ANSC 2400: Prelim 2
51 Cards in this Set
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glycoprotein
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Polypeptide hormones that contain carbohydrate moieties. Some are composed of 2 side-by-side polypeptide chains that have carbs attached to each chain. These chains are a and B subunits.
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subunits
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The anterior lobe of the pituitary synthesizes and secretes glycoprotein hormones that have the same a but different B ___. They have no biological activity. If an alpha subunit of one hormone is combined with a beta subunit of another hormone, the activity will be determined by the hormo…
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alpha subunit
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The _ subunit for FSH, LH, and TSH are identical within species.
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beta subunit
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The _ subunit is unique to each individual hormone and gives each of these glycoprotein hormones a high degree of specificity and function.
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inhibin
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A glycoprotein hormone that contains an alpha and 1 of 2 possible beta subunits. This hormone has the same physiologic activity regardless of what beta subunit is present. It suppresses FSH secretion from the anterior lobe of the pituitary.
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relaxin
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A protein from follicular fluid that contains of 2 beta subunits called ___. It causes release of FSH in pituitary cells. Has the opposite effect of inhibin.
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follistatin
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A glycoprotein that was isolated from ovarian follicular fluid. It inhibits FSH secretion from pituitary cells. Compared to inhibin, it has low physiologic activity. It binds to activin and limits widespread actions of activin.
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function of carbohydrate moities
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These are thought to protect the molecule from short-term degradation. The quantity of ___ on the surface of a protein is thought to determine the duration of the hormone's half life.
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steroids
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___ hormones have a common molecular nucleus called the cyclopentanoperhydrophenanthrene. This molecule is composed of four rings. ___ are synthesized from cholesterol through a series of complex pathways involving enzymatic conversions.
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pheromones
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substances secreted to the outside of the body. They are generally detected by the olfactory system by members of the same species. They are known to influence the onset of puberty, the identification of females in estrus by males, etc.
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endocrine glands
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composed of many cells that synthesize and secrete specific hormones. These hormone molecules enter the blood and are transported to every cell in the body.
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hormone receptors
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___ have a specific affinity for a specific hormone and thus bind it. Once the ___ in the target tissue has bound the hormone, the target tissue begins to perform a new function.
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3 domains of the receptors for protein hormones
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extracellular domain, transmembrane domain, intracellular domain
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extracellular domain
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___ has a specific site that binds the specific hormone. When this site is occupied, the transmembrane domain changes its configuration and activates other membrane proteins known as G-proteins.
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Steps of action for protein hormones
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1) hormone-receptor binding
2) adenylate cyclase activation
3) protein kinase activation
4) synthesis of new products
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hormone-receptor binding
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During this step, the hormone diffuses from the blood into the interstitial compartment and binds to a membrane receptor that is specific for the hormone.
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adenylate cyclase activation
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During this step, the hormone-receptor complex activates a membrane bound enzyme known as adenylate cyclase and membrane bound G-proteins. When the hormone receptor complex is formed, the G-protein is transformed in a way that activates adenylate cyclase. The active form of this enzyme co…
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protein kinase activation
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During this step, cAMP activates a family of control enzymes located in the cytoplasm called protein kinases. They are responsible for activating enzymes in the cytoplasm that convert substrates into products. Protein kinases consist of a regulatory (binds cAMP causing activation of catal…
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synthesis of new products
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During this step, the products made by the cell are generally secreted and these secretory products have specific functions that enhance reproductive processes. For example, the gonadotropins bind to follicle cells in the ovary that results in the synthesis of a new product, estradiol.
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Nuclear receptor binding of steroids
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____ causes "slow" responses that require transcriptional involvement, followed by product synthesis and secretion by the target cell.
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membrane-receptor binding of steroids
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____ results in "fast" responses.
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Steps of action for steroid hormones: Membrane receptors ("fast response")
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1) Steroid binding to membrane receptors
2) adenylate cyclase activation
3) protein kinase activation
4) changes in Ca++ channel permability
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Steps of action for steroid hormones: Nuclear receptors ("slow response")
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1) steroid transport
2) movement through the cell membrane and cytoplasm
3) binding of steroid to nuclear receptor
4) mRNA synthesis and protein synthesis
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steroid transport
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During this step, steroid hormones are transported in the blood by a complex system. Steroids are not water soluble and cannot be transported as free molecules. They must attach to molecules that are water soluble (e.g. plasma proteins).
