Endocrine System Flashcards
What is the endocrine system?
- chemical mediators called hormones are released from
one part of the body and travel (usually via the blood) to another part of the
body
What are endocrine glands?
- secrete hormones into the blood
What are exocrine glands?
- secrete substances into ducts that transport them to the external environment (e.g., sweat, saliva, digestive enzymes)
What are artificial hormone analogues?
- some “mimic” the hormone and cause the cell to respond as if
the hormone was present (“agonist”) - some “block” the receptor thus preventing the hormone from
binding, but will have no effect on the target cell (“antagonist”)
What is tamoxifen?
- analogue of estrogen
- antagonist in breast tissue (used to fight breast cancer)
- agonist in uterine tissue (can cause uterine cancer)
Describe water soluble hormones.
- must be injected as they are digested in the gut
- can travel through the blood in a free form
- receptors are located on the target cell’s cell membrane
Describe lipid-soluble hormones.
- can be taken orally as they are not digested in the gut
- require a transport protein to carry them through the blood
- receptors are located inside the target cell
What are some examples of stimuli that can induce a gland to secrete a hormone?
- signals from the nervous system
- levels of circulating ions or compounds in the blood
- the action of other hormones
What re some of the important functions of hormones?
- regulate the growth and development of tissues and organs
- regulate metabolic processes
- regulate the chemical composition of the blood and internal environment
- cause contraction of cardiac muscle and smooth muscle
How are hormones that are not used “deactivated”?
- deactivated by the liver and excreted by the kidneys
What are some endocrine glands?
- parathyroid glands (4)
- pineal gland
- pituitary gland
- thyroid gland
- adrenal glands (2)
- hypothalamus
- pancreas
- ovaries
- testes
Where is the hypothalamus and pituitary gland located?
- in the sella turcica of the sphenoid bones
What does the anterior pituitary gland do?
- produces 7 hormones whose secretion is controlled by “releasing” and “inhibiting” hormones secreted by the hypothalamus
What does the posterior pituitary gland do?
- Made up of the axons of hypothalamic neurons that produce 2 hormones
How do hormones secreted by the pituitary gland enter the bloodstream?
- branches of the internal carotid arteries form capillary networks around the lobes of the pituitary.
- hormones enter the bloodstream via these capillary networks
What are the seven hormones released by the anterior pituitary gland?
- Human growth hormone (hGH)
- Thyroid-stimulating hormone (TSH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Prolactin
- Adrenocorticotropic hormone (ACTH)
- Melanocyte-stimulating hormone
What two hormones do the posterior pituitary gland release?
- oxytocin
- antidiuretic hormone (ADH)
Where is the pineal gland located?
- small gland in the posterior portion of the roof of the third ventricle
What does the pineal gland do?
- secrete melatonin, which
induces drowsiness - visual input from the eyes either stimulates (dark) or inhibits (light) the
secretion of melatonin
What does the thyroid gland produce?
- T4 and T3
- calcitonin
Do fetuses produce T4 and T3?
- they don’t produce much of either in the first half of pregnancy
- they rely on their mothers production
How is the parathyroid gland stimulated?
- by a drop in Ca++ in the blood
What hormone does the parathyroid gland secrete?
- parathyroid hormone
What is the main function of the parathyroid hormone?
- stimulates osteoclasts (bone)
- decreases Ca++ excretion (kidneys)
- increases Ca++ absorption (GI tract)
