Hormone Synthesis and Action Flashcards
List 2 differences between endocrine and exocrine glands.
1 - Endocrine glands release secretions directly into the blood, whereas exocrine glands release their secretions onto surfaces.
2 - Endocrine glands are ductless whereas exocrine glands may be ducted.
List 3 routes by which hormones can reach their targets.
1 - Endocrine.
2 - Autocrine.
3 - Paracrine.
Describe the hypothalmo-pituitary-adrenal axis.
1 - The hypothalamus synthesises and releases corticotropin releasing hormone, which travels to the anterior pituitary gland.
2 - The anterior pituitary gland is stimulated to synthesise and release adrenocorticotropic hormone, which travels to the zona fasciculata of the adrenal gland.
3 - The zona fasciculata synthesises and releases cortisol, which acts through negative feedback to reduce the synthesis and release of corticotropin releasing hormone at the hypothalamus and adrenocorticotropic hormone at the pituitary.
Describe the hypothalamic-pituitary-thyroid axis.
1 - The hypothalamus synthesises and releases thyrotropin releasing hormone, which travels to the anterior pituitary gland.
2 - The anterior pituitary gland is stimulated to release thyroid stimulating hormone, which travels to the thyroid gland.
3 - The thyroid gland synthesises and releases T3 and T4, which act through negative feedback to reduce the synthesis and release of thyrotropin releasing hormone at the hypothalamus and thyroid stimulating hormone at the anterior pituitary gland.
List the three main groups of hormones.
1 - Protein / peptide hormones.
2 - Steroid hormones.
3 - Amine hormones.
List two examples of protein / peptide hormones.
1 - Insulin.
2 - Thyrotropin releasing hormone.
List two examples of steroid hormones.
1 - Cholesterol.
2 - Cortisol.
List 3 examples of amine hormones.
1 - Tyrosine.
2 - Thyroxine.
3 - Noradrenaline.
Are protein / peptide hormones hypdrophobic or hydrophilic?
Hydrophilic.
In the anterior pituitary, which cells produce adrenocorticotropic hormone?
Corticotrophs.
In the corticotroph, what is the pre-prohormone to adrenocorticotropic hormone?
Pre-pro-opiomelanocortin.
How are TSH, LH, FSH and hCG related?
1 - They are all released from the anterior pituitary.
2 - All have an alpha and beta subunit, of which they share a common alpha subunit.
What is the precursor of all steroid hormones?
Cholesterol.
Are steroid hormones hydrophobic or hydrophilic?
Hydrophobic.
In steroid hormone synthesis, what is the source of cholesterol?
Hydrolysis of esters.
In steroid hormone synthesis, what is cholesterol converted to?
Where does this occur?
- Pregnenolone.
- In the mitochondria.
What is the role of steroid acute regulatory protein (StAR) in steroid hormone synthesis?
To facilitate movement of cholesterol to the mitochondria.
In steroid hormone synthesis, what regulates StAR activity?
Adrenocorticotropic hormone.
Give an example of a hormone that is produced in the zona glomerulosa of the adrenal gland.
Aldosterone.
Give an example of a hormone that is produced in the zona fasciculata of the adrenal gland.
Cortisol.
Give an example of a class of hormone that is produced in the zona reticularis of the adrenal gland.
Adrenal androgens
Why do increases in secretion of steroid hormones reflect accelerated rates of synthesis, whereas increases in secretion of peptide / protein hormones do not necessarily reflect accelerated rates of synthesis?
Because peptide / protein hormones can be stored, whereas steroid hormones cannot (as they are hydrophobic / lipophilic).
What do the numbers ‘3’ and ‘4’ represent with T3 and T4?
The number of iodine atoms.
Are amine hormones hydrophobic or hydrophilic?
Hydrophobic.
