Chapter 11 - Endocrine Flashcards
What is the definition of a hormone (H)?
A Hormone is biology active compound release from on tissue into the blood, which carries it to its target tissue. Virtually every tissue produces hormones. (Notes) (pg 306)
What is a “target tissue” (TT)?
Target Tissues are a group of cells, which contain specific receptor proteins for the hormones and which therefore, can respond in a specific fashion. (306)
What does the TT do that makes it a TT for a hormone?
The TT allows the hormone to respond in a specific fashion according to the receptor protein. (306)
The hormone must bind to the receptor protein to have an action (notes)
“Exocrine gland”
“Exocrine gland”: (exo = Outside Greek) secrete chemicals through a duct that leads to the outside of the membrane and thus to the outside of a body surface. (pg 13)
“Endocrine gland”
“Endocrine gland”: (endon = Within Greek) secrete chemicals called hormones into the blood. (pg. 13 & 306)
What are some of the “classic” endocrine glands? (Fig 11.1)
Classic endocrine glands include: Pituitary Gland, Pineal gland, Hypothalamus, thyroid gland, adrenal gland, pancreas, ovary, test(ies)
Today we know that most tissues produce _____________s.
Hormones
What are “neurohormones”?
Neurohormones are specialized neurons, particularly in the hypothalamus, which secrete chemical messengers into the blood rather than into a narrow synaptic cleft. (pg. 306)
Hormones affect the _________ of their TT:
Receptor Proteins.
We can “classify” hormones (H) in 2 ways:
by their chemical structure and function
Chemical Categories:
Steroids – lipids derived from cholesterol. (testosterone, estradiol, progesterone, cortisol). Only secreted by the adrenal cortex (corticosteroids) and the gonads (sex steroids).
Amines – lipids derived from the amino acids tyrosine and tryptophan (hormones secreted by the adrenal medulla, thyroid, and pineal glands)
Polypeptides & Proteins – Polypeps contain less than 100 amino acids (generally, ex ADH). Proteins are polypeps with mot than 100 amino acids (ex GH). Insulin contains both.
Glycoproteins: Consist of long polypeps bound to one or more CHO group. Ex. Follicle Stimulating hormone (FSH) and luteinizing hormone (LH).
Polar Hormones:
Polypeps/proteins, glycoproteins and catecholamines (secreted by the adrenal medulla, epinephrine, and norepinephrines Derived from Tyrosine) (pg. 308-09)
Non-Polar Hormones:
Steroids and Thyroid hormones. These are known as lypophilic hormones, because they are non-polar.
What are the 2 types of “lipid soluble” Hormones? What glands produce them? (pg 307-08)
Lipid Soluble hormones are: Steroids and Amines (thyroid hormones). They are known as lypophilic hormones, because they are non-polar.
Steroids: Only secreted by the adrenal cortex (corticosteroids) and the gonads (sex steroids).
Aminies: Thyroid (Triodothyonine (T3) and Tyroxine/Tetraiodothyronine (T4)
When looking at Fig. 11.2, understand why different tissues release different steroids even though the metabolic pathway could go all the way from cholesterol to estradiol-17B.
The tissues release differing steroids because each steroids serves a specific purpose in the reproductive/sex system (e.g. ovulation, ejaculation, estrogen, testosterone)
Be able to discuss the structure of thyroxine and what its parent molecule is.
Thyroxin, T4, always converted into T3 cannot entire the nucleus.
When we use the terms “Pro-“ or “Pre-hormone” what is meant?
In the Inactive form of the hormone (per notes, not important)
Why are only some tissues the TT for a particular hormone?
???????
What do the terms “synergistic”, “permissive” and “antagonistic” mean with respect to H interactions? (pg 310)
Synergistic: When two or more hormones work together to produce a particular results. These effects may be additive or complementary.
Permissive: An H is said to have a permissive effect on the action of a second hormone when it enhances the responsiveness of a target organ to the second hormone or when it increases the activity of the second hormone. The second H won’t work w/o the other. (Notes)
Antagonistic: Hormones not working together. (e.g. Insulin lowers blood sugar, gluc. Raises blood sugar)
When we say a H has a ½ life of 3 days, what do we mean?
Half-Life: the time required for the plasma concentration of a given amount of the hormone to be reduced to half of its reference levels. How long does it take for ½ of it to disappear. (Notes)
A ½ life of 3 days is equal to a total of 6 days before the H is fully used.
In what ways did I tell you H are removed from the blood?
H’s are removed from the blood by (CANT FIND IN NOTES)
What is the “Priming Effect” (upregulation)?
Upregulation increases the # of receptor proteins. (Notes, pg 311)
What is “desensitization” or “downregulation”?
