Endocrine System Flashcards
1
Q
What is the definition of a hormone?
A
Chemical released by the body that affects cells in other parts of the organism
2
Q
What is the difference between endocrine and exocrine hormones?
A
Endocrine hormones are secreted directly into the blood stream and have effects on downstream targets
Exocrine hormones are secreted right into a duct
3
Q
What is the difference between Autocrine and Paracrine? Are they hormones?
A
Autocrine –> chemicals that exert effects on the same cells
Paracrine –> locally acting chemicals that effect nearby cells
*they are not hormones because they do not travel long distances to effect change
4
Q
What are the two ways hormones alter target cell activity?
A
- Second messengers –> regulatory G proteins tend to be amino acid based hormones
- Direct gene activation –> tend to be steroid hormones
5
Q
What are the 5 main actions a hormone could take?
A
- change plasma membrane permeability
- stimulate protein synthesis
- activate or deactivate enzyme systems
- induce secretory activity
- stimulate mitosis
6
Q
What are the three factors that target cell activation by hormones depends on?
A
- blood levels of hormone
- number of receptors on a target cell
- affinity of receptors for the hormone
7
Q
What is the difference between up-regulation and down-regulation?
A
Up-regulation –> target cells form more receptors in response to the hormone
Down-regulation –> target cells lose receptors in response to hormone
*receptors are modulated using gene expression
8
Q
What types of hormones are bound to plasma proteins?
A
Steroids and thyroid hormone
9
Q
Hormones are synthesized and released in response to what 3 things?
A
Humoral stimuli - changes in ion concentration
Neural stimui - nerves stimulate
Hormonal stimuli - more hormones released in response to other hormones
10
Q
What are the three main types of hormones and what do they include?
A
- Eicosanoids –> leukotrienes and prostaglandins
- Amino acid based –> amines, thyroxine, peptides and protein hormones
- Steroids –> gonadal and adrenocortical
11
Q
What is an Eicosanoid and what is it made of?
A
Eicosanoid is a short-lived biologically active lipid with autocrine and paracrine activity –> classified in hormones because depending on how much is made and how much gets into the blood stream, it has hormone activity
Made from arachidonic acid which is produced from omega fatty acids (we take these up in our diet)
12
Q
Name 3 Eicosanoids
A
- prostaglandin
- thromboxanes
- leukotrines
13
Q
What does a prostaglandin do and what enzyme makes it?
A
inflammation, fever production, prevents platelet aggregation (prevent clotting) and induces labour
*made by cyclooxygenase from PGH2
14
Q
What does a thromboxane do and what enzyme makes it?
A
promotes blood clotting
*made by cyclooxygenase from PGH2
15
Q
What does a leukotriene do and what enzyme makes it?
A
modulates allergic reactions
*made by lipoxygenase from AA
16
Q
What hormones stimulate the activation of PKA and what types of hormones are these?
A
- catecholamines
- ACTH
- FSH
- LH
- Glucagon
- PTH
- TSH
- Calcitonin
*amino acid based hormone action, regulated through G proteins
17
Q
What enzyme turns off the signalling in the cAMP second messenger pathway?
A
Phosphodiesterase E
18
Q
Can steroid hormones freely diffuse across a lipid membrane? Why or why not?
A
They can freely diffuse across a lipid membrane because they are hydrophobic in nature
19
Q
What is Herceptin and why is it important?
A
Antibody for treatment of women with HER2 positive mestatic breast cancer
This is one of the few treatments that has demonstrated survival benefit in women with HER2 positive breast cancer (this is a more agressive disease that halves the life expectancy of women with higher likelyhood of recurrence)
20
Q
How does Herceptin work?
A
It is a dimer that blocks signalling of HER2 as well as tagging it for destruction by the immune cells
21
Q
What is neurohyphophysis and what does it do?
A
Neurohypophysis is the posterior lobe of the pituitary gland
- it receives, stores, and releases hormones from the hypothalamus
22
Q
What is the adenohypophysis and what does it do?
A
Adenohypophysis = anterior lobe of pituitary
- synthesizes and secretes many hormones
- involved in stress, growth and reproduction
23
Q
What is the name of the connecting stock to the pituitary gland?
