Questions and Answers
What are the energy sources stored in skeletal muscle?
What is the name of the protein found in muscle tissue that can bind oxygen?
In addition to ATP, what other high-energy molecule can be used to power high-intensity muscle activity?
What is the storage form of glucose in the muscle?
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Which part of the energy continuum is primarily used for a 50-yard dash?
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The source of ATP for a given activity is dependent on which two factors?
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Which energy system would an athlete primarily use during a marathon?
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What type of metabolism yields the most energy?
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In the absence of adequate carbohydrates in the body, what is the metabolic fate of triglycerides?
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Which of the following activities rely on ATP and creatine phosphate?
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What is a limitation of the ATP-PC system?
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Which of the following is a possible side effect of creatine monohydrate supplementation?
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Where in the muscle cell does anaerobic glycolysis occur?
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How much energy (ATP) can be produced from one molecule of glucose using anaerobic glycolysis?
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Without adequate oxygen, what is the fate of pyruvate?
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What is the oxygen deficit?
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What eventually happens to the lactic acid produced during exercise?
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What is the Cori cycle?
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In a working muscle cell, what organelle is responsible for aerobic metabolism?
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What are the waste products of aerobic metabolism?
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Under normal dietary conditions, why can't muscles rely solely on triglycerides as an energy source?
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What is beta oxidation?
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How does beta oxidation allow fatty acids to be oxidized to produce ATP?
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What does the phrase 'fats burn in a carbohydrate flame' mean?
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What is the physiological phenomenon of 'hitting the wall'?
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Name some examples of low carbohydrate states that can lead to ketosis.
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Which tissues in the body can be adequately fueled by ketones?
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In what organ does ketogenesis take place?
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What are the three ketones formed from acetyl-CoA?
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How does ketosis affect insulin and blood glucose levels?
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Which of the following can hasten or produce muscle fatigue?
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Muscle fatigue refers to:
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Which muscle fiber type is best suited for endurance?
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Which muscle fiber type will hypertrophy with resistance training?
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What are the physiological features of Type I muscle fibers?
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Which dominant energy system is utilized by Type IIb fibers?
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How does ventilation change at the onset of exercise?
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What is the mechanism that triggers the change in ventilation at the onset of exercise?
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How do the ventilatory changes of well-trained athletes compare with those of untrained individuals?
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During aerobic exercise, how does ventilation change 4–6 minutes after the onset?
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What is the anaerobic threshold?
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If exercise exceeds the anaerobic threshold, what changes can be observed in the blood?
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How does the increase in blood lactate and hydrogen ions lead to a change in ventilation?
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Which function is NOT a primary role of the female reproductive system?
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What is the final stage of ova maturation?
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Which phase is NOT part of the uterine cycle?
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Which phase of the female sex act is regulated by the autonomic nervous system?
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Which hormone does NOT play a significant role in the female reproductive cycle?
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Which hormone stimulates the anterior pituitary to release FSH and LH?
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What is the primary function of FSH in the ovarian cycle?
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What triggers the LH surge in the ovarian cycle?
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What occurs during the follicular phase of the ovarian cycle?
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What event marks the end of the follicular phase?
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What hormone is primarily responsible for the luteal phase of the ovarian cycle?
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Which estrogen is the most potent and abundant in females?
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What is the primary role of progesterone in the female reproductive system?
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Which phase of the uterine cycle involves shedding of the uterine lining?
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During which phase does the endometrium rebuild itself?
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What initiates the early follicular phase of the ovarian cycle?
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What hormonal change triggers ovulation?
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What is the primary hormone secreted by the corpus luteum during the luteal phase?
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Which phase of the female sexual act is characterized by rhythmic contractions of the pelvic muscles?
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Which hormone is known to enhance libido in females?
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What is the typical viability period of the ovum?
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What is the primary mechanism of action for oral contraceptives?
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Which form of contraception has the lowest failure rate with typical use?
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What are the energy sources stored in skeletal muscle?
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What is the name of the protein found in muscle tissue that can bind oxygen?
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In addition to ATP, what other high-energy molecule can be used to power high-intensity muscle activity?
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What is the storage form of glucose in the muscle?
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Which part of the energy continuum is primarily used for a 50-yard dash?
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The source of ATP for a given activity is dependent on which two factors?
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Which energy system would an athlete primarily use during a marathon?
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What type of metabolism yields the most energy?