Prolonged exposure to high concentrations of polypeps hormones desensitize the T. Cells, which produces less of a response. This causes a decreased # of receptor proteins, which is call downregulation. (e.g. drug addicts).
Read the “Fitness” box concerning “Anabolic Steroids”. (pg 311)
Synthetic androgens (male Hs), causes men to develop gynecomastia (an abnormal growth of femalelike mammary tissue.) Female users display masculinization and antisocial behaviors. Inhibits the secretion of FSH and LH from the pituitary.
Mechanics of H action: The 2 mechanisms of “Non-polar” (lipophilic) H. (pg 312-314)
Two domains: ligand binding domains, and DNA binding Domains.
Steroid: Some Steroids bind to a cytoplasmic receptor, which then translocates to the nucleus Other Steroid hormones enter the nucleus and then bind to their receptor. In both cases, the steroid-receptor complex can then bind to a specific area of DNA and activate specific genes.
Thyroid: T4 is 1st converted into T3 within the cytoplasm of the target cell. T3 then enters the nucleus and binds to its nuclear receptor. The hormone-receptor complex can then bind to a specific area of DNA and activate specific genes.
Why do steroids and thyroxine need a carrier protein in the plasma?
Because they are lipophilic and do not travel dissolved in the aqueous portion of the plasma. After which they mush disassociation from their carrier proteins in the blood in order to pass through the lipid component of the plasma membrane and enter the T. Cell.
Be able to understand and describe what is shown in figures: 11.4, 11.5, 11.6, & 11.
- 4 & 11.5 pgs. 312 & 313
11. 6 & 11.7 pgs. 314 & 315
Where are the receptor proteins for steroids located? For Thyroxine?
Steroids: RP is located in the cytoplasm. (Notes) Two domains: ligand binding domains, and DNA.
Thyroxine: RP is only found in the nucleus.
What does “dimerization” mean?
The Process of two receptor units coming together. Both RP’s coming bind to the DNA. Two types Hetero (mixed) & Homo (similar)
What are “2nd messengers”? i.e. What do they do? Where are they formed?
Adenylate Cyclase-Cyclic AMP – 1st 2nd Mess to be discovered. When H binds to RP, causes dissociation of subunit from G- Proteins. The subunit moves through the membrane until it reaches the enzyme Adenylate Cyclaes, then binds to and activates this enzyme. ATP → cAMP + PPi cAMP activates the previously inactive enzyme in the cytoplasm called protein kinase. Fig 11.8 (1) The hormone binds to its receptor in the plasma membrane of the target cell. (2) This causes the dissociation of G-proteins, allowing the free α (alpha) subunit to activate adenylate cyclase. (3) This enzyme catalyzes the production of cAMP (cyclic AMP), which (4) removes the regulatory subunit from protein kinase. (5) Active protein kinase phosphorylates other enzyme proteins, activating or inactivating specific enzymes and thereby producing the hormonal effects on the target cell. (pg 315-16)
Phospholipase C–Ca2+
Fig. 11.9. Must bind to a Adrenergic receptor, causes constriction of smooth muscles, splits phospholipids into two units (insoitol triphosphate IP3) and (Diacylglycerol DAG). Binds to a protein called calmodulin. See also Tab. 11.5
Fig. 11.9 (1) The hormone binds to its receptor in the plasma membrane of its target cell, (2) causing the dissociation of G-proteins. (3) A G-protein subunit travels through the plasma membrane and activates phospholipase C, which catalyzes the breakdown of a particular membrane phospholipids into diacylglycerol and IP3 (inositol triphosphate). (4) IP3 enters the cytoplasm and binds to receptors in the endoplasmic reticulum, causing the release of stored Ca2+. The Ca2+ then diffuses into the cytoplasm, where it acts as a second messenger to promote the hormonal effects in the target cell.
Tyrosine Kinase:
See Fig 11.11, pg 318-319. - Activated when phosphorlated. Growth factors (EGF epidermal growth factors, PDGF platelet-derived growth factor, and IGFs insulin-like growth factors).
Fig. 11.11 - The insulin receptor consists of two parts, each containing a beta polypeptide chain that spans the membrane, and an alpha chain that contains the insulin-binding site. (a) When two insulin molecules bind to the receptor, the two parts of the receptor phosphorylate each other. (b) This greatly increases the tyrosine kinase activity of the receptor. (c) The activated receptor tyrosine kinase then phosphorylates a variety of “signal molecules” that produce a cascade of effects in the target cell.
What are the 1st messengers?
The first messengers are_______
Re-study the “adenylate cyclase –cAMP system, especially as shown in Fig 11.8 This system is the same as the ____________ receptor system
Norepinephrine (fig. 7.31, pg 189)
