Download Chapter 11 Endocrine Glands

Chapter 11 Endocrine Glands
 Are _____________________ and secrete hormones into bloodstream
 Hormones go to target cells with receptor proteins for it
 Neurohormones are secreted into blood by specialized neurons
 Hormones affect metabolism of targets
Chemical Classification of Hormones
 __________________ hormones are derived from tyrosine or tryptophan
 Include NE, Epi, thyroxine, melatonin
 Polypeptide/protein hormones are chains of amino acids
 Include ADH, GH, insulin, oxytocin, glucagon, ACTH, PTH
 Glycoproteins include LH, FSH, TSH
 ____________________ are lipids derived from cholesterol
 Include testosterone, estrogen, progesterone and cortisol
 Steroid and thyroid hormones are lipids. Can ________________ into target cells
Prohormones and Prehormones
 Prohormones are precursors of hormones. E.g. proinsulin
 Prehormones are precursors of prohormones. E.g. preproinsulin
 Some hormones are inactive until activated by target _______________________
 E.g. thyroxine (T4) is inactive until converted to T3 in target cells
Common Aspects of Neural and Endocrine Regulation
 Both NS and endocrine system use chemicals to communicate
 Hormones are transported in blood and has more ________________________ of
effects in targets
 Some chemicals are used as hormones and NTs
 Targets for both must have specific receptor proteins. Must be rapidly inactivated
Hormone Interactions
 A tissue usually responds to number of hormones
 2 hormones are ___________________ if work together to produce an effect
 A hormone has permissive effect if it enhances responsiveness of a target organ to
2nd hormone. If action of 1 hormone inhibits effect of another, it is antagonistic
Hormone Levels and Tissue Responses
 _______________________ is time required for blood level to be reduced by half
 Ranges from mins to hrs for most (days for thyroid hormones)
 Normal tissue responses are produced only within physiological range
 High (pharmacological) doses can cause number of side effects
 Probably by binding to _______________________ of other hormones
 Priming effect (upregulation) occurs when a hormone induces more of its own
receptors in target cells. Results in greater response in target cell
 Desensitization (downregulation) occurs after long exposure to high levels of
polypeptide hormone. Subsequent exposure produces a lesser response
 Most peptide hormones have _______________ __________________ which
prevents downregulation
Mechanisms of Hormone Action
 Target cell receptors show specificity, high affinity, and low capacity for hormone
 Lipophilic hormones have receptors in target's cytoplasm and/or nucleus;
 Called __________________ action and takes at least 30 mins
 Receptors for water-solubles are on surface of target cell
 These act through 2nd messengers; effects are ____________
 Some steroids act on cell surface receptors - nongenomic action
Hormones That Bind to Nuclear Receptor Proteins
 Lipid hormones dissociate from carriers to pass thru plasma membrane of target
 Receptors are called _________________ hormone receptors
 Serve as transcription factors when bound to hormone ligands
 Activate transcription
 Have ligand (hormone)-binding and DNA-binding domains
 Binds hormone and translocates to nucleus
 Binds to _____________________________ element (HRE) on DNA,
next to target gene
Mechanisms of Steroid Hormones
 HRE consists of 2 half-sites
 2 ligand-bound receptors have to bind to each HRE (____________________)
 This stimulates transcription of target gene
Hormones That Use 2nd Messengers
 Water soluble hormones use cell surface receptors, can’t pass through membrane
 Actions are mediated by 2nd messengers
 2nd messenger carries ______________ from receptor to inside of cell
Adenylate Cyclase-cAMP and Phospholipase-C-Ca2+
 Mediate effects of many polypeptide and glycoprotein hormones
 Epi can act via two 2nd Messengers cAMP and Ca2+
Tyrosine Kinase 2nd Messenger System
 Is used by ________________ and many growth factors to cause cellular effects
Pituitary Gland
 Is structurally and functionally divided into anterior and posterior lobes
 Hangs below hypothalamus by infundibulum
 Anterior produces own hormones. Controlled by _____________________
 Post. pituitary stores and releases vasopressin and oxytocin made in hypothalamus
Anterior Pituitary
 Secretes 6 trophic hormones that maintain size of targets
 High blood levels cause target to hypertrophy. Low levels cause atrophy
