A&P CH.16.6 : THE ENDOCRINE SYSTEM

Where is the pituitary gland located

in the sella turcica of the
sphenoid bone

Hypophysis means to

grow under

what are the two sections of the pituitary gland?

– Posterior pituitary
– Anterior pituitary

How do action potentials traveling down the axons of hypothalamic neurons result in hormone release from their axon terminals in the posterior pituitary?

Action potentials travel down the axons of hypothalamic neurons,
causing hormone release from their axon terminals in the posterior pituitary

Posterior pituitary is largely composed of _________that consists of
axon terminals of the hypothalamic neurons

neural tissue

Paraventricular neurons
produce

oxytocin

Supraoptic neurons produce

antidiuretic hormone (ADH)

what neurohormones does the pituitary gland release that are received ready made from the hypothalamus

Paraventricular neurons, Supraoptic neurons

The posterior lobe + infundibulum

= neurohypophysis

Anterior pituitary=

adenohypophysis

what produces oxytocin

the hypothalamus

what releases oxytocin released into the blood stream

the pituitary gland. it stores and releases it into the blood stream.

what does Oxytocin stimulate

uterine contractions released during childbirth
(works in a positive feedback loop during childbirth)

Oxytocin

acts as hormonal trigger for milk ejection (“letdown”) in the
breast (also positive feedback)

Oxytocin

Acts as neurotransmitter in brain (“the cuddle hormone”)

what does the Antidiuretic hormone (ADH) do

Targets kidney tubules to reabsorb more water to prevent wide
swings in water balance by inhibiting/preventing urine formation

drinking alcohol

inhibits ADH, causing MORE urine
output

oxytocin

stimulated by impulses from hypothalamic neurons in response to stretching of the uterine cervix or suckling of infant at breast

Antidiuretic hormone

stimulated by impulses from hypothalamic neurons in response to increased blood solute concentration or decreased blood volume; also stimulated by pain, some drugs, low blood pressure

Anterior Pituitary

Hypothalamic hormones released into special blood vessels
(the hypophyseal portal system) control the release of anterior pituitary hormones

Hypophyseal
portal system

A portal system is two
capillary plexuses
(beds) connected by
veins

what is known as the master endocrine gland

Anterior lobe

what is the Anterior lobe made of

glandular tissue derived from an outpocketing of oral
mucosa

Anterior lobe characteristic

Vascularly connected to hypothalamus via hypophyseal portal
system

what does the hypophyseal portal system consist of

▪ Primary capillary plexus
▪ Hypophyseal portal veins
▪ Secondary capillary plexus

Hypothalamus secretes __________ to
anterior pituitary to regulate hormone secretion

releasing and inhibiting hormones

what type of hormones are the Anterior Pituitary Hormones primarily

peptides

what Anterior Pituitary Hormone does not activate target cells via cAMP second-
messenger system

growth hormone (GH)

what two Anterior Pituitary Hormones are tropins that regulate secretion of other hormones

follicle stimulating hormone and luteinizing hormone

what are the Anterior Pituitary Hormones

– Growth hormone (GH)
– Thyroid-stimulating hormone (TSH) (tropic)
– Adrenocorticotropic hormone (ACTH) (tropic)
– Follicle-stimulating hormone (FSH) (tropic)
– Luteinizing hormone (LH) (tropic)
– Prolactin (PRL)

what does the Growth hormone (GH) do

– actions on metabolism and growth-promoting actions
– Highest levels of secretion occurs during sleep

Direct actions of the growth hormone on metabolism

▪ decreases rate of cellular glucose uptake and metabolism (anti-
insulin effects)
▪ Triggers liver to break down glycogen into glucose
▪ Increases blood levels of fatty acids for use as fuel and encourages
cellular protein synthesis

Indirect actions of growth hormone on growth

GH triggers liver, skeletal muscle, and bone to produce
insulin-like growth factors (IGFs)

what are IGFs

growth promoting proteins. – IGFs produced by the liver act as hormone, while IGFs produced by
other tissues act as paracrine

Thyroid-stimulating
hormone (TSH)

stimulates normal
development and
secretory activity of
thyroid

what does the Adrenocorticotropic hormone (ACTH) stimulate

stimulates adrenal cortex to release corticosteroids

Follicle-stimulating hormone (FSH)

stimulates production of gametes
(egg or sperm)

Luteinizing hormone (LH)

promotes production of gonadal hormones
(sex hormones)

Prolactin (PRL)

stimulates milk production in females; role in males is
not well understood