Summary Hormonal Control and Adrenaline

Hormonal Control and Adrenaline:
 Exocrine glands – Secretes molecules (not hormones) into
ducts.
 Endocrine glands – Secretes hormones into blood capillaries.
 There are protein-based (or amino acid-based) hormones and
steroids (lipid-based hormones).

 Steroids can pass directly through the plasma membrane (since
they are non-polar) to bind to a receptor in the cytoplasm.
 This steroid hormone–receptor complex then enters the
nucleus and acts as a transcription factor on DNA (it either
promotes or inhibits the transcription of a gene).


 Protein based hormones are polar, and so they can’t pass
through the plasma membrane.
 Instead they bind to a receptor on the plasma membrane that
triggers the release of a secondary messenger within the cell
that then binds with a receptor within the cell nucleus.
 The binding of the protein-based hormone to the receptor
often causes a G-protein to be released, which then activate
the conversion of ATP into cAMP (controlled by the enzyme
adenyl cyclase).
 cAMP activates a cascade of enzyme-controlled reactions
(cAMP is the secondary messenger).


Adrenal Glands:
 Adrenal glands are split into the outer adrenal cortex, and inner
adrenal medulla.