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Anatomy
Endocrine system
Endo 2
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Prostaglandins
Powerful substances found in a
wide variety of body tissues
Produced in a
tissue
and
diffuse
only a
short
distance to act on
cells
in that tissue
Several class include:
PGA, PGE, and PGF
Influence many body functions, including
respiration, blood pressure, gastrointestinal secretions, and reproduction
Pituitary (
Hypophysis
) Gland
Location:
Diencephalon
Pituitary gland:
Two-lobed
organ that
secrets
important
hormones
Adenohypophysis (
True gland
)
Anterior
lobe; made of
glandular tissue
Synthesizes and secrets
a number of hormones
Neurohypophysis (
Storage
area)
Posterior
lobe; made of
neural tissue
Receives, stores, and releases
hormones from the hypothalamus
Six hormones of the anterior pituitary
Growth hormone
(GH)
Prolactin
(PRL)
Thyroid-stimulating hormone
(TSH)
Adrenocorticotropic hormone
(ACTH)
Follicle-stimulating hormone
(FSH)
Luteinizing hormone
(LH)
Anterior Pituitary
Trophic effects:
High blood
[hormone] causes target organ to
hypertrophy.
Low blood
[hormone] causes target organ to
atrophy.
TSH
: Stimulates
growth
of the
thyroid
gland; also stimulates it to
secrete thyroid
hormone
ACTH
: Stimulates growth of the
adrenal cortex
and stimulates it to secrete
glucocorticoids
(mainly
cortisol
)
FSH
Initiates
growth
of
ovarian follicles
each month in the
ovary
and stimulates one or more
follicles
to develop to the stage of
maturity
and
ovulation
Stimulates
estrogen
secretion by developing
follicles
Stimulates
sperm
production in the
male
LH
Acts with
FSH
to stimulate
estrogen
secretion and
follicle growth
to maturity
Causes
ovulation
Causes
luteinization
of the ruptured
follicle
and stimulates
progesterone
secretion by
corpus luteum
Causes
interstitial cells
in the
testes
to secrete
testosterone
in the male
GH
Stimulates
growth
by
accelerating
protein anabolism
Accelerates
fat catabolism
and slows glucose catabolism
By slowing glucose catabolism, tends to
increase blood glucose to higher than normal level
(
hyperglycemia
)
PRL
: Stimulates
breast development
during
pregnancy
and
secretion
of
milk
after the
delivery
of the baby
Hypothalamic Control of the Anterior Pituitary
Hormonal
control rather than
neural
Hypothalamus neurons synthesize
releasing and inhibiting hormones
Hormones are transported to
axon endings of median eminence
Hormones secreted into the
hypothalamo-hypophyseal portal system
regulate the secretions of the
anterior pituitary
Hypothalamic Control of Posterior Pituitary
Hypothalamus
neuron cell bodies produce:
ADH
: supraoptic nuclei
Oxytocin
: paraventricular nuclei.
Transported along the
hypothalamo-hypophyseal
tract
Stored in
posterior
pituitary
Release controlled by
neuroendocrine
reflexes.
Physiology of posterior Pituitary gland
Posterior
pituitary hormones
ADH
also known as
Vasopressin
Oxytocin
These hormones are
synthesized
in the
neuron cell bodies in the hypothalamus
and packed in
secretory vesicles with neurophysin
(carrier protein)
Does not synthesize hormones
Consists of axon terminals of hypothalamic neurons
Hypothalamic-Pituitary Relationships:
Posterior Lobe
The
posterior
lobe is a down growth of
hypothalamic neural
tissue
Has a
neural
connection with the
hypothalamus
(hypothalamic-hypophyseal tract)
Secretions of the posterior pituitary are controlled by
nervous signals
from
hypothalamus
Synthesis
of
ADH
ADH
synthesized
in the cell bodies of
hypothalamic
neurons(
supraoptic nucleus
)
ADH is
stored
in the
posterior pituitary
Two
types of receptors for ADH
V1: Mediate
vasoconstriction
V2: Located in the
principle cells
in
distal convoluted tubule
and
collecting ducts
in the
kidneys
The most important function of ADH is to
conserve
body water by
reducing urine output
Osmotic pressure:
Osmoreceptors
in the
hypothalamus
↑Osmotic pressure =
↑ADH
secretion
↓Osmotic pressure =
↓ADH
secretion
Blood volume
Baroreceptor
in carotid artery and aortic arch, and
Stretch
receptors in
left
atrium
↑Blood pressure =
↓ADH
secretion
↓Blood pressure =
↑ADH
secretion
Synthesis of Oxytocin
Oxytocin is
synthesized
in the cell bodies of
hypothalamic neurons
(
paraventricular nucleus
)
Oxytocin is stored in the
posterior pituitary
Function of oxytocin
Stimulates the pregnant uterus to
contract
May initiate
labor
Causes
glandular cells
of the breast to release
milk
into ducts
Enhances
social bonding
Hypothalamus
Actual
production of
ADH and oxytocin
occurs in the hypothalamus
After production in the hypothalamus,
hormones
pass along
axons
into the
pituitary gland
The secretion and release of
posterior pituitary hormones
is controlled by
nervous stimulation
The hypothalamus controls many body functions related to
homeostasis
(temperature, appetite, and thirst)