During the short busts of hormones releasing, how much secretion is there?
little to none
When will an endocrine gland release its hormone in more frequent bursts?
What happens during the absence of stimulation of hormones?
The blood level of the hormone decreases.
What is hormone secretion regulated by? (3 things)
1. Signals from the nervous system
2. chemical changes in the blood
3. other hormone
Most hormonal regulatory ststems work via negative feedback, but a few operate via...
What, for many years, was called the "master" endocrine gland & why?
The pituitary gland because it secretes several hormones that control other endocrine glands
Not the pituitary gland, but the ___ is the "master" endocrine gland?
Where is the major link between the nervous and endocrine systems?
The hypothalamus--the small region of the brain below the thalamus
How many different hormones does the hypothalamus synthesize?, pituitary gland?
Together the hypothalamus and pituitary gland play important roles in the regulation of virtually all aspects of what?
growth, development, metabolism and homeostasis
The pituitary gland is a pea-shaped structure that lies where?
In the hypophyseal fossa of the sella turcica of the sphenoid bone.
How does the pituitary gland attach
It attaches to the hypothalamus by a stalk, the infundibulum.
What are the 2 anatomically and functionally seperate portions of the pituitary gland called?
the anterior pituitary and the posterior pituitary.
What secretes hormones that regulate a wide range of bodily activities, from growth to reproduction?
The anterior pituitary
What releases the hormones in the anterior pituitary? Inhibits hormones in the anterior?
Where do the hormones that release and inhibit the anterior pituitary come from?
what are an important link between te nervous and endocrine system?
the hypothalamic hormones
How do hypothalamic hormones reach the anterior pituitary?
thru a portal system
How does the portal system work?
blood flows from one capillary network into a portal vein, and then into a second capillary network without passing thru the heart.
How does the hypophyseal portal system work?
blood flows from capillaries in the hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary.
What are the branches of the internal carotid arteries that bring blood into the hypothalamus?
the superior hypophyseal ateries
At the junction of the median eminence of the hypothalamus and the infundibulum, the arteries divide into a capillary network called what?
primary plexus of the hypophyseal portal system
From the primary plexus, blood drains into the ____ ____ that pass down the outside of the infundibulum.
hypophyseal portal veins
In the anterior pituitary, the hypophyseal portal veins divide again and for another capillary network called the ____ ____ __ __ _____ ____ ____.
secondary plexus of the hypophyseal portal system
Near the median eminence and above the optic chiasm are clusters of specialized neurons called...
What do neurosecretory cells do?
Synthesize the hypothalamic releasing and inhibiting hormones in their cell bodies and package the hormones inside vesicles, which reach the axon terminals by axonal transport.
What are the naterior pituitary hormones that act on other endocrine glands called?
What are the 5 types of anterior pituitary cells that secrete seven hormones?
somatotrophs, thyrotrophs, gonadotrophs, lactotrophs, and corticotrophs
What do somatotrophs secrete?
HGH and HGH in turn stimulates several tissues to secrete insulinelike growth factors
What do thyrotrophs secrete?
thyroid-stimulating hormone (TSH)
What do gonadotrophs secrete?
2 gonadotropins: follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
What do lactotrophs secrete?
What do corticotrophs secrete?
adrenocorticotropic hormone (ACTH)
What does thyrotropin control?
The secretions and other activities of the thyroid gland
What do follicle-stimulating hormone (FSH) and luteininzing hormone (LH) stimulate?
secretion of estrogens and progesterones and the maturation of oocytes in the ovaries. They also simulate sperm production and secretions of testosterone in the testes
What does prolactin (PRL) stimulate?
Initiates milk production in the mammary gland
What does adrenocorticotropic hormone (ACTH) stimulate?
the adrenal cortex to secrete glucocorticoids such as cortisol.
What are the 2 ways in which the secretion of anterior pituitary hormones are regulated?
Neurosecretory cells in the hypothalamus and negative feedback in the form of hormones released by target glands decreases secretions.
What cells are the most numerous in the anterior pituitary?
What is the most plentiful hormone in the anterior pituitary?
What is the main function of HGH?
to promote synthesis and secretion of small protein hormones called insulinlike growth factors (IGFs)
What causes cells in the liver, skeletal muscles, cartilage, bones and other tissues to secrete IGFs?
What are some of the funtions of IGFs?
1. Cause cells to grow and multiply, also decrease the breakdown of proteins and the use of amino acids for ATP production
2. During childhood increases the rate of growth of the skeletal system and skeletal muscles
3. During adulthood help maintain the mass of muscles and bones and promote healing of injuries and tissue repair
4. Enhance lipolysis in adipose tissue, resulting in increased use of the released fatty acids for ATP production by body cells
5. influence carbohydrate metabolism by decreasing glucose uptake, which decreses the use of glucose for ATP production
When do somatrotrphs in the anterior pituitary release bursts of human growth hormone every few hours?
especially during sleep
somatotrophs secretory activity is controlled mainly by 2 hypothalamic hormones:
growth hormone-releasing hormone (GHRH)
growth hormone-inhibiting hormone (GHIH)
What does growth hormone-releasing hormone do?
promotes secretion of human growth hormone
what does growth hormone-inhibiting hormone do?
suppresses secretion of human growth hormone
What is a major regulator of GHRH and GHIH?
blood glucose level
What is hypoglycemia?
an abnormally low blood glucose concentration that stimulates the hypothalamus to secrete GHRH
What is hyperglycemia?
