STRUCTURAL AND FUNCTIONAL ORGANIZATION OF THE ENDOCRINE SYSTEM Flashcards
Major glands of the Endocrine system
(1) Hypothalamus
(2) Pituitary
(3) Thyroid
(4) Parathyroid
(5) Pancreas
(6) Adrenals
(7) Ovaries and testes
(8) Pineal body
These glands secrete hormones to regulate many bodily functions, including
growth and
metabolism.
A specific cell with specific receptors that will respond to specific
hormones.
Target Cell
T/F: Only the target cells for a given hormone have receptors that bind and
recognize that hormone.
T
A target cell will have how many receptors for a particular hormone.
2,000 to 100,000
Hormones are either
lipid-soluble or water-soluble.
lipid-soluble or water-soluble:
(a) Steroid hormones
(b) Thyroid hormones
(c) Nitric Oxide
Lipid
lipid-soluble or water-soluble:
(a) Amino Acids
Water
1) Short-chain; Antidiuretic hormone
2) Long-chain; Insulin
___ influence their target cells by chemically binding to specific protein
receptors.
Hormones
What is the “master” gland of the pituitary.
hypothalamus
Hypothalamus secretes a total of ____hormones and the pituitary gland
secretes ____.
9
7
What is a stalk like structure that attaches the pituitary gland to the hypothalamus.
, the infundibulum,
What blood vessels connect capillaries in the hypothalamus to in the anterior pituitary and where are they located
termed hypophyseal portal veins
Infundibulum
Gonadotropin-releasing hormone
stimulates FSH & LH
Growth hormone-releasing hormone
stimulates HGH & IGF
Growth hormone-inhibiting hormone
inhibits HGH & IGF
Thyroid-releasing hormone
stimulates TSH
Prolactin-releasing hormone
stimulates PR
Prolactin-inhibiting hormone
inhibits PR
Corticotropin-releasing hormone
stimulates ACTH
The pituitary gland it about the size of a ____ and has two lobes.
Small Grape
Ant pit and Post pit
Both lobes of the pituitary rest where
hypophyseal fossa
a cup shaped
depression in the sphenoid bone.
hypophyseal fossa
A hormone that stimulates an endocrine gland to grow
and secrete its hormones.
Tropic Hormones
1) Stimulate protein synthesis, help maintain muscle and bone mass, and
promote healing of injury and tissue repair.
2) Enhance breakdown of triglycerides, which release fatty acid into the blood, and breakdown of liver glycogen, which releases glucose into the
blood.
Insulin Growth Factors (IGFs)
Promote synthesis and secretion of Insulin Growth Factors (IGFs)
Maintains blood concentration by means of a negative feedback loop.
Human Growth Hormone (hGH)
(c) Two hypothalamic hormones control secretion of hGH.
1) Growth Hormone-Releasing Hormone (GHRH) is released when
2) Growth Hormone- Inhibiting Hormone (GHIH) is released when
1) – Low blood glucose levels
2) Above normal blood glucose levels
Stimulates the synthesis and secretion of thyroid hormones by the thyroid gland.
Thyroid-Stimulating Hormone (TSH)
Thyrotropin-Releasing Hormone (TRH) from the hypothalamus controls what
TSH secretion
Follicle-Stimulation Hormone (FSH) in females does what
1) Initiates the development of ovarian follicles.
2) Stimulates follicular cells to excrete estrogen.
Follicle-Stimulation Hormone (FSH) in men does what
1) Stimulates sperm production in the testes
*Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus
controls FSH secretion
Luteinizing Hormone (LH) in females does what
1) Triggers ovulation.
2) Stimulates formation of the corpus luteum in the ovary and the
secretion of progesterone by the corpus luteum.
3) Along with FSH stimulates follicular cells to secrete estrogen.
Luteinizing Hormone (LH) in males does what
1) Stimulates the testes to secrete Testosterone.
*Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus
controls LH secretion.
Initiates and maintains milk production by the mammary glands.
