L2: hormone receptors and pituitary gland

3 hormone classes

• amino acid derivatives

• peptide hormones

• lipid derivatives

amino acid derivatives

• thyroid hormones

• catecholamines

• tryptophan derivatives

thyroid hormones

• tyrosine derivative

• ex. thyroxine

catecholamines

• tyrosine derivative

• ex. epinephrine

tryptophan derivatives

melatonin

peptide hormones

• synthesized as prehormones

• secreted in an inactive form

• ex. glycoproteins such as TSH, LH, FSH

small protein peptide hormones

• ADH

• oxytocin

large protein peptide hormones

• insulin

• GH

• prolactin

lipid derivatives

• eicosanoids

• steroid hormones

eicosanoids

• fatty acid derivative

• release paracrine

• ex. prostaglandin E

steroid hormones

• cholesterol based

• ex. reproductive hormones such as estrogen

• secreted by adrenal gland and kidneys

steroid hormone released by adrenal glands

corticosteroids

steroid hormone released by kidneys

calcitriol

what does the heart regulate

blood volume

what does the thymus regulate

immune response

what does the digestive tract regulate

• digestive function coordination

• glucose metabolism

• appetite

• have their own endocrine system

what do the kidneys regulate

• blood cell production

• rate of calcium and phosphorus absorption by digestive tract

• an enzyme involved in regulating blood pressure

what do the gonads regulate

• growth

• metabolism

• sexual characteristics

• activities of organs in the reproductive system

what must a target cell have to respond to a hormone

• the appropriate protein receptor

• without it, the hormone has no effect

receptors on cells

• contain various ones

• combo of receptors produce differential effects on specific tissues

2 possible receptors on target cells

• receptor in plasma membrane (extracellular)

• receptor in cytoplasm or nucleus (intracellular)

what type of hormones use extracellular receptors

• catecholamines

• peptide hormones

• eicosanoids

extracellular receptors

• act as first messenger

• relay message to an intracellular intermediary - secondary messenger

what does the secondary messenger do

• affects enzyme activity

• changes cellular metabolic reactions

• exerts hormone’s effects in the cell

what does extracellular messages usually involve

G protein

what is a G protein

enzyme complex coupled to a receptor

what happens when a hormone binds to a extracellular receptor

• G protein becomes activated

• acts as the first messenger

• activates cAMP

what could an activated G protein do

• change the [] of cAMP

• change the levels of Ca2+

2 possible secondary messengers in extracellular messaging

• cAMP

• Ca2+ ions

how does G protein increase cAMP production

• ATP gets converted to cAMP which acts as a secondary messenger

• high volumes of cAMP can open ion channels and activate enzymes

how does G protein inhibit cAMP production

cAMP gets broken down to AMP which reduces enzyme activity

what do G proteins do with Ca2+

• releases Ca from ER and SER

• opens Ca2+ ion channels

• Ca2+ acts as secondary messenger

• Ca forms calmodulin and activates enzymes

what type of hormones use intracellular receptors

• steroid hormones

• thyroid hormones

steroid hormones and intracellular receptors

• diffuse through plasma membrane

• alter activity of specific genes

• affect DNA transcription rate

• changes pattern of protein synthesis

• change synthesis of enzyme and structural proteins affecting cell’s metabolic activity and structure

steps of steroid hormone binding to receptor

1. hormone diffused through membrane

2. binds to cytoplasmic or nuclear receptor

3. binding of hormone-receptor complex to DNA

4. gene activation

5. transcription and mRNA production

6. translation and protein synthesis

7. target cell response

how are thyroid hormones different compared to steroid during intracellular comm

thyroid hormones bind to mitochondria

thyroid hormone binding to receptor steps

1. diffuses through membrane

2. binds to receptors on mitochondria and within nucleus

3. binding of hormone-receptor complex to DNA

4. gene activation

5. transcription and mRNA production

6. translation and protein synthesis

7. target cell response

infundibulum

stalk like structure that connects the hypothalamus to the pituitary gland

what is the pituitary gland aka

hypophysis

2 lobes in pit gland

• anterior lobe (adenohypophysis)

