Ch 16: Endocrine System

What are the 2 types of glands?

exocrine and endocrine

How do exocrine glands secrete products?

through ducts that travel to a membrane surface

How do exocrine glands secrete products?

secrete products directly into bloodstream and act on far cells, neighboring cells, or the producing/secreting cell

What kind of glands do not utilize ducts?

endocrine

What types of signaling are considered local?

autocrine and paracrine

Are local signaling methods long- or short-lasting?

short

Is endocrine signaling long- or short-lasting?

long

What is autocrine signaling?

chemical is secreted out and then diffuses back into the secreting cell

What is neuroendocrine signaling?

neurosecretory cell secretes molecule that enters blood to bind a receptor on the target cell

What is paracrine signaling?

cell secretes chemical that diffuses to a nearby cell

What is synaptic signaling?

neuron secretes a neurotransmitter that diffuses across the synaptic cleft to bind to target cell

What are the two main classes of hormones?

amino acid-based and steroid-based

What class of hormones is the most common?

amino acid-based

Are amino acid-based hormones water- or lipid-soluble, and what kind of molecules are they?

water soluble; hydrophilic and polar

Are steroid-based hormones water- or lipid-soluble, and what kind of molecules are they?

lipid soluble; hydrophobic and nonpolar

How are amino-acid based hormones found in the blood?

circulating freely in blood plasma

How are steroid based hormones found in the blood?

attached to carrier molecules

What kind of receptors do amino acid-based hormones bind to?

surface receptors

What kind of receptors do steroid-based hormones bind to?

intracellular receptors

Where are steroid hormones produced?

gonads and adrenal cortex

What are steroid hormones synthesized from?

cholesterol

What class of hormones mostly act through second messenger systems?

amino-acid based

What class of hormones acts through direct gene activation?

steroid

What is the only amino acid-based hormone that does NOT act through a second messenger system?

thyroid hormone

What is the best understood second messenger system?

cAMP signaling mechanism

What is the first messenger in the second messenger system?

hormone

What is the second messenger in the second messenger system?

cAMP

What causes activation of the G protein?

binding of the hormone to its receptor on the cell membrane

How are amino acid-based hormones secreted?

exocytosis

How are steroid hormones secreted?

diffusion

What molecule activates adenylate cyclase?

activated G protein

What molecule converts ATP to cAMP?

adenylate cyclase

What molecule activates protein kinase?

cAMP

What are protein kinases?

enzymes that phosphorylate other intracellular proteins to activate or deactivate them

What is the role of phosphodiesterase in the second messenger system?

regulates the system by rapidly degrading cAMP to stop the cascade of events

What do steroid hormones need to bind to in order to bind to intracellular receptors?

receptor proteins

How does the receptor-hormone complex alter gene expression?

by binding to a specific DNA region and initiating transcription for the production of specific protein

What are the 3 types of stimuli that cause hormone release?

humoral, neural, hormonal

What is a humoral stimulus?

altered levels of ions or nutrients that causes hormone release

What is a neural stimulus?

neural input that causes hormone release

What is a hormonal stimulus?

tropic hormone that causes release of a different hormone

What is the hypothalamic-pituitary-target endocrine organ feedback loop?

hypothalamus releases tropic hormone that stimulates the anterior pituitary, which releases a hormone that stimulates the thyroid, adrenal cortex, and gonads

What endocrine gland regulates overall body homeostasis?

hypothalamus

Where is the pituitary gland located?

at the base of the hypothalamus

What structure connects the hypothalamus to the pituitary gland?

infundibulum

Does the posterior pituitary produce hormones?

no, it only stores and secretes hormones produced by the hypothalamus

What does the neurohypophysis include?

posterior pituitary and infundibulum

What is the posterior pituitary composed of?

neural tissue

What hormones are stored in and secreted by the posterior pituitary?

