What is the basic difference between endocrine glands & exocrine glands?
- Secretions of endocrine glands diffuse into interstitial fluid and then into the blood.
- Exocrine secrections flow into ducts that lead into body cavities or to the body surface.
In the stomach, one stimulus for secretion of hydrocloric acid by parietal cells is the release of histamine by neighboring mast cells. Is histamine an autocrine or a paracrine in this situation?
In the stomach, histamine is a paracrine because it acts on nearby parietal cells without entering the blood.
What is the action of the receptor-hormone complex?
The receptor-hormone complex alters gene expression by turning specific genes of nuclear DNA on or off
Why is CAMP called a "second messenger"?
Cyclic AMP is termed a second messenger because it translates the presence of the first messenger-the water soluble hormone into a response inside the cell.
What is the fuctional importance of the hypophyseal portal veins?
The hypophyseal portal veins carry blood from the median eminence of the hypothalamus, where hypothalamic releasing and inhibiting hormones are secreted, to the anterior pituitary, where these hormones act.
Which other target gland hormones suppress secretion of hypothalamic and anterior pituitary hormones by negative feedback?
Thyroid hormones suppress secretionof TSH by thyrotrophs and of TRH by hypothalamic neurosecretory cells, gonadal hormones suppress secretion of FSH and LH by gonadtrophs and of GnRH by hypothalamic neurosecretory cells.
If a person has a pituitary tumor that secretes a large amount of hGH and the tumor cells are not responsive to regulation by GHRH and GHIH, will hyperglycemia or hypoglycemia be more likely?
Excess levels of hGH would cause hyperglycemia
Functionally, how are the hypothalamohypophyseal tract and the hypophyseal portal veins similar? Structurally, how are they different?
- Functionally, both the hypothalamohypophyseal tract and the hypophyseal portal veins carry hypothalamic hormones to the pituitary gland.
- Structurally, the tract is composed ofaxons and neurons that extend from the hypothalamus to the anterior pituitary.