 Growth hormone (GH) promotes growth, protein synthesis, movement of
___________ _______________ into cells
 Thyroid stimulating hormone (TSH) stimulates thyroid to produce T4 and T3
 Adrenocorticotrophic hormone (ACTH) stimulates adrenal cortex to secrete
cortisol, aldosterone
 Follicle stimulating hormone (FSH) stimulates growth of ____________ follicles
and sperm production
 Luteinizing hormone (LH) causes ovulation and secretion of testosterone in testes
 Prolactin (PRL) stimulates milk production by mammary glands
 Release of A. Pit. hormones is controlled by hypothalamic _______________ and
_____________ factors and by feedback from levels of target gland hormones
Higher Brain Function and Anterior Pituitary Secretion
Emotional states and psychological stress can affect circadian rhythms, menstrual
cycle, and adrenal hormones
Adrenal Glands
Sit on top of kidneys. Each consists of outer cortex and inner medulla
Medulla synthesizes and secretes 80% Epi and 20% NE
Controlled by sympathetic
Cortex is controlled by ________________ and secretes:
Cortisol: inhibits glucose utilization and stimulate gluconeogenesis
Aldosterone which stimulate kidneys to reabsorb Na+ & secrete K+
And some supplementary sex steroids
Adrenal Medulla
Hormonal effects of Epi/NE last 10X ____________ than sympathetic NS
Activated during "fight or flight" response. Causes effects like:
Increased respiratory rate. Increased HR and cardiac output
Stress and the Adrenal Glands
Stress induces a non-specific response called __________ _____________
____________________(GAS)
Causes ACTH and cortisol release
Chronic stress can induce high levels of cortisol that causes effects like:
atrophy of hippocampus (involved in memory)
reduced sensitivity of tissues to insulin (insulin resistance)
Thyroid Gland
Is located just below the larynx
Secretes T4 and T3 which set ______ and are needed for growth and development
Consists of microscopic thyroid follicles
Outer layer is follicle cells that synthesize T4
Interior filled with __________________, a protein-rich fluid
Production of Thyroid Hormones
Iodide (I-) is oxidized to iodine (I2) and attached to thyroglobulin
TSH hydrolysis T4 and T3s from thyroglobulin and then it’s secreted
Diseases of the Thyroid – Goiter
_______ T4 and T3 don’t provide negative feedback and TSH levels go up
Thyroid gland grows, resulting in a goiter
Hypothyroidism: People with inadequate T4 and T3 levels are hypothyroid
Have low BMR, weight gain, lethargy, cold intolerance
And ___________________ = puffy face, hands, feet
Hyperthyroid: Goiters are also produced by Grave's disease (autoimmune)
Antibodies stimulate thyroid gland to over secrete. Characterized by
Exopthalmos, weight loss, heat intolerance, irritability, high BMR
Parathyroid Glands
Are _________ glands embedded in lateral lobes of thyroid gland
Secrete Parathyroid hormone (PTH)
Most important hormone for control of blood Ca2+ levels
Release stimulated by ____________________ blood Ca2+
Acts on bones, kidney, and intestines to increase blood Ca2+ levels
Islets of Langerhans
Are scattered clusters of endocrine cells in pancreas. Contain alpha and beta cells
Alphas secrete glucagon in response to low blood glucose
Stimulates glycogenolysis and lipolysis. _______________ blood glucose
Betas secrete insulin in response to high blood glucose
Promotes entry of glucose into cells
Converts glucose into glycogen and fat. Decreases blood glucose
Pineal Gland
Is located in basal forebrain near thalamus
Secretes ______________ in response to activity of suprachiasmatic nucleus (SCN)
of hypothalamus
SCN is 10 timing center for circadian rhythms. Reset by daily light/dark changes
Melatonin is involved in aligning physiology with sleep/wake cycle and _______
Secreted at night and is inhibited by light
Thymus
Is located around trachea below thyroid
Produces ______________ of immune system and hormones that stimulate them
Sex and Reproductive Hormones
 Gonads (testes and ovaries) secrete steroid hormones testosterone, estrogen, and
progesterone
 ______________ secretes estrogen, progesterone, hCG, and somatomammotropin
Autocrine and Paracrine Regulation
 Autocrine regulators are produced and act within same tissue of an organ
 All autocrines control gene expression in target cells
 ___________________ regulators are autocrines that are produced within
one tissue and act on different tissue in same organ.
