Endocrine System Hormones Quiz

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Questions and Answers

What is the primary role of hormones in the endocrine system?

To provide structural support to organs

To transmit nerve impulses quickly

To facilitate muscle contractions

To regulate distant target cells (correct)

Which of the following major processes is NOT regulated by the endocrine system?

Electrolyte balance

Muscle growth (correct)

Cellular metabolism

Reproduction

Which gland is primarily responsible for regulating growth and development?

Pineal gland

Thyroid gland (correct)

Adrenal glands

Pancreas

What is the study of hormones and endocrine organs called?

Endocrinology Signup and view all the answers

Which glands have a partial endocrine function?

Pancreas and gonads Signup and view all the answers

What initiates penile erection during male sexual stimulation?

Parasympathetic impulses Signup and view all the answers

What is the role of nitric oxide in the male sexual act?

Causing vasodilation of penile arteries Signup and view all the answers

Which hormone is crucial for triggering the secretion of GnRH at the onset of puberty?

Leptin Signup and view all the answers

What marks the beginning of the ovarian cycle in females?

Menarche Signup and view all the answers

During which phase of the ovarian cycle does the formation of corpus luteum occur?

Luteal phase Signup and view all the answers

What is the primary function of the bulbourethral glands during male sexual activity?

Secrete mucus Signup and view all the answers

What is the primary site for fertilization in the female reproductive system?

Fallopian tubes Signup and view all the answers

What happens to the smooth muscle sphincter at the base of the urinary bladder during ejaculation?

It closes to prevent backflow Signup and view all the answers

Which hormone is the more biologically active form?

T3 Signup and view all the answers

What stimulates the secretion of TRH?

Exposure to cold Signup and view all the answers

How is the majority of T3 produced in the body?

By converting T4 in peripheral tissues Signup and view all the answers

What are the effects of sympathetic nervous system stimulation on TSH secretion?

TSH secretion decreases Signup and view all the answers

Which condition is characterized by high levels of T4 and T3 along with low levels of TSH?

Hyperthyroidism Signup and view all the answers

What is the role of lysosomal enzymes in thyroid hormone production?

They cleave T3 and T4 from thyroglobulin Signup and view all the answers

What happens to TSH levels during hypothyroidism?

TSH levels are high Signup and view all the answers

What substance is combined with thyroglobulin during thyroid hormone production?

Iodine Signup and view all the answers

What is the primary hormone produced in the adrenal cortex responsible for increasing blood glucose levels?

Cortisol Signup and view all the answers

Which hormone is mainly involved in the development of secondary sex characteristics in females during puberty?

DHEA Signup and view all the answers

Which of the following statements about sex hormones is correct?

Gonads are primarily responsible for the production of sex hormones. Signup and view all the answers

What effect does cortisol have on protein metabolism during stress?

It increases protein breakdown. Signup and view all the answers

What is the primary role of aldosterone?

Regulate blood pressure Signup and view all the answers

Which hormone listed is primarily responsible for vasoconstriction in response to stress?

Epinephrine Signup and view all the answers

Which of the following hormones is primarily produced in the ovaries?

Estrogen Signup and view all the answers

Which of the following is NOT a function of glucocorticoids like cortisol?

Decreasing blood glucose Signup and view all the answers

Which hormone primarily stimulates the secretion of cortisol from the adrenal cortex?

Adrenocorticotropic Hormone Signup and view all the answers

What is the effect of Growth Hormone (GH) on bone and soft tissues?

Promotes growth and metabolism Signup and view all the answers

Which hormone is primarily responsible for breast development and milk secretion?

Prolactin Signup and view all the answers

How does IGF-I influence growth hormone levels?

Causes negative feedback on the anterior pituitary Signup and view all the answers

Which gland produces Growth Hormone (GH)?

Anterior pituitary Signup and view all the answers

What hormone is released in response to GHRH from the hypothalamus?

Growth Hormone Signup and view all the answers

Which of the following is NOT a target tissue of Growth Hormone?

Thyroid gland Signup and view all the answers

What is the primary role of Gonadotropin-releasing Hormone (GnRH)?

Promote secretion of FSH and LH Signup and view all the answers

Which hormone plays a major role in protein synthesis and cellular growth?

