Lecture 8 Flashcards
3 Main types of Hormones
- Peptide/Protein
- Steroid
- Amine
2 classifications of hormones
- Hydrophilic
- Hydrophobic
Hydrophilic Hormones
- Water soluble, plasma soluble
- Lipid insoluble (lipophobic)
- Unable to cross through plasma membranes
Hydrophobic hormones
- Water insoluble, plasma insoluble
- Lipid soluble (lipophilic)
- Rapidly crosses the plasma membrane
What are peptide/protein hormones derived from?
3 or more amino acids
What are steroid hormones derived from?
cholesterol
What are amine hormones derived from?
single amino acids
Melatonin
- Secreted at night (sleep)
- Made in the pineal gland (also gi tract, leukocytes and other brain regions)
Amine Hormones
Synthesized only from tryptophan or tyrosine
Tryptophan derivative
melatonin (behaves like peptides or steroids)
Tyrosine derivatives
- catecholamines (behave like peptides)
- Thyroid hormones (behave like steroids)
Control of hormone release
endocrine cells directly sense stimuli, then secrete the hormone
Synergistic Effects
- Multiple hormones act together for greater effect
- Synergism between FSH and testosterone on sperm production
Permissive Effects
- One hormone enhances the target organ’s response to a second later hormone
- Estrogen prepares the uterus for action of progesterone
Antagonistic Effects
- One hormone opposes the action of another
- Insulin lowers blood glucose and glucagon raises it
Where do protein hormones act?
react with receptors on the surface of the cell, and the sequence of events that results in hormone action is relatively rapid
Where do steroid hormones act?
The complex is broken down inside the lysosome, and free steroid hormone diffuses into the cell, where it subsequently exerts its action at the genomic level or undergoes metabolism
