intro to endocrine system Flashcards
What is the primary function of the endocrine system?
To maintain internal homestasis in response to external and internal stimuli.
Do hormones work rapidly or at a slower pace?
They work slowly but last much longer as a result
For a target cell to respond to a hormone, what must it have?
The target cell must have the appropriate receptors.
Name the 6 major endocrine glands in the body
the hypothalamus, pituitary gland, thyroid gland, parathyroid gland, thymus and adrenal glands.
NOTE: these are just the endocrine glands, not organs.
What is humoral hormone release?
When factors in the blood, or changed conditions are detected by the endocrine gland and hormone release is triggered.
What is neural hormone release?
when either pre or postganglionic nerve fibres stimulate an endocrine gland to secrete a hormone.
What is traditional hormone based hormone release?
When an tropic hormone binds to and stimulates the endocrine gland to secrete more hormones.
What are tropic hormones? (Tropic not trophic hormones)
Hormones designed to target other endocrine glands.
what are sex hormones
Special hormones of the reproductive system that target reproductive organs and tissue.
What are anabolic hormones?
A hormone that promotes anabolism on its target cells. Anabolism causes increased cellular growth and build-up, consuming energy.
What is the difference between peptide and steroid hormones?
Composition- peptide hormones are protein based, like insulin. Steroid hormones are lipid based and derived from cholesterol.
With what mechanism do hormones bind to receptors?
They use the lock-and-key mechanism.
What is the relationship between steroid hormones and diffusion through cell membranes?
Steroid hormones are hydrophobic, just like the lipid membranes. Thus they diffuse across into the cell easily.
what is the aim of steroid hormones once in a cell?
Steroid hormones help regulate production of proteins inside the cell. It does this by controlling protein gene expression in the nucleus.
Do steroid hormones elicit this response quickly?
No. It is a slow process that can take days.
What are non-steroid hormones?
Basically, protein hormones (g-protein family) and gonadotrophins.
Which mechanism do non-steroid hormones use to stimulate target tissue?
They use the second messenger mechanism. They are hydrophilic and cannot diffuse into the cell directly.
So they bind to the fixed g-protein receptors on the cell membrane. The g-proteins then send the signal to the second messenger chemical.
Name 2 important second messengers in the cell.
cyclic AMP and calmodulin (calcium based)
Hormonal synthesis and secretion is regulated by which feedback mechanism?
Negative feedback
Where is the pituitary gland located?
On the ventral surface (underneath) the brain
What are the 3 parts of the pituitary gland?
The infundibulum is the stalk that connects the hypothalamus above to the pituitary below. The pituitary comprises of the anterior (adenohypophysis) and posterior (neuropophysis) halves.
What are the 5 types of secretory cells in the anterior pituitary gland?
Somatotrophs-secrete growth hormone Corticotrophs-secrete ACTH thyrotrophs-secrete thyroid stimulating hormone lactotrophs- secrete prolactin gonadotrophs-secrete LH and FSH
What other structure controls the activities of the anterior pituitary gland?
The hypothalamus
Name the 4 key tropic hormones (hormones that stimulate other endocrine glands).
Thyroid stimulating hormone, follicle stimulating hormone, lutenising hormone and adrenocorticotropic hormone.
Name the 2 main hormones secreted from the posterior pituitary gland.
Antidiuretic hormone and oxytocin
Where is the the pineal gland located?
On the dorsal aspect of the brain
What does the pineal gland secrete?
Melatonin. This fuels the body clock
Where is the thyroid gland located?
Sits below the larynx but above the trachea in the neck.
Name the 3 thyroid gland hormones
T3(precursor to T4), T4 (thyroxine) and calcitonin (decreases blood Ca levels).
What hormones are secreted by the parathyroid glands?
Parathyroid hormone. It is the antagonist to calcitonin because it increases blood calcium levels.
Where are the parathyroid glands located?
They are embedded within the posterior surface of the thyroid gland, in little clumps.
Explain how calcitonin and parathyroid hormone work together to maintain calcium homeostasis?
Increased blood calcium levels causes increased calcitonin secretion from the thyroid gland. Increased calcitonin causes decreased bone breakdown by the osteoclasts. This results in decreased blood calcium levels
Decreased blood calcium levels cause increased PTH from the parathryoid hormone. Inceased PTH causes increased bone breakdown by osteoclasts. This results in increased blood calcium levels.
Where are the adrenal glands located and what 2 regions is it comprised of?
The adrenal glands sit on top of either kidney.
They have an internal medulla and an external cortex. The cortex is normal endocrine tissue whilst the medulla is neurosecretory tissue.
Which 3 types of hormones are secreted from which of the 3 layers of the adrenal cortex?
Mineralcorticoids from the zona glomerulosa (superficial)
Glucocorticoids from the zona fasciculata (middle)
Precursor androgens (DHEA and adrostenedione) from the zona reticularis (deep)
What is the main mineralcorticoid produced by the zona glomerulosa of the adrenal cortex?
Aldosterone.
It increases blood pressure by increasing ECF volume. It does this by increasing Na+ and water retention. Part of the Renin-Angiotensin-Aldoserone system.
What is the function of glucocorticoids like cortisol in the body?
Glucocorticoids like cortisol are released in times of stress. They put the body into a catabolic state, where breakdown of body tissue increases the amount of available nutrients.
What hormones are secreted from the neurosecretory part of the adrenal gland, the medulla?
The androgens, noradrenaline and adrenaline are produced here. The environment is hydrophobic, and is needed for the production of hydrophobic steroid hormones.
What 2 hormones are secreted by the pancreas and from where?
Insulin is secreted from the beta (islet) cells whilst glucagon is secreted from the alpha cells.
What hormone does the testes produce?
Testosterone, under instruction from LH and FSH.
What hormones does the ovaries produce?
Oestrogen (developing follicles) and progesterone (corpus luteum).
What 3 hormones does the placenta produce during pregnancy?
hCG (Human chorionic gonadotrophin), oestrogen and progesterone.
Where is the thymus located?
In the mediastinum. It is larger in children and atrophies into adulthood.
What 2 hormones does the thymus secrete?
Thymosin and thymopoietin for t-cell development.
What are paracrines (tissue hormones)?
Localised hormones that only act on nearby tissue and cells.
Which prostaglandin type is responsible for uterine contractions?
Type F.
What effect does aging have on the endocrine system?
It causes atrophy of endocrine glands and thus decreased hormone production and levels.
