Hormones: Water-Soluble, Amine, and Peptide Hormones

Water-Soluble Hormones

• Bind to receptors in the plasma membrane of a cell.

Amine Hormones

• Include serotonin, melatonin, histamine, epinephrine, and norepinephrine (catecholamines).

Peptide and Protein Hormones

• Include all hypothalamic releasing and inhibiting hormones.
• Examples: oxytocin, growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, prolactin, melanocyte-stimulating hormone, insulin, glucagon, somatostatin, pancreatic polypeptide, parathyroid hormone, calcitonin, gastrin, secretin, cholecystokinin, and erythropoietin.

Action of Water-Soluble Hormones

• Eicosanoids are involved.

Hormone Interactions

Permissive Effect

• A second hormone strengthens the effects of the first, e.g., thyroid hormone strengthens epinephrine's effect on lipolysis.

Synergistic Effect

• Two hormones act together for a greater effect, e.g., estrogen and luteinizing hormone (LH) are both needed for oocyte production.

Antagonistic Effects

• Two hormones have opposite effects, e.g., insulin promotes glycogen formation, while glucagon stimulates glycogen breakdown.

Control of Hormone Secretion

• Regulated by signals from the nervous system, chemical changes in the blood, or by other hormones.

Negative Feedback Control

• The most common type, where a decrease or increase in blood level is reversed.

Positive Feedback Control

• The change produced by the hormone causes more hormones to be released.

Disorders

• Involve either hyposecretion or hypersecretion of a hormone.

Glands

Exocrine Glands (Ducted Glands)

• Secrete substances into ducts, which empty into body cavities or the body surface.
• Examples: sweat glands, oil glands, earwax glands, salivary glands, and pancreas.

Endocrine Glands (Ductless Glands)

• Secrete hormones into the bloodstream.
• Examples: pituitary, thyroid, parathyroid, adrenal, and pineal glands.
• Regulate metabolic and physiological activities to maintain homeostasis.

Chemical Classes of Hormones

Lipid-Soluble Hormones

• Include steroids, thyroid hormones, eicosanoids, and nitric oxide.
• Use transport proteins and bind to intracellular or nuclear receptors.

Water-Soluble Hormones

• Include peptides, 5-HT, peptides/proteins, and glycans.
• Circulate in plasma and bind to receptors on the cell membrane.

Hormones

• Affect only specific target tissues with specific receptors.
• Various cells respond differently to the same hormone.
• Receptors are constantly synthesized and broken down, leading to down-regulation or up-regulation.

Action of Lipid-Soluble Hormones

• Free hormone diffuses into the cell through the blood capillary.
• The hormone binds to a receptor in the cytosol, forming an activated receptor-hormone complex.
• The complex alters gene expression, leading to the synthesis of specific proteins on ribosomes.

This quiz covers the characteristics and types of water-soluble hormones, including amine hormones like serotonin and peptide hormones like oxytocin and insulin. Learn about the different hormones and their functions.