Topic 5 - Hormones & Homeostasis Flashcards
(169 cards)
1
Q
What is the hormone which helps us regulate blood sugar levels?
A
Insulin
2
Q
What are the two types of diabetes and what are their causes?
A
- Type 1 diabetes - caused by an autoimmune disorder
* Type 2 diabetes - caused by obesity
3
Q
In type 1 diabetes, how much insulin does the body produce?
A
Little/virtually none
4
Q
In type 2 diabetes, how much insulin does the body produce?
A
Normal/above normal
5
Q
In a healthy person, what are the three main factors which help maintain a normal blood sugar balance?
A
- Type of food eaten (amount of glucose ingested)
- The pancreas releases insulin which reduces blood glucose levels
- The liver releases stored glucose into the blood as needed to provide energy
6
Q
Which ethnic groups have higher risks of developing diabetes?
A
People of South Asian, African-Caribbean and Native American descents
7
Q
How many people (in 2014) did the WHO estimate to have diabetes?
A
422 million
8
Q
In respect to genetics, what is programming hypothesis?
A
The idea that stresses during pregnancy (eg undernutrition, exposure to toxins/disease) can predispose the offspring in later life to certain conditions (eg high blood pressure/type 2 diabetes)
9
Q
What happens if there are excessive amounts of glucose in the body?
A
There can be irreversible damage to proteins in the body which will affect their functions
10
Q
What is glycation?
A
Covalent bonding of sugars to proteins
11
Q
What are advanced glycation end products, or AGEs?
A
Damaging molecules which are due to persistently high blood sugar levels
12
Q
Under what circumstances and how are AGEs (advanced glycation end products) produced?
A
- When there are persistently high blood sugar levels
* Sugars covalently bond to proteins
13
Q
What parts of the body can AEGs (advanced glycation end products, the result of persistently high blood sugar) damage?
A
- Blood vessels
- Tissues
- Organs
- Nerves
- Kidneys
- Eyes
- Heart
14
Q
What type of hormone is insulin?
A
A polypeptide
15
Q
What is a polypeptide?
A
Short chains of amino acids
16
Q
What are the three stages of insulin production?
A
- Pre-pro-hormone
- Pro-hormone
- Insulin
17
Q
What does insulin consist of?
A
The chain A and chain B components of pre-pro-insulin
18
Q
What connects the chain A and chain B components of insulin?
A
- Two disulfide bonds
* Chain A also has a third disulfide bond for additional stabilisation
19
Q
How many more amino acids does insulin have than pre-pro-insulin?
A
59
20
Q
How do beta cells sense the intracellular concentration of ATP?
A
With their potassium channel
21
Q
Are the potassium channels open or closed if ATP concentration is high?
A
Closed
22
Q
Do beta cells require insulin in order to be able to uptake glucose from blood?
A
No
23
Q
How is the level of glucose in beta cells determined?
A
By the concentration of glucose in the blood
24
Q
Which two processes convert glucose into ATP?
A
Glycolysis and the TCA cycle
25
What kind of channel do beta cells have?
A potassium channel
26
What happens to the membrane potential of a beta cell when a potassium channel opens?
The cell becomes more negative due to potassium ions (which are positively charged) leaving the cell
27
Are potassium ions positively or negatively charged?
Positively
28
What is the term for what happens to the charge of a beta cell when the potassium channel is open and ions have left the cell?
Hyperpolarisation
29
What are the first steps involved in the synthesis of a polypeptide?
DNA is transcribed to mRNA, then translated into a polypeptide chain
30
What is a pre-pro-hormone?
An inactive peptide precursor of an inactive pro-hormone
31
What is a pro-hormone?
An inactive peptide precursor of an active peptide hormone
32
What causes the calcium channels in beta cell membranes to close?
Hyperpolarisation of the membrane and an intracellular decrease in calcium concentration
33
Can insulin cross the cell membrane, and why not?
No, because it is a water-soluble polypeptide
34
What kind of receptors does insulin activate?
Tyrosine kinase receptors
35
What is a kinase?
A protein which modifies the actions of other proteins
36
How does a kinase perform its function?
It adds a phosphate group to proteins
37
What is the term for the action of kinase?
Phosphorylation
38
What is a dimer?
A molecule/molecular complex consisting of two molecules of the same type linked together
39
How can glucose enter cells?
By glucose transporter proteins (GLUT)
40
How are glucose transporter proteins regulated?
By the activation of insulin receptors
41
Under what conditions can glucose transporter proteins actually transport glucose into the cell?
If insulin receptors are stimulated
42
Where are glucose transporter proteins located within the cell?
In vesicles within the cytosol
43
How does insulin affect the storage of glycogen?
Activated insulin receptors stimulate the synthesis of glycogen from glucose and inhibit the breakdown of glycogen into glucose
44
What does hyperpolarisation mean?