Prolactin (PRL)
During pregnancy, very high levels of ____ promote secretion of
Prolactin- Releasing Hormone (PRH), which in turn stimulates the
release of _____
estrogens
prolactin.
Controls the production and secretion of hormones called Glucocorticoids
by the cortex (outer portion) of the adrenal gland.
Adrenocorticotropic Hormone (ACTH)
Corticotropin-Releasing Hormone from the hypothalamus stimulates
secretion of ____
ACTH
(a) Very little in humans.
(b) Excessive amount can cause darkening of the skin.
Melanocyte-Stimulating Hormone (MSH)
contains axons and axon terminals of neurosecretory cells
whose cell bodies are in the hypothalamus.
posterior pituitary
Which lobe of the pituitary does not synthesize hormones, it does store and
release two hormones.
posterior pituitary
Which organs does oxytocin act on and home
1) Uterus
a) Released in large quantities just prior to childbirth to enhance contraction of smooth muscle cells in the wall of the uterus.
2) Breast
a) Stimulates milk ejection from the mammary glands in response to the suckling infant.
How does ADH act on the body
1) Decreases urine production.
2) Causes the kidneys to retain more water, thus decreasing urine volume.
3) Decreases water loss through sweating.
4) Causes constriction of arterioles, thus causing an increase in blood pressure.
*In the absence of ADH, an individual’s urine output will increase from 1-2 liters per day to 20 liters.
Function of the thyroid gland
run the basal metabolic rate (BMR)
the rate at which the body uses energy while at rest to keep vital functions going, such as breathing, keeping the heart beating, and keeping the body warm.
BMR
Structure of the Thyroid Gland
(a) The butterfly shaped thyroid gland is located just below the larynx.
(b) Composed of right and left lobes on either side of the trachea.
(c) Spherical sacs called thyroid follicles make up most of the gland.
(d) The walls of each follicle consists of cells called follicular cells which
produce the two thyroid hormones.
follicular cells produce what two thyroid hormones.
1) Thyroxine (T4)
2) Triiodothyronine (T3)
Actions of Thyroid Hormones
(1) Most body cells have receptors for thyroid hormones.
(2) Thyroid hormones increase basal metabolic rate (BMR), the rate of
oxygen consumption under standard or basal conditions (awake, at rest, and fasting).
(3) maintenance of normal body temperature.
(4) stimulate protein synthesis, increase the use of glucose and fatty acid for ATP production, increase the breakdown of triglycerides, and enhance cholesterol excretion, thus reducing blood cholesterol.
(5) Together with human growth hormone and insulin, thyroid hormones stimulate body growth, particularly the nervous and skeletal systems.
(1) Produced by the parafollicular cells of the thyroid gland.
(2) Decreases the level of calcium in the blood by inhibiting the action of osteoclasts, the cells that break down bone.
Calcitonin (CT)
Structure of the parathyroid gland
(a) Small round masses of glandular tissue that are partially embedded in the
posterior surface of the thyroid gland.
(b) Within the parathyroid glands are secretory cells called chief cells that
release parathyroid hormone (PTH).
Actions of parathyroid hormone (PTH)
(a) Regulates levels of calcium, magnesium, and phosphate ions in the blood.
(b) PTH increases the number and activity of osteoclasts and release calcium and phosphate into the blood.
(c) PTH produces changes in the kidney
What three changes does PTH perform on the kidneys
1) Slows the rate at which calcium and magnesium are lost from blood into
urine.
2) Increases loss of phosphate from blood to urine.
3) Promotes formation of the hormone Calcitrol, the active form of
vitamin D. Calcitrol acts in the gut to increase the rate of calcium,
magnesium, and phosphate absorption from food into the blood.
Structure of the pancreas
(a) Flattened organ located in the curve of the duodenum, the first part of the small intestine.
(b) It has both endocrine and exocrine functions.
(c) The endocrine part consists of clusters of cells called pancreatic islets or Islets of Langerhans.
(d) Cells of the pancreatic islets
What are the cells of the pancreatic islets
1) Alpha cells secrete the hormone glucagon.
2) Beta cells secrete the hormone insulin.