 Autocrines and paracrines include:
 Cytokines (lymphokines, interleukins)
 Growth factors (promote growth and cell division)
 Neutrophins (provides trophic support for normal and regenerating
neurons)
Prostagladins
Have wide variety of functions
Different PGs may exert ____________________ effects in tissues
Some promote smooth muscle contraction and some relaxation
Some promote clotting; some inhibit
Promotes inflammatory process of immune system
Plays role in ovulation
Inhibits gastric secretion in digestive system
Chapter 19: Regulation of Metabolism
Nutritional Requirements
 Living tissue is maintained by constant expenditure of energy (ATP)
 ATP derived from glucose, fatty acids, ketones, amino acids, and others
 ____________________ of food is commonly measured in kilocalories (1 kcal =
1000 calories)
 Carbohydrates and proteins yield 4kcal/gm; fats-9kcal/gm
Metabolic Rate and Caloric Requirements
 Metabolic rate (MR) is total rate of body metabolism
 = amount of __________________ consumed by body/min
 Basal metabolic rate (BMR) is MR of awake relaxed person 12–14 hrs after
eating and at a comfortable temperature
 BMR depends on age, sex, body surface area, _____________________ level,
and thyroid hormone levels
 Hyperthyroids have high BMR; hypothyroids have low BMR
Metabolism
 Is all chemical reactions in body
 Includes synthesis and energy storage reactions (____________________); and
energy liberating reactions (________________________)
Anabolic Requirements
 Anabolic reactions synthesize DNA and RNA, proteins, fats, and carbohydrates
 Must occur constantly to replace molecules that are hydrolyzed in
catabolic reactions
Turnover Rate
 Is rate at which a molecule is broken down and ________________________
 Average turnover for Carbs is 250 g/day
 Some glucose is reused so net need ~150 g/day
 Average turnover for protein is 150 g/day
 Some is reused for protein synthesis so net need ~35 g/day
 9 _______________________ amino acids must be supplied in diet
because can't be synthesized
 Average turnover for fats is 100 g/day
 Little is required in diet because can be synthesized from ___________
 2 essential fatty acids must be supplied in diet
Vitamins
 Are small organic molecules that serve as coenzymes in metabolism or have
highly specific functions
 Must be obtained in diet because body does not produce them, or does so in
insufficient amounts
 Can be placed in 2 classes
 ___________-solubles include A, D, E, and K
 _____________-solubles include B1, B2, B3, B6, B12, pantothenic acid,
biotin, folic acid, and vitamin C
 Serve as coenzymes in metabolism
Minerals (Elements)
 Are needed as _______________ for specific enzymes and other critical functions
 Sodium, potassium, magnesium, calcium, phosphate, and chloride are needed
daily in large amounts
 Iron, zinc, manganese, fluorine, copper, molybdenum, chromium, and selenium
are ________________ elements required in small amounts/day
Free Radicals
 Are highly reactive and oxidize or reduce other atoms
 Because they have an ____________________ electron in their outer
orbital
 The major free radicals are reactive oxygen or reactive nitrogen species
 NO radical, superoxide radical, and hydroxyl radical
 Serve important physiological functions
 Help to destroy bacteria
 Can produce vasodilation
 Can stimulate cell proliferation
 In excess can exert __________________________ contributing to disease states
 Can damage lipids, proteins, and DNA
 Promote apoptosis, aging, inflammatory disease, degenerative, and
malignant growth
 Body uses enzymatic and nonezymatic means to protect itself against oxidative
stress
 Enzymes like ____________________ neutralize free radicals
 Nonenzymes like vitamin C and E react with free radicals
Regulation of Energy Metabolism
 Blood contains glucose, fatty acids, amino acids, and others that can be used for
energy
 _____________________ energy substrates
Control of Adipose Tissue Levels
 Body appears to have negative feedback loops (an adipostat) to maintain a certain
amount of adipose tissue
 Adipose cells (adipocytes) store and release fat under ________________ control
 And may release their own hormone(s) to influence metabolism
Development of Adipose Tissue
 Number of adipocytes increases greatly after birth
 Differentiation promoted by high levels of ___________________
Endocrine Functions of Adipocytes
