Endocrine System Flashcards
(158 cards)
1
Q
Define homeostasis?
A
The presence of a stable internal environment
2
Q
The normal range of a given variable is specific to…
A
each individual
3
Q
Is the population reference range tending to be wider or thinner than an individual’s range?
A
Wider
4
Q
Can an individual’s normal range move out of the population range?
A
Yes
5
Q
True or False?
An individual cannot experience symptoms if outside of the population reference range.
A
False
6
Q
What is the synaptic (or neural) system?
A
involves endocrine gland cells that secrete hormones that are carried in the bloodstream to act on target cells.
7
Q
Is the synaptic system slow or fast?
A
Slow but produces long responses that are widespread.
8
Q
What are hormones?
A
chemical messengers that are produced in one location and travel to the target cell via the bloodstream to cause a repsonse.
9
Q
What can hormones act upon?
A
cells that have specific receptors to the hormone either in the target cell membrane or inside the target cell.
10
Q
What is the chemical classification of water-soluble hormones?
A
Peptides (75%) and catecholamines
11
Q
What is the chemical classification of lipid-soluble hormones?
A
Steroids, thyroid hormones
12
Q
What is the storage for water-soluble hormones?
A
Stored until required
13
Q
What is the storage for lipid-soluble hormones?
A
Made when required
14
Q
What is the transport system for water-soluble hormones?
A
Dissolved in the blood
15
Q
What is the transport system for lipid-soluble hormones?
A
Bound to a carrier protein in the blood.
16
Q
Where is the receptor location for water-soluble hormones?
A
Cell membrane
17
Q
Where is the receptor location for lipid-soluble hormones?
A
Intracellular – in cytoplasm or nucleus
18
Q
What is the response speed for water-soluble hormones?
A
Rapid
19
Q
What is the response speed for lipid-soluble hormones?
A
Slow
20
Q
What is the mechanism of action for water-soluble hormones?
A
- Hormone binds to a receptor on the target cell membrane, activating an associated G-protein.
- The G-protein either activates/inhibits adenylyl cyclase or increases intracellular Ca2+.
- A 2nd messenger is produced or reduced.
- Downstream proteins/pathways are either activated or deactivated.
21
Q
What is the mechanism of action for water-soluble hormones?
A
Before acting, lipid-soluble hormones must dissociate from a carrier protein.
- Hormone diffuses across the cell membrane and binds to an intracellular receptor.
- hormone-receptor complex acts as a transcription factor.
- A target gene is activated and transcribed to make mRNA.
- mRNA is translated to make a new protein.
- This protein mediates a cell-specific response.
22
Q
What does the amount of hormone in the blood depend on?
A
Hormone secretion and the rate of removal from the blood
23
Q
What leads to endocrine disorders?
A
if hormone levels are not controlled
24
Q
What is negative feedback?
A
The maintenance of a function when it exceeds the normal range
25
What is the pancreas?
exocrine gland due to its pancreatic acini cells that secrete digestive enzymes and is also an endocrine gland due to its pancreatic islets
26
What are pancreatic islets?
contains beta cells and alpha cells
27
What do beta cells secrete?
insulin
28
What do alpha cells secrete?
glucagon
29
What should blood glucose concentration be?
between 70 and 110 mg dL-1
30
What are the 2 metabolic states that individuals move between?
Fed state and fasting state
31
What is the fed state?
cellular uptake of nutrients, anabolic metabolism – glycogen, protein and fat synthesis.
32
What is the fasting state?
mobilisation of nutrients, catabolic metabolism – glycogen, protein and fat breakdown.
33
What is the function of insulin?
Increase fuel storage
34
What is the function of glucagon?
Increase fuel release
35
What is Secreted in response to insulin?
Increased blood glucose concentration
36
What is Secreted in response to glucagon?
Decreased blood glucose concentration
37
What is secreted by insulin?
Pancreatic islet beta cells
38
What is secreted by glucagon?
Pancreatic islet alpha cells
39
What influence does insulin have on the liver?
Glucose output stops, increased net glucose uptake
| Glycogen and fat synthesis
40
What influence does glucagon have on the liver?
Increased breakdown of glycogen
| Increase glucose and ketone synthesis
41
What effect does insulin have on muscles cells?
Increased glucose uptake
| Increased amino acid uptake, glycogen and protein synthesis
42
What effect does insulin have on adipose cells?
