Pharmacology Flashcards
Features of endocrine control
1-Direct release of the hormones into the bloodstream
2-Speed on onset of action and duration differs
Adrenaline - fast, stays only for a couple of seconds
Insulin - Slow, but the effect can stay for hours, days or weeks
3-Each gland is separate but work together as a functional unit
4-low concentration of hormones required
5-High potency - high receptivity of the receptors to the specific hormones at very low concentrations
6-One hormone –> many targets (insulin –> kidney, adipose tissue, skeletal muscle, hepatocytes etc..)
7-Many hormones can act on the same target cell
8- Amplification of the original signal - 1 hormone –> 1000s of secondary messengers
9 - Inactivation
Adrenaline - locally
Steroid hormones - in the liver before they are eliminated via the kidney
Features of exocrine glands
Release of the secretions through the ducts
What is the hypothalamic-pituitary-adrenal axis?
Complex set on feedback interactions
Stress –> Hypothalamus - release Corticotrophin-releasing factor(CRF) –> Anterior pituitary gland - release ACTH –> Adrenal cortex - release cortisol
Cortisol - Stress hormone
negative feedback on Anterior Pituitary and Hypothalamus
How is specificity in endocrine signalling achieved?
1- Chemically distinct hormones
2- Specific receptors for each type of hormone
3- Distribution and localisation of the specific receptors at specific target cells
What are the seven classic endocrine glands?
Pituitary gland Thyroid gland Thymus Adrenal gland Pancreas Ovary Testis
What influences the stay of the hormone in the body?
the chemical nature of the hormone
-determines if the hormone will stay in the inter-cellular or extra-cellular space
Chemical nature of hormones
- Modified amino acids
- Steroids
- Peptides (from larger precursor proteins)
- Proteins
1- Adrenaline, Thyroid hormones (T3 and T4) - from modified amino acids like tyrosine and tyramine
2- Cortisol, progesterone and testosterone - from cholesterol
3- ACTH, Oxytocin and ADH
- Insulin
What are the chemical classes of these hormones?
1- Adrenaline, Thyroid hormones (T3 and T4)
2- Cortisol, progesterone and testosterone
3- ACTH, Oxytocin and ADH
- Insulin
- Modified amino acids, from tyrosine and tyramine
2- Steroids, from cholesterol
3- Peptides (from large precursor proteins)
4- Proteins
Which type of signalling is this an example of?
1 -White cells signalling each other
2- Histamine release
3- Insulin release and action
1- Autocrine
2- Paracrine
3- Endocrine
In which hormone is the modality of chemical signalling not absolute? Explain.
Somatostatin -
paracrine fasion - pancreas
endocrine fashion - brain
Examples of complementary actions of hormones
Adrenaline, cortisol and glucagon - in response to short-term intense exercise, prevents hypoglycaemia and hypokalemia, enhances performance
Insulin, Growth hormone (GH), IGH-1 and sex steroids - essential in long-term growth
Which hormones are stimulated during short-term intense exercise? What are their effects?
Adrenaline, cortisol and glucagon
Effects:
1 - enhances performance
2- prevents hypoglycaemia and hypokalaemia
Examples of antagonistic actions of hormones.
Insulin - lowers the blood sugar levels, decreases glycogenolysis and gluconeogenesis
Glucagon - increases the blood sugar levels, increases the rate of glycogenolysis and gluconeogenesis
What are the actions of insulin?
lowers the blood sugar levels, decreases glycogenolysis and gluconeogenesis
What are the actions of glucagon?
increases the blood sugar levels, increases the rate of glycogenolysis and gluconeogenesis
Which enzyme converts cholesterol to cortisol?
Pregnenolone
What is the rate limiting step in the production of steroids?
Conversion of cholesterol to cortisol by pregnenolone
Which form of steroid is active?
The unbound steroid molecules in the biophase (free in the blood)
Where are steroids stored in the body?
They are not stored, they are produced on demand and released after production
What type of hormones are Thryoxine (T4) and triiodothyronine (T3)?
they are modified amino-acid based hormones, but they are hydrophobic and lipid-solbule hormones
What are the uses of carrier proteins in the blood?
1-Increase the amount of hormone transported in the blood
2- extends the half-life of the hormone
reservoir for the hormone
3- helps dampen the surge of hormones (by binding and docking the molecules of hormones)
4- acts as a buffer
5- helps to maintain the equilibrium btw bound and unbound steroid molecules
Examples of insoluble hormones in the blood?
Steroids, thyroxine (T4) and triiodothyronine (T3)
What are the specific carrier proteins and the hormones they carry?
- Cortisol binding globulin (CBG)– cortisol in a selective manner (aldosterone as well)
- Thyroxine binding globulin (TBG) – T4 selectively and some T3
- Sex-steroid binding globulin (SSBG) – testosterone and oestradiol
What are the general carrier proteins and the hormones they carry?
- Albumin – many steroids and thyroxine
* Transthyretin – some steroids and mostly thyroxine