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In the absence of adequate carbohydrates in the body, what is the metabolic fate of triglycerides?
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Which of the following activities rely on ATP and creatine phosphate?
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What is a limitation of the ATP-PC system?
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Which of the following is a possible side effect of creatine monohydrate supplementation?
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Where in the muscle cell does anaerobic glycolysis occur?
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How much energy (ATP) can be produced from one molecule of glucose using anaerobic glycolysis?
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Without adequate oxygen, what is the fate of pyruvate?
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What is the oxygen deficit?
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What eventually happens to the lactic acid produced during exercise?
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What is the Cori cycle?
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In a working muscle cell, what organelle is responsible for aerobic metabolism?
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What are the waste products of aerobic metabolism?
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Under normal dietary conditions, why can't muscles rely solely on triglycerides as an energy source?
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What is beta oxidation?
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How does beta oxidation allow fatty acids to be oxidized to produce ATP?
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What does the phrase 'fats burn in a carbohydrate flame' mean?
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What is the physiological phenomenon of 'hitting the wall'?
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Name some examples of low carbohydrate states that can lead to ketosis.
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Which tissues in the body can be adequately fueled by ketones?
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In what organ does ketogenesis take place?
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What are the three ketones formed from acetyl-CoA?
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How does ketosis affect insulin and blood glucose levels?
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Which of the following can hasten or produce muscle fatigue?
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Muscle fatigue refers to:
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Which muscle fiber type is best suited for endurance?
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Which muscle fiber type will hypertrophy with resistance training?
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What are the physiological features of Type I muscle fibers?
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Which dominant energy system is utilized by Type IIb fibers?
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How does ventilation change at the onset of exercise?
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What is the mechanism that triggers the change in ventilation at the onset of exercise?
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How do the ventilatory changes of well-trained athletes compare with those of untrained individuals?
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During aerobic exercise, how does ventilation change 4–6 minutes after the onset?
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What is the anaerobic threshold?
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If exercise exceeds the anaerobic threshold, what changes can be observed in the blood?
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How does the increase in blood lactate and hydrogen ions lead to a change in ventilation?
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What is the primary function of the testes in males?
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What structures are included in the internal genital tract of males?
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Which structures are considered external genitalia in females?
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What determines genetic sex?
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Gonadal sex is determined by the presence of:
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Phenotypic sex is influenced by:
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During the first 5 weeks of gestational life, the gonads are:
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At what gestational age do the testes begin to develop in genetic males?
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At what gestational age do the ovaries begin to develop in genetic females?
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What structures determine gonadal sex?
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In males, what are the germ cells and steroid hormone-secreting cells?
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What structures determine phenotypic sex?
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Which hormone stimulates the growth and differentiation of the Wolffian ducts?
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What hormone causes atrophy of the Müllerian ducts?
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The Wolffian ducts give rise to which structures in males?
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What hormone is secreted by the hypothalamus to regulate reproductive function?
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What hormones are secreted by the anterior pituitary in response to GnRH?
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Which cells in the testes are stimulated by LH to produce testosterone?
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Which hormones are required for the development of the male phenotype?
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What is the function of the epididymis?
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What is the role of the seminal vesicles in the male reproductive system?
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Why do the testes reside outside the abdominal cavity in the scrotum?
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What is the primary function of the seminiferous tubules?
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What cells are found inside the seminiferous tubules and provide support to developing sperm cells?
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What is the role of Leydig cells in the testes?
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What is the function of the blood-testis barrier?
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What hormone do Sertoli cells secrete to inhibit FSH production?
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Why are Sertoli cells referred to as 'nurse cells'?
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What protein do Sertoli cells produce to concentrate testosterone within the seminiferous tubules?
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What hormone do Sertoli cells secrete during embryonic development to prevent the formation of female reproductive structures?
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Which hormone stimulates Leydig cells to produce testosterone?
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What is the role of GnRH in the hypothalamic-pituitary axis?
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What enzyme converts testosterone to dihydrotestosterone (DHT)?
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What is the role of sex hormone-binding globulin (SHBG)?
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Which hormone is converted to estradiol by the enzyme aromatase?
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Which androgen is responsible for inducing and maintaining secondary sex characteristics in males?
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What are the effects of dihydrotestosterone (DHT) at puberty in males?
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What is the role of 17 beta-estradiol in mature sperm cells?
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Which structures are part of the male reproductive tract?
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Which nervous system is primarily active during erection?
