Objectives – 1, BIO 2320, Endocrine SystemAnswers
C. ENDOCRINE SYSTEM
1.Reproduction, growth and development, internal homeostasis, helps to cope with environmental changes
2.Endocrine make hormones & are released into the bloodstream; exocrine make a substance released directly onto skin surface or into a duct, e.g. salivary duct.
3.Hormone is made by an endocrine gland & is a chemical messenger traveling in the bloodstream. The target cell responds to the hormone because it has matching receptors for the hormone
4.Most are amino acids, some are cholesterol based. All are organic compounds and are transported in the bloodstream; usually they are attached to some carrier protein making them physically larger so that they are not urinated out.
5.It can go to the nucleus and act upon the genes, or it can stimulate and intermediate compound such as cAMP, which acts as a second messenger and stimulates or inhibits a process or metabolic pathway in the cell.
6.Pituitary gland
7.Sella turcica of sphenoid bone
8.Anterior pituitary: FSH causes sperm production in male and follicle maturation in female; LH=ICSH causes interstitial cells of testes to make testosterone in male and causes ovulation in female; TSH stimulates the thyroid gland to make hormone; ACTH stimulates the adrenal cortex to make hormone; GH causes growth; Prolactin causes milk production in females; MSH causes skin pigment (melanin) to be produced.
Posterior pituitary releases: ADH causes water reabsorption (from urine to blood) in kidney; Oxytocin causes uterine contractions during childbirth and milk secretion.
9.Morphine like compound made by anterior pituitary gland, but is really a neuromodulator, not a hormone.
10.Hypothalamus makes stimulatory hormones called releasing hormones and inhibitory hormones; Negative feedback
11.It doesn’t make ADH and Oxytocin. They are made by hypothalamus but stored and released by posterior pituitary.
12.Inferior to larynx, and histology shows follicles filled with thyroid hormone (colloid), and the surrounding follicle cells make the hormone. The interstitial cells are called parafollicular cells and make calcitonin.
13.Made from an amino acid called tyrosine. Three iodine molecules in T3 and four in T4.
14.Attached to TBG
15.Negative feedback, TSH from ant. pituitary and Thyroid releasing hormone from hypothalamus.
16.Parafollicular cells of thyroid gland = C cells
17.Decreases blood calcium levels
18.Embedded in the thyroid gland. It makes Parathyroid hormone which increases blood calcium levels. Obviously, blood calcium levels determine whether PTH or Calcitonin should be released.
19.Above the kidneys. Outer region is adrenal cortex, inner region is adrenal medulla.
20.Epinephrine & Norepinephrine are released under fight of flight situations. They exaggerate the fight or flight response. Mostly, epinephrine is released.
21.Outer is the zona glomerulosa where aldosterone is made which causes sodium reabsorption in the kidneys (sodium goes from urine back to blood, and water passively follows); Zona fasciculata is middle layer making glucocorticoids that help one deal with long term stress by conserving energy for later. It is also anti-inflammatory. Inner zone is zona reticularis making sex hormones to be discussed under reproduction.
Of course ACTH from the ant. pituitary stimulates the release of these hormones. Also, low blood sodium would stimulate release of aldosterone. If your blood pressure is low, the kidneys release renin. Renin is an enzyme that converts angiotensinogen to angiotensin. These will be discussed under cardiovascular system. However, angiotensin can cause the adrenal cortex to release aldosterone. Since aldosterone causes more salt to be in the bloodstream, and water passively follows, it will help to restore the low blood pressure to a more normal value.
22.Islets of Langerhans = pancreatic islets and are the endocrine cells of the pancreas. The chromaffin cells are the endocrine cells of the adrenal medulla.
23.Pancreas
24.Inferior to stomach. The pancreas is mostly exocrine – only the islets are the endocrine portion
25.The islets, specifically beta cells make insulin which lowers blood glucose by allowing it to go into cells. Alpha cells make glucagon which raises blood glucose by bringing it out of storage, and delta cells make somatostatin which opposes GH release.
26.High blood glucose leads to insulin release; Low blood glucose leads to glucagon release.
27.Male – testes; Female – Ovaries
28.Roof of third ventricle. Makes melatonin which depresses reproductive activity
29.Thymus. It has a lymphatic role, in that T lymphocytes are made and “trained” here. The endocrine role is that it releases thymic hormone to stimulate these T cells.
30.Fatty acids that have a variety of functions. They are unique in that they tend to act locally. For example, a prostaglandin released by the uterus into the bloodstream has target cells in the uterus and acts upon the uterus.