 Adipocytes secrete regulatory hormones called adipokines
 Regulate hunger, metabolism, and insulin sensitivity
 The adipocyte hormones TNFa, resistin, retinol BP4, and leptin are increased in
____________________ and Type II diabetes
 Leptin signals the hypothalamus on how much fat is stored, thereby
regulating hunger and food intake
Low Adiposity: Starvation
 Starvation and malnutrition diminish immune function
 Low adipose levels cause low leptin levels
 _________________________ cells have leptin receptors
 Low leptin thus diminishes immune function
 Leptin may play role in timing of puberty and in the amenorrhea of
underweight women
Obesity
 Childhood obesity involves increases in both size and number of adipocytes
 Weight gain in adulthood is due mainly to _________________ in adipocyte size
 Obesity is often diagnosed by using using a body mass index (BMI)

BMI = w/h2
 w = weight in kilograms, h = height in meters
 Healthy weight is BMI between 19 – 25
 Obesity defined as BMI > 30
 60% of pop in US is either ___________________ (BMI>25) or obese (BMI>30)
Regulation of Hunger
 Is at least partially controlled by hypothalamus
 Involves a number of NTs: endorphins (promote overeating), Norepi (promotes
overeating), serotonin (____________________ overeating)
Calorie Expenditure of body
 Has 3 components:
 Number of calories used at the BMR make up 60% of total
 Number used in response to temperature changes and during digestion/
absorption (adaptive ______________________) make-up 10% of total
 Starvation can lower MR 40%; eating raises MR 25-40% (thermic
effect of food)
 Number used during physical activity depends on type and intensity
Absorptive and Post absorptive States
 Absorptive state is ______ hr period after eating
 Energy substrates from digestion are used and deposited in storage forms
(anabolism)
 Postabsorptive or fasting state follows absorptive state
 Energy is ___________________ from storage (catabolism)
Hormonal Regulation of Metabolism
 Balance between anabolism and catabolism depends on levels of insulin,
glucagon, GH, thyroxine, and others
Pancreatic Islets of Langerhans
 Contain 2 cell types involved in energy homeostasis:
 α cells secrete _____________________ when glucose levels are low
 Increases glucose by stimulating glycogenolysis in liver
 β cells secrete insulin when glucose levels are high
 Reduces blood glucose by promoting its uptake by tissues
Insulin and Glucagon Secretion
 Normal ______________________ glucose level is 65–105 mg/dl
 Insulin and glucagon normally prevent levels from rising above 170mg/dl
after meals or falling below 50mg/dl between meals
Insulin
 Overall effect is to promote anabolism
 Promotes storage of digestion products
 ____________________ breakdown of fat and protein
 Inhibits secretion of glucagon
 Stimulates insertion of GLUT4 transporters in cell membrane of skeletal
muscle, liver, and fat
 Transports by _______________________ diffusion
Oral Glucose Tolerance Test
Measures response to drinking a glucose solution
Assesses ability of β cells to secrete insulin and insulin's ability to
____________________ blood glucose
In non-diabetics, glucose levels return to normal within 2 hrs
Glucagon
Maintains blood glucose concentration above 50mg/dl
Stimulates glycogenolysis in liver
Stimulates _________________________, lipolysis, and ketogenesis
Skeletal muscle, heart, liver, and kidneys use fatty acids for energy
Chapter 20: Reproduction Sexual Development and Disorders
Sexual Differentiation
 Y chromosome induces formation of testes
 Testosterone (T) from testes induces formation of male sex organs
 In absence of T, female sex organs develop
Sexual Reproduction
Gametes (sperm or eggs) are formed in gonads by meiosis
Each has haploid number of chromosomes (23)
Fertilization results in diploid zygote with 46 chromosomes
Each zygote inherits 23 pairs of homologous chromosomes
22 of these are autosomal chromosomes
23rd pair are sex chromosomes: XX in females; XY in males
All ova contain an X chromosome; half the sperm, X and half contain Y
Chromosomal gender of zygote determined by the fertilizing sperm
Only 1 of 2 Xs in females becomes active
Other forms clump of inactive heterochromatin called a Barr body
Formation of Testes and Ovaries
Gonads have potential to become testes or ovaries until testis-determining factor
(TDF) causes conversion to testes.
