Chapter 31 Principles of Endocrinology

Question 1

What is homeostasis?

Answer 1

It is a stability that is contained in the intracellular and extracellular compartments of the body

Question 2

in the endocrine system, what are the 3 general hormone classes?

Answer 2

1. Amine
2. Proteins and peptides
3. Steroids

Question 3

What are the properties of each of the 3 general hormone classes?

Answer 3

1. Amines are smaller molecules derived from amino acids
2. proteins and peptides come in a variety of shapes and sizes and functions but they are usually strings of amino acids
3. Steroids are usually derived from either cholesterol or sterol

Question 4

How is signal transportation accomplished in both endocrine and neural response?

Answer 4

In endocrine it is done via blood

In neural it is done via neurons

Question 5

What is used as the signal in both endocrine and neural responses?

Answer 5

In endocrine it is done via a hormone

In neural it is done via a Nerve impulse or a neurotransmitter

Question 6

What is the speed of the response in both endocrine and neural response and how far is the signal being sent?

Answer 6

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

Question 7

What are the 3 main things that take place in an Endocrine system ?

Answer 7

1. Regulated secretion of biological products (hormones) in the blood
2. Circulation of hormones throughout the body
3. Binding hormone to a specific receptor within a target cell

Question 8

What are the 2 types of hormone receptors?

Answer 8

Membrane receptors
Nuclear hormone receptors

Question 9

What hormones bind to the membrane receptors and where are these receptors located and name specific examples?

Answer 9

• 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

Question 10

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?

Answer 10

• 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

Question 11

Under which condition can several hormones bind to the same receptor?

Answer 11

• ONLY IF the concentration of those hormones are the SAME

Question 12

What does the term “ Enzyme Cascade” mean?

Answer 12

It is when one enzyme activates several other enzymes

Question 13

What does the term “integration” mean in terms of a hormone response?

Answer 13

This is when there are 2 different signals going into 2 separate receptors and then coming together to result in 1 net response

Question 14

Are hormones limited to effecting only one tissue and one function?

Answer 14

No, hormones can influence several different tissues and hormones can even have different functions depending on the target tissue

Question 15

Can one protein be only used for one effect?

Answer 15

No , proteins like proglucagon can be chopped up into smaller hormones that all may have different effects

Question 16

Review slide 17- hormone action -adenylate cyclase cyclic AMP (cAMP)

Question 17

What type of receptor is used in the Adenylate cyclase cyclic AMP(cAMP) and what activates the enzyme cascade?

Answer 17

-G coupled receptor
-Protein kinase A (PKA) starts the enzyme cascade

Question 18

What is the process of PKA going from inactive to Active?

Answer 18

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

Question 19

How does the insulin action work and how does the tyrosine kinase get activated ?

Answer 19

1. Insulin comes in and binds to the receptor
2. The receptor dimerization happens which leads to the activation of tyrosine kinase
3. Phosphorylation of receptor occurs with the help of ATP and the phosphorylation of downstream signalling molecules also with the help of ATP
4. Then the alteration of activity happens of downstream signalling molecules
5. last step is the altered metabolism in this insulin action example- glucose uptake and anabolic reactions occur

Question 20

Where are thyroid hormones found?

Answer 20

They are intracellular receptors found in the nucleus

Question 21

What does a Thyroid hormone do?

Answer 21

It binds to the hormone sensitive element of target DNA and then that leads to gene transcription

Question 22

Where are Steroid Hormones found ?

Answer 22

They are intracellular receptors found in the cytoplasm

Question 23

What does a steroid hormone do?

Answer 23

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

Question 24

How is the hormone action controlled?

Answer 24

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

Question 25

How does the Circadian rhythm of hormone secretion work ?

Answer 25

In this rhythm the hormone secretion occurs during around 11pm-7am aka the dark period.

Question 26

What helps regulate most circadian rhythms in our body and also known as the biological clock ?

Answer 26

the Suprachiasmatic nucleus (SCN) in the hypothalamus

Question 27

How does the pulsatile secretion of hormones work ?

Answer 27

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)