Endrocrinology Flashcards
Describe a hormone.
A physiologic, organic substance synthesized by a ductless endocrine gland, which travels in the circulation in nanomolar to picomolar amounts to interact with specific receptors to inhibit, stimulate or regulate the functional activity of a target organ.
Which Areas are concerned with the tonic release of GnRH?
ME, ARC, VMN
What region is the hypothalamus within?
third ventricle from the optic chiasm to mammillary bodies
Areas concerned with the surge release of GnRH and gonadotropins include?
PON, AHA, SCN
Where is the pituitary gland located?
sella turcica in a depression of the sphnoid
What three parts are divided into the pituitary?
Anterior, intermediate and posterior lobes
What other terms are used to describe the anterior pituitary gland?
pars anterior, pars distalis, adenohypophysis
What terms are used to describe the posterior pituitary?
pars nervosa, neurohypophysis
What does pars mean?
Pituitary
Name the 5 cell types and which of the six hormone they secrete.
1) Somatotrophs-GH
2) Corticortrophs-ACTH
3) Mammotrophs-Prolactin
4) Thyrotrophs-TSH
5) Gonadotrophs-FSH and LH
How does the arterial blood enter the pituitary?
superior and inferior hypophseal artery
What does the superior hypophseal artery form?
Capillary loops at the median eminence and anterior pituitary
Where does the blood flow after the capillaries?
the portal system which begins and ends in capillaries without going through the heart
Describe retrograde flow.
Blood flow from the pituitarty back to the hypthalamus
What is the purpose of the retrograde flow?
Provide the pituitary negative flow
Which pituitary does not contain a portal system?
Posterior
Where are the growth factors produced?
From different tissues to diffuse into target cells.
Hormone related substances control the growth and development of what?
Several organs, tissue and cultured cells
What does the hypothalamus consist of?
Clusters of nerve cells bodies called hypothalamic nuclei
What is the third ventricle and what surrounds it?
Hypothalamic nuclei surround the third ventricle which is a small cavity in the center of the brain
What does the hypothalamus have VASCULAR connections to?
The anterior lobe of the pituitary
Describe the neural connections of the hypothalamus
the connect to the posterior lobe of the pituitary through the hypothalamic-hypophseal tract
What does sella turcica translation mean?
Turkey Saddle
Where does the superior hypophyseal artery divide?
It divides into smaller capillaries at the level of the pituitary stalk into the primary portal plexus
Describe the releasing and inhibitory hormones role in the blood flow.
These hormones are transferred to the secondary portal plexus and cause the release or inhibition of hormones from pituitary cells
What hormones are made in the posterior pituitary?
None they are only stored there
Where is the neurohormone released from and where does it go?
Release from the posterior pituitary and released into a simple arteroveneous capillary plexus
What do gonads produce?
Gametes and gonadal hormones
Describe the male gonads.
The interstitial cells in the ST, called Leydig cells produce testosterone
Describe the gonads of the female.
Granulosa cells of the follicle make E2
After ovulation the theca interna and granulosa cells make up the CL and produce P4
How are the reproductive hormones divided?
By chemical structure
- Proteins
- Steroids
- Fatty Acids
- Amines
Describe protein hormones
Polypeptides
Oxytocin, FSH, LH
Describe the steroid hormones.
Derived from cholesterol
Testosterone, E2 and P4
Describe half life of a hormone.
The time required of half the quantity of a hormone to disappear from the blood or body
Describe the fatty acid hormones
Derived from arachidonic acid
PGF2a
Describe amine hormones
Derived from tyrosine or tryptophan
Melatonin
What has to happen for a hormone to cause a response?
It must interact with the target tissue. The cells of the target tissue must have receptors to bind the hormone
What does the affinity mean in receptor signaling?
hold or grasp that the receptors have on the hormone
What are the two factors of hormonal potency?
Receptor density and hormone receptor affinity
Compare and contrast hormone agonists and antagonists.
Agonists are artificial, cause the same biological effects as the native hormone, promote greater physiological activity
Antagonists- have a greater affinity but promote weaker biological activity, prevents the native hormone from binding by sitting on the receptor and blocking
Name the four steps of the protein hormone signaling.
1) Hormone Receptor Binding
2) Adenylate Cyclase Activation
3) Protein Kinase Activation
4) Synthesis of New Products
What occurs in the first step of protein hormone signaling?
1) Hormone diffuses from the blood into the interstitial compartment
2) Binds to the membrane bound receptor
Where does the lock and key binding occur for protein hormones?
On the surface
What happens in the second stage of protein hormone signaling?
Hormone receptor complex activates a membrane bound enzyme know as adenylate cyclase. Hormone receptor is formed when G protein is transformed to activate the AC enzyme
What membrane bound protein mediates the AC activity?
G-protein
The activation of AC causes what conversion?
ATP to cAMP + PPi in the cytoplasm of the cell
What are the two messengers in protein hormone signaling?
- Hormone is the primary messenger
- cAMP is the second messenger
What happens in stage three of the protein hormone signaling.
cAMP activates a family of control enzymes located in the cytoplasm called in protein kinases
What does PK do?
Activate the enzymes in the cytoplasm to convert substrates to products
How is the catalytic subunit of protein hormone signaling activated?
cAMP binds to the regulatory unit of PK
What occurs in step 4 of the protein hormone signaling?
Products made by the cells are secreted
Name the three pituitary hormones.
FSH, LH and Prolactin
How is prolactin the exception of the pituitary hormones?
Secretion is under tonic inhibition by dopamine
What does prolactin do in rodents?
Initiates and maintains lactation and is luteotrophic