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movement through the cell membrane and cytoplasm
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During this step, the steroid-carrier protein complex travels into the interstitium and comes in contact with target cells. Then the steroid disassociates from the carrier protein and diffuses through the plasma membrane. After it enters the cell, it diffuses through the cytoplasm and int…
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binding of steroid to nuclear receptor
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During this step, the steroid binds to a specific nuclear receptor. It must fit the receptor. The steroid-receptor complex is referred to as a transcription factor and initiates DNA-directed messenger RNA synthesis (transcription).
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mRNA synthesis and protein synthesis
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During this step, the newly synthesized mRNA leaves the nucleus and attaches to ribosomes where it directs the synthesis of specific proteins that will enhance the reproductive process. (e.g. mucus from the cervix during estrus)
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Strength of hormone action depends on...
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-pattern and duration of secretion
-half-life
-receptor density
-receptor-hormone affinity
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patterns of hormonal secretion by the reproductive system
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-episodic
-basal
-sustained
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episodic secretion
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type of secretion associate with hormones under nervous control. When nerves in the hypothalamus fire, neuropeptides are released in a sudden burst and thus hormones from the anterior lobe of the pituitary tend to be released in an episodic manner as well.
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basal secretion
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In this type of secretion, the hormone stays low, but fluctuates with low amplitude pulses. (e.g. GnRH secretion)
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sustained secretion
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In this type of secretion, the hormone remains elevated but in a relatively steady fashion for a long period of time. (e.g. high progesterone during diestrus)
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Hormonal potency is influenced by...
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-receptor density
-hormone receptor affinity
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hormone agonists
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Analogs that bind to the specific receptor and initially cause the same biologic effect as the native hormone. Some ___ promote greater physiological activity.
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hormone antagonists
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Analogs that promote weaker biologic activity than the native hormone.
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2 ways the liver inactivates steroids
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1) any double bond within the steroid becomes saturated.
2) a sulfate or glucuronide residue is attached. B/c it is water soluble, it can be excreted into the urine.
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radioimmunoassay (RIA)
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blood test that uses radioactively tagged hormones and antibodies to measure the quantity of hormone in the plasma
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puberty
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The ability to accomplish reproduction successfully. Secretion of GnRH. Gonadotropins release by pituitary promotes gametogenesis, steroidogenesis, and the development of reproductive tissues.
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Enzyme-linked immunosorbent assay ELISA
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technique that uses enzyme-labeled antibodies to detect antigens or antibodies
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Advantage of ELISA over RIA
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No radioisotopes are required in ELISA; the test can be conducted on site. It has no health/safety hazard issues and is cheap.
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alpha-fetoprotein
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A glycoprotein synthesized by the embryonic yolk sac and later the fetal liver. It serves as a fetal blood osmotic regulator and a carrier of fatty acids.
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fundamental difference in the endocrine profile of the postpubertal male and female
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LH does not surge in the postpubertal male, but maintains a relatively consistent pulsatile pattern of secretion (every 2-6 hrs). In females, estradiol and LH surge every 20 days; low amplitude, repeated LH pulses are present between surges.
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age of first estrus (heat)
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Age that the female becomes sexually reecptive.
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Age of first ovulation
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This is the age when the first ovulation occurs. To determine this critically, manual/visual validation is required (e.g. palpation, ultrasonography of the ovary).
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Age when behavioral traits are expressed
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Age at which males of most species acquire reproductive behavioral traits (mounting and erection)
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Age at first ejaculation
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Age at which development of the nerves, muscles and secretion of seminal fluids from the accessory sex glands is complete. Precedes the ability to produce sufficient spermatozoa.
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Age when spermatozoa first appear in the ejaculate
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Age at which spermatozoa appear in the ejaculate. Ability to produce seminal fluid is acquired before spermatozoa are available.
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age when the ejaculate contains a threshold number of spermatozoa
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presences of a minimum # of spermatozoa; minimum seminal characteristics to achieve pregnancy
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Two general factors that impact the development of the hypothalamic GnRH neurons in the female
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1) development of a threshold body size and/or composition
2) exposure to certain environment or social cues
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a-FP in the female
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Prevents E2 from entering the brain. The hypothalamus is thus "feminized" and the surge center develops.
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a-FP in the male
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Testosterone freely enters the brain because __ does not bind it. Testosterone is aromatizes into E2 and the male brain is "defeminized". Therefore, a GnRH surge center does not develop.
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ANSC 2400: Prelim 2