Pituitary

Question 1

Hormones secreted by the post. Pituitary

Answer 1

Vasopressin and oxytocin

Question 2

Oxytocin

Answer 2

. Stimulates contraction of myoepithelial cells around alveoli in breasts
. Contraction empties milk into nipple
. Contracts uterine myometrium, promoting expulsion of fetus and placenta

Question 3

Vasopressin

Answer 3

. Promote aquaporin insertion via cAMP activation
. Vasoconstriction of vascular smooth m. Via V1 receptors
. Half life short (15-20 min)
. Stimulates thirst

Question 4

Vasopressin regulation

Answer 4

. Osmoreceptors
. Dec. firing causes inc. ADH
. Low BV (only large loss, not sensitive mechanism) sensed by atrial baroreceptors

Question 5

Conflicting signals with ADH

Answer 5

. When plasma osmolality is dec. below normal while at the same time the BV is dec.
. Volume-regulating stimulus overrides the osmoregulation mechanism
. Overall effect would be inc. ADH secretion

Question 6

Additional stimuli to vasopressin secretion

Answer 6

. Cholinergic agents
. AII
. Estrogen
. Progesterone
. Endorphins
. Nausea 
. Pain
. Traction on intestines 
. Hypoxia and stress
. Exercise and inc. body temp.

Question 7

Vasopressin inhibitors

Answer 7

. Dec. body temp. 
. Adrenergic agents (alpha)
. Glucocorticoids
. Ethanol 
. Lithium

Question 8

Pituitary portal system

Answer 8

. Hypothalamo-hypophyseal veins connecting hypothalamus and ant. Pituitary
. Portal veins
. Hypothalamic hormones are secreted via fenestrated capillaries into this pituitary portal system
.hypothalamic hormones stimulate differentiation and proliferation of their target cells in the ant. Pituitary (hypophysiotropic hormones)

Question 9

Hypothalamic hormone characteristics

Answer 9

. All peptides except dopamine (catecholamine)
. Synthesized by cells contains in discrete nuclei in specific parts of hypothalamus
. Act as neuromodulators in GI tract
. Stimulators input predominates for 5/6 hormones (exception is prolactin that is normally suppressed by dopamine)

Question 10

Families of hormones in ant. Pituitary

Answer 10

. Glycoproteins: follicle-stimulating hormone, lutenizing hormone, thyroid-stimulating hormone
. Somatomammotropins: growth hormone, prolactin
. Pro-opiomelanocortin: metabolized to ACTH
. All considered tropic hormones and control growth and secretion of target tissues

Question 11

Corticotropin releasing hormone (CRH) effect

Answer 11

. Stimulates secretion of ACTH

Question 12

Thyrotropin releasing hormone (TRH) effect

Answer 12

. Stimulates secretion of TSH

Question 13

Growth hormone releasing hormone (GHRH) effect

Answer 13

. Stimulates GH

Question 14

Somatostatin effect

Answer 14

Inhibits secretion of GH

Question 15

Gonadotropin releasing hormone (GnRH) effect

Answer 15

Stimulates secretion of LH and FSH

Question 16

Dopamine (DA) effect on ant. Pituitary

Answer 16

. Inhibits secretion of prolactin

Question 17

Modulation of ant. Pituitary hormone secretion via CNS input

Answer 17

. Neurons from neocortex, basal forebrain, brainstem, and reticular formation impinge on neurosecretroy cells in hypothalamus
. Nerves carry info related to environmental conditions, physical stress, emotions, physiological stimuli, or diurnal. Rhythms (light/dark, sleep cycles)

Question 18

Neg. feedback by hormones w/in multi-endocrine systems

Answer 18

. Hormone secreted by third target endocrine gland may suppress secretion from ant. Pituitary and secretion from hypothalamus (long feedback loop)
. Ant. Pituitary may also suppress the secretion from hypothalamus (short feedback loop)