Introduction to the Endocrine System Flashcards
What is the role of hormones?
Hormones contribute to the function of everything in our body
What are three things hormones do?
- Turn children into adults
- Affect our passions
- Govern our appetites
The discovery of hormones - people had know that animals that were … could not develop secondary … characteristic
castrated
sexual
Arnold Adolph Berthold (1803-1861) performed what experiment with roosters?
testes transplanted into abdomens emasculated birds develop secondary sexual characterises indicating that the testes functioned effectively normally
in the experiment with roosters, what happened to the testes on autopsy?
they had developed a new vasculature
conclusion of experiment on roosters: whatever was controlling the secondary sexual characteristics was transported from … via the … This was considered to be what?
testes via the bloodstream
- this was the sexual hormone
Define ‘Hormone’
chemical messengers
The endocrine system is a system of … … which secrete chemical messengers (…) into the blood
ductless glands hormones
hormones are carried in the … and are able to act on cells possessing the appropriate hormone … (… …) Each hormone may act on several of these
blood receptors target tissues
Where are the endocrine glands?
distributed throughout the body
What is this image showing?
The endocrine glands
Where is the pituitary gland situated?
Below the brain, encased in skull
How much does the pituitary gland weigh?
0.5 grams
Hormones secreted from the pituitary gland help to control what? (9 things)
- Growth
- Blood Pressue
- Energy Management
- All Functions of the Sex Organs
- Thyroid Glands (therefore metabolism)
- Aspects of pregnancy, childbirth and breastfeeding
- Water/Salt concentration of the Kidneys
- Temperature Regulation
- Pain Relief
Christopher Paul Greener had pituitary …
gigantism
Christopher Paul Greener - where was his tumour?
pituitary
Christopher Paul Greener - what cured his tumour?
radiation cured the tumour - he stopped growing
Where are the thyroid and parathyroid glands situated?
In the neck
What are the thyroid and parathyroid glands important for?
Control of metabolic rate and calcium homeostasis
What is this image showing?
Thyroid gland
What gland can you see from the front only?
What gland can you see from the back only?
Thyroid
Parathryoid
How many parathyroid glands are there?
4
First successful treatment in endocrinology was for a disease related to the mysfunction of what gland?
thyroid gland
What is myxedema?
severely advanced hypothryoidism
The term also applies to the effects that hypothyroidism can have on the skin, making it appear swollen and puffy.
What is Cretinism?
a severe deficiency of thyroid hormone in newborns.
What disease is present in this person?
Myxedema / Cretinism
What did Victor Horsley discover after removing thyroid glands in monkeys?
They developed myxedema.
Lost hair, skin swollen and easily damaged.
He knew that thyroid glands were therefore responsible for this illness.
What did Victor Horsley propose after his discovery?
Did it work?
he proposed transplant of sheep thryoids -> dangerous surgery
no - effect only lasted one week
What did George Murray do in 1891? (Thyroid glands)
He prepared sheep thyroid juice and gave it to patients - it worked
Was George Murray’s experiement a success?
Yes - patients were cured
Where is the pancreas located?
In the abdomen behind the stomach
What are the two main functions of the pancreas?
Endocrine function
Exocrine function
Explain the endocrine function of the pancreas
Secretes the hormone insulin and glucagon into the blood
Both hormones regulate blood glucose concentration and glucose utilisation
Explain the exocrine function of the pancreas
Secretes digestive enzymes directly into GI tract
What two hormones are secreted by the pancreas?
insulin and glucagon
In diabetes, what hormone is not made/not made enough/doesnt work properly?
insulin
There used to be no cure for diabetes. Who discovered a cure?
Frederick Banting.
Why is having no insulin a problem?
No insulin = body cannot use the glucose that you ingest to make energy / energy reserves.
Glucose passed out in urine instead
If you prepare an extract of pancreas you get nothing, why?
What does the pancreas do that affects this working?
Pancreas produces enzymes which degrade insulin
What did Frederick Banting come up with to treat diabetes?
Ligate pancreatic duct - enzymatic producing cells die
Extract is enriched of insulin
1922 - tested in patient and cured
When was the first diabetes treatment tested?
1922 - tested in patient and cured
What is this image showing?
A patient before and after treatment with insulin for diabetes
Where are the adrenal glands located? (also known as suprarenal glands)
They lie on top of the kidneys.
What are the two main regions of the adrenal glands? (visible if you make a transverse cut of the kidneys)
The cortex and the medulla
What is the medulla of the kidneys concerned with? (1)
The stress response
What is the cortex of the kidneys concerned with? (3)
Stress, sodium and glucose homeostasis
What are the gonads? (male v female)
Testes and ovaries
What do the testes and ovaries secrete?
The male and female reproductive hormones respectively
What are the gonaads responsible for?
The development of secondary sexual characteristics and reproduction.
What is this image showing?
The gonads
Hormones can be divided into two broad classes, what are they?
Peptide hormones
Steroid hormones (+thyroid hormone)
Peptide hormones are made of chains of what?
What does this mean in terms of their solubility?
amino acids
highly water soluble
What are peptide hormones susceptible to?
Protease attack
Are peptide hormones able to cross the cell membrane?
No
What do peptide hormones act on?
Cell-membrane receptors
What does protease attack mean?
