Endocrinology Flashcards
What are the two communication systems of the body?
The endocrine system and nervous sytem
Give 5 examples of hormone regulated activities
- Growth and development of physical, sexual and mental characterisitcs
- Utilisation of nutrients by the cell
- Adjustment of salt and water balance
- Metabolic rate
- Dealing with stress
What are the 5 principal endocrine glands?
Name 5 other organs that also secrete hormones.
- Pituitary, the thyroid, the parathyroids, adrenal, gonads
2. Islets of Langerhans, the heart, the gastrointestinal tract, the brain and the kidneys.
What are endocrine cells?
Endocrine cells secrete hormone into the blood vessel which is transported to its target cells.
What are paracrine cells?
Paracrine cells secrete local hormones which act on neighbouring cells.
What are autocrine cells?
Autocrine cells secrete hormones which act on the same cell.
What are neuroendocrine cells?
Neuroendocrine cells secrete hormone directly from neural axon terminals into the bloodstream.
What are the 5 different forms that a hormone can take?
- Proteins or polypeptides e.g. insulin
- Glycoproteins e.g. LH, FSH and TSH
- Derivatives of the amino acid, tyrosine e.g. adrenaline, and thyroid hormones (T3 and T4)
- Steroids derived from cholesterol
- Lipid-derived molecules such as prostaglandins
How are peptide or protein hormones e.g.adrenaline stored and released?
Peptide or protein hormones are stored as pre-formed molecules in secretory vesicles. A stimulus will cause the release of the secretory vesicles by exocytosis where the plasma membrane fuses with the vesicle membranes leading to the release of the contents to the cell exterior.
How are steroids stored and released?
Steroids are lipophilic (tend to combine with or dissolve in lipids or fats) and are therefore not stored in cells. They are synthesised on demand from cholesterol.
Are most peptide and protein hormones hydrophilic or hydrophobic? How does this affect how they travel in the blood?
Hydrophilic
Hence peptide and protein hormones circulate in the blood in the free form.
Are steroid and thyroid hormones (thyroxine) are hydrophilic or hydrophobic? How does this affect how they travel in the blood?
Hydrophobic
Hence steroids and thyroid hormones are transported in the blood bound to serum proteins (protein in blood).
e.g. thyroxine binds to thyroxine binding globulin and cortisol binds to cortisol binding protein.
Each globulin (makes up a large proportion of serum protein) is specific to its hormone.
What are ‘active hormones’?
Active hormones are free circulating hormones. The remainder act as a reservoir,
Describe one way in which hormone levels can be adjusted.
Hormone levels can be altered by changes in the level of the binding proteins themselves. (will then either be active or reservoir)
Which organs remove hormones from the circulation?
The kidneys, liver and occasionally the lungs.
Define the half life of a hormone?
What determines the half-life of a hormone?
Hal-life of a hormone is defined as the time required to reduce the circulating hormone concentration by half.
Which two places in the cell do hormone receptors exist?
Where do hydrophilic/ hydrophobic molecules act on the cell?
The cell surface and or in the nucleus.
Most hydrophilic molecules act on the cell surface but steroid hormones and thyroid hormones have their receptors in the nucleus.
Hormones acting at the …. ….. act by generating …… ….. or by …. ….. of specific target proteins.
- cell surface
- second messengers
- tyrosine phosphorylation
Give two examples of second messenger systems which are widely used?
Name the 3 (+1) secondary messengers of these systems.
1.
2. cAMP, diacylglycerol, Ca2+ (other second messengers are cGMP).
How many transmembrane regions do GPCRs have?
Seven.
