Introduction to the endocrine system Flashcards
Which cell signalling is transported via the blood stream?
Endocrine
Which cell signalling is via a local mediator into target cells nearby?
Paracrine
Which cell signalling involves neurons binding at a synapse?
Neuronal
Which cell signalling releases a signal to act on itself?
Autocrine
Which glands are ductless?
Endocrine glands
What are the major endocrine glands?
Hypothalamus
Pineal gland
Pituitary
Thyroid
Parathyroid
Thymus
Adrenal
Pancreas
Ovaries
Testes
Which is the pituitary gland also known as?
Hypophysis
How is the pituitary gland connected to the hypothalamus?
Via the pituitary stalk (infundibulum)
Which gland controls almost all pituitary secretions?
Hypothalamus
How many hormones are secreted in the pituitary?
Anterior - 6
Posterior - 2
Which functions does the pituitary gland regulate?
What is acromegaly and what can cause it?
Dysfunction of the pituitary gland.
Increased growth hormone in adults = bigger bones
What is gigantism and what can cause it?
Increased growth hormones in children before bone fusion, leads to abnormal height and bone growth.
Caused by pituitary gland dysfunction.
The parathyroid glands are involved in which ion?
Calcium concentration
What hormones does the pancreas release?
Insulin (beta cells) and Glugagon
Also secretes digestive enzymes into GI tract
Where are the adrenal glands located?
Above kidneys
What does the medulla of the adrenal glands secrete?
Adrenaline and noradrenaline in response to SS
What does the cortex of the adrenal glands secrete?
Corticosteroids - synthesised from cholesterol
Which syndrome is caused by too much cortisol?
Cushings syndrome
Which condition is caused by too much aldosterone?
Hyperaldosteronism - leads to HTN
Can peptide hormones cross the cell membrane?
No as they’re hydrophilic, they bind to cell surface receptors instead
Hormones can be stored in cells until required as what?
Prohormones (inactive) –> get cleaved into active hormones via enzymes
Can steroids cross the cell membrane?
Yes as they are hydrophobic
Which type of hormones cannot be stored in cells?
Steroids, but they can be rapidly synthesised
What are steroids synthesised from?
Cholesterol
What is the pathway of Tyrosine to thyroid hormones?
Tyrosine –> 3-lodo-L-tyrosine –> 3-5-lodo-L-Tyrosine –> Thyroxine or Triiodothyronine
What is the pathway of tyrosine to adrenaline?
Tyrosine –> Dopamine –> Noradrenaline –> Adrenaline
Which type of hormones have a short half life, short duration of action and a rapid onset of action?
Peptide hormones
Which type of hormones have a slow onset of action, a long plasma half life and a long duration of action?
Steroid and thyroid hormones
Which type of hormones are not orally active?
Peptides.
Steroids and thyroid hormones are orally active.
What are steroid and thyroid hormones transported in the blood with?
Plasma proteins.
Peptide hormones are not bound and can freely circulate.
What are three primary receptor classes?
GPCR
Tyrosine kinase receptors
Steroid hormone receptors
Which receptor does adrenaline bind to?
G-protein a-adrenergic receptors (Gaq)
What is the GPCR Gaq pathway?
PLC activated –> PIP2 cleavage into DAG and IP3 –> Ca2+ influx, cAMP activation –> protein phosphorylation
What is the pathway of a tyrosine kinase receptor?
What is the pathway of steroid hormone receptors?
1 - enters through cell membrane due to small size and hydrophobic nature
2 - steroid hormone binds with cytoplasmic receptor forming hormone receptor complex (HRC)
3 - HRC enters the nucleus and cytoplasmic receptor aspect of the HRC binds to DNA
4 - HRC binding to genes is able to turn genes on or off
5 - cell undergoes transcription and protein synthesis
When is serum TSH at it’s highest throughout the day?
At night - there is diurnal variation, TSH then reduces during the day
What is the pathway of the hypothalamus-pituitary-adrenal (HPA) axis?
- hypothalamus secretes corticotropin releasing hormone (CRH)
- CRH binds to anterior pituitary gland causing release of adrenocorticotropic hormone (ACTH)
- ACTH is released into blood and binds to adrenal cortex
- adrenal cortex releases glucocorticoids (cortisol)
- glucocorticoids bind to pituitary gland and hypothalamus, inhibits further release of glucocorticoids
What type of receptor class would insulin bind to?
Cell surface receptor
What type of receptor class would thyroid hormones bind to?
Cytosolic receptors