A change to the cell membrane which makes it more negative
45
What happens if there is an insufficient intake of iodine?
Levels of TSH and TRH will increase
46
What does excessively high levels of TSH cause, and what is a common symptom of this?
* Hypothyroidism
| * A goitre
47
What condition can extreme iodine deficiency, especially if in early life, cause and what are the symptoms?
* Cretinism
* Poor physical development
* Learning deficiencies
48
What is glycogenesis?
The process where cells in the muscles/liver convert glucose to glycogen so that it can be stored
49
What is lipogenesis?
The process which synthesises fats and carbohydrates which can be then stored as adipocytes or in the liver (literally, ‘creating fat’)
50
What are insulin’s functions?
* To enable cells to take up glucose
* Promote synthesis of molecules to store energy for later
* Promote feelings of satiety
51
Where are the endocrine cells in the pancreas located?
Islets of Langerhans
52
Does the pancreas have an endocrine or exocrine role within the body?
Both
53
Does the pancreas’ endocrine or exocrine system relate to the regulation of blood glucose?
Endocrine
54
Of all the complications diabetes usually causes, which two cause the majority of issues?
Poor blood supply and nerve damage (which can be due to poor blood supply)
55
What are some of the areas of the body which suffer complications due to diabetes?
* Neurological system
* Vision
* Hearing
* Cardiovascular system
56
What is the HP axis?
The hypothalamic-pituitary axis
57
What does the HP axis do?
It is a signalling mechanism involving the hypothalamus and pituitary glands, which regulate the endocrine glands and certain body tissues
58
What is thyrotropin-releasing hormone, TRH, and what does it do?
A peptide neurohormone which stimulates the thyroid gland to produce thyroxine
59
What is thyroid-stimulating hormone, TSH, and what does it do?
It stimulates production of thyroid hormones, which increase metabolic rate and heat
60
Are T3 and T4 hydrophobic or hydrophilic?
Hydrophilic
61
Name the tissues/organs which are affected by thyroid hormones?
* All cells
* Liver
* Adipose tissue
* Lungs
* Heart
62
How do thyroid hormones affect the liver?
* They increase it's ability to generate glucose
| * They also inhibit further production of glycogen from glucose (enhances efficiency of glucose release)
63
What condition is a common result of iodine deficiency?
An enlarged thyroid, which can cause a goitre to grow
| Hypothyroidism (insufficient thyroid hormone production)
64
What can chronic thyroid deficiency cause?
Cretinism (especially if the deficiency was in early life)
65
What is cretinism?
An impairment of growth and mental development
66
What can cause increased production/secretion of thyroid hormones?
TSI - thyroid-stimulating immunoglobulins
67
How do TSIs effect the body?
* They bind to TSH receptors, mimicking its effects
* This causes excessive amounts of TSH to be secreted into the blood (because TSI levels are not under the control of the HP axis)
68
What condition can TSIs cause?
Graves' Disease
69
What is one of the more common symptoms of Graves' Disease?
Bulging eyes
70
What is the name of the condition when blood calcium levels are high?
Hypercalcaemia
71
What hormone is released in response to high blood calcium levels?
Calcitonin
72
What do water-soluble peptide hormones bind to?
Surface receptors
73
What does calcitonin target?
A class of cell called osteoclasts
75
What is the difference between osteoblasts and osteoclasts?
* Osteoblasts help build bone
| * Osteoclasts destroy bone
76
Why does calcitonin target osteoclasts?
Osteoclasts destroy bone. Calcitonin inhibits their activity, which means that the bone is free to uptake as much calcium from the blood as it wants
77
Where is the parathyroid gland located?
Behind the thyroid
78
What is the main regulatory hormone of blood calcium levels?
Parathyroid hormone
78
How does parathyroid hormone work?
It increases calcium reabsorption, increases calcium release from bone and increases absorption of dietary calcium
78
What is required in order to raise blood calcium levels?
Parathyroid hormone and the active form of VitD in the blood (calcite ion)
79
What is the condition which triggers the release of parathyroid hormone and when does it occur?
* Hypocalcaemia
| * When blood calcium levels are low
80
What do lipophilic peptide hormones bind to?
Intracellular receptors
81
What are the two main ways hormones can be classified?
Hydrophilic or hydrophobic
82
What do all neurohormones use as their building blocks?
* Amino acids
| * Dopamine uses catecholamine but this is derived from the amino acid tyrosine
83
What do alpha cells secrete?
Glucagon
84
What do beta cells secrete?
Insulin
85
If ATP levels are high, what state will the potassium channels be in?
They will be closed
86
What triggers the ATP-sensitive potassium channels in beta cells to open?