An abnormally high blood glucose concentration, stimulates the hypothalamus to secrete GHIH
Name some other stimuli that promote secretion of HGH
decreased fatty acids, increased amino acids in blood; deep sleep;increased activity of the sympathetic division of the autonomic nervous system (stress or vigerous exercise); other hormones-glucagon, estrogens, cortisol, and insulin
Name some factors that inhibit HGH secretion.
Increased levels of fatty acids and decreased levels of amino acids in the blood; REM sleep; emotional deprivation; obesity; low levels of thyroid hormones; and HGH itself (thru negative feedback)
Thyroid-stimulating hormone(TSH) stimulates the synthesis and secretion of what 2 thyroid hormones?
triiodothyronine (T3) and thyroxine(T4)
What controls thyroid-stimulating hormone (TSH)?
Thyrotropin-releasing hormone (TRH) from the hypothalamus
What in turn does the release of TRH depend on?
the blood levels of T3 and T4--high levels inhibit secretion of TRH via negative feedback
Is there such a thing as thyrotropin-inhibiting hormone?
In females, what are the targets for follicle-stimulating hormone (FSH)?
What does follicle-stimulating hormone (FSH) stimulate to secrete estrogens?
In the testes, what stimulates sperm production?
FSH follicle-stimulating hormone
What releases FSH?
the gonadotropin-releasing hormone (GnRH) from the hypothalamus
What supresses the release of FSH and GnRH in males and females?
estrogens and testosterone
Is there a gonadotropin-inhibiting hormone?
What triggers ovulation?
luteinizing hormone (LH)
What is ovulation?
the release of a seconary oocyte by an ovary
What stimulates formation of the corpus luteum?
What together simulate secretion of estrogens by ovarian cells?
FSH & LH
What prepare the uterus for implantation of a fertilized ovum and help prepare the mammary glands for milk secretion?
estrogens and progesterone
what stimulates cells in the testes to secrete testosterone?
Secretion of LH is controlled by what?
gonadotropin-releasing hormone (GnRH)
What happens after the mammary glands have been primed by estrogens, progesterone, glucocorticoids, HGH, thyroxine, and insulin?--along with prolactin?
PRL brings about milk production
What does the ejection of milk from the mammary glands depend on?
the hormone oxytocin
What happens when there is milk production and milk ejection?
What is the prolactin-inhibiting hormone called in females?
what does dopamine do?
inhibits the release of prolactin from the anterior pituitary most of the time.
When does the secretion of PIH diminish and the blood level of prolactin rise, but not enough to stimulate milk production?
just before menstruation begins
What causes breast tenderness just before nenstruation?
During pregnancy, does prolactin levels rise or drop?
When an infant is nursing, what happens with the secretion of PIH? (dopamine)
The sucking action causes a reduction in PIH
If a male has an overproduction of PIH, what can happen?
it can cause erectile dysfunction
What can happen if a female has an overproduction of PIH?
inappropriate lactation and absence of menstrual cycle
What does adrenocorticotropic hormone (ACTH) control?
the production and secretion of cortisol and other glucocorticoids by the cortex of the adrenal glands
What stimulates secretion of adrenocorticotropic hormone (ACTH)?
Corticotropin-relaeasing hormone (CRH) by corticotrophs
Other than CRH, what else can stimulate ACTH?
low blood glucose
interleukin-1-something produced by macrophages
what inhibits CRH and ACTH?
glucocortcoids via negative feedback
What increases skin pigmentation in amphibians?
What does MSH do for humans? (melanocyte-stimulating hormone)
Not sure, but think it may have something to do with brain activity...excessive levels will produce a darkening of the skin
What stimulates melanocyte-stimulating hormone? (MSH) What inhibits it?
What is the target tissue for hGH?
What is the target tissue for thyroid-stimulating hormone (TSH)
what is the target tissue for FSH?
ovaries and testes
What is the target tissue for LH
ovaries and testes
what is the target tissue for PRL?
what is the target tissue for ACTH (adrenocorticotropic hormone)
what is the target tissue for MSH (melanocyte-stimulating hormone
What does the posterior pituitary not do, but does do?
the posterior pituitary does not synthesize hormones, it does store and release 2 hormones
What does the posterior pituitary consist of?
axons and axon terminals of more than 10,000 hypothalamic neurosecretory cells
The cell bodies of the neurosecretory cells of the posterior pituitary are where?
in the paraventricular and supraoptic nuclei of the hypothalamus
What do the axons of the posterior pituitary form?
the hypothalamohypophyseal tract
Where does the hypothalamohypophyseal tract begin and end?
The tract begins in the hypothalamus and ends near blood capillaries in the posterior pituitary
What produces antidiuretic hormone ADH?
the supraoptic nucleus
What are the specialized neuroglia called in the axon terminals in the posterior pituitary?
What supplies blood to the posterior pituitary?
the inferior hypophyseal arteries
Where do the inferior hypophyseal arteries drain into?
the capillary plexus of the infundibular process
During and after delivery of a baby, oxytocin affects 2 target tissues. They are
the mother's uterus and breasts
During delivery what enhances contraction of smooth muscle cells in the wall of the uterus?..and after delivery stimulates milk ejection from the mammary glands in response to the mechanical stimulus provided by a suckling infant?
What is a substance that decreases urine production?
ADH, antidiuretic hormone
What can alter the secretion of ADH?
Pain, stress, trauma, anxiety, acetylcholine, nicotine and drugs like morphine, tranquilizers and some anesthetics
Hyposecretion or nonfunctional ____ receptors causes diabetes insipidus