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Which phase of the male sexual act is controlled by the sympathetic nervous system?
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During the menses phase of the menstrual cycle, the levels of LH and FSH are:
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What triggers the increase in LH and FSH during the proliferative phase?
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What event is triggered by the peak of LH?
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What happens to LH and FSH levels during the secretory phase with no fertilization?
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What hormone is primarily responsible for the negative feedback during the secretory phase?
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What hormone significantly suppresses the maternal hypothalamic-pituitary-ovarian axis during pregnancy?
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What type of feedback system involves oxytocin during labor?
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When does the trophoblast begin secreting human chorionic gonadotropin (HCG)?
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What is the role of HCG in early pregnancy?
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How does estrogen affect oxytocin receptors toward the end of gestation?
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What is the main source of estrogen and progesterone production in the second and third trimesters of pregnancy?
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What is the effect of estrogen on uterine contractility?
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What hormone stimulates milk production by inducing the synthesis of lactose, casein, and lipids?
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What happens to the corpus luteum around 16-20 weeks of gestation?
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What marks the time of highest progesterone output by the corpus luteum?
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What structural change occurs in the uterine endometrium during pregnancy?
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Which hormone's levels peak at around gestational week 9 and then decline?
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What does the blastocyst contribute to during pregnancy?
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What specialized layer forms in the endometrium under the influence of progesterone?
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What process occurs in the placenta involving cholesterol during late pregnancy?
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What is the main function of the placenta during pregnancy?
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Where is DHEA-sulfate hydroxylated to 16-OH DHEA-sulfate during pregnancy?
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What hormone is produced by the placenta from 16-OH DHEA-sulfate?
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Which hormone's production shifts from the corpus luteum to the placenta in the second trimester?
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What triggers the formation of the corpus luteum?
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What happens to the uterine endometrium if fertilization does not occur?
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During which phase does the corpus luteum form?
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What is the primary role of the corpus luteum in early pregnancy?
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What happens to estrogen levels during the secretory phase without fertilization?
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Which structure forms after the corpus luteum degenerates?
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What hormone increases due to the action of LH from the corpus luteum?
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What is the state of LH and FSH levels during the menses phase?
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What is the primary role of estrogen during the proliferative phase?
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What happens to progesterone levels if fertilization occurs?
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Which phase is characterized by the formation of the placenta?
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During which trimester does the placenta assume the role of steroid hormone production?
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What happens to new follicle maturation during pregnancy?
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What significant role does the placenta play in late pregnancy regarding progesterone?
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During the menses phase of the menstrual cycle, the levels of LH and FSH are:
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What triggers the increase in LH and FSH during the proliferative phase?
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What event is triggered by the peak of LH?
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What happens to LH and FSH levels during the secretory phase with no fertilization?
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What hormone is primarily responsible for the negative feedback during the secretory phase?
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What hormone significantly suppresses the maternal hypothalamic-pituitary-ovarian axis during pregnancy?
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When does the trophoblast begin secreting human chorionic gonadotropin (HCG)?
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What is the role of HCG in early pregnancy?
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What is the main source of estrogen and progesterone production in the second and third trimesters of pregnancy?
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What happens to the corpus luteum around 16-20 weeks of gestation?
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What structural change occurs in the uterine endometrium during pregnancy?
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Which hormone's levels peak at around gestational week 9 and then decline?
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What process occurs in the placenta involving cholesterol during late pregnancy?
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Where is DHEA-sulfate hydroxylated to 16-OH DHEA-sulfate during pregnancy?
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What hormone is produced by the placenta from 16-OH DHEA-sulfate?
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Which hormone's production shifts from the corpus luteum to the placenta in the second trimester?
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What triggers the formation of the corpus luteum?
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What happens to the uterine endometrium if fertilization does not occur?
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During which phase does the corpus luteum form?
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What is the primary role of the corpus luteum in early pregnancy?
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What happens to estrogen levels during the secretory phase without fertilization?
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Which structure forms after the corpus luteum degenerates?
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What hormone increases due to the action of LH from the corpus luteum?
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What is the state of LH and FSH levels during the menses phase?
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What is the primary role of estrogen during the proliferative phase?
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What happens to progesterone levels if fertilization occurs?
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Which phase is characterized by the formation of the placenta?
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During which trimester does the placenta assume the role of steroid hormone production?
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What happens to new follicle maturation during pregnancy?
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What significant role does the placenta play in late pregnancy regarding progesterone?
