Endocrine System Flashcards
(10 cards)
Explain the difference in mechanism of action between water-soluble and lipid-soluble hormones.
Water-soluble hormones bind to receptors on the cell membrane and initiate a signaling cascade involving second messengers because they cannot cross the hydrophobic cell membrane. Lipid-soluble hormones can cross the cell membrane, bind to intracellular receptors, and directly influence gene transcription, leading to protein synthesis.
Describe how cAMP acts as a second messenger in a hormone signaling pathway.
cAMP is produced from ATP by adenylate cyclase when a hormone binds to its receptor. As a second messenger, it activates protein kinases, which then phosphorylate other proteins, altering their activity and ultimately changing cell function.
Give an example of a humoral stimulus and explain how it triggers hormone release.
An example of a humoral stimulus is high blood glucose. When the pancreas detects elevated blood glucose levels, it releases insulin to decrease the blood sugar concentration back to homeostasis.
What role does cortisol play in the resistance phase of the general adaptation syndrome?
Cortisol, released during the resistance phase, increases blood glucose levels by stimulating the liver to produce glucose and inhibiting insulin release. This ensures the brain has enough glucose, while other tissues are directed to use fats for energy.
Explain how the sympathetic nervous system contributes to the alarm reaction (fight-or-flight response).
The sympathetic nervous system, as part of the alarm reaction, causes the release of epinephrine and norepinephrine, increasing heart rate, blood pressure, and blood glucose levels. This prepares the body for immediate action by increasing the availability of energy and oxygen to critical tissues.
Explain the role of testosterone in the male body.
Testosterone is essential for the development of male reproductive organs and secondary sexual characteristics, as well as stimulating protein anabolism. It is converted to estrogen in the bone to help stop growth, and it also directly stimulates spermatogenesis, or sperm production.
Describe how FSH and LH contribute to the follicular phase of the ovarian cycle.
FSH stimulates the development of primary follicles into secondary follicles, while LH stimulates estrogen production from the cells of these follicles. These hormones trigger a sequence of events that leads to estrogen secretion and follicle maturation.
How does progesterone influence the uterine lining during the secretory phase?
Progesterone, secreted by the corpus luteum, prepares the endometrium for implantation by increasing its vascularity and thickness. It also causes the uterine lining to store glycogen and inhibits uterine contractions.
Explain how oral contraceptives prevent pregnancy from an endocrinological perspective.
Oral contraceptives, containing estrogen and progesterone, inhibit the release of GnRH, which in turn suppresses FSH and LH secretion. This prevents follicle maturation and ovulation, thus preventing pregnancy.
What hormones does the placenta secrete, and what is the function of hCG?
The placenta secretes estrogen, progesterone, and hCG. hCG maintains the corpus luteum during early pregnancy, ensuring the continued production of progesterone and estrogen until the placenta can take over this role.
