens when renin is released?
A
- activates the renin-angiotensin system by cleaving angiotensinogen into angiotensin I
25
What secretes angiotensinogen?
the liver
26
What happens to angiotensin I?
it is converted into angiotensin II by (angiotensin converting enzyme) in the lung
27
What is the effects of angiotensin II?
- induces thirst
- release of aldosterone
- ADH secretion
- vasoconstriction (sympathetic activation)
28
How does angiotensin II trigger the release of aldosterone?
- binds onto receptors on the intraglomerular messenger cells
- cell contraction
- release of aldosterone in the zona glomerulosa of the adrenal cortex
29
What does aldosterone do?
```
Influences:
- sodium reabsorption
- potassium excretion
and therefore,
- water retention
```
30
What happens when there is a reduction in fat mass?
- increase in food intake
- reduction in energy expenditure
- reduces the effect of the thyroid gland
- sympathetic inhibition
31
What happens when there is adipose tissue expansion?
- reduces food intake
- increases energy expenditure
- sympathetic activation
32
What is the impact of changes in adipose tissue?
activates responses that favour the return to the previous/original weight
33
Which part of the brain regulates hunger?
hypothalamus
34
What are the 2 main gut hormones involved in appetite regulation (peripheral signalling)?
- Ghrelin
| - PYY
35
What is the long term hormonal appetite regulation?
leptin system
36
What are the 3 main factors involved in appetite regulation?
- Ghrelin/PYY
- neural input from periphery/other brain regions
- Leptin
37
What does orexigenic mean?
appetite stimulant
38
What does anorectic mean?
appetite supressive
39
What is the role of the arcuate nucleus?
- regulation of food intake
| - both orexigenic and anorectic
40
What is the role of the paraventricular nucleus?
- neurones to the posterior pituitary (oxytocin)
| - regulates appetite
41
What is the role of the lateral hypothalamus?
produces orexigenic peptides
42
What is the role of the ventromedial hypothalamus?
- satiety
43
What is the effect of lesions in the ventromedial hypothalamus?
severe obesity
44
What is the effect of arcuate nucleus pro-opiomelanocortin (POMC) neurones activate?
reduced food intake
45
What is also thought to be implicated in appetite regulation?
- endocannabinoids
- AMP (activated protein kinase)
- protein tyrosine phosphokinase
46
What is so advantageous about the arcuate nucleus?
- incomplete blood-brain barrier
- allows access to the peripheral hormones in the plasma
- able to integrate peripheral and central feeding signals
47
What are the 2 different types of neurones in the arcuate nucleous?
```
Stimulatory
- Neuropeptide Y (NPY)
- Agouti-related peptide (Agrp neuron)
Inhibitory
- pro-opiomelanocortin sensitising (POMC neuron)
```
48
Where are NPY/Agrp neurones found?
only in the arcuate nucleus
49
How do NPY/Agrp neurones stimulate food intake?
make peptides that:
- increasing neuropeptide Y signaling
- reducing melanocortin signaling
by AGRP release
50
What is ARGP?
an endogenous melanocortin receptor antagonist
51
What can activate NPY/Agrp neurones?
decrease in:
- leptin
- insulin
52
What conditions cause an increase in food intake by impacting the NPY/Agrp neurones?
- fasting
- uncontrolled diabetes
- genetic leptin deficiency
53
What is the arcuate nucleus involved in?
- feeding
- fertility
- cardiovascular regulation
54
What is the central melanocortin system?
collection of:
- NPY
- AGRP neurones
- POMC
55
What are melanocortins?
products of the POMC
56
What is an example of melanocortin
alpha-MSH
57
What is the role of the central melanocortin system?
central regulator of energy balance
including:
- feeding behaviours
- energy expenditure
58
Where are melanocortin-4 receptors expressed?
paraventricular nucleus
59
What stimulates melanocortin-4 receptors?
serotonin
60
What is the effect of the stimulation of melanocortin-4 receptors?
- reduction of appetite
- weight loss
- reduced food intake
61
What has a encouraging/stimulating effect on melanocortin-4 receptor?
alpha-MSH
62
What has a inhibiting effect on melanocortin-4 receptor?