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What hormone initiates the ovarian cycle by stimulating the anterior pituitary?
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What is the primary function of FSH and LH during the ovarian cycle?
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What effect do inhibin and low levels of estrogen have on the hypothalamus and anterior pituitary?
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What hormone assists in the development of the dominant ovarian follicle?
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What triggers the LH surge that induces ovulation?
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What structure forms from the ovulated follicle?
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What does the corpus luteum secrete after ovulation?
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What happens to the corpus luteum if the oocyte is not fertilized?
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What restarts the ovarian cycle if the oocyte is not fertilized?
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What hormones stimulate the growth and development of breasts during pregnancy?
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What hormone is primarily responsible for milk production?
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What blocks the action of prolactin on the breast during pregnancy?
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What triggers the secretion of prolactin during breastfeeding?
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What effect does dopamine have on prolactin secretion in non-pregnant individuals?
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What hormone is responsible for milk ejection?
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What stimulates oxytocin secretion from the posterior pituitary?
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How does breastfeeding affect ovulation?
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What is the 'tend-and-befriend' response in females attributed to?
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What hormone helps to regulate the inhibitory effect of dopamine on prolactin?
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What hormone is produced by the trophoblast approximately 8 days after ovulation?
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What is the primary role of HCG in early pregnancy?
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What is the source of steroid hormones during the first trimester of pregnancy?
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How is estriol synthesized during pregnancy?
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What triggers the production of fetal cortisol near term?
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What is the effect of fetal cortisol on the uterus?
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What hormone increases uterine contractility by increasing intracellular calcium concentration in smooth muscle?
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What triggers the release of oxytocin during labor?
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Study Notes
Energy Sources
- Skeletal muscle stores energy primarily in the forms of ATP and phosphocreatine.
- Myoglobin is the protein in muscle tissue that binds oxygen, essential for aerobic metabolism.
- Phosphocreatine serves as a high-energy molecule to power intense muscle activity alongside ATP.
- Glycogen is the storage form of glucose in muscle, providing a readily available energy source.
Energy Continuum
- For short bursts of energy like a 50-yard dash, the phosphagen system is predominantly used.
- The source of ATP during activity is influenced by both intensity and duration.
- Aerobic metabolism is utilized primarily by athletes during long-distance events, such as marathons.
- The highest energy yield comes from aerobic metabolism, making it the most efficient system.
- In low carbohydrate conditions, triglycerides are transformed into fatty acids and ketones for energy.
Anaerobic Glycolysis
- Anaerobic glycolysis occurs in the cytoplasm of muscle cells.
- It produces 2 ATP from one glucose molecule.
- In the absence of sufficient oxygen, pyruvate is converted into lactic acid.
- "Oxygen deficit" refers to the difference between oxygen demand and supply during exercise.
- Lactic acid produced during exercise can be converted back to pyruvate for energy or used in the Cori cycle to regenerate glucose.
Ketogenesis and Ketosis
- Ketogenesis occurs in the liver, producing ketones from acetyl-CoA.
- The main ketones are acetoacetate, beta-hydroxybutyrate, and acetone.
- Ketosis leads to decreased insulin and stabilized blood glucose levels.
- Ketones can fuel heart, skeletal muscle, kidneys, and brain.
Muscle Fatigue and Fiber Types
- Muscle fatigue results in a reduced capacity of muscles to perform work, often due to dehydration and nutrient depletion.
- Type I muscle fibers are suited for endurance, demonstrating slow contraction and high fatigue resistance.
- Type IIb fibers are primarily involved in anaerobic glycolysis and hypertrophy with resistance training.
Ventilation and Exercise
- Ventilation increases rapidly at the onset of exercise due to neural input and chemical changes in the blood.
- Well-trained athletes exhibit more efficient ventilatory responses than untrained individuals.
- Ventilation adjusts after 4-6 minutes of aerobic exercise to meet steady-state demands.
- The anaerobic threshold is the point where lactate begins to accumulate in the bloodstream during intense exercise.
Blood Lactate Response
- Exceeding the anaerobic threshold results in increased blood lactate levels and hydrogen ions, causing a drop in pH.
- Increased lactate and hydrogen ions stimulate chemoreceptors, leading to enhanced ventilation to expel CO2 and restore balance.
Energy Sources
- Skeletal muscle stores energy primarily in the forms of ATP and phosphocreatine.
