Peripheral Endocrine Glands Flashcards
What are the major peripheral endocrine glands?
1.) thyroid gland
2.) adrenal glands
3.) endocrine pancreas
4.) parathyroid glands
What types of cells make up the thyroid gland?
follicular cells (arranged into spherical layers forming a follicle)
What is a follicle in the thyroid gland?
spheres of follicular cells that are filled with colloid (substance containing thyroid hormone) seperate from ECF
What are the two molecules that are referred to as thyroid hormone?
1.) tetraiodothyronine (T4)
2.) triiodothyronine (T3)
Where is the receptor for thyroid hormone? What does its activation do?
thyroid-response element:
causes transcription and synthesis of new proteins that bring about hormone’s effect
What thyroid hormone is more prevalent in the body?
While T4 is 90% of the hormone secreted, T3 is 10 times more potent, and most of T4 is converted to T3, making T3 the most abundant
Could you identify the physiological effects of thyroid hormone from a list?
1.) increases cellular respiration, which increases basal metabolic rate, which increases body heat
2.) increases number of NE and E receptors on target cells of sns, increasing effects of sympathetic nervous system stimulation (sympathomimetic effect)
3.) increases heart rate and force of contraction
4.) promotes secretion of growth hormone and production of IGF-1 by liver, necessary for proper growth
How is thyroid secretion regulated?
controlled by a 3-hormone chain starting at the hypothalamus, constant secretion of thyroid hormone— negative feedback prevents runaway secretion
What is hypothyroidism? Why would too much thyroid-stimulating hormone lead to a
goiter?
hypothyroidism: due to failure of thyroid gland, lack of TSH production or lack of dietary iodine
Why would too much thyroid-stimulating hormone lead to a
goiter?
TSH is a tropic hormone with trophic properties, stimulates maintenance of target gland
excessive TSH levels –> leads to hypertrophy and hyperplasia of follicular cells (in thyroid gland)
Do the adrenal cortex and medulla secrete the same hormones?
no, they secrete different hormones
adrenocortical: aldosterone, cortisol, DHEA
medulla: epinephrine, norepinephrine
what are the 3 layers of the adrenal cortex?
1.) zona glomerulosa
2.) zona fasciculata
3.) zona reticularis
Is hormone stimulation the same in the adrenal cortex and medulla?
adrenal cortex: stimulated by hormones from the pituitary gland (ACTH)… except aldosterone secretion primarily regulated by RAAS and K levels in blood (not by ACTH)
medulla: stimulated directly by the sympathetic NS
What are the three categories of adrenocortical hormones?
1.) mineralocorticoid
2.) glucocorticoids
3.) sex hormones
What is the main mineralocorticoid produced by the adrenal cortex?
aldosterone (influence balance of Na+ and K+)
produced in zona glomerulosa
What is the main glucocorticoid produced by the adrenal cortex?
cortisol (plays role in glucose metabolism, also lipid and protein, and stress response)
produced in zona fasciculata (also zona reticularis)
What is the main sex hormone produced by the adrenal cortex?
DHEA
produced in zona fasciculata and reticularis
How do lipophilic hormones move through the blood? How about hydrophilic hormones?
lipophilic: (steroid and thyroid hormones)… bind to transport proteins in blood (longer half-life)
hydrophilic: (peptide hormones (insulin, glucagon), epinephrine and norepinephrine)… soluble in blood plasma and circulate freely in blood stream and interact with cell-surface receptors on target cells
Are adrenocortical hormones lipophilic or hydrophilic?
lipophilic
Where are the target cell receptors located for lipophilic hormones?
lipophilic target cell receptors located in the cytoplasm
What is the main function of aldosterone? What organ does it mainly act on?
acts to increase sodium reabsorption in distal and collecting tubules of the kidneys (increases ECF volume)
What directly controls aldosterone secretion?
Direct detection of increased plasma K+