Agrp
63
What is the effect of Agrp and NPY mutations?
No associated effects to appetite
64
What is the effect of POMC deficiency and MC4-R mutations?
causes morbid obesity
65
What role does the amygdala play?
controls reward related motivation pathways, affects appetite
66
How is neural information from the digestive tract passed on to the hypothalamus?
carried by the vagus to the brain stem and eventually the hypothalamus
67
What is the adipostat mechanism?
- circulating hormones are produced by adipose tissue (more=more hormone)
- sensed by the hypothalamus
- hypothalamus alters neuropeptides to change food intake
68
What produces leptin?
made by:
- adipocytes in white adipose tissue
- enterocytes
69
What does leptin impact?
acts on the hypothalamus to regulate:
- decreases appetite (intake)
- increases thermogenesis (expenditure)
70
Where in the hypothalamus does leptin act?
cell receptors in:
- arcuate nuclei
- ventromedial nuclei
71
What is the role of leptin?
- regulation of adipose tissue mass
| - development of atherosclerosis (innate system)
72
What conditions have been associated with low levels of leptin?
- Alzheimer's disease
| - Depression
73
What happens in congenital leptin deficiency?
RARE
morbid/severe obesity
low serum leptin levels
74
How can congenital leptin deficiency be managed?
leptin to reduce body weight
75
What happens to serum leptin in obesity?
serum leptin concentration is correlated to the body fat %
| - obesity, leptin resistance
76
What is the mechanism of leptin in obesity?
- absent leptin
- leptin resistance
- regulatory defect in leptin (signalling issue)
77
Would leptin be an effective weight control drug?
No, due to leptin resistance
78
What reduces hunger after a meal?
hormonal signalling from the gut
79
What secretes gut hormones?
enteroendocrine cells in:
- stomach
- pancreas
- small intestine
- colon
80
What are the roles of the gut hormones?
- motility regulation
- appetite regulation
- satiety
- salvation
81
What gut hormones regulate appetite?
- Ghrelin
| - Peptide YY (PYY)
82
What is the effect of Ghrelin?
- stimualtes appetite
| - increases gastric emptying
83
What is the effect of Peptide YY?
- inhibits food intake
84
When is Ghrelin highest?
- before meals
- increases gastric motility and acid secretion
- prepares for food
85
What impact does Ghrelin have in the hypothalamus?
- stimulates NPY/Agrp neurones
| - inhibits POMC neurones
86
What does Ghrelin regulate?
- reward
- taste sensation
- memory
- circadian rhythm
87
What rhythm is seen by Ghrelin levels?
diurnal rhythm
88
What does circulating Ghrelin correlate with?
- time of day
| - positive with age
89
What is the physiological role of Ghrelin?
meal initiation
90
Where is Peptide tyrosine tyrosine (PYY) released?
- terminal ileum and colon
| - response to feeding
91
What is the effect of PYY in the hypothalamus?
- stimulates: POMC neurones
| - inhibits: NPY release
92
What types of food trigger PYY release?
- dietary fibres
- wholegrains
- enzymatic breakdown of crude fish proteins
93
What does PPY do?
induces satiety
94
What is the degree of PPY release proportional to?
calorie intake
95
What is the impact of PPY on food/calorie intake?
reduces it
96
What are the side effects of PYY?
- nausea
- fullness
- less hunger
- early fullness
97
What co-morbidities are associated with obesity?
- depression
- stroke
- sleep apnoea
- MI
- hypertension
- diabetes
- bowel cancer
- osteoarthritis
- peripheral vascular disease
- gout
98
Which factors are most dominant in terms of increasing risk of obesity?
environmental factors and genetic predisposition
99
What is polydipsia?
excessive thirst or drinking
100
What is adipsia?
inappropriate lack of thirst
| - consequent failure to drink
101
What is anorexia?
loss/lack of appetite for food
102
What is obesity?
abnormal or excessive fat accumulation that presents health risks
103
What can cause secondary polydipsia?
- chronic medical issues that disrupt any step in osmoregulation or alter ADH
- medications
- dehydration
104
What does ADH do?
regulates the volume and osmolality of urine
105
Where does ADH act?
