A&P 2: chapter 16 endocrine system

definition: hormones

interact with target cells and influence their functions in order to maintain fluid electrolyte, and acid-base homeostasis, promote growth, and regulate metabolic reactions

chemical messangers secreted by endocrine glands that regulate functions of other cells

what is the purpose of hormones?

hormone is secreted into blood and travels to affect distant tissues

endocrine hormone → secretion location → affected location

definition: endocrine glands

diverse group of organs found throughout the body; all regulate other cell types by producing and seceting hormones

two types of organs in endocrine system

primary organs: only endocrine functions

secondary organs: have both endocrine and a variety of non-endocrine functions

list primary endocrine organs (6)

anterior pituitary gland → sphenoid bone of skull

throid gland → anterior neck

parathyroid gland → posterior side of thyroid gland

adrenal cortices → on superior side of thyroid gland

endocrine pancreas → in left side of abdominal cavity mostly posterior to stomach

thymus → in superior mediastinum

list secondary neuroendocrine organs

hypothalamus → in brain

pineal gland → in brain

adrenal medulla → core of adrenal gland

what is the difference between neuroendocrine organs and endocrine organs?

neuroendocrine organs anatomically consist of nervous tissue

list other secondary organs (neither neural nor endocrine)

testes

ovaries

heart

kidneys

adipose tissue

(3) basic classes of hormones (according to chemical structure)

amino-acid based

peptide/protein

steroid

features associated with all hormones

can cause widespread effects thru body in seconds or several hours

can travel as unbound chemicals (hydrophilic) or bound chemicals attached to plasma protein carriers (hydrophobic)

continue to circulate blood until taken up by target cell or broken down and deactivated

amount of hormone in blood depends on how fast and how much hormone an endocrine gland has produced and how fast secreted hormone is removed from blood

relationship between hormones and target cells/receptors

hormones are able to affect only particular cells (target cells); these cells contain specific protein receptors to which hormones bind

either embedded in plasma membrane or cytosol or nucleus of cell

hydrophilic hormones cannot do what?

readily cross plasma membrane

interact with receptors found embedded in target cell’s plasma membrane

hydrophobic hormones can do what?

able to cross thru plasma membrane

interact with receptors in cytosol or nucleus

list amino-acid hormones (5)

amine hormones → catecholamines

peptide hormones → glucagon and oxytocin

protein hormones → insulin and growth hormone

list steroid hormones (5)

sex hormones → testosterone, estrogen, and progesterone

cortisol

aldosterone

what is different about thyroid hormones?

T₃ and T₄ are exceptions

they are amino acid derived but they are hydrophobic

order of cellular activity using extracellular receptors

1. hydrophilic hromone binds to its receptor in plasma membrane

2. receptor activates a peripheral protein

3. peripheral protein activates an enzyme

4. enzyme catalyzes formation of a second messanger

5. the second messanger initiates a series of events in the cell that leads to changes in its activity

types of stimuli that inhibit or initiate secretions (3)

hormonal: endocrine cells increase or decrease secretion in response to other hormones

humoral: endocrine cells response to concentration of certain chemicals in blood or extracellular fluid

neural: endocrine cells respond to signals from nervous system

how does vitamin D affect Ca²⁺?

vitamin D helps your body absorb calcium from the food you eat in your gut

definition: permissiveness

one hormone cannot exert its effects without another hormone being present

definition: synergist

hormones that can act on same target cell to exert the same effect; the effect is more pronounced with interaction of multiple hormones

definition: antagonists

hormones that act on same cells but have opposite effects

feedback loop order

stimulus

receptor

control center

effector/response

definition: tropic

hormones that control the secretion of hormones from other endocrine glands

definition: trophic

induce growth in target cells

note: some hormones have both tropic and trophic effects

name for anterior pituitary gland

what does it mean?

adenohypophysis

“adeno” = gland

composed of glandular epithelium

name for posterior pituitary gland, what does it mean?

neurohypophysis

“neuro” = nervous tissue

composed of nervous tissue

list the hormones stored in posterior pituitary (2)

ADH → antidiueretic hormone

OT → oxytocin

non-tropic

what are the effects of ADH?

