Chapter 15: Endocrine System

endocrine system controls and integrates

1. reproduction

2. growth and development

3. maintenance of blood

4. regulation of cell metabolism and energy

5. body defenses

6. maintains homeostasis

exocrine glands

produce nonhormonal substances through ducts

endocrine glands

produces hormones; lack ducts

true endocrine organs

1. pineal

2. pituitary

3. parathyroid

4. thyroid

5. adrenal

hormones

long distance chemical signals that travel via blood or lymph

autocrines

act on the same cells that secrete them

paracrines

affect cells other than those than secrete them, but act locally

hormone classification

1. amino-acid

2. steroid

amino-acid hormones

1. water-soluble

2. receptor on plasma membrane

steroid hormones

1. derived from cholesterol

2. lipid-soluble

3. receptor inside cell

4. function as transcription factors

what inactivates peptide hormones

gastric acid and peptidases

carrier proteins

proteins that attach to lipid hormones to aid in their circulation throughout the bloodstream

hormones alter….

target cell activity

how do water-soluble hormones initiate a cellular response

G protein 2nd messengers

g-protein 2nd messenger system (cAMP)

1. hormone binds receptor

2. receptor activates G protein

3. G protein activates adenylate cyclase

4. Adenylate cyclase converts ATP to cAMP

5. cAMP activates protein kinases

mechanism of steroid hormones

1. steroid hormones binds intracellular receptor

2. receptor-hormone complex enters the nucleus

3. complex binds a specific DNA region

4. binding initiates transcription of gene

5. protein synthesis

hormone blood levels are controlled by…

negative feedback systems

release of hormones are triggered by

endocrine gland stimuli (NS can override)

humoral stimuli

hormone is released due to changes in the blood concentrations of ions/nutrients

neural stimuli

hormone is released in response to the AP in sympathetic NS fibers

hormonal stimuli

hormone is released to a hormone

target cell activation depends on 3 factors

1. blood levels of hormone

2. relative number of receptors on/in target cell

3. affinity of binding

up-regulation

cells synthesize more receptors in response to low hormone levels

down-regulation

cell lose receptors in response to low hormone levels

infundibulum

connects hypothalamus to pituitary gland

posterior pituitary

neural tissue that secretes neurohormones

anterior pituitary

glandular tissue a

activation of posterior pit

A.P.s from hypothalamus

activation of anterior pit

hormones from hypothalamus

hormones of anterior pit

1. TSH

2. ACTH

3. FSH

4. LH

5. GH

6. PRL

what does TSH target

thyroid wh

what does ACTH target

adrenal cortex

what does FSH and LH target

gonads

what does GH target

entire body

what does PRL target

mammary glands

hypothalamic-hypophyseal tract

runs through infundibulum to connect hypothalamus to posterior pit

neurohomones of posterior pit

1. oxytocin

2. ADH

mechanism of oxytocin and ADH release

1. hormones stored in axon terminals in posterior pit

2. released into blood when neurons fire

anterior lobe is (blank) connected to hypothalamus

vascularly

hypophyseal portal system

1. primary capillary plexus

2. hypophyseal portal veins

3. secondary capillary plexus

hypothalamus secretes what to the anterior pit

releasing and inhibiting hormones

hypothalamic hormones

1. GHRH

2. GHIH

3. TRH

4. CRH

5. GnRH

6. PIH

primary capillary plexus

where hypothalamic hormones are released

hypophyseal portal veins

where hypothalamic hormones travel through to reach the anterior pit

secondary capillary plexus

where anterior pit secretes its hormones

oxytocin

1. uterine contractions

2. milk ejection

ADH

targets kidney tubules to reabsorb water to inhibit urine formation

tropic hormone

hormone that influences target cells to release a hormone

GH

muscle tissue and bone growth

TSH

thyroid gland

ACTH

targets adrenal gland

FSH

targets ovaries and testes

LH causes the

release of hormone from reproductive organs

PRL

targets breast tissue, milk production

GH metabolic actions

1. increases blood glucose; anti-insulin

2. increases fat breakdown and release

GH indirect actions

targets liver and other tissues that secrete IGFs

IGFs functions

1. skeletal growth

2. cartilage growth

3. protein synthesis and cell growth and proliferation

thyroid gland effects

1. increases basal metabolic rate

2. regulates tissue growth + development

3. maintains blood pressure

calcitonin

hormone secreted by parafollicular (C) cells in response to high calcium levels

calcitonin effect

inhibits osteoclast activity

adrenal gland

1. adrenal cortex

2. adrenal medulla

adrenal cortex

3 layers of glandular tissue that synthesizes and secretes several hormones

adrenal medulla

nervous tissue that is part of sympathetic nervous system

rate of release depends on…

rate of synthesis

zona glomerulosa

mineralocorticoids (aldosterone)

zone fasciculata

glucocorticoids

zona reticularis

gonadocorticoids

aldosterone

1. stimulates Na+ reabsorption by kidneys

2. stimulates K+ elimination by kidneys

importance of Na+

affects ECF volume, blood volume, blood pressure

importance of K+

sets resting membrane potential of cells

aldosteronism

hypersecretion due to adrenal tumors

problems of aldosteronism

1. hypertension and edema

2. excretion of K+, leading to nonresponsive neurons and muscle

cortisol

1. resist stressors

2. keeps glucose constant

adrenal sex hormones

sex hormone precursors

weak androgens are converted into…

testosterone, some to estrogens

short-term stress reponse

adrenal medulla; secretes epinephrine and norepinephrine

adrenal medulla neural stimulation effects

1. increase heart rate and BP

2. increase glucose + metabolism

3. bronchioles dilate

long-term stressors

adrenal cortex; secretes cortisol and aldosterone

metabolic effects of glucocorticoids

1. increased AA, glucose, and FA

2. kidneys retain sodium + H2O

3. blood volume and BP rise

4. suppresses immune response

FSH effect

stimulates production of gametes

LH

production of gonadal hormones

gonadal hormones

1. estrogen

2. progesterone

3. testosterone

4. inhibin

prolactin

stimulates milk production

pineal gland

secretes melatonin

PTH

increases Ca2+ by stimulating osteoclast activity

target organs of PTH

1. skeleton

2. kidneys

3. small intestine

PTH and skeleton

increased osteoclast activity causes Ca2+ and phosphate release in blood

PTH and kidney tubules

increased calcium absorption

PTH and kidney (indirect)

increased activation of vit D by kidneys; increased absorption of calcium from food in small intestine

pseudoendocrine organs

1. pancreas

2. gonads

exocrine cells of pancreas

produce enzyme-rich juice for digestion pa

pancreatic islets (endocrine cells)

1. alpha cells: produce glucagon

2. beta cells: produce insulin

ovaries

produce estrogens and progesterone

testes

produce testosterone

placenta

secretes estrogens, progesterone, human chorionic gonadotropin (hCG)