Actions of the Pancreas
(1) The main action of glucagon is to increase blood glucose level when it falls
below normal.
(2) In contrast, insulin helps glucose move into cells, especially muscle fibers, which
lower blood glucose level when it is too high.
(3) The level of blood glucose controls secretion of both glucagon and insulin via
negative feedback. (Figure 13.12).
(4) Insulin promotes uptake of amino acids into the body cells and increases the
synthesis of protein and fatty acid within the cells. Therefore, insulin is an important hormone when tissues are developing, growing and being repaired
Structure of the adrenal gland
two adrenal glands, one lying atop each kidney
Adrenal Cortex
Adrenal Medulla
Consists of three zones, each of which synthesizes and secretes different steroid hormones.
Adrenal Cortex
layers of the adrenal cortex
a) The Outer Zone (Zona Glomerulosa) releases hormones called mineral corticoids because of their effect on mineral homeostasis.
(1 Aldosterone
b) The Middle Zone (Zona Fasciculata) releases hormones called glucocorticoids because they affect glucose homeostasis.
(1 Cortisol
c) The Inner Zone (Zona Reticularis) releases androgens. (male & female sex hormones)
Inner most region of the adrenal gland. Consists of sympathetic postganglionic cells of the autonomic nervous system (ANS) that are specialized to secrete hormones known as catecholamines
Adrenal Medulla
a) Epinephrine
b) Norepinephrine
Zona Glomerulosa
Adrenal Cortex
the major mineralcorticoid
Aldosterone
What does aldosterone regulate
1) Regulates homeostasis of two mineral ions, , sodium ions (Na+) and potassium ions (K+). a) Increases reabsorption of Na+ from the urine into the blood. b) Stimulates excretion of K+ into urine.
Functions of aldosterone besides regulating Na and K
2) Helps adjust blood pressure and blood volume, and promotes excretion of
H+ in the urine. Such removal of acids from the body can help prevent
metabolic acidosis
3) Secretion of aldosterone occurs as part of the renin-angiotensinaldosterone pathway.
a) Conditions that initiate this pathway include dehydration, Na+
deficiency, or hemorrhage, which decreases blood pressure and blood
volume.
b) Lowered blood pressure stimulates the kidney to secrete the enzyme
renin, which promotes a reaction in the blood that forms
angiotensin I,
c) As blood flows through the lungs, another enzyme called
angiotensin converting enzyme (ACE) converts inactive
angiotensin I into the active hormone angiotensin II.
d) Angiotensin II stimulates the adrenal cortex to secrete aldosterone.
4) Aldosterone, in turn, acts on the kidneys to promote the return of Na+
and water to the blood. As more water returns to the blood (and less is
lost in the urine) blood volume increases, increasing blood pressure to normal
Zona Fasciculata
Adrenal Cortex
The most abundant glucocorticoid is
cortisol
Actions of glucocorticoids
(a) Protein breakdown –
(b) Glucose formation
(c) Breakdown of triglycerides
(d) Anti-inflammatory effects
(e) Depression of immune response.
(f) A low blood level of cortisol stimulates neurosecretory cells in the
hypothalamus to secrete corticotropin-releasing hormone (CRH) to the
anterior pituitary’ where it stimulates release of ACTH (adrenocorticotropic
hormone. ACTH in turn stimulates cells of the adrenal cortex to secrete
cortisol.
Does the adrenal cortex secrete androgens
a lil bit
How does the Adrenal Medulla respond to stressful situations and exercise
1) Impulses from the hypothalamus stimulate the sympathetic
preganglionic neurons, which in turn stimulate the cells of the
adrenal medulla to secrete epinephrine and norepinephrine.
2) These two hormones greatly augment the fight-or-flight response.
3) By increasing heart rate and force of contraction, epinephrine and
norepinephrine increase the pumping output of the heart, which increases
blood pressure.
4) They also increase blood flow to the heart, liver, skeletal muscle, and
adipose tissue; dilate airways to the lungs; and increase blood levels of
glucose and fatty acid. Epinephrine and norepinephrine also help the
body resist stress.
