Endocrine System 3 Flashcards
What are the 3 glands controlled by the Anterior Pituitary Gland?
Thyroid, parathyroid and adrenal gland
Where is the thyroid gland found?
Just below the larynx
on the anterior and lateral surface of the trachea
What hormones are made and secreted in the thyroid gland? What are their functions?
Thyroid hormone - involved in optimal metabolic activity
Calcitonin - involved in calcium homeostasis
In the thyroid gland, these are small spherical sacs
Follicles
This is what surrounds the small spherical sacs in the thyroid gland.
Follicular cells (cuboidal epithelial cells)
Where is the site of thyroid hormone synthesis?
Follicular cells
These cells (in thyroid gland) are found in clusters between the follicles. They are responsible for making the hormone calcitonin (which is mainly involved in calcium homeostasis.
Clear (C) cells
How are thyroid hormones stored? Since thyroid hormones are the only lipid soluble hormones that CAN be stored.
Because when iodine enters the follicle cell to react with tyrosine (which forms the thyroid hormone) => the protein this takes place in (TGB) remains in the thyroid gland, and is able to STORE the thyroid hormone.
So when thyroid hormones are needed, they are able to detach from iodised TGB as needed.
How do the T4 and T3 hormones (thyroid hormones) travel to target cells?
Via a carrier protein (TBG)
What is the purpose of secreting thyroid hormones?
To increase the basal metabolic rate
This is the body’s rate of energy expenditure under basal conditions
Basal metabolic rate
What does the secretion pathway of thyroid hormone look like?
Hypothalamus secretes TRH (thyroid releasing hormone) to stimulate the Anterior Pituitary
Anterior pituitary secretes TSH (thyroid stimulating hormone) to stimulate the Thyroid Gland
Thyroid gland secretes thyroid hormones into the bloodstream to effector organs
Hormones bind to specific receptors on effector organs
Common effects: Increased metabolic rate
increased: heat production, oxygen consumption and ATP hydrolysis, proteolysis (breakdown of protein)
stimulates carbohydrate metabolism
Where is the body’s main store of calcium?
In the bone
What 3 hormones are involved in calcium regulation?
Parathyroid hormone, calcitriol, calcitonin
This gland secretes parathyroid hormones.
Parathyroid gland
Where is the parathyroid gland located?
In the posterior surface of the thyroid
What does the secretion pathway for the parathyroid hormone look like?
- this PATHWAY IS NOT CONTROLLED BY THE HYPOTHALAMUS * hence why stimulus directly stimulates parathyroid gland
Stimulus: low blood glucose concentration
Stimulates parathyroid gland to secrete PTH
PTH is released to kidneys and bone
- kidneys: increased bone reabsorption to convert vit. D into calcitriol
- bone: increases bone breakdown => increases release of Calcium into blood
How do the kidneys form calcitriol?
By increasing the bone reabsorption to convert it into vit. D.
Decrease in plasma Ca2+ leads to:
Increase in PTH release
- regulation of blood calcium concentration is a NEGATIVE feedback system
Increase in plasma Ca2+ leads to:
Decrease in PTH release
Where are the adrenal glands located?
Superior to each kidney (like little hats)
What are the hormones secreted by the adrenal cortex? What type of hormone are they?
Aldosterone, cortisol and androgens (these are steroid hormones)
What are the hormones secreted by the adrenal medulla? What type of hormone are they?
Adrenalin and noradrenalin (there are water soluble hormones)
What are the two separate glands of the adrenal glands?
Adrenal medulla and adrenal cortex
These are secreted as a part of the sympathetic nervous system’s response to stress.
- secreted in response to neural signals and causes increased use of stored energy
Adrenalin and noradrenalin from adrenal medulla