A
Infundibulum
24
Q
Explain the pathway of the neurohypophysis
A
originates in the hypothalamic 2 clusters of cell bodies - SON (supraoptic nuclei) and PVN (Paraventricular nuclei)
Axons extend through ifundibulum forming the hypothalamic hypophyseal tract
synapses in posterior pituitary
Releases oxytocin and ADH from venule
25
Explain the anatomic pathway of the adenohypophysis
1. Hypothalamic neurons secrete hormones into the primary capillary plexus (neuronal bodies from VH- ventral hypothalamus)
2. Hormones travel through hypophyseal portal veins to anterior pituitary
3. hormones are secreted from pituitary to secondary capillary plexus
26
What are the two classes of hormones in the adenophypophysis?
1. Tropic hormones (modulate secretion of more hormones)
- TSH (thyroid stimulating hormone)
- ACTH (adrenocorticotropic hormone)
- FSH
- LH
- GH
2. Other hormones
- PRL (prolactin)
- beta-lipotropin
- MSH (melanocyte stimulating hormone)
27
What is the endocrine cell type with the highest and lowest population in the adenohyphophysis?
```
#1 somatotroph: 40-50%
- makes GH
```
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#5 thyrotroph: 3-5%
- makes TSH
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28
What does GH do and what are its key targets?
Anabolic = tissue building
Stimulates increase in size and division of most cells, its key targets are the liver, bone and skeletal muscle
29
How is GH indirectly mediated?
Somatomedins --> growth promoting family of proteins
Ex. IGF (insulin-like growth factor)
30
What is IGFBP and what does it do?
IGFBP = insulin-like growth factor binding protein
binds to IGF and helps stabilize it in the blood stream,
31
What is acromegaly?
When the pituitary gland produces too much GH (growth hormone) after the closure of the epiphyseal plate closure
*causes tissue swelling in skin and organs, changes pigmentation and expands skull
32
What is giantism?
Excess GH before the closure of the epiphyseal plate during puberty --> this is a pituitary TUMOUR that causes abnormal growth in the long bones
33
Explain the pathway of TSH
1. hypothalamus releases TRH (thyrotropin release hormone) to anterior/adenohypophysis
2. Pituitary releases TSH to the thyroid which then makes T4 and T3
3. The liver makes TBP (thyroid binding proteins) and binds the hormone
* Release of TSH is inhibited by the excess of free T4 and T3
34
Explain the pathway of ATCH and what causes it
1. Stressor, fever or gypolycemia trigger the release of CRH (corticotropin releasing hormone) from the hypothalamus
2. Goes to the pituitary gland (adenohypophysis) which releases ACTH (adrenocorticotropic hormone)
3. This goes to the adrenal medulla to cause release of cortisol, norepinephrine and epinephrine into the blood stream
4. Activates immune response
35
What is POMC and what does it break into?
POMC = pro-opiomelanocortin
Splits into
1. ACTH
2. Beta-lipotropin
3. opiates --> beta-endorphrin
4. yMSH (melanocyte stimulating hormone)
36
What is GnRH and what does it trigger the release of?
GnRH = gonadotropin-releasing hormone --> comes from the hypothalamus and triggers the release of gonadotropins
37
What are the two gonadotropins and what do they do?
FSH (follicle stimulating hormone) --> stimulates gamete production
LH (lutenizing hormone)
-->In females, causes maturation of ovarian follicle with FSH, triggers ovulation, and promotes synthesis and release of estrogens and progesterone
-->In males, causes spermatogenisis and sperm maturation
38
What is PRL and what does it do?
PRL = Prolactin
Stimulates milk production in females (suckling)
Helps induce labour
39
What inhibits PRL?
Prolactin inhibiting hormone, dopamine
40
What is the pathway inside the posterior pituitary?
1. Hypothalamic neurons (SON and PVN) synthesize oxytocin and ADH
2. those are transported along the hypothalamic-hypophyseal tract to the posterior pituitary
3. Oxytocin and ADH are stored in axon terminals in the posterior pituitary
4. Released into the blood when the hypothalamic neurons fire
41
What does oxytocin do?
- positive feedback regulation allows increased intensity of uterine contractions
- triggers milk ejection (letdown reflex)
- plays a role in sexual arousal/satisfaction in males and non-lactating females
42
What causes the release of ADH and what does that stand for?
ADH = antidiuretic hormone
When plasma osmolarity is high --> ADH releases and causes preservation of water
*large decreases in blood volume/pressure will also trigger release of ADH
When plasma osmolarity is low --> ADH is inhibited and allows water loss
43
What else, besides low solutes in the plasma, causes inhibition of the release of ADH?
Alcohol
44
What do follicle cells in the thyroid produce?
Thyroglobulin which is a precursor for thyroid hormone (TH)
45
What does colloid consist of?
