M3 U3 Endocrine System Flashcards
both function to achieve and
maintain stability of the internal environment.
NEUROENDOCRINE SYSTEM
neuroendocrine system general functions within the body
communication, integration and
control.
perform their regulatory
functions by means of chemical messengers sent to specific cells.
NEUROENDOCRINE SYSTEM
-released in one part of the body
-regulates the activity of cells in other parts of the body.
-enter interstitial fluid and then the bloodstream.
- sent to signal specific target cells or target organs
Hormone`
- Pass from the secretory cells that make them into
interstitial fluid and then into the blood
Circulating hormones
- act locally on neighboring cells or on the same
cell that secreted them without entering the
bloodstream
Local hormones
Local hormones that act on neighboring cells
Paracrines
- act on the same cell that secreted them
Autocrines
, “lying under”
Hypophysis
a pea-shaped structure that lies in the hypophyseal fossa of the sella turcica of the
sphenoid bone. Attached to the hypothalamus by the infundibulum
Pituitary gland
anatomically and functionally separate portions of pituitary glands
A. Anterior pituitary (adenohypophysis)
B. Posterior pituitary
larger portion anterior
pars distalis
- forms a sheath
around the infundibulum
pars tuberalis
– larger bulbar
portion
- pars nervosa
present only in
fetal development
pars intermedia
secrete growth hormones
(GH)
Somatotrophs
secrete adrenocorticotropic
hormone (ACTH)
Corticotrophs
Secrete melanocytestimulating hormone
(MSH)
Corticotrophs
– secrete thyroid-stimulating
hormone (TSH)
Thyrotrophs
secrete prolactin (PL)
Lactotrophs
– secrete luteinizing hormone
(LH) and follicle-stimulating hormone (FSH)
Gonadotrophs
*promotes growth and
regulates certain aspects of
metabolism
Growth Hormone (GH)
secreted by the liver,
skeletal muscle, cartilage and
bone in response to GH
IGFs
secreted by the liver,
skeletal muscle, cartilage and
bone in response to GH
IGFs
Metabolism
*Enhance lipolysis in adipose tissue
*Decrease glucose uptake
- Promotes and maintains the growth and
development of the thyroid gland, and
causes it to secrete its hormones
Thyroid-stimulating hormone (TSH)
- Thyrotropin
- Promotes and maintains normal growth
and development of the cortex of the
adrenal gland - Also stimulates the adrenal cortex to
secrete its hormones
- Adrenocorticotropic hormone
(ACTH)
- Adrenocorticotropin
- Stimulates follicle cells to synthesize and
secrete estrogens in females - Stimulates the development of the
seminiferous tubules of the testes and
maintains spermatogenesis in males
- Follicle-stimulating hormone (FSH)
- Stimulates the formation and activity of the
corpus luteum in the ovary. The corpus luteum
secretes progesterone and estrogens when
stimulated by LH. - Also supports FSH in stimulating the
maturation of the follicles - In males, stimulates interstitial cells in the
testes to develop, then synthesize and secrete
testosterone
Luteinizing hormone (LH)
(neurohypophysis)
POSTERIOR PITUITARY
Serves as a storage and release site for
two hormones:
1. Antidiuretic hormone
2. Oxytocin
POSTERIOR PITUITARY
- Prevents the formation of large volume of
urine - Helps maintain water balance in the body
- Conserves water in the body during
dehydration, causing water to be
reabsorbed from the kidneys into the blood
- Antidiuretic hormone
- Stimulates contraction of uretine muscles
and causes milk ejection from the breasts
of lactating women - Stimulates uterine contractions (“swift
childbirth”)
- Oxytocin
*decreases urine production
ADH/ vasopressin
- small region of the brain below the thalamus
is the major link between the nervous and
endocrine systems - Almost all secretion by the pituitary is
controlled by either hormonal or nervous
signals from the hypothalamus - Special neurons in the hypothalamus
synthesize and secrete the hypothalamic
releasing and inhibitory hormones that
