Endocrine System Flashcards
What kinds of glands synthesize substances that are released into ducts connecting to another structure?
exocrine
What kinds of glands synthesize substances that are released into the bloodstream to affect target tissue?
endocrine
Endocrine cells can comprise a single gland or…
be scattered throughout the tissue of an organ with other functions
The endocrine system and nervous system work together to keep the body in…
homeostasis
Endocrine cells produce substances that are released into the bloodstream to have an effect on target structures - these substances are called…
hormones
What are hormones?
substances released into the bloodstream that are chemical messengers that will have an effect on tissues/structures that have receptors for the specific hormone
Hormone levels in the blood are regulated by self-adjusting mechanisms, or…
feedback loops
- can be either positive or negative
What is the master controller of the endocrine system?
hypothalamus
How does the hypothalamus control the endocrine functions of the body?
- Produces regulatory hormones which have an effect on the anterior pituitary gland (which produces its own hormones). Regulating hormones can either stimulate the release of hormones or inhibit them.
- Produces hormones that are transported and stored in the posterior pituitary gland until they are needed.
Stimulates sympathetics to the adrenal medulla during “fight or flight” which causes the adrenal medulla to release adrenaline.
Pituitary Gland (AKA Hypohphysis)
- sits in the hypohyseal fossa of the sphenoid bone
- suspended from hypothalamus by a stalk or infundibulum
- divided into anterior and posterior parts
What part of the pituitary gland synthesizes and releases hormones into the bloodstream under the control of the hypothalamus?
the anterior pituitary
What hormones do the anterior pituitary glands make?
- thyroid-stimulating hormone
- growth hormone
- follicle stimulating hormone & lutenizing hormone
- prolactin
- adrenococorticotropic hormones
- melanocyte-stimulating hormones
Thyroid-Stimulating Hormone
acts on the thyroid gland to release thyroid hormone, especially when cold or stressed
Growth Hormone
acts on all body tissues (especially bones and muscles to stimulate growth and size of the body
Follicle-Stimulating Hormone and Lutenizing Hormone
acts on the gonads (testes and ovaries) to stimulate the development of gametes (sperm cells and oocytes)
Prolactin
acts on the mammary glands of the breast to stimulate growth and milk production (not ejection)
Adrenocorticotropic Hormone
acts on the adrenal cortex to cause the release of corticosteroids
Melanocyte-Stimulating Hormone
acts on the melanocytes in the skin to produce melanin
The hypothalamus controls the anterior pituitary glandby releasing its regulating hormones in to the…
hypothalamic-hypophyseal portal system
Venous blood carrying regulating hormones from the hypothalamus to the capillary plexus surrounding the anterior pituitary gland are called the…
hypophyseal portal veins
The regulating hormones leave the capillary plexus to have an effect on the…
anterior pituitary
The anterior pituitary releases its hormones into the capillary plexus and are carried away by the __________ ______, back to the heart to be distributed throughout the body.
hypophyseal vein
The stalk of the pituitary gland is made up of _______ _______ running from the hypothalamus into the posterior.
nerve axons
There are ___ nuclei in the hypothalamus whose axons make up the stalk and carry hormones to the posterior pituitary gland for storage.
2
What do neurons in the paraventricular nucleus do?
synthesize and transport oxytocin to the posterior pituitary gland
What do neurons in the supraoptic nucleus do?
produce and transport anti-diuretic hormone to the posterior pituitary gland
The posterior pituitary gland does not produce any hormones of its own, but stores…
oxytocin and anti-diuretic hormone until needed
What are hormones from the posterior pituitary released into?
its own capillary plexus to access the general bloodstream
Oxytocin
- stimulates the ejection of milk from the breast (not production) during breastfeeding
- causes contraction of the smooth muscle of the uterus during birth
- in males, oxytocin causes the contraction of the prostate gland to release its products during sexual activity
Anti-Diuretic Hormone
- released when blood volume is low, causing water to be retained by the body (kidneys) to help increase blood volume
- it also causes vasoconstriction, which helps to increase blood pressure; for this reason, anti-diuretic hormone is also referred to as vasopressin (vaso; vessel… pressin; to press down)
What is the largest endocrine gland in the body?
thyroid
Where is the thyroid gland located?
lower neck, anterior to the trachea
The right and left lobes of the thyroid are connected by the…
isthmus
Where does the thyroid get its blood supply?
through superior and inferior thyroid arteries
The thyroid produces thyroid hormone, which does what?
regulate metabolic activity of cells in the body, temperature
What are follicles in the thyroid gland?
follicular cells surrounding a cavity filled with colloid
Colloid
contains precursors of thyroid hormone
What cells of the thyroid produce thyroid hormone?
follicular cells
What nutrient is essential for thyroid hormone production?
iodine
Goiter
enlargement of the thyroid gland due to lack of iodine in diet
Grave’s Disease
an immune system disorder that results in the overproduction of thyroid hormones (hyperthyroidism). This disease is more common among women and before the age of 40.
Exophthalmos
bulging of the eyes (seen with Grave’s disease)
How many parathyroid glands are typically embedded in the posterior thyroid gland?
4
Parathyroid gland cells produce what, and what is this hormone’s purpose?
parathyroid hormone (PTH) which regulates blood calcium levels
PTH is released into the bloodstream in response to…
low blood calcium levels
How does PTH work?
- causes osteoclasts to release calcium from bone
- causes kidneys to reabsorb more calcium from tubular fluid
- causes small intestine to absorb more calcium
Are parathyroid glands under control of the hypothalamus?
no, they release their hormones in response to calcium levels in the blood
Medulla of the Adrenal Gland
has chromaffin cells that release epinephrine and norepinephrine
The cortex of the adrenal gland has three layers, or zones:
- zona glomerulosa
- zona fasciculate
- zona reticularis
Zona Glomerulosa of the Adrenal Gland
secretes mineralcorticoids to regulate composition of electrolytes in the body (aldosterone is a mineralcorticoid)
Zona Fasciculate of the Adrenal Gland
secretes glucocorticoids which stimulate metabolism of lipids and proteins and helps regulate blood glucose levels (cortisol is a glucocorticoid)
Zona Reticularis of the Adrenal Gland
secretes gonadocorticoids (androgens are gonadocorticoids)
Cushing Syndrome
excessive glucocorticoid (chronic exposure) such as when taking corticosteroids as therapy for rheumatoid arthritis
- decreased bone mass
- muscle weakness
- redistribution of body fat
- salt retention (swelling)
Addison Disease
adrenal insufficiency
- weight loss
- general fatigue and weakness
- hypotension
Which organ has both exocrine and endocrine functions?
pancreas
Acinar Cells of Pancreas
exocrine - produce digestive enzymes that enter the duodenum through the pancreatic duct
What are the endocrine cells of the pancreas?
pancreatic islet cells (islets of Langerhands)
- alpha and beta cells
What do the alpha cells of the pancreas do?
secrete glucagon which cause cells in the liver to break down glycogen into glucose
What do the beta cells of the pancreas do?
secrete insulin to facilitate movement of glucose from blood to tissues/cells of the body
- insulin can also promote glycogen synthesis in liver
Delta cells of the pancreas
stimulated by high levels of nutrients in the bloodstream. Synthesize somatostatin, which slows the release of insulin (keeps glucose in blood longer) as well as the activity of the digestive organs (this slows the rate of nutrients entering the bloodstream)
