pg 86-90 book notes and Male ENDOCRINOLOGY lecture notes
pg 86-90 book notes and Male ENDOCRINOLOGY lecture notes Biol360
Cal State Fullerton
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This 5 page Class Notes was uploaded by Monique Magpayo on Monday February 22, 2016. The Class Notes belongs to Biol360 at California State University - Fullerton taught by Maryanne Menvielle in Spring 2016. Since its upload, it has received 27 views. For similar materials see Biology of Human Sex in Biology at California State University - Fullerton.
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Date Created: 02/22/16
CH 3 PG 86-90 BOOK NOTES Like women’s ovaries, men’s testicles manufacture and secrete three kinds of SEX STEROIDS ANDROGENS (chiefly testosterone) ESTROGENS (chiefly estradiol) PROGESTINS (chiefly progesterone) These hormones are synthesized by the interstitial cells Men have higher concentrations of testosterone and estradiol and progesterone is lower Circulating TESTOSTERONE has a half life of less than an hour THE MAIN FUNCTIONS OF SEX HORMONES IN MEN o ANDROGENS- Before birth, Testosterone drives development of the fetus- especially in the fetal genitalia- in the male direction. o Testosterone is also responsible for most of the changes associated with male puberty and for maintenance of these characteristics thereafter o TESTOSTERONE acts on the brain in fetal and adult life, promoting the establishment and expression of male typical gendered traits. o It’s the main hormone responsible for the maintenance of the sex drive in men. Testosterone does not regulate sexuality on a minute to minute hour to hour basis, rather it influences some fairly durable feature of brain organization o IT IS AN ANABOLIC HORMONE- it promotes the buildup of tissue, especially muscle, and it increases the oxygen carrying capacity of the blood The ANABOLIC effects of testosterone is related androgens are the reason that athletes of both sexes use them to promote tissue growth, including muscle development TESTOSTERONE has to be converted to the more potent ANDROGEN: 5a- DIHYDROTESTOSTERONE (DHT) in the target tissues. This is true for genital tissues and the skin, but not the brain. o (DHT is an ANDROGEN that plays an important role in the development of the male external genitalia) o Drugs that block this conversion are used to treat enlargement of the prostate. o ANDROGENS SUCH AS TESTOSTERONE AND DHT STRONGLY INFLUENCE THE DISTRIBUTION OF HEAD, BODY, AND PUBIC HAIR IN BOTH SEXES STEROIDS AND SPORTS: Androgens such as testosterone have anabolic effects- they increase muscle bulk and strength which is beneficial for athletes. THG is the notorious example for designer steroids (TETRAHYDROGESTRINONE) which is detected through standard urine or blood tests HYPERANDROGENISM: abnormally high levels of testosterone or other androgens o ESTROGENS: helps maintain bone density and also terminate the growth of the limb bones after puberty. o ESTROGENS are required for male fertility: they promote the maturation and concentration of sperm in the epididymis. (Men who are genetically insensitive to estrogen continue to grow after the end of puberty reaching more than 7 ft) o PROGESTINS: the only clearly established function for progestins in men is as metabolic precursors for androgen and estrogen. o When given as drugs, progestins lower men’s sex drive, suggesting that natural progestins may have a hormonal effect on the brain that counteracts the effect of androgens THE BRAIN AND PITUITARY GLAND REGULATE HORMONE LEVELS Men’s testicles are linked to the HYPOTHALAMUS AND PITUITARY GLAND by a hormonal control loop. The same hormonal messengers- play similar roles in both sexes o GONADOTROPIN- releasing hormone (GnRH) , secreted by the HYPOTHALAMUS stimulates the secretion of FSH and LH by the pituitary gland o Follicle -stimulating hormone (FSH). FSH stimulates spermatogenesis in the testicles o AND luteinizing hormone (LH). LH stimulates the synthesis and secretion of sex hormones o The male sex steroids in turn can exert a negative feedback effect, damping the secretion of hormones from the hypothalamus and pituitary Men’s body do not experience any monthly hormonal cycle equivalent to that in women, but the level of testosterone in the blood do peak every 3 hours or so and are higher between midnight and noon than between noon and midnight The function of these short term oscillations is not known- they do not correlate with variations in sexual feelings or behavior. Because the brain is involved in the regulation of testicular function, life experiences can affect a man’s testosterone levels LECTURE NOTES 2 MAIN CONCEPTS: brief intro to endocrinology and the hormones and glands and their role in the male ENDOCRINOLOGY: is the study of glands and hormones ENDOCRINE GLANDS: structures that produce hormones and release them into the blood stream. The hypothalamus and the testes are examples HORMONES: chemical signals o HYPOTHALAMUS-pituitary-gonad axis (HPG axis): regulates sex hormone production by coordinating with each other The HYPOTHALAMUS is located within the brain which produces the GONADOTROPIN-RELEASING HORMONE (GnRH) GnRH is responsible for communicating with the pituitary and it regulates the hormones produced by the pituitary o The next structure of the HPG AXIS: the PITUITARY The PITUITARY is also located in the brain like the HYPOTHALAMUS The role of the PITUITARY is to regulate the gonads and other reproductive structures o In order to regulate the other reproductive structures, the PITUITARY