ADH and oxytocin

What is another name for ADH?

vasopressin

What is the major role of ADH?

regulation of water balance by reabsorbing water

What does ADH target?

kidney tubule cells

What stimulates ADH secretion?

impulses from hypothalamic neurons

Primarily what part of the hypothalamus produces ADH?

supraoptic nucleus

What are some stimuli that could trigger ADH production?

high solute concentration, low blood volume, pain, low BP, drugs (morphine, barbituates, nicotine)

What could inhibit ADH secretion?

adequate hydration, alcohol use

What causes diabetes insipidus?

hyposecretion of ADH

What are the effects of diabetes insipidus?

dehydration, electrolyte imbalances

What causes syndrome of inappropriate ADH (SIADH)?

hypersecretion of ADH

What are the effects of SIADH?

fluid retention, headaches, disorientation, weight gain, low solute concentration

Primarily what part of the hypothalamus produces oxytocin (OT)?

paraventricular nuclei

What are the 2 major targets of oxytocin?

uterine smooth muscle and mammary glands

What is the effect of oxytocin on mammary glands?

release of milk

What is the letdown reflex and what hormone is involved?

suckling stimulates OT secretion which stimulates milk release

Which hormone shows positive feedback mechanisms for both of its targets?

oxytocin

What is another name for the anterior pituitary?

adenohypophysis

What tissue is the anterior pituitary composed of?

glandular tissue

What is another name for the anterior pituitary?

adenohypophysis

What are the 3 components of the hypophyseal portal system?

primary capillary plexus, hypophyseal portal veins, secondary capillary plexus

What is a portal system?

two capillary plexuses connected by veins

Does anterior pituitary have a vascular or neural connection to the hypothalamus?

vascular

Does posterior pituitary have a vascular or neural connection to the hypothalamus?

neural

What is the major role of the hypophyseal portal system?

carries hypothalamic inhibiting and releasing hormones to anterior pituitary to regulate its hormone secretions

What 6 hormones are synthesized and released by the anterior pituitary?

growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, prolactin

Where is growth hormone produced?

anterior pituitary

What stimuli cause GH to be synthesized/released?

low blood GH, deep sleep, low blood glucose, exercise, stressors

What hormones does the hypothalamus release to regulate GH production?

growth hormone-releasing hormone and growth hormone-inhibiting hormone

What is another name for GHIH?

somatostatin

What organs does GH target?

liver, skeletal muscle, bone, cartilage

What effects are produced by direct action of GH?

metabolic actions: increases blood glucose, anti-insulin effects, increase fat breakdown/release

What products are produced by indirect action of GH?

insulin-like growth factors

What is are the major roles of IGFs?

growth-promoting: increase skeletal and cartilage growth and promote protein synthesis and cell growth

What inhibits the production/release of GH?

negative feedback resulting from GH and IGFs both being present in the blood

What causes pituitary dwarfism?

hyposecretion of GH in children

What causes gigantism?

hypersecretion of GH in children

What causes acromegaly?

hypersecretion of GH in adults

What 2 endocrine disorders result from hypersecretion of GH?

gigantism and acromegaly

How do the effects of gigantism and acromegaly differ?

gigantism causes overly tall but proportional stature whereas acromegaly causes only the extremities to be oversized

What hormone regulates prolactin levels?

prolactin-inhibiting hormone/dopamine

What organ does prolactin target?

mammary glands

What is the major role of prolactin?

milk production

What chemical does the hypothalamus secrete to stimulate prolactin?

prolactin-releasing factors

What hormone is involved (besides prolactin) in lactation?

oxytocin

What are the effects of PRL hypersecretion in women?

inappropriate milk production and stopping of menstruation

What are the effects of PRL hypersecretion in men?

impotency

PRL levels rise and fall along with what other hormone?

estrogen

What stimuli can increase PRL release?

suckling, dopamine-blocking drugs, estrogen, BC pills

What are the 2 gonadotropin hormones?

follicle stimulating hormone and luteinizing hormone

What is gonadotropin-releasing hormone (GnRH)?

hormone produced by the hypothalamus that stimulates FSH and LH production in the anterior pituitary

What kind of cells in the AP produce FSH and LH?

gonadotropic cells that are activated in puberty