Growth Hormone Signup and view all the answers

What is one of the functions of Growth Hormone related to metabolism?

Increases blood glucose Signup and view all the answers

Which gland produces vasopressin?

Hypothalamus Signup and view all the answers

What is the primary function of oxytocin during childbirth?

Stimulate uterine contractions Signup and view all the answers

Which structure is responsible for the release of both vasopressin and oxytocin?

Posterior pituitary Signup and view all the answers

What role do osmoreceptors play in the regulation of vasopressin?

They sense changes in blood osmolarity. Signup and view all the answers

Which of the following structures increases the permeability of the distal and collecting tubules to water?

Vasopressin Signup and view all the answers

During breastfeeding, oxytocin promotes which action?

Milk ejection Signup and view all the answers

Which receptors are involved in the regulation of vasopressin release aside from osmoreceptors?

Baroreceptors Signup and view all the answers

What effect does vasopressin have on arterioles?

Vasoconstriction Signup and view all the answers

Which hormone released by the hypothalamus regulates the anterior pituitary’s secretion?

Releasing hormones Signup and view all the answers

What is the target organ of vasopressin?

Kidneys Signup and view all the answers

What triggers the release of oxytocin during childbirth?

Cervical dilation Signup and view all the answers

Which cells in the hypothalamus are responsible for producing both vasopressin and oxytocin?

Neurosecretory cells Signup and view all the answers

What main action does vasopressin perform in the kidneys?

Conserve water Signup and view all the answers

What type of muscle contraction is stimulated by oxytocin in the uterus?

Smooth muscle contraction Signup and view all the answers

Study Notes

The Endocrine System

Regulates homeostasis over hours, days, and weeks by releasing hormones into the blood.
Hormones are chemical messengers that regulate distant target cells.
Endocrinology is the study of hormones and endocrine organs.

Endocrine Processes

Reproduction
Growth and development
Electrolyte, water, and nutrient balance of blood
Cellular metabolism and energy balance
Immune defenses

Major Endocrine Glands

Hypothalamus
Pituitary gland
- Anterior pituitary
- Posterior pituitary
Thyroid gland
Parathyroid glands
Adrenal glands
Pineal gland
Pancreas
Gonads (ovaries and testes)
Thymus

The Hypothalamus-Pituitary Axis of Control

Hypothalamus releases hormones that regulate the anterior and posterior pituitary.
Anterior pituitary releases tropic hormones that regulate other endocrine glands.
Peripheral endocrine glands release hormones that target cells to change in homeostatic factors.

Hypothalamus – Pituitary: Functional Connections

Hypothalamus → Anterior Pituitary
- Releasing hormones increase the release of anterior pituitary hormones.
- Inhibiting hormones decrease the release of anterior pituitary hormones.
Hypothalamus → Posterior Pituitary
- Hypothalamus produces hormones stored and released by the posterior pituitary.

Hypothalamus-Posterior Pituitary

The posterior pituitary does not produce hormones, it only stores and releases 2 hormones produced in the hypothalamus:
- ADH/Vasopressin
- Oxytocin

ADH/Vasopressin

Produced in the hypothalamus, released by posterior pituitary.
Target: kidneys, arterioles
Function: conserve water by preventing water release into urine, contract arteriole smooth muscle (vasoconstriction) to increase blood pressure.
Regulation: osmoreceptors in hypothalamus, atrial (heart) blood volume receptors.

Oxytocin

Produced in the hypothalamus, released by posterior pituitary.
Target: uterus, mammary glands, brain
Function: stimulates uterine contraction during childbirth, promote milk release during breastfeeding, maternal behavior, bonding, attachment.
Regulation: birth canal reflexes.

