Fundamentals of Endocrinology Flashcards
What is a hormone?
What is a tropic hormone?
Hormone= specialised substance secreted directly into the blood stream by a specialised cell, travels in the blood and binds to specific receptors on a target cell
Tropic hormones= target other endocrine tissues
Name the major endocrine glands? (10)
Pineal Hypothalamus Pituitary Thyroid Parathyroid Thymus Adrenal Pancreas Ovaries Testes
Difference between Endocrine, Exocrine and mixed glands?
Endocrine glands release heroes directly into the blood from cells. They are ductless!
Exocrine glands release their secretions outside the body (e.g. gut) and may be ducted
Mixed glands
e.g. pancreas do both
Wha the key mechanisms of cellular signalling (5)
Neuroendocrine endocrine paracrine autocrine intracrine
What is negative feedback? Why is it so important?
Procedure by which the body sense change and activates a mechanism to reduce it.
The endocrine system relies on N feedback
final product of an endocrine cascade acts to inhibit the release of hormones higher up the cascade.
Whats an axis in endocrinology?
Axis means how the different glands communicate with each other.
Hypothalmo-pituitary-adrenal axis
Hypothalamus releases CRH via neurosecretion which causes anterior pituitary to release ACTH (Adrenocorticotropic hormone)
Rise of glucocorticoid levels switches of CHR + ACTH production
Peptide hormones
Where are they made?
Biosynthesis? two ways?
Majority of body hormes
preformed in the RER as large precursor molecules, sent to golgi for post translational modification
packaged into secretory vesicles (regulated secretion) require as signal to trigger release via exocytosis
synthesised in steps pre-prohomone (RER), prohomone(golgi), hormone
Or
made up of two units stuck together. Alpha subunit is common between the hormones however the B subunit confers specificity
a unit cleaved functional hormone realised (LH, FSH,TSH)
How are protein hormones transported and how do they effect target cells
hydrophilic charged molecules therefore soluble transported in blood.
Cannot pass hydrophobic core of PPL bilayer must bind to specific receptors and trigger a 2nd messenger system.
Steroid hormones
Originated from where
have common biosynthesis? what are the first major steps?
All originate from the adrenal gland
Made from cholesterol this is coverted by CYP11A to pregnenolone which is the staring point of all steroid hormone syntheis.
What enzyme convertes cholesterol to X in steroid hormone synthesis. (name X too)
CYP11A converts cholesterol to Pregnenolone which is the starting point of all SH synthesis
What are the properties of steroid hormones? How does this affect their transport and effects on target cells
hydrophobic lipophilic molecules (once synthesied cannot be stored)
Cannot be transported in blood (primarily water) alone must bind to a transport protein
lipophillic so once at specific target cell pass feely into cell and bind to intracellular receptors.
Zona glomerulosa contains enzymes allowing for production of?
aldosterone (mineralocorticoid) from pregnenolone
Zone fasiciculata contains enzymes allowing for?
cortisol (glucocorticoid) production from pregnenolone
Zone reticularis contains enzymes allowing for?
Adrenal adrogen synthesis from pregnenolone
Amine hormones/Tyrosine derivatives? properties
made from tyrosine (amino acid)
Thyroid hormones are small non polar molecules (hydrophobic) therefore need a transporter in the blood. (freely pass through csm)
Catecholamines act like proteins ie don’t need transporter and trigger 2nd messenger system.