Increased glucose uptake and fat synthesis
43
What is the overal effect of insulin?
Decreased blood glucose concentration
44
What is the overall effect of glucagon?
Increased blood glucose concentration
| Increased blood ketones concentration
45
What is the pituitary gland?
found attached to the hypothalamus, inferior to the brain, and has posterior and anterior lobes
46
What does the hypothalamus control?
pituitary secretion of hormones via neural and hormonal input
47
What are pituitary hormones?
act on target cells or stimulate secretion of further hormones by other glands.
48
What is the connection to the hypothalamus for the posterior pituitary?
Via neurons whose axons extend into the pituitary
49
What is the connection to the hypothalamus for the anterior pituitary?
Via blood vessels
50
What is the hormone synthesis posterior pituitary?
Made in neuron cell bodies in the hypothalamus
51
What is the hormone synthesis and storage for the posterior pituitary?
pituitary
52
What is the storage for the posterior pituitary?
stored in axon terminals in the pituitary
53
What is the storage for the anterior pituitary?
pituitary
54
What is the action of the hypothalamus on the gland for the posterior pituitary?
Neural communication to stimulate hormone release
55
What is the action of the hypothalamus on the gland for the anterior pituitary?
Endocrine communication using releasing hormones to stimulate or inhibit hormone release by binding to cell membrane receptors.
56
What is the travel of hormones for the posterior pituitary?
Blood vessels
57
What is the travel of hormones for the anterior pituitary?
Blood vessels
58
What is an example of a (peptide) hormone for the posterior pituitary?
```
Antidiuretic hormone (kidney water reabsorption)
Oxytocin (uterine contraction, release of breast milk)
```
59
What is an example of a (peptide) hormone for the anterior pituitary?
Prolactin
| Growth hormone
60
What is the anterior pituiatary?
releasing hormone stimulates pituitary hormones which stimulate another hormone
61
What is the growth hormone directly act on?
muscle, liver and fat cells
62
What does growth hormone stimulate?
protein synthesis
63
What does growth hormone inhibit?
glucose uptake in muscle cells, glucose synthesis in liver cells and triglyceride breakdown in fat (adipose) cells
64
What does growth hormone promote?
promotes bone, muscle and other tissue growth by causing the release of Somatomedin C (a hormonal growth factor) that promotes cell division
65
When is the growth hormone at its highest conc?
During sleep and in a lifetime as a child
66
Where is the growth hormone released from?
the anterior pituitary gland in response to growth hormone-releasing hormone (GR-RH)
67
Where is a growth hormone-releasing hormone (GR-RH) released from?
GHRH neurons in the hypothalamus.
68
What is growth hormone inhibited by?
the release of growth hormone inhibiting hormone (GH-IH or somatostatin - SS)
69
What is the release of growth hormone inhibiting hormone (GH-IH or somatostatin - SS) released by?
somatostatin neurons in the hypothalamus.
70
Where is the thyroid gland located?
inferior to the larynx and covers the anterior and lateral surfaces of the trachea.
71
What is the thyroid gland composed of?
Spherical sacs called follicles, which are surrounded by follicular cells that function to synthesise thyroid hormones. Clear cells are clustered in the gaps between follicles and function to synthesise calcitonin
72
What is the thyroid hormone?
a hormone essential for metabolic activity.
73
What hormone is involved in calcium homeostasis?
Calcitonin
74
What is thyroglobulin (TGB) made up of?
thyroid follicles
75
What does iodine react with when it enters the blood?
tyrosine
76
What does iodine reacting with tyrosine form?
thyroid hormone
77
What does the thyroid hormone do when it is needed?
detach from TGB and travel bound to a carrier protein to target cells
78
What are the 2 types of thyroid hormones?
T3 – the active form, and T4 – the more plentiful form
79
What is the action of T3?
First must detach from a carrier protein in the blood
1. Enters target cell and binds to a T3 receptor (bound to a specific DNA site) in the nucleus.
2. Specific genes are activated to transcribe mRNA.
3. mRNA translation occurs in the cytoplasm, synthesising specific proteins (e.g. Na+/K+ pump).
80
What is the response time for T3?
45 minutes - days
81
What is the basal metabolic rate?
the body’s energy expenditure when the person is under basal conditions
82
What are the basal conditions?