Thyroglobulin and iodine
46
What does TH play a role in? (4)
1. Maintaining blood pressure
2. regulating tissue growth
3. developing skeletal and nervous systems
4. Maturation and reproductive capabilities
47
What are the exceptions for tissues that TH targets?
USTAT - uterus, spleen, testis, adult brain and thyroid gland
48
What is the more biologically related iodine containing compound in TH?
T3 --> two tyrosines and 3 iodines
49
Explain the process of the synthesis of thyroid hormone
1. thyroglobulin is synthesized and discharged into the lumen/colloid
2. Iodines are actively taken into the cell, oxidized to iodine (I2) and released into the lumen/colloid
3. Thyroid peroxidase attaches iodine to tyrosine forming T1 and T2
4. Thyroid peroxidase then attaches T1 and T2 to make T3 and T4
5. Endocytosis of T3 and T4 are cleaved in lysosomes and diffuse into blood stream
50
What is TBG and what do they do?
TBG - thyroxine-binding globulins
produced by the liver and bind to T3 and T4 to make them more stable when travelling through the body
51
If more T3 is needed, what happens?
Peripheral tissues convert T4 to T3 using deiodinase
*T3 is 5-10 times more active in the body
52
What causes hypothyroidism and what are the symptoms?
Hypothyroidism (unless from a problem in the pituitary) is from low T4 and possibly T3 leading to higher TSH
Lack of iodine in diet can lead to enlarged thyroid
Symptoms: low metabolic rate, lethargy, mental sluggishness
53
What is cretinism?
Form of hypothyroidism found in infants
54
What is the name for an enlarged thyroid?
goiter --> usually from lack of Iodine in diet
55
What is Graves disease and its symptoms?
Autoimmune disease that causes the thyroid to grow to twice the normal size --> abnormal antibodies that mimic TSH continuously release TH
symptoms: increased heartbeat, muscle weakness, disturbed sleep, and irritability, could cause bulging eyes (exophthalmos)
56
What is calcitonin, where is it made and what does it do?
Peptide hormone made by the parafollicular cells/C-cells of the thyroid
Lowers blood Ca2+ in children and targets the skeleton
- inhibits osteoclast activity (breaking down of bones)
- stimulates Ca2+ incorporation into bone matrix
57
What kinds of cells are found in the parathyroid gland and what do they do?
Oxyphil cells and Chief cells
--> chief cells or principle cells secrete PTH (parathyroid hormone) which regulates Ca2+ in the blood
-->oxyphil cells do not really have a known function at this time
58
What are the effects of PTH?
PTH = parathyroid hormone and it increases Ca2+ levels in the blood by:
1. stimulating osteoclasts
2. Enhances reabsorption of Ca2+ and secretion of phosphate in kidneys
3. promotes vitamin D activation to calcitrol (increases Ca2+ absorption in the intestine)
59
What inhibits the release of PTH?
Increased Ca2+
60
What is the difference between the adrenal medulla and the adrenal cortex?
Adrenal medulla --> middle part of the adrenal gland; neural tissue that acts as part of the SNS
Adrenal cortex --> outside part of the adrenal gland; releases steroid hormones called corticosteroids
61
What are the layers of the adrenal cortex?
from top to bottom:
1. Zona glomerulosa
2. Zona Fasciculata
3. Zona Reticularis
62
What corticosteroid does the Glomerulosa produce?
Aldosterone
63
What corticosteroid does Zona fasciculata release?
Cortisol
64
What corticosteroid does Zona reticularis release?
Androgens
65
What is the molecule from which the cortocosteroids are derived?
Cholesterol
66
What do mineralcorticoids do?
Mineralcorticoids (aldosterone is most important) come from the Zona glomerulosa of the adrenal cortex
They regulate electrolytes in extracellular fluids
67
How does aldosterone work and what stimulates its secretion?
Aldosterone comes from Zona glomerulosa of adrenal cortex
- maintains Na+ by reducing the excretion from the body
- stimulates reabsorption of Na+ by the kidneys
Secretion stimulated by:
- rising levels of K+
- low blood Na+
- decreasing blood volume or pressure
68
What is the renin-angiotensin mechanism?
Angiotensin II stimulates aldosterone release
69
What effect does ACTH have on aldosterone?
ACTH (adrenocorticopic hormone) will increase aldosterone during times of stress
70
What does ANP stand for and what does it do?
ANP = atrial natriuretic peptide
Inhibits the activity of zona glomerulosa --> stops release of aldosterone
71
What do glucocorticoids do and what is the most important one?