Aquaporin 2 channel of the collecting duct in the kidneys
106
What happens when ADH is low?
large volume of urine excretion (water diuresis)
107
What happens when ADH is high?
small volume of urine excreted (anti-diuresis)
108
Where is ADH stored?
in the posterior pituitary
109
What chronic medical conditions can cause secondary polydipsia?
- Diabetes Insipidus and Mellitus
- Kidney failure
- Conn's syndrome
- Addison's disease
- Sickle cell anaemia
110
What medications can cause secondary polydipsia?
- diuretics
- laxatives
- antidepressants
111
What chronic medical conditions can cause dehydration?
- acute illness
- sweating
- fevers
- vomiting
- diarrhoea
- underhydration
112
What is the difference between diabetes insipidis and mellitus?
DM: blood sugar
DI: impaired ADH production
113
What are the symptoms of diabetes?
- always tired
- frequent urination
- sudden weight loss
- wounds that don't heal
- sexual dysfunction
- constant hunger
- blurry vision
- numb of tingling peripherals
- constant thirst
- vaginal infections
114
What is Conn's syndrome?
primary aldosteronism
115
What is Addison's syndrome?
hypoadrenocorticism
116
What are the causes of primary polydipsia?
- mental illness
- brain injuries
- organic brain damage
117
What mental illnesses can cause primary polydipsia?
- psychogenic polydipsia
- schizophrenia
- mood disorders (depression and anxiety)
- anorexia
- drug use
118
What can polydipsia cause?
- kidney and bone damage
- headache
- nausea
- cramps
- slow reflexes
- slurred speech
- low energy
- confusion
- seizures
119
What can cause adipsia?
- increased osmolality of urine
- stimulates the secretion of ADH
- water retention
- decreased thirst sensation
120
How many different types of adipsia are there?
4
121
What receptors are used to detect ADH levels?
osmoreceptors
122
What triggers the release of ADH?
- cells shrink when plasma is more concentrated
- proportion of cation channels increases - depolarizing the membrane
- sends signals to the ADH producing cells to increase ADH
- fluid retention that invokes drinking
123
What is an eating disorder?
a mental disorder defined by abnormal eating habits
124
What are some examples of eating disorders?
- binge eating disorder
- anorexia nervosa
- bulimia nervosa
- PICA
- rumination syndrome
- avoidant/restrictive food intake disorder
125
What are the signs of anorexia?
- Low BMI
- continuous weight loss
- amenorrhea
- halitosis
- mood swings
- dry hair
- skin and hair thinning
126
What are the causes of anorexia?
- genetic
- environmental
- psychological
- sociological
127
What is the mechanism of anorexia?
serotonin
128
What BMI would classify anorexia as mild?
>17
129
What BMI would classify anorexia as moderate?
16-16.99
130
What BMI would classify anorexia as severe?
15-15.99
131
What BMI would classify anorexia as extreme?
<15
132
What co-morbidities are associated with anorexia?
- depression
- sleep apnoea
- bowel cancer
- osteoarthritis
- gout
- peripheral vascular disease
- diabetes
- hypertension
- MI
- stroke
133
What is included in a screening for obesity?
- height
- weight
- abdominal girth
- BMI
Medical history
- dietary and physical activity
- psychosocial factors
- weight-gaining medications
- familial traits
134
What is necessary for a classification of obesity?
BMI >/= 30
or
BMI >/= 25 + co-morbidity/risk factor
135
What is involved in the treatment of obesity?
```
Lifestyle modification
- diet
- exercise
Surgical treatment
- gastric bypass
- gastric sleeve
```
136
What is needed to qualify for bariatric surgery for obesity treatment?
BMI >40
or
BMI >35 + co-morbiditiesx
137
What is the effect of GLP1 and GLP2?
- stimulate insulin release
| - inhibit glucagon release
138
What is the effect of ghrelin?
NPY activation to initiate appetite
139
What is the effect of PYY?
- satiety
| - anorexgenic
140
What is the impact of bariatric surgery on Ghrelin?
- decreases
| stomach fills easier/quicker therefore, when full ghrelin inhibition
141
What is the impact of bariatric surgery on GLP1/2 and PYY?
- increases