TDF is produced by SRY (sex-determining region of Y) gene
Seminiferous tubules (STs), contain germinal cells and nongerminal Sertoli cells
At ~day 65, Leydig cells (produce T) appear in clusters around STs
In absence of TDF, ovaries develop. Ovarian follicles don't appear until day 105
Development of Testes
 Leydig cells secretions masculinizes embryonic structures
 Testes descend into scrotum shortly before birth
 Spermatogenesis doesn't occur in cryptorchidism (undescended testes)
Development of Accessory Sex Organs
Male accessory sex organs are derived from wolffian ducts
Include epididymis, vas deferens, seminal vesicles, and ejaculatory duct
Female acc.sex organs are from Müllerian ducts, includes uterus & fallopian tubes
Development of External Genitalia
 External genitalia are same during 1st 6 wks
 Testis secretions masculinize these to form penis, male urethra, prostate, scrotum
 In absence of T, clitoris forms instead of penis and labia instead of scrotum
Disorders of Embryonic Sexual Development
 Hermaphroditism occurs when individuals have both ovary and testis tissue
 Pseudohermaphrodites have either testes or ovaries but have accessory organs and
external genitalia that are incompletely developed or inappropriate
Onset of Puberty
At beginning of female puberty, high E stimulates growth
High pubertal T in boys causes growth spurt that lags that of girls
Girls with low body fat and high activity levels enter puberty at older age
4 Phases of Human Sexual Response
Excitation phase (arousal) is characterized by increased muscle tone and engorgement
of sexual organs with blood
Includes nipples, clitoris, penis, and labia minor. Vagina lubricates
During plateau phase clitoris is partially hidden by swelling labia
Areolae continue swelling. Outer third of vagina engorges
During orgasm, men ejaculate, and women have contractions of uterus and vagina
In the resolution phase, body returns to preexcitation conditions
Men enter refractory period
Male Reproductive System
 Testes contain seminiferous tubules (STs) where spermatogenesis occurs; and
interstitial tissue housing T-secreting Leydig cells
 Sertoli cells of STs contain receptors for FSH. FSH stimulates spermatogenesis
 Leydig cells contain LH receptors. LH stimulates secretion of T
Testosterone and Age
Secretion of T declines gradually and varyingly in men> 50. Causes are unknown
Not due to low GnRH, LH, or FSH because their levels are elevated
Spermatogenesis
 Germ cells become spermatogonia (stem cells) and replicate thru life by mitosis.
 Give rise to haploid sperm by meiosis. Spermatogenesis occurs in wall of STs
 Spermatogonia and 1o spermatocytes are located in outer part of ST
 Spermatids and mature spermatozoa are located toward lumen. Tails are in lumen
Spermiogenesis
 Is maturation and separation of spermatids into mature spermatozoa
 Requires participation of Sertoli cells
 At end of 2nd meiotic division, 4 spermatids are still interconnected
 During spermiogenesis, proteins protamines replace the DNA-associated histones
 Cause extreme compaction of chromatin, changing nuclear shape
 Sertoli cells phagocytize cytoplasm of developing sperm
 A flagellum and acrosome (cap of digestive enzymes) develop
 At end of spermiogenesis, spermatozoa are released into the lumen
Sertoli Cell Function
Spermatogonia and developing spermatozoa are embedded in, and nurtured by,
adjacent Sertolis.