When hormone is in the blood, enzymes can be degraded by proteases
Solubility of Steroid and Thyroid Hormones
Are they lipid soluble?
Are they water soluble?
Highly lipid soluble
Poorly water soluble
How must Steroid and Thyroid Hormones be transported in the blood?
Bound to plasma protein
Is bound or unbound steroid/thyroid hormone biologically active?
only the unbound hormone is biologically active
Are steroid and thyroid hormones able to cross the cell membrane?
Where do they act?
Yes
Intracellular receptors
What are the 5 characteristics of Peptide hormones in terms of their:
1) solubility
2) onset of action
3) plasma half-life
4) duration of action
5) orally active ?
Water soluble
rapid onset of action
short plasma half-life
short duration of action
not orally active
Anaphylaxia - use what?
Epinephrine pen - extremely fast, injectible, rapid response.
What are the 5 characteristics of Steroid and Thyroid hormones in terms of their:
1) solubility
2) onset of action
3) plasma half-life
4) duration of action
5) orally active ?
Poorly water soluble
Slow onset of action
Long plasma half-life
Long duration of action
Orally active
What hormone is generated by the thyroid gland?
Thyroxine (T4)
How is thyroxine (T4) administered?
How long does the effect last?
Orally (as tablets)
About 7 days before action vanishes - dependent on dose
What do hormones act on?
target tissues
How do hormones produce their effects?
via interaction with receptors
What are the two types of receptors which hormones interact with?
Intracellular receptors
Cell-surface receptors
What are the 3 major classes of receptors? (with regards to hormones)
- G-Protein Couples Receptors
- Tyrosine Kinase Receptors
- Steroid Hormone Receptors
Where are G-Protein Coupled Receptors and Tyrosine Kinase Receptors?
In the membrane of cells
Where are Steroid Hormone Receptors?
In the cell
How does a G-Protein Coupled Receptor work?
what does the hormone bind to specifically?
What does the activation of G-protein cause?
The hormone binds to the 7 transmembrane helices receptor, activating G protein
Causing synthesis of a second messenger, e.g inositol, triphosphate or cyclic AMP
What do second messengers do? (with regards to G-protein coupled receptors)
2 pathways …
Second messengers phosphorylate intracellular, regulatory protein to influence cellular activity (e.g. cause smooth muscle contraction)
Second messengers also phosphorylate target protein that can then modify gene expression - slower
What is a tyrosine kinase receptor?
A membrane-bound enzyme which is a single strand of protein
How many tyrosine kinase receptors must be usually present for hormone action?
2
Because of their kinase activity, what can tyrosine kinase receptors do?
phosphorylate eachother - dimerized receptor - now active
One hormone binds to each tyrosine kinase receptor, then the receptor acts as an …. to do what to the tyrosine components?
enzyme
to phosphorylate tyrosine components of the intracellular, regulatory proteins
Once the tyrosine components are phosphorylated, they can then activate what?
different downstream pathways
Once phosphorylated tyrosines have activated different downstream pathways and impacted gene transcription and protein synthesis, through further signalling, what can the cell now control? (4 things)
cell proliferation
survival
migration
differentiation
How does a hormone bind to a steroid hormone receptor?
what does this create?
Hormone crosses the cell membrane and binds to a receptor in the cytoplasm - creating a hormone-receptor complex
Where does the hormone-receptor complex travel to? and what does it it bind to?
the nucleus, where it binds to the hormone-response element of the DNA to influence gene transcription.
The G-protein coupled receptor response is faster than what response?
Steroid hormone receptor
Typically, but not in all cases, the secretion of a hormone by a given gland is controlled by what?
the anterior pituitary gland
the anterior pituitary gland secretes what?
stimulating (or trophic) hormones
What hormone stimulates the thyroid and activates it via the anterior pituitary gland?
thyroid stimulating hormone
Once the thyroid is stimulated, it secretes hormones. What hormones may be secreted?
T3 & T4
What is this graph illustrating?
what does it tell us about ACTH (a stimulating hormone) vs Cortisol (hormone produced by suprarenal) ?
relationship between pituitary trophic hormone secretion and primary gland activity (suprarenal)
ACTH and cortisol have similar time courses but ACTH is slightly advanced compared to cortisol
The secretion of a hormone by the anterior pituitary gland is also controlled by the
hypothalamus
The hypothalamus secretes what hormones?
releasing hormones
Hypothalamus secretes what releasing hormone?
This then stimulates what?
In turn, this stimulates the secretion of what?
End result is …
thyrotrophin releasing hormone (TRH)
The pituitary
Thyroid stimulating hormone - stimulating the thyroid to produce thryoid hormones (T3 and T4)
To ensure that the correct amount of T3 and T4 are secreted, hormonal secretion is also controlled by what?
Feedback - usually negative feedback
T3 and T4 produce what type of feedback onto the anterior pituitary
negative feedback
blocks production of TSH
T4 produces a lesser effect on the hypothalamus via what kind of feedback?
negative feedback
less TRH produced
The T3 and T4 hormones ‘inform’ the … and the … that they have achieved the correct level
Hypothalamus and pituitary
A common consequence of negative feedback is cyclical variation in …
hormone concentration
Leptin is secreted by cells in what tissue?
What does it act on?
What does leptin control?
adipose tissue
hypothalamus of the brain
it controls appetite (inhibits)
