Hunger and Thirst Flashcards
1
Q
What is an injestive behavior?
A
eating or drinking
1
Q
What is homeostasis?
A
Process by which substances in the body and characteristics of the body are maintained at an optimal level.
2
Q
What are predictive patterns? How are they useful for homeostasis?
A
- The body will turn hunger “on” before we reach starvation and turn it “off” before we feel satiation because it takes time for nutrients to get to the cells
3
Q
What is a system variable?
A
A variable that is controlled by a regulatory system
4
Q
What is a set point?
A
Optimal value of the system variable
5
Q
What is a regulatory system?
A
System/dispositive that aims to keep a variable near, above, or below a set point
6
Q
What is a correctional mechanism?
A
Mechanism of a regulatory system that can control the regulated system variable
7
Q
What is a negative feedback in a regulatory system?
A
process by which the effect of a correctional mechanism diminishes or terminates further corrective action
8
Q
What type of feedback is involved in the satiety mechanism?
A
negative feedback mechanism
9
Q
What is the satiety mechanism?
A
- negative feedback brain mechanism
- causes cessation of hunger or thirst
10
Q
What is the satiety mechanism associated with?
A
- adequate supply of readily available food and water
- adequate long-term supply of fat
11
Q
When is the satiety mechanism activated?
A
- when food and water are ingested
- before most cells in the body have access to the ingested substances
12
Q
What are the two tpes of thirst?
A
- osmometric thirst
- volumetric thirst
13
Q
What are the steps of the physiological regulatory mechanism of thirst?
A
1) Body loses water
2) Detectors signal loss of water
3) Drinking occurs
4) Stomach fills with water
5) Stomach sends signals to brain
6) Satiety mechanism inhibits further drinking
7) Water is absorbed: body fluid levels go back to normal
14
Q
What occurs when a person ingests salt?
A
- the interstitial fluid becomes very salty
- cells lose water to the hypertonic interstitial solution
- cells shrink in size
15
Q
What is tonicity?
A
relative concentration of dissolved solutes on either side of a membrane that is permeable to water, that allows you to describe the direction and amount of water flow across the membrane
16
Q
What is an isotonic solution?
A
- similar concentration of solutes on either side of a membrane
17
Q
What is the movement of water in a case where you have an isotonic solution?
A
- No movement of water
18
Q
What is the movement of water in a hypotonic solution?
A
- Water enters the cell
19
Q
What is a hypertonic solution?
A
- solute is more concentrated insed the cell than out
20
Q
What is a hypertonic solution?
A
- solute more concentrated outside the cell than in
21
Q
What is the movement of water in a hypertonic solution?
A
- water exits the cell, which shrinks the size of the cell
22
Q
What is osmometric thirst?
A
- thirst caused by the shrinking of cells that dehydrate due to a hypertonic interstitial fluid
23
Q
What are osmoreceptors?
A
neurons that detect changes in cell size and react to them
24
What is the reaction of osmoreceptors to changes in cell size?
- change in membrane potential
- release of neurotransmitters
25
What is volumetric thirst?
thirst that occurs in cases of hypovolemia
26
What is hypovolemia?
There is not enough blood circulating through the body
27
What hormone is released when there is not enough blood in the body?
renin
28
What signaling molecule tells the brain that there is not enough blood in the body?
angiostensin
29
What organ is responsible for monitoring the amount of blood in the body?
the kidneys
30
What is the difference between the signaling of osmometric thirst and volumetric thirst?
Osmometric thirst is linked to the firing of action potentials through neurons, whilst volumetric thirst is linked to a hormonal cascade initiated by the kidneys
31
What region of the brain is activated to signal volumetric thirst? What activates this region of the brain?
- activation of hypothalamic neurons near the anteroventral tip of the third ventricle
- angiotensin
32
What region of the brain is linked to osmometric and volumetric thirst?
The AV3V region
33
What are the two regions of the brain that show activation in cases of thirst?
- AV3V
- Anterior cingulate cortex
34
how are nutrients made accessible to the body?
- interstitial fluid
35
Where are situated osmoreceptors?
AV3V region of the brain
36
What composes the rapid feedback drinking mechanism?
- cold sensors in the mouth
- sensory fibers in the stomach
37
What is the effect of the rapid feedback drinking mechanism?
Reduces activity in the anterior cingulate cortex
38
What does the pancreas detect?
blood glucose levels
39
What happens when blood glucose levels are high?
pancreas releases insulin
40
What occurs after the pancreas releases insulin?
the liver and muscles store glucose as glycogen
41
What happens when blood sugar levels are low?
pancreas releases gluagon
42
What happens when the pancreas releases glucagon?
Liver and muscles convert glycogen back into glucose
43
What is glycogen broken down into?
- triglicerids
- fatty acids
44
What is the difference between the glucose consumption of cells outside the brain and cells inside the brain?
- cells outside the brain have a glucose transporter that is only functional in the presence of insuline, so they can only use glucose in the blood if it is in excess levels
- cells within the brain have a glucose transporter that works in the absence of insulin
45
When is glucagon released?
Low blood sugar levels
46
When is insulin released?
high blood sugar levels
47
What is the animal short-term soure of nutrients?
glycogen
48
Where is glycogen stored?
- liver
- muscle cells
49
What are the functions of insulin?
- facilitates entry of glucose in cells for immediate use
- facilitates conversion of glucose into glycogen for short-term storage
- facilitates the storage of fatty acids in adipose tissue for long-term storage
50
What are the two pancreatic hormones?