Autoimmune destruction of developing sperm is prevented by blood-testes barrier
created by Sertolis
Spermatozoa
Have oval-shaped head with DNA and the acrosome (a cap of digestive enzymes)
Have a midpiece and flagellar tail. Tail will become motile in epididymus
Male Accessory Sex Organs
 Spermatozoa and fluids exit STs via rete testis
 Pass through efferent ductules to epididymis and leave through vas deferens
 Spermatozoa entering epididymis are non-motile and cannot fertilize (pH is low)
 Spermatozoa mature and become motile in epididymis
 Prostatic fluid neutralizes pH during ejaculation
 Vas deferens carries sperm into pelvic cavity
 Seminal vesicles add fluid (constituting 60% of ejaculate) to that coming from
epididymis. Contains fructose for energy for sperm
 Vas deferens becomes ejaculatory duct which merges with urethra in prostate
 Fluid becomes semen when prostate adds secretions containing citric acid, Ca2+
and coagulation proteins. Which coagulate semen during ejaculation
Erection
Occurs as result of Parasymp-induced blood flow into erectile tissues of penis
NO is the neurotransmitter
Erectile tissues include corpus cavernosum and spongiosum
Venous outflow is partially occluded, aiding erection
Emission and Ejaculation
 Emission is movement of semen into urethra
 Ejaculation is forcible expulsion of semen from urethra out of penis
 Both are stimulated by sympathetic activity
 Which also causes peristalsis of tubular system, contractions of seminal
vesicles, prostate, and muscles at base of penis
Male Fertility
 Normal volume of ejaculate is 1-5 ml. With 60-150 million sperm/ml
 Sperm count of < 20 million/ml constitutes oligospermia.
 Associated with decreased fertility. Caused by heat, lead or arsenic poisoning, and
drugs. Including marijuana, cocaine, and anabolic steroids
Male Contraception
 Vasectomy is one of most widely used methods.
 Each vas deferens is cut and tied. Sperm can’t enter urethra; accumulate in
crypts along reproductive tract. Where sperm are phagocytosed by
immune system. 70% develop anti-sperm antibodies
Female Reproductive System
 Ovaries contain large number of follicles that produce female gametes (eggs/ ova)
 Extensions of fallopian tubes called fimbriae partially cover each ovary
 The cilia of its lining draw in ovulated eggs
 Uterus has 3 layers:
 Perimetrium is outer layer of connective tissue
 Myometrium is middle layer of smooth muscle
 Endometrium is hormonally-responsive inner epithelial layer that is shed during
menstruation. Between uterus and vagina is cervix
Accessory Sex Organs
Consist of vagina, uterus, and fallopian tubes
Vaginal opening is just posterior to urethra
Both are covered by labia minora and majora
Erectile clitoris is at anterior margin of labia minora
Production of Oocytes
 Germ cells in ovaries multiply into 6-7 million oogonia by 5 mo. gestation,
 At end of gestation, oogonia (1o oocytes) begin meiosis but arrest in prophase I
 There is a continual loss of 1o oocytes throughout life
 At birth are 2 million left. At puberty 400,000 are left
 400 oocytes are ovulated during reproductive years; rest undergo apoptosis
Ovarian Cycle
 1o oocytes are contained in 1o follicles. Consisting of oocyte + follicle cells
 In response to FSH some follicles enter ovarian cycle and grow, producing layers
of granulosa cells
 Some 1o follicles continue, developing vesicles and becoming 2o follicles
 One follicle continues growth. Vesicles fuse, forming fluid-filled cavity called an
antrum. Is now called a graafian follicle
 As graafian follicle develops, 1o oocyte completes meiosis I
 1 daughter cell (the 2o oocyte) gets all cytoplasm. Other daughter is a small polar
body which will degenerate
 2o oocyte arrests at metaphase II. Only fertilized eggs complete meiosis II
o
 2 oocyte is part of graafian follicle
 Granulosa cells form layer around outside of follicle