control secretion of the anterior pituitary
hormones
Hypothalamus
- Carries blood from the hypothalamus directly to
the adenohypophysis, where the target cells of the
releasing hormones are located
Hypophyseal portal system
Stimulates growth hormone (GH)
secretion
Growth hormone-releasing
hormone (GRH)
- Inhibits growth hormone (GH)
secretion
Growth hormone-inhibiting
hormone (GIH) – somatostatin
- Stimulates release of
adrenocorticotropic hormone (ACTH)
Corticotropin-releasing hormone
(CRH)
- Stimulates release of thyroid-
stimulating hormone (TSH)
Thyrotropin-releasing hormone
(TRH)
- Stimulates release of gonadotropins
(FSH and LH)
Gonadotropin-releasing hormone
(GNRH)
- Stimulates prolactin secretion
Prolactin-releasing hormone (PRH)
- Inhibits prolactin secretion
Prolactin-inhibiting hormone (PIH)
- tiny pine cone-shaped structure
-dorsal aspect of the brain’s diencephalon region - Acts as part of the nervous system (receives visual
stimuli) and part of the endocrine system (secretes a
hormone) - Supports the body’s biological clock that regulates our
patterns of eating, sleeping, reproduction (female
reproductive cycle), and behavior. - Secretes Melatonin
PINEAL GLAND
: thought to induce sleep
melatonin
Inhibited by the presence of sunlight
Melatonin:
- Made up of two large lateral lobes and a narrow
connecting isthmus - Only organ to store its own hormones before
secreting - Produces thyroid hormone (TH) and Calcitonin
THYROID GLAND
Thyroid hormones:
- Tetraiodothyronine (T4) or Thyroxine
- Triiodothyronine (T3)
- Helps regulate the metabolic rate of all cells,
as well as the processes of cell growth and
tissue differentiation. Because thyroid
hormone can potentially interact with any cell
in the body, its is said to have a “general”
target. - Produced by follicular cells
Thyroid hormones:
Storage form of thyroid hormones
Thyroglobulin
- Produced by parafollicular cells
- controls calcium content of the blood by
increasing bone formation by osteoblasts
and inhibiting bone breakdown by
osteoclasts - Thus, osteoblasts remove calcium from the
blood and less calcium is released into the
blood by osteoclasts.
Calcitonin
Low blood levels of T3 and T4 or low
metabolic rate stimulate the
hypothalamus to secrete
TRH
TRH enters the hypothalamic–
hypophyseal portal system and flows to
the anterior pituitary, where it
stimulates thyrotrophs to secrete
TSH
stimulates virtually all aspects of
thyroid follicular cell activity, including
iodide trapping, hormone synthesis and
secretion, and growth of the follicular
cells
TSH
release T3 and T4 into the blood until the
metabolic rate returns to normal
thyroid follicular
inhibits release of TRH and TSH
elevated level of T3
Appear as four or five tiny rounded
bodies within thyroid tissues formed by
compact, irregular rows of cells
- Secretes parathyroid hormone
PARATHYROID GLAND
- the major regulator of the levels of calcium
(Ca2+), magnesium (Mg2+), and phosphate
(HPO4 2−) ions in the blood.
parathyroid hormone
(parathormone)
it increases the number and activity of
osteoclasts, resulting in elevated bone resorption.
Bone resorption leads to release of Ca++ and
HPO4
2-
into the blood.
Bone:
- it slows the rate at which Ca2+ and Mg2+ are
lost from blood into the urine. - it increases loss of HPO4
2− from blood into the
urine. Because more HPO4
2− is lost in the urine
than is gained from the bones, PTH decreases
blood HPO4
2− level and increases blood Ca++
and Mg++ levels.
3. promote formation of the hormone calcitriol,
the active form of Vitamin D
- Kidneys
Calcitriol increases the rate
of Ca++ , HPO4
2−, and Mg++ absorption
Gastrointestinal tract:
- Suprarenal glands
- Located superior to the kidneys, fitting like a cap over
these organs. - Have a flattened, pyramidal shape
- The outer portion is called the adrenal cortex, and
inner portion is the adrenal medulla.
ADRENAL GLANDS
- produces steroid hormones that are essential for life.
