HRR: anterior pituitary hormones Flashcards
What is the median eminence?
A specialized, highly vascularized area that serves as the functional link between the hypothalamus and the pituitary gland.
What is the function (generally) of the hypothalamus?
It is a major regulator of homeostasis.
The anterior pituitary is derived from…
Ectodermal tissue.
What are the 3 lobes of the anterior pituitary?
Pars distalis, pars intermedia, pars tuberalis.
The posterior pituitary is derived from…
Neural tissue.
What are the 2 parts of the posterior pituitary?
Pars nervosa and infundibular stalk.
Describe the infundibular stalk.
Super vascularized area composed of nerve fibers of the neurohypophyseal tract that innervate the posterior pituitary.
Describe the arterial supply of the pituitary gland.
It receives supply from inferior and superior hypophyseal arteries. The inferior hypophyseal artery directly supplies the posterior lobe, while the anterior lobe does NOT have a direct supply.
Describe venous supply of the anterior pituitary.
It receives venous blood that has already traversed in stalk and the median eminence.
Describe portal veins in the pituitary.
The pituitary has capillary beds in the medial eminence area and pituitary stalk. These are drained by either long portal veins (medial eminence) or short portal veins (stalk).
Describe dimeric pituitary hormones and list examples.
Proteins with an alpha and beta subunit; examples are TSH, LH, and FSH.
Which subunit in dimeric pituitary hormones gives the hormone its distinct characteristics?
The beta subunit.
Describe the short negative feedback loop.
- Positive or negative stimulation reaches the hypothalamus. 2. Hypothalamus signals the pituitary. 3. Pituitary releases tropic hormones. 4. Enough tropic hormone exists in the system that it serves as a negative feedback signal onto the hypothalamus.
Describe the long negative feedback loop.
- Positive or negative stimulation reaches the hypothalamus. 2. Hypothalamus signals the pituitary. 3. Pituitary releases tropic hormones. 4. The target gland releases inhibitory hormones to the pituitary and hypothalamus to stop the secretion of tropic hormones.
What is POM-C (pro-opiomelanocortin)?
A precursor that will give off ACTH, B-LPH, and alpha/beta melanocyte stimulating hormones when cleaved.
What is the primary receptor for CRH?
CRHR1.
Describe the HPA axis.
- Stimulus to a CRH neuron. 2. CRH binds CRH receptors on surface of anterior pituitary corticotrope cells. 3. AVP binds its respective receptor. 4. ACTH is produced in the anterior pituitary. 5. ACTH moves to the adrenal cortex to stimulate release of hormones such as cortisol.
What is AVP (arginine vasopressin)?
A hormone released because of CRH neurons; co-expressed with CRH.
What contributes to negative feedback in the HPA axis?
ACTH and cortisol.
Describe how cortisol provides negative feedback to the HPA axis.
- Neural: inhibits CRH release from the hypothalamic neurons.
- Pituitary: inhibits binding of CRH to CRHR1. This inhibits cAMP needed for ACTH release and inhibits POMC gene transcription to prevent ACTH release.
How might IL-1 and IL-6 impact ACTH?
They can directly stimulate ACTH or stimulate CRH neurons to upregulate ACTH. Both will increase cortisol, which is the goal.
Cortisol levels above ___ is related to stress.
25 ug/dl.
When do cortisol/ACTH levels tend to be the lowest?
Around bedtime and during sleep.
When are cortisol/ACTH levels the highest?
In the early morning.