 Oocyte sits on mound in this layer called cumulus oophorus
 2o oocyte is enclosed by ring of granulosa cells called corona radiata
 Between oocyte and radiata is gelatinous layer called zona pellucida
 Which forms barrier to sperm penetration
Ovulation
 By 14 days, only 1 follicle survives. Others become atretic follicles (degenerate)
 Surviving graafian follicle forms bulge on surface of ovary. Secretes increasing E
 Graafian follicle releases egg into fallopian tube at ovulation
 If fertilized, egg completes meiosis II with formation of another polar body
 Egg degenerates in 2 days if not fertilized
 LH causes empty follicle to become corpus luteum (CL)
 Which secretes progesterone (P) and E
 If no fertilization, becomes corpus albicans (non- functional remnant)
Menstrual Cycle
 LH causes empty follicle to become corpus luteum (CL)
 Which secretes progesterone (P) and E
 If no fertilization, becomes corpus albicans (non- functional remnant)
 In humans is ~28 days. Day 1 is taken to be first day of menstruation
 Days 1 thru ovulation constitute the follicular phase
 Time from ovulation to menstruation is luteal phase
 Endometrial changes are called: menstrual, proliferative, and secretory phases
Follicular Phase
 Lasts from day 1 to about 13. Is growth and death of 1o follicles into 2o follicles
 With 1 survivor becoming a graafian follicle. Which undergoes ovulation
 As follicles grow, secrete larger amounts of E. Reaches peak about day 12
 Follicular growth and E secretion are dependent on FSH from Ant Pit
 At same time, FSH and E recruit LH receptors in graafian follicle
 A positive feedback between E and Ant Pit secretion develops
 Resulting in LH surge that peaks 16 hrs before ovulation. Cause ovulation
Luteal Phase
 After ovulation, LH causes empty follicle to become the corpus luteum (CL)
which secretes E and P
 P levels rise and peak about a week after ovulation
 Development of new follicles and another ovulation are inhibited by:
 High P and E exert strong negative feedback on LH and FSH
 With no fertilization, CL regresses
 Consequently E and P levels decline
 Causing menstruation and allowing new cycle of follicle development
Cyclic Changes in the Endometrium
 Are driven by cyclic changes in E and P levels
 Proliferative phase occurs during follicular phase; E levels increase
 E stimulates growth of endometrial lining. Spiral arteries develop
 E causes cervical mucus to become thin and watery to allow sperm
penetration
 Secretory phase occurs during luteal phase; endometrium becomes ready for
implantation
 P stimulates development of uterine glands
 P and E cause endometrium to become thick, vascular, and spongy
 P causes cervical mucus to thicken and become sticky
 Menstrual phase results from drop in P and E following CL degeneration
 Low P causes constriction of spiral arteries
 Blood flow stops, causing necrosis and sloughing of endometrium
Factors Affecting Menstrual Cycle
 Limbic system input to the hypothalamus in times of stress can cause functional
amenorrhea (cessation of menstruation)
 Also occurs in thin or athletic females with low body weight
Contraceptive Methods
 Oral contraceptive pills usually contain synthetic E and P taken daily for 3 wks
after menstrual period
 Mimic CL so that negative feedback inhibits ovulation
 Placebo pills are taken in 4th wk to permit menstruation
 Rhythm method involves daily measurement of oral basal body temperature (BT)
upon awakening
 Because ovarian steroids cause BT changes
 Declining E on day of LH surge causes a slight drop in BT
 Rising P on day after LH peak causes elevated BT for rest of luteal phase
Menopause
 Is cessation of ovarian activity and menstruation at ~50 years
 Ovaries are depleted of follicles and thus produce no E
 LH and FSH are high because of no negative feedback
 Lack of E from ovaries is most responsible for hot flashes, osteoporosis, and
increased risk of atherosclerosis