lec 6. hypothalamus, pituitary gland, thyroid/parathyroid

role of the endocrine/neuroendocrine system

regulation of growth, metabolism, and reproduction

key players in the endocrine system

hormones, neurohormones

what brain structure has neural and endocrine control

hypothalamus

list 3 types of neurohormones that neurons can secrete into the blood

catecholamines, hypothalamic neurohormones

list the two types of hormones based on function

releasing hormone, effector hormone

define a releasing hormone

hormone that acts on endocrine cells to regulate the secretion of other hormones

are releasing hormones stimulatory or inhibitory

both

give an example of a releasing hormone

GHRH

what does GHRH stand for

growth hormone releasing hormone

define an effector hormone

a hormone that acts on a target = physiological response

GHRH is a releasing hormone. what is it’s effector hormone

GH (growth hormone)

what structure releases GH

pituitary

describe negative feedback

end product acts on upstream structures to stop hormone production when enough of the product has been made = maintain homeostasis

describe positive feedback

end product amplifies a stimulus

which gland is the hypothalamus connected to

pituitary

which structure connects the hypothalamus to the pituitary

infundibulum

T or F: the hypothalamus and the pituitary is the link between the nervous system and the endocrine system

true

list the parts of the pituitary

anterior, posterior

alternative name for the anterior pituitary

adenohypophysis

role of the anterior pituitary

produces and secretes hormones

alternative name for the posterior pituitary

neurohypophysis

role of posterior pituitary

stores and secretes hormones that the hypothalamus produced

which pituitary produces hormones

anterior

describe how the hypothalamic-hypophyseal portal system works

neurons release neurohormones into the capillaries of the portal system, the portal veins carry them to the anterior pituitary where they act on the endocrine cells, then the endocrine cells release their peptide hormones into the second set of capillaries to be carried to the rest of the body

the superior hypophyseal artery leads to the poral system of the hypothalamus. what is this a branch of

internal carotid

the anterior hypophyseal vein exits the hypothalamus. what does this drain into

cavernous sinus

how does arterial blood enter the posterior pituitary

inferior hypophyseal artery

how does blood leave the posterior pituitary

hypophyseal veins drain the blood and drain into the cavernous sinuses (like the anterior pituitary)

posterior pituitary hormones store and release 2 hormones. name them

oxytocin, vasopressin

alternative name for vasopressin

antidiuretic hormone

posterior pituitary stores and releases oxytocin and vasopressin, but where are these hormones produced

hypothalamus

what part of the hypothalamus produces oxytocin and vasopressin

paraventricular and supraoptic nuclei

oxytocin and vasopressin and produced in the hypothalamus. describe how they get to the posterior pituitary to be stored/released

secretory vesicles containing these hormones travel down the axon to reach the posterior pituitary

T or F: the posterior pituitary produces hormones

false

what triggers vasopressin/ADH production in the hypothalamus

hypothalamic osmoreceptors detect changes in blood solute concentrations

define high blood osmotic pressure

blood is more concentrated = low water concentration

what does ADH/vasopressin do to water reabsorption by the kidneys

increases

what does ADH/vasopressin do to urine output

decreases

what does ADH/vasopressin do to blood vessels

causes them to constrict

what does ADH/vasopressin do to BP

increases

what does ADH/vasopressin do to water loss by sweat glands

decreases

does high or low blood osmotic pressure trigger ADH production by the hypothalamus

high

effects of oxytocin

contraction of uterine smooth muscle during childbirth, lactation

does oxytocin use a positive or negative feedback loop? explain

positive: more oxytocin = more uterine contraction

how many hormones does the anterior pituitary produce and secrete

7

list the 2 structural components of the anterior pituitary

pars intermedia, pars distalis

describe the pars intermedia vs the pars distalis in terms of structure (anterior pituitary)

pars intermedia is a thin layer between the anterior and posterior pituitary. pars distalis is the larger portion

list the hormones produced by the pars intermedia of the anterior pituitary

melanocyte stimulating hormone (MSH)

what structure does MSH effect

skin

list the hormones produced by the pars distalis of the anterior pituitary

prolactin, growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, gonadotropins (LH and FSH)

which hormones regulate GH activity

growth hormone releasing hormone (GHRH) and growth hormone inhibiting hormone (GHIH)

alternative name for GHIH

somatostatin

GHRH and GHIH regulate GH activity. where are these two produced

hypothalamus

target of GH

liver, skeletal muscle, bone, adipose tissue

effects of GH

growth and maintenance of muscle and bone, increase blood glucose levels

what does GH do in the liver

stimulates synthesis of insulin-like growth factor (IGF)

what type of feedback does GH use

negative feedback

describe the negative feedback mechanism of GH

elevated levels of IGF (which is made when there is GH) inhibits the hypothalamus from releasing GHRH + anterior pituitary from releasing GH

what stimulates the release of adrenocorticotropic hormone (ACTH)

corticotropin releasing hormone (CRH)

where is corticotropin releasing hormone produced

hypothalamus

effects of ACTH

stimulates synthesis and secretion of cortisol

where is cortisol produced and secreted

adrenal cortex of the adrenal gland

what type of feedback mechanism does ACTH use

negative feedback

describe the negative feedback of ACTH

high cortisol inhibits CRH and ACTH release

what are FSH and LH regulated by

gonadotropin releasing hormone

where is GnRH produced and secreted from

hypothalamus

in females, what do FSH and LH act on

ovaries

in males, what does FSH act on

testes

T or F: LH acts on the testes in males

false; LH is in females only

role of FSH and LH

gamete + sex hormone development

what type of feedback does FSH and LH have

can be use positive and negative

what regulates prolactin (PRL)

prolactin releasing hormone (PRH) and prolactin inhibiting hormone (PIH)

where are PRH and PIH produced

hypothalamus

role of prolactin

initiates and maintains mammary gland development and milk production

what regulates melanocyte stimulating hormone (MSH)

corticotropin releasing hormone (CRH) and melanocyte inhibiting factor (MIF)

where are CRH and MIF produced

hypothalamus

role of MSH

enhances skin pigmentation

what is thyroid stimulating hormone (TSH) regulated by

thyrotropin releasing hormone (TRH)

when is TSH produced

when there are low thyroid hormone levels or low metabolic rate

effects of TSH

stimulates the synthesis and secretion of thyroid hormones from the thyroid gland

what type of feedback mechanism does TSH use? explain

negative: elevated levels of thyroid hormones inhibit TRH and TSH release