5.5. Endocrine system

Question 1

Endocrine glands

Answer 1

clusters of cells that release products directly into blood because they are ductless but highly vascularized, have extensive rER (and sER) because their main function is production of proteins and lipids (hormones)

Question 2

hormone pathway to tissue (FSH example)

Answer 2

released into blood, binds to a specific receptor on the cells of the target tissue and changes its metabolic activity
the pituitary gland releases FSH, it reaches tissue inside ovaries and stimulates cells to produce oestrogen (smooth ER activated, steroid hormone)

Question 3

what are hormones. What are different types of hormones?

Answer 3

chemical messengers produced by endocrine glands that travel through blood and affect target tissue
steroids (oestrogen, testosterone), peptide derivatives (insulin) or tyrosine derivatives (thyroid hormones like T3 and T4)

Question 4

what is homeostasis

Answer 4

maintenance of the internal environment (variables of body fluids) between narrow and defined limits

Question 5

pancreas structure

Answer 5

located below the stomach, both an endo and exocrine gland
exo: digestive enzymes are released via pancreatic duct into the beginning of the small intestine (amylase, protease, nuclease and lipase)
endo: between exocrine glands and ducts there are islets of Langerhans (clusters of endocrine cells), two types of endocrine cells: alpha cells (glucagon) and beta cells (insulin), islets are separated from the exocrine tissue by a thin capsule and are extensively vascularized

Question 6

glucose blood concentration regulation

Answer 6

Set range for blood glucose concentration is 4-8 mmol/L.
If the level is too high (eating sugar), beta cells in islets are stimulated and they release insulin into the blood (targeting all body cells). Body cells absorb glucose through glucose channels and use it for cell respiration (more E produced). Liver and muscle cells will do the same but most of glucose will be polymerized and stored as glycogen.
If the level is too low (exercising, skipping meals), alpha cells will be activated, and glucagon will be released into the blood. Only liver and muscle cells are affected in this case as glucagon will enter them and hydrolyse glycogen into glucose. Glucose will be released into the blood and thus its levels will be raised.

Question 7

Which cells don’t have to be stimulated by pancreas to take up glucose?

Answer 7

brain cells and intestinal cells