insertion of water channels into tubule cells so more water is reabsorbed from the tubule fluid back into the blood

increases blood volume

decreases urine production by increasing the amount of water retained by the body

decreases solute concentration of the blood

antagonist pairings

insulin vs glucagon

PTH vs calcitonin

aldosterone vs ANP

GH vs insulin

synergist pairings

glucagon with epinephrine and cortisol

FSH with testosterone/estrogen

GH with T₃/T₄

PRL with OT

what are the target tissue(s) for ADH?

kidneys and brain

what is the stimulus for release of ADH?

what kind of response is this?

increased solute of the concentration of the blood

osmoreceptors that monitor changes in the solute concentration of blood

humoral

what is the inhibtor for release of ADH?

decreased solute concentration of the blood

what is the stimulus for OT?

what kind of response is this?

infant suckling and stretching of the uterus

neural

what is the inhibitor of release for OT?

lack of appropriate stimuli

what is the primary function of OT?

what are the effects?

supporting reproduction

mammary glands contract resulting milk let down reflex and uterine contractions

what is the target tissue(s) for OT?

mammary glands of breast tissue and smooth muscle of uterus

list the hormones stored in anterior pituitary (6)

TSH → thyroid-stimulating hormone

ACTH → adrenocorticotropic hormone
PRL → prolactin
LH → luteinizing hormone
FSH → follicle-stimulating hormone

GH → growth hormone

tropic

what is the stimulus for release of TSH?

what kind of response is this?

TRH → thyrotropin-releasing hormone, exposure to cold, or stress

hormonal

what is the inhibitor of release for TSH?

increased levels of thyroid hormones and somatostatin from the hypothalamus

what is the target tissue(s) of TSH?

thyroid gland

what are the effects of TSH?

growth and development of the thyroid gland

synthesis of thyroid hormones

what is the stimulus for release of ACTH?

what kind of response is this?

corticotropin-releasing hormone (CRH) from the hypothalamus or stress

hormonal

what is the inhibitor of release for ACTH?

increased level of cortisol and increased level of aldosterone

what is the target tissue(s) for ACTH?

adrenal cortex

what are the effects of ACTH?

growth and development of adrenal cortices and release of adrenal steroids and catecholamines

what is the stimulus for release of PRL?

what kind of response is this?

infant suckling at the nipple and thyrotropin-releasing hormone (TRH) from the hypothalamus

hormonal

what is the inhibitor of release for PRL?

prolactin-inhibiting factor (dopamine) from the hypothalamus

what is the target tissue(s) of PRL?

mammary gland

what are the effects of PRL?

development of mammary glands and milk production

what is the stimulus for release of LH?

what kind of response is this?

gonadotropin-releasing hormone (GnRH) from the hypothalamus

hormonal

what are the inhibitors of release for LH?

increased levels of testosterone (in males) and estrogens and progesterone (in females)

what are the target tissue(s) of LH?

male gonads and female gonads

what are the effects of LH?

male gonads:

development of gonads and testosterone production

female gonads:

development of gonads, production of estrogens and progesterone, and ovulation

what is the stimulus for release of FSH?

what kind of response is this?

gonadotropin-releasing hormone (GnRH) from the hypothalamus

hormonal

what is the inhibitor of release of FSH?

increased levels of testosteroen (males) and estrogens (females)

what are the target tissue(s) of FSH?

male gonads and female gonads

what are the effects of FSH?

male gonads: stimulates cells of testes to produce chemicals that bind and concentrate testosterone; under direction of GnRH

female gonads: FSH and LH together trigger production of estrogen; FSH also triggers maturation of ovarian follicles; under direction of GnRH

what is the stimulus for release of GH?

what kind of response is this?

growth hormone-releasing hormone (GHRH) from the hypothalamus, stress/exercise, ingestion of protein, and fasting

what is the inhibitor of release for GH?

somatostatin from the hypothalamus

what are the target tissue(s) of GH?

liver, adipose tissue, muscle tissue, bone and cartilage

what are the effects of GH?

gluconeogenesis, fat breakdown (lipolysis), protein breakdown, production of insulin-like growth factor (IGF), which stimulates cell division and protein synthesis

what is the cell type of the thyroid gland that secrets T₃ and T₄?

follicle cells

what is the cell type of the thyroid gland that secrets calcitonin?

parafollicular cells

what is the stimulus for secretion of T₃ and T₄?

what kind of response is this?