Falling cellular levels of ATP, which is triggered by blood glucose levels dropping
87
What triggers the voltage-sensitive calcium channels in beta cells to open?
Partial depolarisation of the cell membrane
88
What triggers insulin to be released into the blood?
An increase in intracellular calcium concentration
89
What is meant by the term ‘endocrine’?
Relating to or denoting glands which secrete hormones or other products directly into the blood
91
As well as cortisol, which other hormone is also involved in increasing blood glucose levels and where is it released from?
Glucagon, released from pancreatic alpha cells
92
What are the names of the two types of thyroid hormones?
| What are their abbreviations?
* Thyroxine (T4)
| * Triiodothyronine (T3)
93
What are the names of the two pancreatic hormones?
* Insulin
| * Glucagon
94
How does the digestive tract absorb iodine from the diet?
In the form of iodide
95
What is iodide trapping?
The storage of iodide which has been transported from a blood capillary to its adjacent follicular cell
96
Which oxidative enzyme aids iodide ions in forming iodine?
Thyro-peroxidase
97
Of the two thyroid hormones (thyroxine (T4) and triiodothyronine (T3)), which is the more physiologically active?
Triiodothyronine (T3)
98
Approximately how much of secreted hormone from the thyroid gland does T4 account for?
70 - 75%
99
Are the thyroid hormones hydrophilic or hydrophobic?
Hydrophobic
100
How are the thyroid hormones transported in the blood?
Most are blood bound to carrier proteins
101
How do thyroid hormones alter cell function?
By interacting with the DNA in the nucleus
102
How do pancreatic hormones alter cell function?
They activate signalling cascades that involve the activation of protein kinases and the generation of second messenger molecules
103
Which part of the brain regulates the levels of thyroid hormones circulating in the blood?
* The hypothalamus
| * The pituitary gland
104
What is the HP (hypothalamic-pituitary) axis>
A signalling mechanism which involves the hypothalamus and pituitary gland, which together regulate the other endocrine glands and certain body tissues
105
Axons in the anterior lobe of the pituitary gland release their neurohormones where?
Into the blood vessels supplying the anterior lobe
106
Axons extending into the posterior lobe of the pituitary gland secrete their neurohormones where?
Directly into the blood supplying the body
107
What detects falling blood levels of thyroid hormones?
TRH (thyrotropin-releasing hormone, a peptide neurohormone)
108
What is the name of the hormone secreted by the anterior pituitary gland into the blood?
TSH (thyroid-stimulating hormone, a peptide neurohormone)
109
What is the purpose of TSH (thyroid-stimulating hormone)?
To stimulate the production and secretion of T3 and T4, in order to increase metabolic rates and generate heat
110
What is the purpose of TRH (thyrotropin-releasing hormone)?
It stimulates the production and secretion of TSH and prolactin
111
How might an increase in the levels of circulating thyroid hormones counteract exposure to cold?
Thyroid hormones increase the body's metabolism, which includes an increase in the rate of ATP production. This in turn increases the rate at which ATP is consumed and liberates heat to help maintain body temperature
112
Which process of metabolic reaction consumes most of the ATP generated in a cell?
The sodium/potassium pumps which maintain the ionic gradients between the inside and outside of the cell
113
What actions can thyroid hormones have on all tissues/organs?
* Increase metabolic rate
* Increase glucose uptake
* Increase the activity of the sodium-potassium pumps
* Increase proteins involved in the TCA cycle
* Increase beta-adrenergic receptors
114
What actions can thyroid hormones have on liver tissues/organs?
* Increase glycogenolysis
* Increase glucogenisis
* Decrease glycogenisis
115
What actions can thyroid hormones have on adipose tissue?
* Increase lipolysis
| * Decrease lipogenisis
116
What actions can thyroid hormones have on lung tissue?
* Increase respiration rate
117
What actions can thyroid hormones have on heart tissue?
* Increase heart rate
| * Increase force of contraction
118
What is the overall effect which thyroid hormones have on the liver?
They increase the liver's ability to generate glucose to fuel the needs of the body, either from the breakdown of glycogen into glucose, or the production of glucose from non-carbohydrate molecules such as amino acids, lactate and fatty acids
119
How might a lack of iodine affect homeostatic function of the thyroid gland?
It will have an effect on the production of T3 and T4. This reduction will in turn cause the hypothalamus and anterior pituitary gland to produce excessive levels of TRH and TSH in an attempt to stimulate the thyroid gland to produce/secrete more thyroid hormones
120
What bodily effect can high levels of circulating TSH cause?
The thyroid gland to grow, often forming a goitre
121
How can the binding of TSH (thyroid-stimulating) hormone to its receptors on the cells of the thyroid gland be disrupted?
By thyroid-stimulating immunoglobulins (TSIs)
122
What are TSIs (thyroid-stimulating antibodies)?
| How do they affect thyroid hormones?