PRODUCES a category of hormones known as GONADOTROPINS GONADOTROPINS are hormones that influence the functioning of the gonads Some KEY GONADOTROPINS include FSH- follicle stimulating hormone: FSH stimulates the production of the gametes (the sperm and the eggs) LH – luteinizing hormone: influences the production of hormones in the gonads Not produced in the pituitary but still is a GONADOTROPIN: HUMAN CHORIONIC GONADOTROPIN (hCG). This is produced by a fertilized egg o hCG signals the female’s ovaries that pregnancy has occurred so that the ovaries produce the hormones that are necessary to sustain pregnancy the last structure of the HPG AXIS are GONADS o the GONADS which include the TESTES AND OVARIES o GONADS produce a variety of hormones such as ANDROGENS such as testosterone ESTROGENS such as estradiol PROGESTINS such as progesterone Additional: INHIBIN which is a communication hormone that is going to help regulate the pituitary back in the brain Produced in MALES only: ANTI-MULLERIAN HORMONE: helps erect the fetal development in the males These 3 hormones are produced in the ovaries and the testes .the difference between males and females are the amounts of hormones produced .so men have more testosterone and females have more estrogen and progestins o HOW HORMONES WORK: 1) they are produced in an endocrine gland .2) then the hormone is released into the blood stream 3) then the chemical message that is carried by the hormone is going to be detected by the target structure 4) once the message is detected, it is going to cause changes or some sort of reaction in the target structure o EX; FSH: 1) FSH is produced in the PITUITARY 2) then it is released into the blood stream 3) eventually the FSH is going to reach the tissues of the testes through the circulatory system. More specifically it is going to target the seminiferous tubules found inside the testes 4) this then leads to the PRODUCTION OF SPERM Regulating the cycle of hormone is important in the body o ( 2 main feedback mechanisms at work to maintain the necessary amount of hormones) these are POSITIVE AND NEGATIVE FEEDBACK NEGATIVE FEEDBACK (feedback inhibition) Works like a furnace heating a home, lets say you set your thermostat to a specific temp of 70 degrees, when the temp drops below that level, the heather TURNS ON. once your house reaches the ideal temp of 70 degrees, the furnace will turn off In our bodies, when a level of our hormone is fluctuating from normal, the body responds to correct those levels. NEGATIVE FEEDBACK CYCLKE Lets say a level of a particular hormone drops the change is detected corrective mechanisms activated hormone level return to normal corrective mechanism turned off Then cycle continues LH AND FSH IS CONTROLLED BY THIS CYCLE o POSITIVE FEEDBACK (amplification effect) Ex: the role of oxytocin during labor o During labor oxytocin levels increase and cause contractions of the uterus, which is then detected by the body, then oxytocin levels increase. The increase in these levels result in more contractions leading to more oxytocin being released o Essentially positive feedback is like A SNOWBALL EFFECT constantly increasing the level of a hormone as opposed to maintaining a certain level like the negative feedback Cycle: hormone level elevated causes change in target structure the change is detected (then back to start and cycle) o SEX HORMONES IN THE MALE GnRH- regulates the pituitary secretion of gonadotrophins o FSH is one of the gonadotrophins produced by the pituitary and is going to control the production of sperm in the seminiferous tubules o LH is another gonadotrophins released by the pituitary which control the amount of testosterone that is produced in the interstitial cells Testosterone is the masculinizing hormone which influenced the secondary sex characteristics of males such as facial hair and broad shoulders as well as sex drive Estrogen and progestin are also going to be produced by the testes but they are lower levels than testosterone Estrogens are important in the maturation of sperm Progesterone IS A PRECURSOR TO ESTROGENS OTHER ANDORGENS INHIBIN plays a role in regulating FSH from the pituitary ANTI-MALLERIAN HORMONE which is involved in the fetal development of the male o HPG AXIS IN THE MALES: One of the main functions of this axis is to maintain testosterone levels NEGATIVE FEEDBACK CYCLE: 1) when there are low levels of testosterone found in the blood, it is going to send a signal to the hypothalamus 2) this signal is detected by the hypothalamus and results with an increase production of GnRH 3) GnRH is going to communicate with the pituitary 4) this will cause an increase in LH 5) which sends a message to the interstitial cells to increase the output of testosterone which will bring things back to normal Low testosterone in blood hypothalamus increases GnRH pituitary increases LH interstitial cells make testosterone o If the testosterone levels are ELEVATED the HPG axis: HIGH testosterone in blood signals hypothalamus to slow GnRH pituitary lowers LH production interstitial cells lower production o HPG axis also regulates sperm production Done through NEGATIVE FEEDBACK involving the INHIBIN INHIBIN is produced by the testes and communicates with the pituitary HIGH LEVELS OF INHIBIN pituitary to lower FSH production slows sperm production LOW LEVELS OF INHIBIN pituitary to increase FSH production increase sperm production There is a hormonal gradual decline in males, not as bad as women going through menopause
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