• posterior lobe (neurohypophysis)

what kind of hormones are released by the pit gland and how many

• 9 peptide hormones

• 7 by anterior lobe and 2 by posterior

• all bind to membrane receptors and use cAMP

1st way the hypothalamus integrates activities of nervous and endocrine system

• hypothalmic neurons synthesize ADH and OXT

• travels down infundibulum into the posterior pit lobe and is released into the bloodstream

2nd way the hypothalamus integrates activities of nervous and endocrine system

• hypothalamus secretes regulatory hormones

• travels down infundibulum into the anterior pit lobe which secretes the hormones

• 7 diff types

3rd way the hypothalamus integrates activities of nervous and endocrine system

• hypothalamus contains autonomic centers that exert direct control over the endocrine cells of the adrenal medulla

• travels through preganglionic motor fibers

• adrenal gland releases epinephrine and norepinephrine which has sympathetic and parasymp effects

what is the adrenal gland made up of

• adrenal cortex

• adrenal medulla

where is ADH synthesized in the hypothalamus

supraoptic nuclei

where is OXT synthesized in the hypothalamus

paraventricular nuclei

what are supraoptic and paraventricular nuclei

• group of neurons

• enter posterior pit gland

hypophyseal portal system

• allow hormones to travel from the hypothalamus to the pit gland

• contains capillary networks supplied by the superior hypophyseal artery

• portal vessels

• secondary capillary network

what are the 7 regulatory hormones secreted by the anterior pit lobe

• thyroid stimulating hormone (TSH)

• adrenocorticotropic hormone (ACTH)

• gonadotropins - follicle stimulating hormone (FSH) and luteinizing hormone (LH)

• growth hormone (GH)

• prolactin (PRL)

• melanocyte stimulating hormone (MSH)

TSH

in thyroid gland

ACTH

in adrenal gland

FSH and LH

• FSH is in ovaries

• LH in testis

GH

• in muskuloskeletal system

• targets fats

• glucose sparing effect

PRL

• in mammary glands

• production of milk

tropic hormones

affect other glands

ADH

• antidiuretic hormone

• inhibits urination

• retains water

• increases blood pressure and volume when needed by retaining water

oxytocin

• involved in childbirth

• causes contractions

• given if contractions are not occuring

• lets down milk

pituitary gland and feedback control of endocrine secretion general pattern

• hypothalamus releases RH

• enters the anterior lobe of the pit gland which releases hormone 1

• hormone 1 affects an endocrine organs which releases hormone 2

• hormone 2 comms with target cell and inhibits RH

pit gland and endocrine system feedback loop variation 1

• GH-RH from hypothalamus enters anterior lobe of pit gland

• GH is secreted which stimulates the liver

• liver produces somatomedins which inhibits GH-RH and stimulates GH-IH

• when GH-RH is inhibited, GH-IH releases is stimulated

somatomedin

• not a hormone by a chemical

• releases by liver

• stimulates growth of skeletal muscle, cartilage and many other tissues

pit gland and endocrine system feedback loop variation 2

• PRH is releases from hypothalamus into anterior lobe of pit gland

• secretes PRL

• PRL inhibits PRH and stimulates PIH

• PRL inhibits the production of itself

TSH: RH, endocrine target organ, hormone 2

• TRH

• thyroid gland

• thyroid hormones

ACTH: RH, endocrine target organ, hormone 2

• CRH

• adrenal cortex

• glucocorticoids

FSH and LH: RH, endocrine target organ, hormone 2

• GnRH

• testes and ovaries

• FSH: testes: inhibin

• FSH: ovaries: inhibin estrogen

• LH: testes: androgens

• LH: ovaries: progesterone, estrogen