Endocrine System Flashcards
Peptide hormones vs steroid hormones
Location of receptors
Peptide hormones: extracellular (cell membrane)
Steroid hormones: intracellular or intranuclear
Peptide hormones vs steroid hormones
Chemical precursor
Peptide hormones: amino acids (polypeptides)
Steroid hormones: cholesterol
Peptide hormones vs steroid hormones
Mechanism of action
Peptide hormones: stimulates a receptor (usually a G protein-coupled receptor), affecting levels of second messengers (commonly cAMP). Initiates a signal cascade
Steroid hormones: binds to a receptor, induces conformational change, and regulates transcription at the level of the DNA
Peptide hormones vs steroid hormones
Method of travel in the bloodstream
Peptide hormones: dissolves and travels freely
Steroid hormones: binds to a carrier protein
Peptide hormones vs steroid hormones
Rapidness of onset
Peptide hormones: quick
Steroid hormones: slow
Peptide hormones vs steroid hormones
Duration of action
Peptide hormones: short-lived
Steroid hormones: long-lived
Synthesis of amino-acid derivative hormones
Made by modifying amino acids, such as the addition of iodine to tyrosine (in thyroid hormone production)
Mechanism of action of the amino acid-derivative hormones
Epinephrine & norepinephrine have extremely fast onset but are short-lived, like peptide hormones. Bind to G protein-coupled receptors.
Thyroxine & triiodothyronine have slower onset but a longer duration, like steroid hormones – they regulate the metabolic rate over a long period of time. Bind intracellularly.
Hypophyseal portal system
A blood vessel system that directly connects the hypothalamus with the anterior pituitary.
Once hormones have been released from the hypothalamus into this portal bloodstream, they travel down the pituitary stalk and bind to receptors in the anterior pituitary, stimulating the release of other hormones.
Triiodothyronine and thyroxine
Produced by the iodination of the amino acid tyrosine in the follicular cells of the thyroid