* Antibodies produced by the immune system which also stimulate the thyroid gland
* They bind to TSH receptors, which mimicks the effects of TSH
123
What is the name of the condition caused by TSIs?
Graves disease
124
What micronutrient is the thyroid gland also involved in the regulation of?
Calcium
125
What is hypercalcaemia?
High blood calcium levels
126
What is the peptide hormone related to calcium which the thyroid gland can relase?
Calcitonin
127
What is calcitonin?
A hormone secreted in the thyroid gland in response to high levels of blood calcium
128
What are osteoblasts?
Cells which incorporate calcium into new bone
129
What are osteoclasts?
Cells which destroy bone
130
What is parathyroid hormone?
A hormone secreted by the parathyroid gland in response to low blood calcium
131
What is parathyroid hormone's effect on the body?
It acts on the kidney tubules to increase calcium reabsorption and also increases calcium release from bone and the activation of vitamin D to increase absorption of dietary calcium
132
Which hormone is released, and from which gland, to reduce calcium levels
* Calcitonin
| * The thyroid gland
133
What is required in the blood to raise calcium levels?
* Parathyroid hormone
| * The active form of vitamin D
134
What body functions does the pineal gland regulate?
* Regulation of sleep
| * The body clock
135
What body functions does the hypothalamus regulate?
The endocrine system which regulates other endocrine tissues within the body
136
What body functions does the pituitary gland regulate?
* Metabolic rate
* Growth and development
* Fertility and reproduction
* Stress
137
What body functions does the thyroid gland regulate?
* Metabolic rate
| * Calcium homeostasis
138
What body functions does the parathyroid gland regulate?
Calcium homeostasis
139
What body functions does the stomach regulate?
* Gastric acid production
| * Feelings of hunger
140
What body functions does the liver regulate?
* Growth
* Blood pressure
* Production of platelets
141
What body functions do the adrenal glands regulate?
Acute/chronic stress responses
142
What body functions does the pancreas regulate?
Blood glucose levels
143
What body functions do the kidneys regulate?
* Erythrocyte production
| * Calcium homeostasis
144
What body functions does the duodenum regulate?
Digestive processes
145
What body functions does adipose tissue regulate?
Satiety
146
What body functions do the ovaries regulate?
* Sexual development
* Fertility
* Reproduction
147
What body functions do the testes regulate?
* Sexual development
| * Fertility
148
What are the two broad groups which hormones can be classified into?
* Water-soluble (hydrophilic)
| * Fat-soluble (hydrophoblic/lipophilic)
149
Can water-soluble hormones easily diffuse across cell membranes?
No
150
Can lipid-soluble hormones easily diffuse across cell membranes?
Yes
151
Which are the catecholamine hormones that are synthesised from the amino acid tyrosine?
* Adrenalin
* Noradrenalin
* Dopamine
152
Aside from catecholamines, what other class of hormones are synthesised from tyrosine?
Thyroid hormones
153
What is the parent molecule which all steroid hormones in humans are derived from?
Cholesterol
154
How does cholesterol influence the properties of the plasma membrane?
It maintains the fluidity of the plasma membrane
155
How many rings of fused carbon do all the steroid hormones have?
Four
156
Which are the three main glands where steroid hormones are synthesised?
* The adrenal gland (cortex)
* Testes
* Ovaries
157
What are eicosanoids?
Hormones synthesised from fatty acids found in the plasma membrane
158
How do eicosanoids exert their action?
They activate membrane receptors coupled to G-proteins
159
Are eicosanoids classed as water or lipid-soluble hormones?
Water-soluble
160
What effects can eicosanoids mediate?
* Pain
* Inflammation
* Fever
* Immune response
* Cell growth
* Blood pressure
161
Which common drug works by preventing the production of eicosanoid hormones?
Aspirin
162
Which gas can act as a hormone?
Nitric oxide
163
What role does nitric oxide play within tissues?
It is critical to the process of regulating blood flow within tissues
164
In which part of the tissue is nitric oxide produced?
The endothelial cells that line the blood vessels
165
Which amino acid is used in the production of nitric oxide?
Arginine
166
What effect does nitric oxide have on tissues?
It causes nearby vascular smooth muscle to relax, increasing blood flow in the surrounding tissue
167
Which group of people produce more nitric oxide, particularly in the lungs?
Those who live at high altitudes
168
Particularly with regards to homeostasis, what is positive feedback?
A cyclic feedback loop which acts on itself to increase the activity that initiated the feedback, producing ever-increasing levels of activity
169
Which biological process is an example of a positive feedback system?
Childbirth; high levels of oxytocin in the blood cause the uterus to contract with ever-increasing frequency. This process of positive reinforcement continues until the baby is born, when the stimuli to signal further release of oxytocin stop
