1. Cellular Mechanisms of Hormone Action Flashcards
What is the effect of a negative feedback loop?
Keeps the hormone within a narrow concentration range
What is the effect of a positive feedback loop?
Reinforces the initial stimulus
Produces a greater response
What are the functions of hormones at a cellular level?
- Change membrane permeability
- Regulate protein expression
- Moderate enzyme activity
- Induce or suppress the release of secretory products
- Stimulate cell division
What determines the rate of delivery of a hormone?
- Rate of synthesis and secretion
- Proximity of target cell
- Dissociation constant
- Rate of conversion to active form
- Rate of clearance from liver/kidney
Which four receptor statuses can influence the degree of cellular response?
- Density
- State of occupancy
- Affinity of receptors for hormone
- Desensitization
What 4 ways can hormones be classified?
Chemical nature
Solubility
Receptor location
Type of receptor
What are steroid hormones derived from?
Cholesterol
Name 2 steroid hormones
Testosterone
Estrogen
Name 2 peptide hormones
Oxytocin
Insulin
Name 2 protein/glycoprotein hormones
LH
TSH
Name 2 amine hormones
Epinephrine
Thyroxine
Which types of hormones are hydrophobic?
Steroid hormones
Some amine hormones
Which types of hormones are hydrophilic?
Some amine hormones
Peptide and protein hormones
How are steroid hormones transported?
Bound to a transport protein
Which amino acids are amine hormones synthesised from?
Tryptophan
Tyrosine
What types of receptors are used by hydrophilic hormones?
Cell membrane receptors
Uses a second messenger
What types of receptors are used by hydrophobic hormones?
Intracellular receptors
Bind to HRE and changes gene expression
How is cAMP signalling controlled?
PKA activates phosphodiesterase which deactivates cAMP
What does phospholipase C cleave membrane bound phospholipids into?
Diacylglycerol
Inositol triphosphate
How does calcium act as a second messenger?
Cofactor for enzymes
Binds to calmodulin which can modulate protein kinase within the cell
What receptor drives the conversion of GTP to cGMP?
Guanylate cyclase
What is released by the cardiac atria when blood pressure is increased?
Atrial Natriuretic Peptide
What does ANP do?
Causes the conversion of GTP to cGMP
cGMP activates protein kinase G and regulates ion channels
Reduction in ECF volume by increasing Na+ secretion
What type of a receptor is an insulin receptor?
Tyrosine-specific protein kinase