- Myoglobin is the protein in muscle tissue that binds oxygen, essential for aerobic metabolism.
- Phosphocreatine serves as a high-energy molecule to power intense muscle activity alongside ATP.
- Glycogen is the storage form of glucose in muscle, providing a readily available energy source.
Energy Continuum
- For short bursts of energy like a 50-yard dash, the phosphagen system is predominantly used.
- The source of ATP during activity is influenced by both intensity and duration.
- Aerobic metabolism is utilized primarily by athletes during long-distance events, such as marathons.
- The highest energy yield comes from aerobic metabolism, making it the most efficient system.
- In low carbohydrate conditions, triglycerides are transformed into fatty acids and ketones for energy.
Anaerobic Glycolysis
- Anaerobic glycolysis occurs in the cytoplasm of muscle cells.
- It produces 2 ATP from one glucose molecule.
- In the absence of sufficient oxygen, pyruvate is converted into lactic acid.
- "Oxygen deficit" refers to the difference between oxygen demand and supply during exercise.
- Lactic acid produced during exercise can be converted back to pyruvate for energy or used in the Cori cycle to regenerate glucose.
Ketogenesis and Ketosis
- Ketogenesis occurs in the liver, producing ketones from acetyl-CoA.
- The main ketones are acetoacetate, beta-hydroxybutyrate, and acetone.
- Ketosis leads to decreased insulin and stabilized blood glucose levels.
- Ketones can fuel heart, skeletal muscle, kidneys, and brain.
Muscle Fatigue and Fiber Types
- Muscle fatigue results in a reduced capacity of muscles to perform work, often due to dehydration and nutrient depletion.
- Type I muscle fibers are suited for endurance, demonstrating slow contraction and high fatigue resistance.
- Type IIb fibers are primarily involved in anaerobic glycolysis and hypertrophy with resistance training.
Ventilation and Exercise
- Ventilation increases rapidly at the onset of exercise due to neural input and chemical changes in the blood.
- Well-trained athletes exhibit more efficient ventilatory responses than untrained individuals.
- Ventilation adjusts after 4-6 minutes of aerobic exercise to meet steady-state demands.
- The anaerobic threshold is the point where lactate begins to accumulate in the bloodstream during intense exercise.
Blood Lactate Response
- Exceeding the anaerobic threshold results in increased blood lactate levels and hydrogen ions, causing a drop in pH.
- Increased lactate and hydrogen ions stimulate chemoreceptors, leading to enhanced ventilation to expel CO2 and restore balance.
Overview of the Female Reproductive System
- The female reproductive system does not regulate blood pressure; its primary roles include gamete production, preparation for conception, and nourishment after birth.
- Final stage of ova maturation is the corpus albicans.
- The luteal phase is not part of the uterine cycle; the three phases are menstrual, proliferative, and secretory.
- The female sex act's arousal, plateau, and orgasm phases are all regulated by the autonomic nervous system.
- Testosterone is not a significant hormone in the female reproductive cycle.
Hormones of the Female Reproductive Cycle
- GnRH stimulates the anterior pituitary to release FSH and LH.
- FSH primarily stimulates follicular growth and maturation in the ovarian cycle.
- High estrogen levels trigger the LH surge crucial for ovulation.
Ovarian Cycle
- The follicular phase involves the maturation of ovarian follicles.
- Ovulation marks the end of the follicular phase.
- Progesterone is the hormone responsible for the luteal phase of the ovarian cycle.
Functions of Ovarian Hormones
- Estradiol is the most potent and abundant estrogen in females.
- Progesterone prepares the uterus for potential pregnancy.
Uterine Cycle
- The menstrual phase involves shedding the uterine lining.
- The proliferative phase is when the endometrium rebuilds itself.
Regulation of the Female Cycle
- The early follicular phase is initiated by an increase in FSH.
- A surge in LH triggers ovulation.
- The primary hormone secreted by the corpus luteum during the luteal phase is progesterone.
Female Sexual Act
- Orgasm in the female sexual act is characterized by rhythmic contractions of the pelvic muscles.
- Testosterone enhances libido in females.
Female Fertility and Birth Control
- The ovum is viable for 12-24 hours after ovulation.
- Oral contraceptives primarily inhibit ovulation by suppressing the release of FSH and LH.
- Hormonal IUDs have the lowest failure rate with typical use among contraceptive methods.
Components of Sexual Differentiation
- Testes produce sperm and secrete testosterone, crucial for male reproductive function.