TSH from anterior pituitary

hormonal

what are the inhibitor(s) of secretion for T₃ and T₄?

increased levels of T₃ and T₄ inhibit TRH and TSH

what are the target tissue(s) of T₃ and T₄?

nearly every cell in the body

what are the effects of T₃ and T₄?

set basal metabolic rate

thermoregulation

growth and development

synergism with SNS (sympathetic nervous system)

what are the effects of calcitonin?

inhibits osteoclast activity under certain conditions which decreases the blood Ca²⁺ concentration

what are the target tissue(s) of calcitonin?

osteoclasts

what are the inhibitor(s) of secretion for calcitonin?

decreased concentration of Ca²⁺ in blood

what is the stimulus for secretion of calcitonin?

what kind of response is this?

decrease concentration of Ca²⁺ in blood

humoral

what is the cell type that secretes calcitonin?

parafollicular cells

what is the cell type that secretes PTH?

chief cells

what is the stimulus for secretion of PTH?

what kind of response is this?

decreased concentration of Ca²⁺ in blood

humoral

what are the inhibitor(s) of secretion for PTH?

increased concentration of Ca²⁺ in blood

what are the target tissue(s) of PTH?

bone, kidneys, and intestines

what are the effects of PTH?

increase Ca²⁺ reabsorption from fluid in kidneys

increase Ca²⁺ absorption from the contents of small intestine

indirectly increases osteoclast activity

all lead to increase in blood Ca²⁺

what is the stimulus for release of aldosterone (mineralocorticoids)?

what kind of response is this?

angiotensin-II

elevated K⁺

ACTH

elevated H⁺

hormonal and humoral

what are the effects of aldosterone?

increase Na⁺ retention directly and water retention indirectly

increase K⁺ loss in urine

increase H⁺ loss in urine

regulates blood pressure

what are the inhibitor(s) of secretion for aldosterone?

increase level of aldosterone

decrease K⁺ concentration

decrease H⁺ concentration

increased blood pressure

what are the target tissue(s) of aldosterone?

tubules of the kidneys

what is the stimulus for release of cortisol (glucocorticoids)?

what kind of response is this?

ACTH

hormonal

what are the inhibitor(s) of release of cortisol?

increased levels of cortisol

what are the target tissue(s) of cortisol?

liver

muscle

adipose

WBC

what are the effects of cortisol?

increases gluconeogenesis in liver

increase protein breakdown in muscle

increases lipolysis in adipose tissue

inhhibits inflammatory response

what is the stimulus for release of androgens (androgenic steroids)?

what kind of response is this?

ACTH

hormonal

what are the inhibitor(s) of release of androgens?

poorly understood

what are the target tissue(s) of androgens?

organs of the reproductive tract

brain

bone

skeletal muscle

what are the effects of androgens?

can be converted to testosterone in the circulation

likely responsible for development of female pubic hair and libido

what are the effects of catecholamines?

increased rate and force of heart contractions

dilate bronchioles

constrict blood vessels to the digestive and urinary organs and the skin

increase the metabolic rate; dilate the pupils

what are the target tissues of catecholamines?

nearly every cell in the body

what are the inhibitor(s) of release of androgens?

lack of sympathetic nervous system stimulation

what is the stimulus for release of catecholamines?

what kind of response is this?

stimulation from preganglionic sympathetic neurons

ACTH

neural

what is the stimulus of release of insulin and glucagon?

what kind of response is this?

high blood glucose and low blood glucose

humoral

what are the target tissue(s) of insulin?

most cells, liver, skeletal and cardiac muscle, and adiposcytes

what are the effects of insulin?

stimulates glucose uptake by most target cells

stimulates glycogenesis

stimulates lipogenesis

what are the effects of glucagon?

stimualtes gluconeogenesis, glycogenolysis, and ketogenesis

stimulates fat and protein breakdown

what are the target tissue(s) of glucagon?

liver, muscle, adipose