* awake
* physical and mental rest
* lying down
* not moving
* at a comfortable temperature
* fasted (12-18 hours)
83
What is thyroid hormone needed for?
normal growth, alertness and metabolism
84
What are the effects of thyroid hormone on a person metabolism?
* Increases body heat production.
* Stimulates fatty acid oxidation in a variety of tissues.
* Increases proteolysis, mostly from muscle.
* Stimulates carbohydrate metabolism, enhances insulin-dependent entry of glucose into cells, increases gluconeogenesis and glycogenolysis.
85
What does calcium do in the body?
can enter the blood from our diet via absorption by the digestive tract, can be reabsorbed by the kidneys and by osteoclasts in bone
86
How can calcium be lost from the body?
faeces, urine, or can be deposited into the bone by osteoblasts
87
What hormones are involved in calcium regulation?
PTH, calcitriol and calcitonin
88
where are the parathyroid glands found?
posterior aspect of the thyroid gland
89
What do parathyroid glands secrete?
parathyroid hormone
90
How is the release of PTH altered?
increased when plasma Ca2+ concentration is low and decreased when it is high.
91
What does PTH release lead to?
increased bone breakdown and kidney Ca2+ reabsorption, thus leading to increased plasma Ca2+ levels.
92
What does PTH stimulate?
conversion of vitamin D to calcitriol, which further stimulates bone breakdown and kidney reabsorption, as well as increasing intestinal Ca2+ reabsorption.
93
What can bone breakdown be stimulated by?
calcitonin
94
where are the adrenal glands situated?
the superior aspect of each kidney
95
What are the 3 layers that secrete steroid hormones?
1. Outer layer – aldosterone
2. Middle layer – cortisol
3. Inner later – androgens
96
What is the adrenal medulla?
innermost region of the glands
97
What does the adrenal medulla secrete mostly?
adrenaline
98
When is noradrenaline secreted?
as part of the sympathetic nervous system response to stress
99
Is adrenaline water-soluble?
yes - thus binds to cell membrane receptors and acts via a second messenger to cause a fast cellular response
100
What happens when adrenaline is secreted?
acts with noradrenaline to cause the fright, flight or fight response in times of stress.
101
A signal from the hypothalamus causes to sympathetic preganglionic fibre to send as action potential to either
Adrenal medulla secretory cells or sympathetic chain ganglion
102
What do Adrenal medulla secretory cells secrete?
adrenaline (80%) and noradrenaline (20%) into the bloodstream to act on effector cells.
103
What does sympathetic chain ganglion do?
send an AP down sympathetic postganglionic fibres, which synapse onto effector cells and secrete noradrenaline.
104
What does adrenaline act on?
skeletal muscle and liver cells to increase the breakdown of glycogen, and on fat cells to increase the breakdown of fat to fatty acids.
105
What does the anterior pituitary secrete?
ACTH
106
What does ACTH stimulate?
the middle layer of the adrenal cortex to secrete cortisol.
107
What is cortisol?
steroid hormone
108
When is cortisol produced?
as required and is carried through the blood via a carrier protein
109
When is cortisol concentration at its highest?
Morning
110
What are the effects of cortisol in response to stress?
• Increasing:
o Blood glucose levels
o Fat, protein and carbohydrate metabolism to maintain blood glucose concentration
o Blood pressure
o Heart and blood vessel tone and contraction
• Promoting anti-inflammatory actions
• Activation of the CNS
111
What is cortisol secretion controlled by?
negative feedback
112
What is cortisol secretion stimulated by?
ACTH secretion
113
What is ACTH secretion stimulated by?
CRH
114
What is the result of cortisol?
stimulates protein breakdown and decreased glucose uptake in muscle cells, increased fat breakdown and decreased glucose uptake in fat cells, and increased glucose synthesis in liver cells
115
What are the other effects of cortisol?
including helping to cope with stress, maintenance of blood pressure and in the long-term it suppresses the immune system
116
What is Hyposecretion
too little (or no) hormone secreted
117
What is Hypersecretion
too much hormone secreted
118
What is Hyposensitive
receptors have little (or no) response
119
What is Hypersensitive
receptors respond too much
120
What is Autoimmunity
destruction of receptors
121
What is Genetic mutation
gain or loss of function caused by mutations
122
What is Tumors
excess tissue leads to hypersecretion, can sometimes prevent release
123
What is Addison's disease?
hyposecretion of cortisol and aldosterone
124
What are the effects of Addison's disease?