Hypothalamus-Anterior Pituitary

The hypothalamus releases 7 hormones that regulate anterior pituitary hormones:
- Thyrotropin-releasing hormone (TRH)
- Corticotropin-releasing hormone (CRH)
- Gonadotropin-releasing hormone (GnRH)
- Prolactin-releasing hormone (PRH)
- Dopamine/Prolactin Inhibiting Hormone (PIH)
- Growth Hormone Releasing Hormone (GHRH)
- Somatostatin/Growth Hormone Inhibiting Hormone (GHIH)

Anterior Pituitary

The anterior pituitary produces and releases 6 tropic hormones that regulate other endocrine glands:
- Growth Hormone (GH)
- Thyroid Stimulating Hormone (TSH)
- Adrenocorticotropic Hormone (ACTH)
- Follicle Stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
- Prolactin (PRL)

Anterior Pituitary Hormones

Growth Hormone (GH): target: bone and soft tissues, liver; function: growth, protein metabolism, fat breakdown, blood glucose increase.
Thyroid Stimulating Hormone (TSH): target: thyroid gland; function: stimulates T3 & T4 production.
Adrenocorticotropic Hormone (ACTH): target: adrenal cortex; function: stimulates cortisol secretion.
Follicle Stimulating Hormone (FSH): target: ovaries, testes; function: ovarian follicle maturation, estrogen secretion, sperm production.
Luteinizing Hormone (LH): target: ovaries, testes; function: ovulation estrogen & progesterone secretion, testosterone secretion.
Prolactin (PRL): target: mammary glands; function: breast development, milk secretion.

Regulation of Growth

Synthesis of proteins, lengthening of bones, and increasing size and number of cells are required for growth.
Growth is regulated by growth hormone in children and adolescents.
Other hormones influencing growth: thyroid hormone, insulin, sex hormones (androgens, estrogens).
Also influenced by genetics, diet, and levels of stress/chronic disease.

Growth Hormone

Growth hormone (somatotropin) increases growth and metabolism.
Produced and released by the anterior pituitary.
Functions: metabolic functions, fat breakdown, increased blood glucose, growth functions, protein synthesis, bone growth, increased cell division.
Regulation: hormonal (GHRH, GHIH from hypothalamus), negative feedback (IGF-I and GH), and neural (diurnal rhythms).

Growth Hormone & IGF's

Growth hormone actions mediate growth by IGFs (insulin-like growth factors), also called somatomedins.
IGF-I: mainly released into blood by liver, local production by individual tissues; stimulates soft tissue cell number and cell size, stimulates long bone growth.
IGF-II: fetal development, adult role unknown.

Growth Hormone Pathway

Stimulus: GHRH (hypothalamus)
Production & Release: Growth Hormone made and released by anterior pituitary
Targets: liver, adipose tissue, and all body cells.
Regulation: IGFs, GH, GHIH (hypothalamus).

T4 to T3 conversion

T4 (tetra-iodothyronine): the major form of thyroid hormone, stored and secreted by the thyroid.
T3 (tri-iodothyronine): 80% of T3 is made from T4; 20% secreted as T3; 10 times more potent and biologically active form.

Thyroid Hormone

T3 and T4 are major metabolic hormones of the body, lipid-soluble, and plasma protein bound.
Produced and released by the thyroid gland.
Function: increased metabolic rate, increased heat production, increased growth, increased CNS development, and increased SNS activity.

Thyroid Hormone Pathway

Stimulus: TRH (hypothalamus), TSH (anterior pituitary)
Production & Release: made and released by the thyroid gland.
Targets: all body cells.
Regulation: T3 and T4.

Thyroid Hormone Synthesis

Thyroid hormone is made from the amino acid tyrosine and iodide.
Synthesis steps: thyroglobulin with tyrosines synthesized in follicular cells, iodide actively transported into follicular cells, iodide converted to iodine, iodine attached to tyrosine in colloid, T3 and T4 made in colloid by attaching to thyroglobulins, T3-thyroglobulins and T4 thyroglobulins cleaved back into follicular cells, T3 and T4 cleaved from thyroglobulins diffuse into blood.

Thyroid Disorders

Hyperthyroidism: T3 and T4 high, TSH low. Symptoms: extreme weight loss, inability to sleep, psychic disorders, muscle weakness, tremors of hands, exophthalmos (protrusion of eyeballs)
Hypothyroidism: T3 and T4 low, TSH high. Symptoms: extreme somnolence, mental sluggishness, deepening of voice, endemic colloid goiter (iodine deficiency), myxedema, cretinism.

