The Endocrine System: Chapter 1-3 Flashcards
Define homeostasis and an example of it.
Homeostasis is your body’s way of dealing with change and keeping everything the same on the inside.
E.g. When you go outside on a cold day, body temp can decrease and if your body doesn’t respond, you could suffer from hypothermia or even death. Skin receptors sends a message to your brain indicating the temperature and the brain would send messages to your skeletal muscles, telling them to shiver to generate heat by muscular activity.
Define endocrine gland.
Glands that secretes their products inside the blood stream only. This is how hormones move around inside you. (Endo = inside, crine = to secrete)
Define exocrine gland.
Glands that secretes their products elsewhere and not in the bloodstream. (Exo = outside, crine = to secrete)
Define endocrine system.
A system made up of endocrine glands and the hormones they secrete.
Define hormones.
Chemical messengers secreted from endocrine glands. Hormone means “to excite” or “set in motion” in Greek.
Compare the endocrine system and the nervous system.
- ES is typically slower than the NS but has longer lasting effects to a broader range of cells
- Some NS tissues secrete hormones as well (E.g. cells in hypothalamus, pituitary gland, and adrenal glands)
- Several chemicals function as both neurotransmitters and hormones depending on location. (E.g. epinephrine)
- Both ES and NS include responses that are regulated by negative feedback loops.
- Regulation of several physiological processes involves both the ES and NS acting in conjunction with each other.
Who proved the existence of chemical messengers in the body? What was his experiment?
Arnold Adolph Berthold in Gottingen Uni in Germany in 1849. He removed testes of roosters and observed the effects on the capons (roosters with no testes). They did not crow, fight with other male roosters, or try to mate. They were smaller and didn’t develop the typical rooster plumage (feathers). Once the testes were reattached, they began to alter to look and behave like male roosters. The organs were not connected to any nerves so Berthold concluded that the testes were releasing something into the bloodstream that caused the developmental changes in the male birds. Scientists discovered this as testosterone.
What hormones does the hypothalamus secrete and what do they do?
Hypothalamus secretes:
• hypothalamic releasing-and-inhibiting hormones, which regulates the anterior pituitary hormones
What hormones does the anterior pituitary secrete and what do they do?
Anterior Pituitary secretes:
• human growth hormone (hGH), which stimulates cell division, bone and muscle growth, and metabolic functions
• thyroid-stimulating hormone (TSH), which stimulates the thyroid gland
• adrenocorticotropic hormone (ACTH), which stimulates the adrenal cortex to secrete glucocorticoids
• follicle-stimulating hormone (FSH), which stimulates production of ova and sperm from ovaries and testes
• luteinizing hormone (LH), which stimulates sex hormone production from the ovaries and testes
• prolactin (PRL), which stimulates milk production from mammary glands
What hormones does the posterior pituitary secrete and what do they do?
Posterior pituitary secretes:
• antidiuerectic hormone (ADH), which promotes the retention of water by the kidneys
• oxytocin (OCT), which targets bones and kidneys to lower blood calcium by inhibiting release of calcium from bone and reabsorption of calcium by kidneys
What hormones does the thyroid secrete and what do they do?
Thyroid secretes:
• thyroxine (T4), which affects all tissues, and increases metabolic rate and regulates growth and development
• secretes calcitonin, which targets bone and kidneys to lower blood calcium by inhibiting release of calcium from bone and reabsorption of calcium by kidneys
What hormones does the parathyroid secrete and what do they do?
Parathyroid secretes:
• parathyroid hormone (PTH), which raises blood calcium levels by stimulating the bone cells to release calcium, the instestine to absorb calcium by kidneys
What hormones does the adrenal cortex secrete and what do they do?
Adrenal cortex secretes:
• glucocorticoids (e.g. cortisol), which stimulates tissues to raise blood glucose and break down protein
• mineralocorticoids (e.g. aldosterone), which promotes reabsorption of sodium and water by the kidneys
• gonadocorticoids, which promotes secondary sexual characteristics
What hormones does the adrenal medulla secrete and what do they do?
Adrenal medulla secretes:
• epinephrine and norepinephrine, which are the fight-or-flight hormones, and raises blood glucose levels
What hormones does the pancreas secrete and what do they do?
Pancreas secretes:
• insulin, which lowers blood glucose levels and promotes the formation of glycogen in the liver
• glucagon, which raises blood glucose levels by converting glycogen to glucose
What hormones do the ovaries secrete and what do they do?
Ovaries secrete:
• estrogen, which stimulates uterine lining growth and promotes development of the female secondary sexual characteristics
• progesterone, which promotes growth of the uterine lining and prevents uterine muscle contractions
What hormones do the testes secrete and what do they do?
Testes secrete:
• testosterone, whcih promotes sperm formation and developmemt of the male secondary sexual characteristics
What are hormones composed of?
Either lipids or amino acids.
Define lipid-soluble hormones and give an example of one.
Lipid-based hormone that can easily diffuse through the lipid bilayer of cell membranes, and can bind to the target call’s receptor proteins.
E.g. Steroid hormones (testosterone, estrogen, cortisol)
Define water-soluble hormones and give an example of one.
Water-soluble hormones (aka amino acid based hormones) cannot diffuse across the cell membrane. Typically, water-soluble hormones will bind to a receptor protein on the surface of a target cell, which begins a cascade of reactions inside the target cell. Each reaction that occurs in the target cell triggers many other reactions so the impact of the hormone is amplified.
E.g. Epinephrine, human growth hormone, thyroxine, and insulin.
How do hormones act on target cells?
Each target cell has receptor proteins which receives and responds to the chemical message sent by the hormone. Circulating hormones bind to their specific receptor proteins, much like a key fits into a lock. When a hormone binds to its specific receptor, this triggers other reactions in the target cell.
Define negative feedback mechanism/loop. Give an example of one.
Mechanism of homeostatic response by which the output of a system suppresses or inhibits activity of the system.
E.g. When a certain blood concentration of a hormone is reached, the endocrine gland releasing the hormone is inhibited by the presence of the hormone. The release of the hormone is slowed.
Define tropic hormone. Describe the generalized pathway of tropic hormones.
Tropic hormone is a hormone that targets endocrine glands and stimulates them to release other hormones.
Typically, the hypothalamus secretes a releasing hormone into the anterior pituitary, which causes the anterior pituitary to release a tropic hormone into the bloodstream. The tropic hormone then stimulates the target gland to release a third hormone into the blood. This hormone travels to another target tissue and produces an effect.
What is the pituitary gland, where is it, and what does it release?
Small endocrine gland that lies just inferior to the hypothalamus; consists of the anterior and posterior pituitary. It sits in a body cavity attached by a thing stalk to the hypothalamus at the base of the brain. It releases tropic hormones.
What is the posterior pituitary gland and what does it release?
Posterior gland is considered to be a part of the nervous system. It does not produce any hormones, instead, it stores and releases hormones. It releases antidiuretic hormone and oxytocin (which are produced in the hypothalamus and transferred to the posterior pituitary by neuronal axons).
What is the anterior pituitary gland and what does it release?
The anterior pituitary gland is the hormone synthesizing gland. Its cells produce and release six major hormones: human growth hormone (hGH), prolactin (PRL), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and leutinizing hormone (LH).
