animal phys exam 4: hypothalamus and pituitary

what are the functions of the hypothalamus

• regulation of hormone secretion

• metabolism

• body temperature regulation

• hunger and thirst

• circadian rhythms

• reproduction

where is the hypothalamus located

at the base of the brain directly above the pituitary gland

how many hypothalamic hormones regulate the anterior pituitary

6

how many hypothalamic hormones are released into capillaries in the posterior pituitary gland

2

thyrotropin-releasing hormone (TRH) role

promote secretion of thyroid-stimulating hormone and prolactin PRL)

corticotropin-releasing hormone (CRH) role

promotes secretion of adrenocorticotropic hormone (ACTH)

Gonadotropin-releasing hormone (GnRH) role

promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

growth hormone-releasing hormone (GHRH) role

promotes secretion of growth hormone (GH)

prolactin-inhibiting hormone (PIH) role

inhibits secretion of prolactin (PRL)

somatostatin role

inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone (TSH)

how are hypothalamic hormones transferred

they reach the anterior pituitary via portal system

where is the pituitary gland located

suspended from the hypothalamus from a stalk (infundibulum) and housed in the sella turcica (bone cavity)

what does the pituitary gland look like

size and shape of a kidney bean, composed of the anterior and posterior pituitary gland

what are the posterior pituitary hormones

ADH (antidiuretic hormone) and oxytocin (OT)

what is ADH (antidiuretic hormone) (vasopressin) role

increases water retention, thus reducing urine volume, and preventing dehydration, can causes vasoconstriction

what is oxytocin’s role

stimulates labor contractions during childbirth, stimulates flow of milk during lactation, promote emotional bonding between lactating mother and infant

what are the anterior pituitary hormones

follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroid stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), prolactin (PRL), and growth hormone (GH)

FSH role

stimulates secretion of ovarian sex hormones, development of ovarian follicles and sperm production, produced by gonadotrope, targets testis and ovary

LH role

stimulates ovulation, stimulates corpus luteum to secrete progesterone, stimulates testes to secrete testosterones, produced by gonadotrope, targets testis and ovary

Thyroid stimulating hormone (TSH) role

stimulates secretion of thyroid hormone, produced by thyrotrope, targets thyroid gland

ACTH role

stimulates adrenal cortex to secrete glucocorticoids, produced by corticotrope, targets adrenal cortex

prolactin role

after birth, stimulates mammary glands to synthesize milk, produced by lactotrope, targets mammary glands

growth hormone role

stimulates cell mitosis and differentiation, produced by somatotrope, targets live, fat, muscle, and bone

how is pituitary secretion regulated

regulated by the hypothalamus, other brain areas, and feedback from target organs

what hormone is triggered in times of stress

hypothalamus triggers release of ACTH

what hormone is triggered during pregnancy

hypothalamus triggers prolactin secretion

what controls posterior pituitary

neuroendocrine reflexes

what happens when there is a rise in blood osmolarity

hypothalamic osmoreceptors triggers the release of ADH

what is a negative feedback loop

it regulates hormone secretion to maintain homeostasis, increased target organ hormone levels inhibit release of hypothalamic and/or pituitary hormones

example of negative feedback loop

increasing concentrations of cortisol inhibit release of CRH by the hypothalamus and ACTH by the pituitary

what is positive feedback loop

it causes the release of a hormone

example of positive feedback loop

calf suckling triggers the sensory receptors in the teat to send signals to the hypothalamus which then signals the posterior pituitary to release oxytocin, the more suckling the more oxytocin is released and milk letdown