Chapter 31 Principles of Endocrinology Flashcards
What is homeostasis?
It is a stability that is contained in the intracellular and extracellular compartments of the body
in the endocrine system, what are the 3 general hormone classes?
- Amine
- Proteins and peptides
- Steroids
What are the properties of each of the 3 general hormone classes?
- Amines are smaller molecules derived from amino acids
- proteins and peptides come in a variety of shapes and sizes and functions but they are usually strings of amino acids
- Steroids are usually derived from either cholesterol or sterol
How is signal transportation accomplished in both endocrine and neural response?
In endocrine it is done via blood
In neural it is done via neurons
What is used as the signal in both endocrine and neural responses?
In endocrine it is done via a hormone
In neural it is done via a Nerve impulse or a neurotransmitter
What is the speed of the response in both endocrine and neural response and how far is the signal being sent?
In endocrine the signal has to travel further via the blood circulation therefore it has a slower speed of response
In neural the signal is being sent very close therefore it has a faster speed of response
What are the 3 main things that take place in an Endocrine system ?
- Regulated secretion of biological products (hormones) in the blood
- Circulation of hormones throughout the body
- Binding hormone to a specific receptor within a target cell
What are the 2 types of hormone receptors?
Membrane receptors
Nuclear hormone receptors
What hormones bind to the membrane receptors and where are these receptors located and name specific examples?
- Hormones that cannot enter cell bind to the membrane receptors and they are usually located on the membrane or the outer membrane
- its usually the peptide or polypeptide hormones that bind to these receptors
- some examples would be : Glucagon , Insulin , TSH
How does a hormone bind to a nuclear hormone receptor and what other events take place at this receptor and name specific examples of hormones that use this receptor?
- Hormone crosses plasma membrane and binds to this receptor INSIDE the cell
- other events like Receptor-DNA binding events also take place here (altering transcriptional complex activity)
- Some examples would be several hydrophobic hormones : Oestrogen, glucocorticoids, retinoids , thyroid hormone
Under which condition can several hormones bind to the same receptor?
- ONLY IF the concentration of those hormones are the SAME
What does the term “ Enzyme Cascade” mean?
It is when one enzyme activates several other enzymes
What does the term “integration” mean in terms of a hormone response?
This is when there are 2 different signals going into 2 separate receptors and then coming together to result in 1 net response
Are hormones limited to effecting only one tissue and one function?
No, hormones can influence several different tissues and hormones can even have different functions depending on the target tissue
Can one protein be only used for one effect?
No , proteins like proglucagon can be chopped up into smaller hormones that all may have different effects
Review slide 17- hormone action -adenylate cyclase cyclic AMP (cAMP)
What type of receptor is used in the Adenylate cyclase cyclic AMP(cAMP) and what activates the enzyme cascade?
-G coupled receptor
-Protein kinase A (PKA) starts the enzyme cascade
What is the process of PKA going from inactive to Active?
It starts with the regulatory sites emptying cAMP sites and the catalytic subunits substrate binding sites are blocked by the autoinhibtory domains of R subunits
Then when the subunits get separated there are 4 cAMP that come and bind to the R subunit which causes the catalytic subunits substrates biding sites to open up starting the enzyme cascade and causing the PKA to be active
How does the insulin action work and how does the tyrosine kinase get activated ?
- Insulin comes in and binds to the receptor
- The receptor dimerization happens which leads to the activation of tyrosine kinase
- Phosphorylation of receptor occurs with the help of ATP and the phosphorylation of downstream signalling molecules also with the help of ATP
- Then the alteration of activity happens of downstream signalling molecules
- last step is the altered metabolism in this insulin action example- glucose uptake and anabolic reactions occur
Where are thyroid hormones found?
They are intracellular receptors found in the nucleus
What does a Thyroid hormone do?
It binds to the hormone sensitive element of target DNA and then that leads to gene transcription
Where are Steroid Hormones found ?
They are intracellular receptors found in the cytoplasm
What does a steroid hormone do?
They are carried in by carrier protein(hydrophobic proteins) that help with nuclear translocation of the hormone bound receptor. which Then leads the binding to the hormone response element of target DNA which generates gene transcription
How is the hormone action controlled?
ENdocrine glans will release a hormone which will transfer to the target cell and have its effect but then it is also sent back to the endocrine gland via the negative feedback loop which has a negative effect on the hormone secretion
How does the Circadian rhythm of hormone secretion work ?
In this rhythm the hormone secretion occurs during around 11pm-7am aka the dark period.
What helps regulate most circadian rhythms in our body and also known as the biological clock ?
the Suprachiasmatic nucleus (SCN) in the hypothalamus
How does the pulsatile secretion of hormones work ?
it all begins in the hypothalamus which is a bundle of nerves that will release GnRH which will then travel to the pituitary and then that triggers a FSH and LH release towards the gonads which then release testosterone (male) and Estradiol (female)