- glucagon
- insuline
51
What are the functions of glucagon?
- promotes conversion of liver glycogen into sugar for immediate use
- promotes conversion of adipose triglycerides into fatty acids
52
What is the difference between glycogen and adipose tissues?
- glycogen is for short-term storage and made of glucose
- adipose tissue is for long-term storage and made from fatty acids
53
What are triglycerides?
- form of fat storage in adipose cells that constitute our long-term store of nutrients
54
What is the composition of a triglyceride molecule?
1 glycerol + 3 fatty acids
55
What is the role of the anterior cingulate cortex?
The anterior cingulate cortex receives information from the cold sensors as well as the fibers in the stomach, which then determines the presence of water and creates a preventive reaction and stops thirst before water actually penetrates the cells
56
What induces hunger?
- ghrelin
- duodenum
57
What is ghrelin?
- peptide hormone
- indicates hunger
58
When is ghrelin released?
- a little before the body runs out of nutrients
OR
- at a learned meal time
59
What is the duodenum?
first portion of the small intestine
60
What is the role of the duodenum in hunger regulation?
the presence or absence of food in the duodenum regulates the release of ghrelin from the stimach
61
When are the long term satiety signals released?
directly after the ingestion of food
62
What are the short term satiety signals sent by the stomach?
- CCK
- GLP-1
63
What is the impact of the injection of CCK?
People eat less at a time, but more meals
64
What is the impact of the injection of GLP-1?
long term weight loss and decreased appetite
65
Other than the regulation of satiety, what is the role of CCK?
causes the gallbladder to release enzymes in the duodenum
66
Other than the regulation of satiety, what is the role of GLP-1
Causes the secretion of insulin from the pancreas
67
Is the release of satiety signaling hormones an anticiaptory process?
Yes, digestion is a long process
68
How do we come to feel satiety from hunger?
- two wave process
- includes an anticipatory and a post-digestion mechanism
69
What is the first portion of the satiety feedback mechanism
- CCK
- GLP-1
70
What is the post-digestion mechanism?
- includes liver and pancreas
71
What is the role of the liver in the signaling of satiety?
- measures glucose and free fatty acid levels in the blood
- sends signaling through the 10th cranial nerve
72
What is the role of the pancreas in the signaling of satiety?
- secretes insuline
73
What is the role of insuline in the sentiment of satiety?
- detected by neurons in the hypothalamus that reduce the feeling of hunger
74
What is the long-term satiety mechanism?
homeostatic regulation of feeding
75
What is the homeostatic regulation of feeding?
- leptin is secreted by adipocytes
76
What are the effects of leptin?
- negative feedback signaling that reduces hunger
- increases the sensitivity of hypothalamic neurons to short-term satiety signals
77
What is congenital leptin deficiency?
the body cannot produce leptin, so it constantly thinks it is starving
78
When are the emergency hunger circuits activated?
when there is a specific critical need to either eat or not eat
79
What are the two types of emergency hunger circuits?
- glucoprivation
- lipoprivation
80
What causes glucoprivation?
- very low blood sugar levels
81
What detects glucoprivation?
- liver
- pancreas
- brainstem
82
What detects lipoprivation?
- Hypothalamus (lack of leptin)
- liver
83
What causes lipoprivation?
- dangerously low levels of fatty acids
84
What are the effects of hypoglycemia?
- suppresses insulin secretion
- triggers glucose production in the liver
- slows down basal metabolic rate
- intense and sustained feeling of hunger
85
What are the effects of lipoprivation?
same as for low blood sugar
86
What causes hyperglycemia?
disruption in insulin signaling that prevents the body from storing glucose as glycogen
87
What are the effects of hyperglycemia?
- high blood sugar
- weight loss => low leptin => extreme hunger
- dehydration (hypertonic interstitial solution
88
What area of the brain is associated with hunger and satiety?
Arcuate nucleus of the hypothalamus
89
What neurons are associated with promoting hunger?
AGRP neurons
90
What neurons are associated with inhibiting hunger?
POMC neurons
91
What neurons does leptin inhibit?
AGRP neurons
92
What neurons does leptin promote?
POMC neurons
93
What neurons does ghrelin promote?
AGRP neurons
94
What neurons does ghrelin inhibit?
POMC neurons
95
Where do AGRP and POMC neurons fire?
Paraventricular nucleus of the hypothalamus
96
What is the main role of the paraventricular nucleus of the hypothalamus?
signaling intense hunger due to a lack of leptin signaling
97
What causes the Prader-Willis syndrome?
insufficient presence of oxytocin neurons in the paraventricular nucleus of the hypothalamus, which prevents from ever feeling satiated
98
Why does hunger have a hedonistic aspect?
neurons in the medulla and hypothalamus release neuropeptides throughout the brain that influence dopamine neuronal activity
99
What is particular about obese person's sensitivity to leptin?
- they are less sensitive, as it seems that they have a more elevated leptin set point
- reduced ability for leptin to cross the blood-brain barrier
- reduced response from hypothalamic neurons to leptin signaling
100
What is the observed difference in brain anatomy in obese animals?
inflammation in the hypothalamic arcuate nucleus
101
What is the purpose of bariatric surgery?
reduce the amount of food that can be eaten during a meal
102
What is the most common method of performing bariatric surgery?
severing of the jujenum
103
What are the effects of bariatric surgery?
reduction of hunger (alters the release of gastric hunger and satiety signals)
