Endrocrine anatomy and physiology

Endocrine glands:

• secrete hormones directly into bloodstream.
• maintain homeostasis by controlling variables such as body temperature,fluid balance.,especially with negative feedback mechanism.

classification:

steroid ,non steroid

Steroid hormones:

• Derived from cholesterol
• produced in adernal glands ,gonad(testes,ovaries)
• Hydrophobic/non polar >travel through bloodstream with transport proteins,diffuse across target cell phospholipid membrane and bind to an intracellular receptor which result in changes in gene expression.

Steroid hormones(Hydrophilic)

Non-steroid hormones:

• Derived from peptides/proteins or single amino acids
• Peptides hormones are hydrophilic>bind surface receptor proteins instead of passing through target cell membrane,which result in gene expression.
• Amino acid hormones derived from tyrosine;generally hydrophilic(e.g.adrenaline/epinephrine and noradrenaline/norepinephrine),apart from thyroid hormones.

Non-steroid hormone(Peptide hormone,Hydrophilic)

Hormone secretion and regulation:

Paracrine signaling:

• effects of hormones released by nearby cells;e.g.glucagon>activates alpha cells, inhibit beta cells.

Sympathetic nervous system:

• Epinephrine /norepinephrine alter secretion depending on adrenargic receptor type;
• e.g.Beta 2:activate beta cells.

Parasympathetic nervous system:

• Acetylcholine activates alpha cells and beta cells via M3 receptors.