Hormones Flashcards
Hormone
- chemical secreted in small amounts by endocrine cells/neurons
- circulate in blood
- only affect specific target receptors
Types of hormones
- proteins
- steroids
- amines
How does the endocrine system deposit hormones into the blood?
exocytosis or defusion
What’s a peptide?
a protein that’s 50 AA or less
Types of stimulation for hormonal release
- Humoral stimulus = change in blood levels of something
- Neural stimuli = neurons stimulate release of hormone
- Hormonal stimuli = hormonse stimulates release of another hormone
MAIN ONE
Classification of Hormones
Lipid soluble/ lipophilic = steroids and thyroid hormones
Water soluble/ lipophobic = proteins/peptides, catecholamines (biogenic amines), melatonin
Lipid soluble hormones
- derived from?
- timing?
- receptors?
- actions?
- derived from cholesterol (steroids) and tyrosine (thyroid hormones)
- synthesized on demand bc they defuse out of cell once made
- released by diffusion
- need carrier proteins to move through blood –> stay in circulation longer
- intracellular receptors –> usually in cytoplasm or nucleus
- genomic effects –> alter protein synthesis –> response time is prolonged
how do lipid soluble hormones affect protein synthesis?
- binding of hormone to specific DNA region initiates transcription of gene into mRNA
- mRNA directs protein synthesis
Water soluble hormones
- when are they made?
- how released?
- time?
- receptor?
- effects?
- produced and stored ahead of time in vesicles
- released by exocytosis when stimulus
- travels easily thru blood, so doesn’t circulate for long
- Membrane receptor –> use intracellular mediators
- non-genomic effects –> fast response where 2nd messenger modifies existing proteins
water soluble second messenger process
- allows magnification of effects + can cause multiple effects at once
- hormone (1st) –> receptor –> G protein –> amplifier enzyme –> 2nd messenger –> effects
Adenylate cyclase/ cAMP system
- ligand binds to membrane receptor
- G protein activated (GDP to GTP)
- Activated G protein activates adenylate cyclase
- conversion of ATP to cAMP
- cAMP activates kinase A
- Phosphorylation of proteins
- alters cell function
Phospholipase C signal transduction
- ligand binds to membrane receptor
- G protein activated (GDP to GTP)
- Activated G protein activates phospholipase C
- PIP2 –> DAG + IP3
- DAG activates kinase C –> phosphorylates proteins
- IP3 opens Ca channels and frees Ca in cytosol
Membrane Receptor Enzymes
- receptor is extracellular
- enzyme is intracellular
- ligand binding acivates kinase (amplifier enzyme)
- phosphorylates stuff
less steps than 2nd messenger
Guanylate cyclase stuff
- hormone binds to receptor
- activates guanylate cyclase to produce cGMP from GTP
- cGMP alters activity of intracellular enzymes
- Phosphodiesterase converts cGMP back to GTP
How are intracellular proteins typically altered and what effects can this have?
-altered with Ca or PO3
- metabolism
- transportation across membranes
- protein activity
- cytoskeleton activity
- muscle contraction
- gene expression