- The internal male genital tract includes epididymis, vas deferens, seminal vesicles, and prostate.
- Female external genitalia consist of labia majora, labia minora, clitoris, and vestibule.
Definitions
- Genetic sex is determined by sex chromosomes: XY for males and XX for females.
- Gonadal sex is dictated by the presence of testes in males and ovaries in females.
- Phenotypic sex results from gonadal hormonal output, specifically testosterone in males and estrogen in females.
Genetic Sex
- Gonads are indifferent or bipotential during the first 5 weeks of gestation.
- Testes begin developing in genetic males around gestational week 6 to 7.
- Ovaries start to develop in genetic females at gestational week 9.
Gonadal Sex
- Gonadal sex is defined by the presence of testes or ovaries.
- Male germ cells are spermatogonia, while Leydig cells secrete testosterone.
Phenotypic Sex
- Phenotypic sex is established through the development of internal genital tract and external genitalia.
- Testosterone stimulates growth and differentiation of Wolffian ducts.
- Anti-Müllerian hormone (AMH) causes the atrophy of Müllerian ducts in males, preventing the development of female structures.
- Wolffian ducts differentiate into male reproductive structures, including epididymis, vas deferens, and seminal vesicles.
Gonadotropin Secretion and the Hypothalamic-Pituitary Axis
- Gonadotropin-releasing hormone (GnRH) regulates reproductive function by signaling the anterior pituitary.
- FSH and LH are secreted by the anterior pituitary in response to GnRH.
- LH stimulates Leydig cells in the testes to produce testosterone.
Components of the Male Reproductive System
- Testosterone and AMH are essential for male phenotype development.
- The epididymis stores and matures sperm after production.
Structure of the Testes
- Testes are located in the scrotum to maintain a lower temperature optimal for sperm development.
Seminiferous Tubules
- Seminiferous tubules are responsible for the germination, maturation, and transportation of sperm cells.
Intratubular Compartment
- Sertoli cells within seminiferous tubules provide structural and nutritional support to developing sperm.
Peritubular Compartment
- Leydig cells produce testosterone, essential for male reproductive functions.
Role of the Sertoli Cells
- The blood-testis barrier prevents immune system attacks on developing sperm.
- Sertoli cells secrete inhibin, which inhibits FSH production, regulating spermatogenesis.
- Sertoli cells concentrate testosterone using androgen-binding protein (ABP).
- Anti-Müllerian hormone secretion by Sertoli cells prevents female reproductive structure development.
Hypothalamic-Pituitary Axis
- LH is crucial for stimulating testosterone production by Leydig cells.
- GnRH's primary role is to stimulate the anterior pituitary to release FSH and LH.
Androgens
- 5-alpha-reductase converts testosterone to dihydrotestosterone (DHT), which is crucial in male development.
- Sex hormone-binding globulin (SHBG) binds testosterone, regulating its availability.
- Testosterone is converted to estradiol by the enzyme aromatase.
Androgen Actions
- Testosterone induces and maintains secondary male sex characteristics.
- DHT causes changes such as facial and body hair growth, deepening voice, and prostate development during puberty.
Actions of 17 Beta-estradiol
- 17 beta-estradiol optimizes spermatogenesis and sperm function in mature sperm cells.
Male Reproductive Tract
- Structures include epididymis, vas deferens, ejaculatory duct, urethra, and distal urinary tract.
Male Sexual Act
- The parasympathetic nervous system primarily controls erection.
- Emission and ejaculation are regulated by the sympathetic nervous system.
Hormonal Changes in the Menstrual Cycle
- LH and FSH levels are low during the menses phase.
- The proliferative phase sees an increase in LH and FSH triggered by follicular estrogen.
- The peak of LH triggers ovulation.
- In the secretory phase without fertilization, LH and FSH levels decline.
- Progesterone is the primary hormone responsible for negative feedback during the secretory phase.
Early Pregnancy and HCG
- During pregnancy, progesterone suppresses the maternal hypothalamic-pituitary-ovarian axis.
- The trophoblast begins secreting human chorionic gonadotropin (HCG) 8 days after ovulation.
- HCG maintains the corpus luteum, preventing it from degenerating.
Hormonal Sources in Pregnancy
- In the second and third trimesters, the placenta becomes the main source of estrogen and progesterone.
- Around 16-20 weeks of gestation, the corpus luteum resolves.