Lowered cortisol leads to increased ACTH secretion, stimulating melanin synthesis which darkens the pigment of your skin. It also can result in low blood pressure and weakness (due to lack of fuel)
125
What is Addison's disease caused by?
autoimmunity and other factors
126
What is Cushing's disease?
hypersecretion of cortisol
127
What are the effects of Cushing's disease?
. This results in high blood pressure and weakness (due to muscle wasting).
128
What is Cushing's disease caused by?
tumors and other factors
129
How does CRH respond when the hypothalamus senses stress?
1. Anterior pituitary secretes ACTH
2. Further APs in sympathetic preganglionic fibres
3. Posterior pituitary secretes ADH
130
What are the effects of ACTH?
* Stimulates the adrenal cortex to synthesise and secrete cortisol
* Cortisol increases blood glucose and blood pressure
131
What are the effects of adrenaline?
• Synapse on the adrenal medulla, stimulating adrenaline secretion
o Increased blood glucose, heart rate and blood pressure
132
What are the effects of ADH?
* Decreased water excretion in kidneys
| * Increased blood volume and blood pressure
133
What does the hypothalamus stimulate during stress?
adrenal glands, SNS and the posterior pituitary
134
What are the 3 phases of stress response?
alarm phase
resistance phase
exhaustion phase
135
What is the alarm phase?
general sympathetic system is activated, causing pupil and blood vessel dilation, increased heart rate and force of contraction, and other responses.
136
What is the resistance phase?
Many effects on the body
137
What is the exhaustion phase caused by?
prolonged stressful stimuli and can lead to heart attacks.
138
What does hyposecretion of GH lead to?
Dwarfism
139
What does hypersecretion of GH lead to?
gigantism
140
What is infantile hypothyroidism caused by?
hyposecretion of thyroid hormone
141
What are the effects of infantile hypothyroidism?
low metabolic rate, cold intolerance, retarded growth and inhibition of brain development.
142
What is infantile hypothyroidism caused by?
by iodine deficiency in the mother’s diet
143
What is a simple goitre?
Iodine deficiency disorder
144
What is simple goitre a result of?
hyposecretion of thyroid hormone
145
What are the effects of simple goitre
When the thyroid hormone store is depleted, the secretion of TRH and TSH increases in attempt to stimulate the thyroid to make more hormone. This excess of TSH leads to thyroid gland growth.
146
What is graves disease?
hypersecretion of thyroid hormone
147
What are the effects of graves disease?
high metabolic rate, weight loss, heat intolerance, increased heart rate, nervousness, hair loss, exophthalmos (bulging eyes) and thyroid swelling.
148
What is graves disease caused by?
autoimmune disorders
149
What is Hyperparathyroidism a result of?
hypersecretion of parathyroid hormone, normally as a result of parathyroid tumours
150
What does Hyperparathyroidism cause?
bones to become soft, deformed and fragile. This also causes increased levels of calcium and phosphate in the blood and promotes the formation of calcium phosphate kidney stones.
151
When does Hypercalcaemia occur?
levels of calcium in the blood are low
152
What are the effects of Hypercalcaemia?
increased excitability of the nervous system due to a shift in RMP to -60 mV. This results in muscle tremors, spasms or cramps. When extremely low this can cause paraesthesia in the hands and face, muscle cramps and laryngospasm which can lead to suffocation
153
What is Hypercalcaemia caused by?
vitamin D deficiency, diarrhoea, thyroid tumours, underactive parathyroid glands, pregnancy and lactation.
154
What is type 1 diabetes a result of?
hyposecretion of insulin caused by the destruction of pancreatic beta cells by the immune system
155
What is type 2 diabetes a result of?
hyposensitivity to insulin caused by desensitisation of insulin receptors. This is associated with obesity
156
What can diabetes result in?
glucosuria, polyuria, polydipsia, diabetic neuropathy, heart problems, diabetic retinopathy, disrupted blood flow and more
157
What can increase blood glucose concentration?
Growth hormone, adrenaline and cortisol, as well as glucagon
158
When might there need to be changed in a set point?
change in altitude, due to the need for higher oxygen-carrying capacity in blood cells. Different climates result in BMR changes. Fevers result in temporary changes in body temperature.
