W2L2 Endocrine regulations Flashcards
I. Basics
1. What are the 2 symptoms that could be associated with endocrine diseases?
- Goiter - enlargement of the thyroid gland
- Exoptalmos (the bulging of the eyeball anteriorly from the orbit)
I. Basics - scientific approaches
2. Describe the experiment of Berthold in 1849
- Removed testes from young male chicken
-> combs failed to grow
-> did not crow
-> didn’t try to mate with females - Preimplantation of testis to the abdominal cavity
-> the above changes are prevented/ reserved
=> Conclusion: the testis somehow “conditions” blood
I. Basics - scientific approaches
3. Describe the experiment of Minkowski and Mering in 1889
- Removed the pancreas from dog
- Result: diabetes mellitus
=> There must be something that affect glucose
I. Basics - Modern endocrinology
4. Describe the experiment of Starling and Bayliss
- HCl to denervated jejunum
- Intravenous administration of jejunal mucosa extract
=> These 2 things lead to pancreas secretion
=> Thus, Palov is not entirely right. Pancreatic secretion is not exclusively regulated by the nervous system => “chemical reflex”
II. Hormone definition
1. What is the definition of hormone?
A chemical substance of low concentration, which is secreted to the blood by an endocrine gland and exerts its effect on distant target tissues
II. Hormone definition
2. How is endocrine gland related to hormone?
Within endocrine glands, there will be…
- Maybe scattered cells (e.g, S cells -> secretin
- Neurocrine secretion (from neuronal axon terminals)
- Other cell types (e.g, atrial myocyte -> ANP)
II. Hormone definition
3. How is BLOOD related to hormone?
Hormones are secreted to the blood
(e.g, testosterone secretion to blood and testicular ducts)
*** Hormones can be secreted to other places (NOT only Blood)
II. Hormone definition
3. How is low concentration related to hormone?
In general, 10^-6 to 10^-12 mol/L (µM, nM, pM)
- High affinity detection -> hormone receptors
- Only cells with specific receptors can respond
- Specificity, but:
+ 1 hormone -> several receptor types
+ More than 1 hormone -> 1 receptor type
+) due to similar chemical structure, concentration, etc.
II. Hormone definition
4. Hormones can not undergo exocytosis.
-> T/F? Why?
False! They can be!
- Hormones are secreted (released)
- E.g, steroid hormones: NO EXOCYTOSIS
II. Hormone definition
5. How is distant target tissue related to hormone definition?
- Maybe another endocrine gland
- In addition: paracrine, autocrine, intracrine effects
- Many hormones (e.g, peptide, protein, biogenic amin) are also neurotransmitters in the CNS
III. Function of hormones
1. What is the main function of hormones
Regulation of
- Homeostasis (stability of the internal environment
- Metabolism
- Growth/development (proliferation/ differentiation)
- reproduction
III. Function of hormones - Theoretical background of endocrine regulations
2. What is the role negative feedback with hormone?
The hormone production stabilizes the function of the target organ (and hormone level)
- Low [hormone] -> increasing [hormone]
- High [hormone] -> decreasing [hormone]
III. Function of hormones - Theoretical background of endocrine regulations
3. Negative feedback means that the “product” inhibits hormone synthesis
-> T/F? Why?
False! This is not always the case
Explain:
- The “product” also stimulates the gland (*target organ is constitutively active in the absence of the hormone)
III. Function of hormones - Theoretical background of endocrine regulations
4. What is “sign-reversal”?
Odd number of the inhibitory interactions in the negative feedback loop
III. Function of hormones - Negative feedback
5A. Give an example of negative feedback related to hormone in kidney?
Due to burn injury or eating bananas
-> Cells in adrenal cortex and zona glomerulosa stimulates aldosterone production
-> K+ excretion in kidney increases
-> Then, the amount of potassium decreases to normalize the balance
-> This will again stimulates cells in adrenal cortex and zona glomerulosa to produce aldosterone
III. Function of hormones - Negative feedback
5B. Give an example of negative feedback related to hormone in pancreas beta-cells?
Eating chocolate
-> Cause an increase in [glucose]
-> increasing insulin production
-> increasing glucose uptake of tissues
-> effect: decreasing [glucose]
≈ - Negative feedback
6. This is a technical model of the negative feedback
-> what does this tell us more than the classical model?
- There is input signal. Input signal may change
- There is amplification: the basis of precise regulation
- Small error signal -> large hormone response
- E.g, plasma [K+]: a few tenth of mM
[Ca2+]: a few hundredth of mM => precision of regulation
III. Function of hormones
7A. What happen in the case of constant input signal and the perturbing effect?
- A perturbing effect throws the regulated parameter off balance
- The feedback signal deviates from the constant input signal
- The increased error signal changes hormone release
- The hormone restores the regulated parameter
III. Function of hormones
7B. Make a schematic diagram in the case of the constant input signal and the pertubing effect
III. Function of hormones
8. What is the fate of the input signal?
The input signal is modified by the effects/regulation targeting the endocrine cell independent of the given negative feedback
III. Function of hormones
9A. What is the example that demonstrate the case “the input signal is modified by the effects/regulations targeting the endocrine cell independent of the given negative feedback?
- Depending in vagus activity and composition of the gastric content, this feedback loop stabilizes acid production at different levels
- THUS: normal function of the negative feedback does not mean in general that the regulated parameter is constant
- There are also other “external” effects/regulations in addition to those acting on the G cell in the above negative feedback loop
(vagus, histamine -> parietal cell
vagus, gastric content -> D cell
Gastric content -> luminal pH, etc.) - Negative feedback loops may co-assemble (2 loops have 1 or more common components)
III. Function of hormones
9B. Examples of other “external” effects/regulations in addition to those acting on the G cell in the above negative feedback loop
- Vagus, histamine -> parietal cell
- Vagus, gastric content -> D cell
- Gastric content -> luminal pH, etc.
III. Function of hormones
9C. Negative feedback loops may co-assemble
-> T/F?
True!
- Two loops have 1 or more common components
III. Function of hormones
10A. What are the characteristics patterns of negative feedback circuit integration, hormonal regulation at the organism level?
- One hormone -> many functions (pleiotropic effects)
+) e.g, insulin -> skeletal muscle: glucose uptake
+) adipose tissue: lipogenesis, etc. - One function <- many hormones
+) e.g, blood [glucose] <- insulin, glucacon, GH