- The uterine endometrium thickens and forms the decidua during pregnancy.
Changes in Hormonal Levels
- HCG levels peak around gestational week 9 before declining.
- Cholesterol is converted to pregnenolone in the placenta during late pregnancy.
- DHEA-sulfate is hydroxylated to 16-OH DHEA-sulfate in the fetal liver.
- Estriol is produced by the placenta from 16-OH DHEA-sulfate.
Transition in Hormonal Production
- Progesterone production shifts from the corpus luteum to the placenta during the second trimester.
- The corpus luteum forms following ovulation induced by the LH surge.
- If fertilization does not occur, the uterine endometrium undergoes necrosis and is eliminated.
Role of the Corpus Luteum
- The corpus luteum forms during the secretory phase and produces large amounts of progesterone and some estrogen.
- Estrogen levels decline during the secretory phase without fertilization.
- After the degeneration of the corpus luteum, the corpus albicans forms.
Follicle Maturation and the Placenta
- LH from the corpus luteum increases progesterone levels.
- LH and FSH remain low during the menses phase.
- Estrogen during the proliferative phase induces rapid proliferation of the uterine endometrium.
- If fertilization occurs, progesterone levels steadily increase.
- The placenta formation occurs during the secretory pregnancy phase.
- During the second trimester, the placenta assumes the role of steroid hormone production, suppressing new follicle maturation.
Late Pregnancy Functions
- The placenta converts cholesterol to pregnenolone, crucial for hormone synthesis in late pregnancy.
Menstrual Cycle Overview
- LH and FSH levels are low during the menses phase.
- The proliferative phase is triggered by increasing follicular estrogen, leading to elevated LH and FSH.
- The peak of LH triggers ovulation, the release of the oocyte.
- In the secretory phase without fertilization, LH and FSH levels decline.
- Progesterone primarily maintains negative feedback during the secretory phase.
Pregnancy Hormones
- Progesterone suppresses the maternal hypothalamic-pituitary-ovarian axis during pregnancy.
- The trophoblast secretes human chorionic gonadotropin (HCG) about 8 days post-ovulation.
- HCG maintains the corpus luteum, which is crucial for early pregnancy.
- The placenta takes over estrogen and progesterone production in the second and third trimesters.
- The corpus luteum resolves around 16-20 weeks of gestation.
Endometrial Changes During Pregnancy
- The uterine endometrium thickens and transforms into the decidua during pregnancy.
- HCG levels peak at around 9 weeks of gestation and then decline.
- Cholesterol is converted to pregnenolone in the placenta during late pregnancy.
- DHEA-sulfate is hydroxylated to 16-OH DHEA-sulfate in the fetal liver.
Estriol Production
- Estriol is produced by the placenta from 16-OH DHEA-sulfate.
- Progesterone production shifts from the corpus luteum to the placenta in the second trimester.
Follicular Development
- The formation of the corpus luteum is stimulated by an LH surge post-ovulation.
- If fertilization does not occur, the endometrium undergoes necrosis and is eliminated as menstruation.
- The corpus luteum forms during the secretory phase and produces progesterone and estrogen.
Hormonal Feedback Mechanisms
- Estrogen levels decline during the secretory phase without fertilization.
- After the corpus luteum degenerates, it becomes the corpus albicans.
- Progesterone increases due to LH action from the corpus luteum.
Lactation and Breast Function
- Estrogen and progesterone stimulate breast development during pregnancy.
- Prolactin is the main hormone responsible for milk production.
- High levels of estrogen and progesterone during pregnancy inhibit prolactin's action.
- Suckling triggers prolactin secretion for milk production; oxytocin is responsible for milk ejection.
Labor and Delivery
- Stretching of the cervix triggers the release of oxytocin during labor.
- Oxytocin's feedback system is positive, enhancing uterine contractions.
- Estrogen up-regulates oxytocin receptors and increases uterine contractility as gestation progresses.
Final Notes on Pregnancy Physiology
- Fetal cortisol production is activated near term, increasing uterine contractility.
- The blastocyst contributes to the fetal portion of the placenta, crucial for nutrient exchange and hormone production.
- The placenta acts as both a transport epithelium and an endocrine gland, vital for maintaining pregnancy.
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This quiz explores the energy sources stored in skeletal muscle, including the roles of various proteins and molecules involved in muscle function. Test your knowledge on glycogen, ATP, myoglobin, and related concepts in muscle physiology.