Endocrinology 3 and 4 Flashcards
What kind of receptor does adrenaline bind to?
A g-protein-linked receptor
How do G-proteins work?
- A ligand binds
- Causes a change in an enzyme in cell membrane (ex. adenylate cyclase)
- Causes the production of a second messenger (cAMP)
- cAMP acts on protein kinase and activates it (pka)
- Protein kinase can cause phosphorylation of proteins
- Proteins can bring about a response in the target cell
What is a very well known second messenger?
cAMP
Where in the cell are intracellular receptors mainly found?
In the cytoplasm or nucleus or bound to DNA in the nucleus
What happens after a ligand binds to the receptor in the cytoplasm?
The combo of hormone and receptor will pass into the nucleus
What does the combination of hormone and receptor do in the cell?
They bind to the DNA and act as a transcription factor
What do transcription factors do?
Bring about changes in transcription and translation
What is interesting about thyroid hormone receptors
They are thought to be bound all the time to the DNA in the nucleus and when the receptor is bound to the DNA it is inactive. When the thyroid hormone comes along and binds to the receptor it is activated
What is the output of hormones controlled by?
Negative and Positive feedback
How does Metabolism affect a hormone?
It can make it more active or less active
How does Binding to plasma proteins affect a hormone?
When a hormone binds to a plasma protein, it solubilizes so it has a harder time diffusing into a cell. So steroid hormones need to be bound and carried in that bound form to their targets
What is the activity of a hormone bound to plasma proteins?
It has no activity for the time that it is bound
What is the relation between protein hormones and catecholamines?
They are separate families but share similar properties
Where do the catecholamines come from?
The adrenal medulla
Which types of hormones are water soluable?
Proteins and catecholamines
What are the protein hormones made of?
Amino acids
What are the catecholamines made of?
Tyrosine
How are Protein hormones stores and secreted?
They are store in granules and secreted by exocytosis
How are protein hormones transported in the blood?
They do not need solubilization in the blood
How fast are the course of actions of Protein hormones?
They are relatively fast
What is another reason for hormones to bind to plasma proteins?
It helps to prevent overly fast breakdown of the hormone
Where are the steroid hormones produced?
- Adrenal cortex
- Ovaries and Testes
- Thyroid gland
What is the solubility of steroid hormones?
They are lipid soluble
What are steroid hormones synthesized from?
From cholesterol
How are steroid hormones stored or secreted?
They are not stored and secreted by diffusion
What is the mechanism of action of steroid hormones?
Mainly by regulation of gene expression in the target cell nucleus
What is the time course of action of steroid hormones?
Relatively slow
What acts as the overall controlling system of most of the other hormones in the body?
The hypothalamus and the pituitary
What are the names of the two parts of the pituitary?
- Anterior pituitary (adenohypophysis)
* Posterior pituitary (neurohypophysis)
What does the pituitary stalk do?
Connects the hypothalamus and the pituitary
What is the upper region of the stalk called?
The medial eminence
What is the Posterior pituitary derived from?
A down growth from the brain
What does the tissue of the posterior pituitary look like?
Neural tissue
What is the anterior pituitary derived from?
An upgrowth from the mouth region
What is the primary capillary plexus?
The network of capillaries that the artery forms in the hypothalamus
What does the primary plexus go on to form?
They rejoin to form Portal Blood Vessels
What is a Portal blood vessel system?
One that has capillaries at both ends of it
Where do the Portal blood vessels go?
They pass down the pituitary stalk and go to the anterior pituitary
What happens one the Portal blood vessels pass down the the stalk?
They turn into the secondary plexus in the anterior pituitary
Where does blood go from the secondary plexus in the anterior pituitary?
The capillaries join together to form the vein
Where do the neurons that affect the pituitary have their cell bodies?
In the hypothalamus
What can the neurons in the hypothalamus do?
Produce hormones
Where do the hormones produced by the neurons go?
Onto the primary plexus
Where do neurohormones go from the primary plexus?
They travel down the portal blood vessels down the secondary plexus and enter the endocrine tissue of the anterior pituitary
What happens once neurohormones leave the pituitary plexus?
They go on to affect cells in the anterior pituitary causing the release of hormones from those cells
What are the Supraoptic nucleus and Paraventricular Nucleus?
Regions in the hypothalamus where there are cell bodies neurons that communicate with the posterior pituitary
Where do hormones produced by the SON and PVN go?
The go down the cell axon to the posterior pituitary and into a network of capillaries of the posterior pituitary
What hormones are released from the Anterior Pituitary?
- FSH
- LH
- Adrenocorticotropic hormones (ACTH)
- TSH
- Prolactin (PRL)
- Growth Hormone GH
What is the main target of FSH?
Ovaries and testes
What are the main targets of LH?
Ovaries and testes
What are the main targets of ACTH?
Adrenal cortex
What are the main targets of TSH?
Thyroid gland
What are the main targets of prolactin?
Mammary glnds
What are the main targets of growth hormone?
Most tissues
What type of hormones are the ones that come from the anterior pituitary?
Protein hormones
What is different about FSH and LH?
They are produced from the same cells
What is the mnemonic to remember the anterior pituitary hormones?
FLATPG (flat pig)
What are the 6 Hypothalamic hormones?
- Gonadotropin releasing hormones (GnRH)
- Corticotropin releasing hormones (CRH)
- Thyrotropin releasing hormones (TRH)
- Prolactin inhibiting hormone (dopamine) (PIH + DA)
- Growth hormone-releasing hormone (GHRH)
- Somatostatin or Growth Hormone Inhibiting hormone (SS or GHIH)
What does Gonadotropin Releasing Hormone do?
Increases FSH and LH
What does Corticotropin Releasing Hormone do?
Increases ACTH
What does Thyrotropin Releasing Hormone do?
Increases TSH
What does Prolactin Inhibiting Hormone (Dopamine) do?
Decreases PRL
What does Growth Hormone Releasing Hormone do?
Increases GH
What does Somatostatin do?
Decreases Growth Hormone
What type of hormones are the hypothalamic hormones?
All are are peptides except for PIH
What is the way to remember to Hypothalamic Hormones?
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