Glucocorticoids include cortisol (made by the zona faciculata of adrenal cortex)
Help the body resist stress by
1. keeping blood sugar levels fairly constant
2. maintaining blood volume and preventing water shift into tissue
72
What does cortisol do?
Forms glucose and rises blood glucose, fatty acids and amino acids
73
If there is an excessive level of glucocorticoids, what happens?
Accumulation could be due to long term stress and causes:
- depression of cartilage and bone formation
- inhibition of the immune system
- promote changes in cardiovascular, neural and GI function
74
What are gonadocorticoids and what do they do?
Most gonadocorticoids are androgens and the most important one is testosterone
Androgens contribute to:
- onset of puberty
- appearance of secondary sex characteristics
- sex drive in females (produced in the adrenal medulla)
75
After menopause, what are androgens converted into?
Estrogens
76
What are the primary cells in the adrenal medulla and what do they secrete?
Chromaffin cells --> secrete catecholamines (epinephrine and norepinephrine)
77
What modulates the secretion of chromaffin cells?
ACh which is secreted by neurons of the sympathetic nervous system
78
Explain the short term stress response
Nerve impulses are sent to the spinal cord and pre-ganglionic sympathetic fibers synapse into the adrenal medulla causing the release of catecholamines
- increases heart and respiratory rate
- increases blood pressure
- dilates pupils
- liver converts glycogen to glucose and releases it into the blood
- increased metabolic rate
79
Explain the long term stress response
Hypothalamus releases CRH (corticotropin releasing hormone) to anterior pituitary to stimulate release of ACTH (adrenocorticopic hormone). This goes to the adrenal cortex which releases mineralocorticoids and glucocorticoids
80
What is the effect of mineralocorticoids in the long term stress response?
1. causes kidneys to keep sodium and water
| 2. increases blood volume and blood pressure
81
What is the role of glucocorticoids in the long term stress response?
1. converts proteins and fats into glucose or are broken down for energy
2. increases blood glucose
3. suppresses the immune system
82
What are the primary cell types in the pancreas, what is their distribution and what do they contain?
1. alpha cells --> contain glucagon (15-20% of islets)
2. beta cells --> contain insulin and amylin (65-80%)
3. delta cells --> contain somatostatin (3-10%)
83
What is glucagon?
29-amino-acid hormone that is an hyperglycemic agent (promotes increase in blood glucose levels)
84
What is insulin?
51-amino-acid protein made of two amino acid chains linked by disulfide bonds
- enhances transport of glucose into body cells
- counters metabolic activity that enhances blood glucose levels
85
What is the normal amount of blood glucose?
~90mg/100mL
86
The stimulus is rising blood glucose levels; what happens?
- pancreas releases insulin which stimulates glucose uptake by cells
- stimulates glycogen formation in the liver
- blood glucose falls to a normal level
87
The stimulus is declining blood glucose levels; what happens?
- pancreas releases glucagon
- glucagon stimulates glycogen breakdown in the liver
- glucose is returned to the blood and levels balance out
88
What is the difference between type 1 and type 2 diabetes?
Type 1: inability to make insulin, body cannot use energy properly and results in beta cell death (autoimmune disorder and usually runs in families)
Type 2: cells do not respond to insulin, usually adult onset and occurs in obese, sedentary people
89
What are the 3 cardinal signs of type 1 diabetes and what are the long term-effects?
1. polyuria --> huge urine output
2. Polydipsia --> excessive thirst
3. Polyphagia --> excessive hunger and food consumption
Long term effects include blindness, nerve damage, loss of limbs, kidney and cardiovascular disease
90
What are the two key hormones in the female gonads and what do they do?
Estrogen and progesterone
- mature te reproductive organs
- cause appearance of secondary sexual characteristics
- breast development and cyclic changes in uterine mucosa
91
What is the key gonad hormone in males and what is it responsible for?
Testosterone
- initiates maturation of male reproductive organs
- causes appearance of secondary sex characteristics
- necessary for sperm production
- maintains sex organs in their functional state
92
What is the name of the endogenous circadian peacemaker in the anterior ventral hypothalamus and what does it do?
SCN = suprachiasmatic nucleus
- like an internal clock that anticipates and synchronizes brain and body functions so they occur at appropriate and optimal times
- melatonin helps the SCN to sense the length of the night
93
What does the pineal gland do?
secretes melatonin to help with sleep/wake cycle
94
What are the hormonal products of the thymus and why are they important?
Thymopoietins and thymosins --> help in the education of T cells
