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Describe the structure and function of the pituitary gland.
- Releases nine peptide hormones
- Seven from endocrine cells of the anterior pituitary (adenohypophysis)
- Called tropic hormones because they “turn on” other endocrine glands
- Two from hypothalamic axons in the posterior pituitary (neurohypophysis)
- All nine bind to membrane receptors and use cAMP as 2nd messenger
What are the two hormones released from the anterior pituitary gland?
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
What is the function of Thyroid-stimulating hormone (TSH)?
Stimulates release of thyroid hormones
When is TSH stimulated to release and when does it stop releasing?
- Released in response to thyrotropin-releasing hormone (TRH) from hypothalamus
- Decreased release when thyroid hormone levels rise (negative feedback)
What is the function of ACTH?
- Stimulates release of steroid hormones from adrenal cortex
- Specifically those that affect glucose metabolism
ACTH is released in response to what?
corticotropin-releasing hormone (CRH) from hypothalamus
What two hormones are released in response to gonadotropin-releasing hormone (GnRH)
- from hypothalamus?
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
What is the function of FSH?
- Females: promotes ovarian follicle development and (in concert with LH) stimulates secretion of estrogens
- Males: promotes maturation of sperm
What is FSH inhibited by?
inhibin (peptide released by gonads)
What is the function of LH?
- Females: induces ovulation, promotes secretion of estrogen and progestins (e.g.,
- Males: stimulates production of sex hormones (androgens), primarily
What is the function of Growth Hormone (GH) ?
Stimulates cell growth and reproduction by stimulating rate of protein synthesis
What stimulates the release of GH?
Released in response to growth hormone–releasing hormone (GH–RH) and growth hormone–inhibiting hormone (GH–IH)
What is the function of Prolactin (PRL)?
Works with other hormones to stimulate mammary gland development and milk production
What is PRL stimulated and inhibited by?
- Released in response to several prolactin-releasing factors
- Inhibited by prolactin-inhibiting hormone (PIH)
What are the two hormones released by the posterior pituitary gland?
- Antidiuretic hormone (ADH)
- Oxytocin (OXT)
ADH is also known as what?
arginine vasopressin (AVP)
What is the function of ADH?
- Primary function is to decrease water lost from kidney
- Also causes vasoconstriction
What causes the release of ADH and what inhibits it?
- Released in response to a variety of stimuli, Primarily increased solute concentration of blood (sensed by osmoreceptors), or a decrease in blood pressure or volume
- Inhibited by increase in extracellular fluid volume, Also inhibited by alcohol
When is the release of Oxytocin (OXT) increased?
- Nursing (suckling)
- Sexual arousal (function unknown)
- Sensory input (neuroendocrine reflex)
OXT stimulates the contraction of what?
- Smooth muscle walls of uterus
- Mammary gland myoepithelial cells, releasing milk