Summary of Classes of Hormones, Second messengers, Up vs Down Regulation, Positive vs Negative Feedback
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Course
Physiology
Institution
Masaryk University
This is a good overview of endocrinology and it's regulation, before diving into the details. It classifies the 3 major types of hormones (Proteins/ peptides, Steroid, Amines) and summarizes all the features they have in common (Synthesis, Secretion, Solubility, Transport, Receptor, Effects, etc). ...
Types of Hormone Regulation
Type Substance secreted Location secreted to Influenced cells Examples
Autocrine Ligand ECF Cells of the same type Lymphocytes - cytokines
Paracrine Ligand ECF Nearby cells of different types Growth factors in cuts
Endocrine Hormone Blood Different cells far from secreting cell Glands
Gap Junctions Substances Membrane - membrane Adhered cells (Rapid transmission) Heart and smooth muscles
General Classes of Hormones
Hormone Synthesis Secretion Solubility Transport Receptor Effect
Nucleus: DNA mRNA Stored in secretory Polar Freely in blood Metabotropic - Outer Second messenger system.
Ribosomes: Preprohormone vesicles of Glands: (Hydrophilic) cell membrane (can’t Fast acting.
Proteins/
ER: Prohormone (needs activation) Pituitary cross membrane) Short half-life.
Peptide
GA: Peptide hormone Pancreas (Faster onset, Shorter duration)
Parathyroid
Cholesterol Pregnenolone (makes Direct release: Non-polar Bound to carrier proteins Usually receptors on Signal transduction for gene
DHEA) Progesterone (makes cortisol Adrenal Cortex, (Lipophilic) (ineffective when bound). cytoplasm or nucleus expression (direct DNA binding).
Steroid and aldosterone) Androstenedione Gonads Sex hormone-binding globulin (can cross cell Slow acting.
(makes testosterone and estradiol) Placenta (SHBG), Corticosteroid- membrane) Long half-life.
binding globulin, and Albumin (Slower onset, Longer duration)
From amino acid Tyrosine Adrenal medulla Polar – Adrenaline Freely Membrane receptors Second messengers
Amine Catecholamines (polar)or Hypothalamus Polar - Dopamine
thyroid (non-polar)
Thyroid Non-polar – T3, T4 Protein-bound Nucleus receptors Alternations of gene expression
SECOND MESSENGERS/ INTRACELLULAR RECEPTORS:
Ionotropic – Form ion channel pore for the hormone or neurotransmitter.
Metabotropic – Causes signal transduction mechanisms for secondary messengers (G-proteins/ protein kinases)
G-Proteins (Guanosine Triphosphate Binding Proteins):
Gs – Stimulate adenylate cyclase (cAMP) – Activates protein kinase A catalyzes phosphorylation of proteins
Gi – Inhibit adenylate cyclase (cAMP)
Gq – Stimulates phospholipase C catalyzes breakdown of membrane phosphatidylinositol biphosphate (PIP2) into:
Inositol triphosphate (IP3) – Activates protein kinase C to mobilize calcium ion secondary messengers.
Diacylglycerol (DAG) – Lipid layer in membrane that activates protein kinase C to phosphorylate proteins.
Insulin receptor Tyrosine Kinase (Tyr-K): (kinases are phosphorylating proteins)
When bound with insulin, the kinase auto-phosphorylates the sub units phosphorylate intracellular proteins activates IP3 and DAG second messengers It
increases GLUT 4 transporters in skeletal muscles.
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