Complete loss of adrenocortical hormones leads to
death due to dehydration and electrolyte imbalances
in a few days to a week, unless hormone replacement
therapy begins promptly - Comprises 80-90% of the gland
Adrenal cortex
- The only physiologically important mineralocorticoid
- Increases sodium reabsorption in the kidneys, causing to be
reabsorbed. The end result is water retention in the body. - Renin-angiotensin mechanism
Aldosterone
- Glucocorticoid
- Accounts for 95% of glucocorticoid activity
- Influences metabolism of food molecules; in large amounts,
it has an anti-inflammatory effect
Cortisol (hydrocortisone)
converted to either androgen
testosterone or androgen estrogen
Precursor hormone
- Precursor hormone – is converted to either androgen
testosterone or androgen estrogen - androgen testosterone is also released in much greater
quantity by the testes. Thus, androgens in males are often
insignificant - all female estrogens come from conversion of adrenal
androgens
Dehydroepiandrosterone (DHEA)
- Composed of neurosecretory tissue that secrete their
products into blood rather than across a synapse
Adrenal medulla
Enhances and prolongs the effects of the sympathetic
division of the autonomic nervous system
- Epinephrine (adrenaline)
Enhances and prolongs the effects of the sympathetic
division of the autonomic nervous system
Norepinephrine
both an endocrine gland and an
exocrine gland. located in the curve of the duodenum,
the first part of the small intestine, and consists of a
head, a body, and a tail.
pancreas
- Produced by alpha cells
- Tends to increase blood glucose levels by
stimulating the conversion of glycogen to glucose
in liver cells. Also stimulates gluconeogenesis in
liver cells. - The glucose produced via the breakdown of
glycogen and by gluconeogenesis is released into
the bloodstream, producing a hyperglycemic effect
Glucagon
- Produced by beta cells
- Promote the movement of glucose, amino acids,
and fatty acids out of the blood and into tissue
cells. Thus, it promotes metabolism of tissue cells
Insulin
- Produced by delta cells
- Regulates the other endocrine cells of the
pancreatic islets - Inhibits the secretion of glucagon, insulin,
and pancreatic polypeptide - Also inhibits the secretion of growth hormone
(somatotropin)
Somatostatin
- Produced by F cells
- Inhibits somatostatin secretion, gallbladder
contraction, and
secretion of pancreatic digestive enzymes.
Pancreatic polypeptide
- Primary sex organs in the male (testes) and in the
females (ovaries)
GONADS
responsible for the growth
and maintenance of male sexual characteristics and
for sperm production
testosterone,
regulated principally by gonadotropin
(especially LH) levels in the blood
Secretion
inhibits secretion of FSH
from the anterior pituitary.
inhibin,
- Paired organs within a sac of skin called the scrotum,
which hangs from the groin area of the trunk - Produce testosterone, responsible for the growth
and maintenance of male sexual characteristics and
for sperm production - Secretion is regulated principally by gonadotropin
(especially LH) levels in the blood - Also produces inhibin, which inhibits secretion of FSH
from the anterior pituitary.
Testes
- A set of paired glands in the pelvis that produce
several types of sex hormones:
Ovaries
- Includes estradiol and estrone
- Steroid hormones
- Promote the development and maintenance of female sexual
characteristics - Responsible for breast development and the proper sequence
of events in the menstrual cycle
Estrogens
- “pregnancy-promoting steroid”
- Secreted by the corpus luteum
- Along with estrogen, maintains the lining of the uterus
necessary for successful pregnancy
Progesterone
- The tissue that forms on the lining of the
uterus as an interface between the circulatory
systems of the mother and developing child - Serves as a temporary endocrine gland
- Produces human chorionic gonadotropin
(hCG)
Inhibin
- Called chorionic because it is secreted by the
chorion, a fetal tissue component of the
placenta - High levels during the early part of the
pregnancy and serves as a signal to the
mother’s gonads to maintain the uterine lining
rather than allow it to degenerate and fall away
(as in menstruation) - As the placenta develops past the first trimester,
hCG production drops as its production of
estrogens and progesterone increase.
human chorionic gonadotropin
(hCG)
