Endocrine System (Final Exam) Flashcards
How does the endocrine system communicate?
Through hormones
In what type of cells do hormones elicit a physiological response?
Target cells that have receptors specific to that hormone
What are exocrine glands?
They are glands that have ducts leading to external system
NOT PART OF THE ENDOCRINE SYSTEM
Describe what endocrine glands are and give a few examples of each.
They are highly vascularized ductless glands that secrete hormones into the blood, and they often receive nervous system stimulation
Examples: Pineal, Pituitary, and Pancreas glands
What is the hormone that the thyroid gland secretes, the target organ, and the function of the hormone?
Hormone is Thyroxin, and the target organ is the liver, and the function is metabolic rate.
How do hormones generally act?
They act through receptors either in the membrane, in the cytoplasm or on the membrane of the nucleus.
THESE RECEPTORS NEED TO BE SPECIFIC TO THE HORMONE
Describe specifically how thyroid hormones act.
They bind to a membrane receptor and are transported into the cell by active transport
Once inside they bind to cytoplasmic or nuclear receptors and are transported into the nucleus to alter gene transcription
Describe specifically how steroid hormones act.
Steroid hormone (test/estrogen) are lipid soluble, so they get inside the membrane easily
Once inside they bind to a protein forming the gene regulatory protein, which will activate or inhibit specific genes
Describe how the second messenger system works.
When hormones (first messengers) are too big or polar to enter the membrane, they will bind to transmembrane proteins.
By binding to the transmembrane protein, it activates the second messenger system in the cytoplasm.
This system stimulates a specific kinase which activates or inactivates enzymes that alter cellular activity
Give an example of a real life second messenger system.
Epinephrine (hormone) attaches to receptor on the cell membrane which activates cAMP, which in turn activates a kinase that alters enzyme activity
Why is it so important that secretion of hormones are controlled?
Because hormones in their wide variety, affect enzyme activity/alter cell metabolism, change membrane permeability, regulate protein synthesis, and stimulate release of other hormones
Describe how negative feedback mechanisms are used to control hormone secretion.
Rising levels of one hormone decrease the secretion of another.
Endocrine cells secrete a hormone that will stimulate another cell that will secrete another different hormone, that when it increases in the blood stream will inhibit the release of the first hormone
Describe how positive feedback mechanisms are used to increase hormone secretion.
During positive feedback, the hormonal signal feeds back to the control system and causes an increase in the initial signal, and that signal becomes amplified to produce an explosive event.
Ex. Oxytocin for birth