Calcitonin

Produced and released by thyroid gland parafollicular cells.
Function: inhibits bone breakdown, stimulates calcium storage in bones, decreases blood calcium.
Regulation: blood (humoral): increased blood calcium.

Parathyroid Hormone

Increases calcium in the blood.
Produced by Parathyroid Glands (3-4 tiny glands on the posterior side of the thyroid).
Function: increases plasma Ca2+, decreases plasma PO43-, stimulates Vitamin D.
Regulation: blood (humoral): Ca2+ levels in blood, thyroid gland (calcitonin)

Parathyroid Hormone Pathway

Stimulus: low blood calcium
Target: bone, kidneys, small intestine.
Bone: increase Ca2+ release from bone, increase in bone breakdown.
Kidneys: increase blood calcium retention, decrease in blood phosphate, increase in Vitamin D activation
Small intestine: Vitamin D needed for calcium absorption in diet.
Regulation: blood (humoral): high levels of Ca2+ inhibit parathyroid hormone production/release.

Ricketts

Mainly occurs in children.
Calcium level slightly depressed.
Phosphate level greatly depressed.
Deficiency of vitamin D.
Pot belly, bow legs, knock knee, enlarged skull, Pigeon chest, hepatosplenomegaly, Extreme osteoclastic resorption of bone.

Adrenal Glands

Small, capped glands above the kidneys.
- Adrenal Cortex (outer region): steroid hormones (mineralocorticoids, glucocorticoids, sex hormones)
- Adrenal Medulla (middle region): catecholamines (epinephrine & norepinephrine)

Adrenal Medulla: Catecholamines

Adrenal Medulla: middle region of the adrenal glands.
Hormones: epinephrine, norepinephrine
Target: SNS organ targets
Functions: enhance sympathetic effects, stress regulation, blood pressure.
Regulation: sympathetic nervous system

Adrenal Steroids

Adrenal Cortex: outer region of the adrenal glands.
Steroid Hormones:
- Mineralocorticoids (aldosterone)
- Glucocorticoids (cortisol)
- Sex hormones (androgens)

Mineralocorticoids (Aldosterone)

Primarily aldosterone.
Fluid Balance:
- Increases Na+ in the blood, retained from urine
- Decreases K+ in the blood, eliminated in urine
Water balance follows Na+ increase, blood volume increases, blood pressure increases.
Aldosterone deficiency is FATAL

Gonadocorticoids (Sex Hormones)

Adrenal cortex is a secondary site for production of androgens
DHEA (weak precursor to testosterone): mainly involved in secondary sex characteristics in females during puberty (growth spurt, hair patterns, sex drive)
Estrogen: mainly from ovaries
Testosterone: mainly from testes

Glucocorticoids (Cortisol)

Metabolism: increase blood glucose, sequester blood glucose for the brain, increase protein breakdown, increase fat breakdown.
Stress Response: permissive vasoconstriction via epinephrine/norepinephrine.
Immune Suppression: blocks inflammation pathways, blocks antibody production.

Cortisol

Maintains blood glucose during fasting; enhances the stress response during trauma; inhibits immune system.
Produced and released by adrenal cortex.
Function: increases gluconeogenesis, breakdown of fats to increase fatty acids, breakdown of protein to increase amino acids, anti-inflammatory, and anti-immune effects.
Regulation: hormonal (CRH by hypothalamus and ACTH by anterior pituitary); neural (stress).

Melatonin

Induces sleep at night (or in the dark).
Produced and released by pineal gland.
Function: induces sleep, inhibits reproduction, seasonal changes in behavior, antioxidant defenses, anti-aging, and increased immune function.
Regulated: light/dark input from the retina.

Insulin

Lowers blood glucose by allowing cells to transport glucose.
Produced and released by pancreas.
Functions: glucose uptake in muscle and fat cells, glycogen storage, inhibit glucose production.
Regulation:
- Blood (humoral): levels of nutrients in the blood
- Neural: PSNS post-eating (inhibited by SNS)
- Hormonal: increased by glucagon, epinephrine, thyroxine, glucocorticoids; decreased by somatostatin

Pancreatic Cells

Endocrine portion: Islets of Langerhans (1% of pancreas)
- Alpha cells: glucagon
- Beta cells: insulin
- Delta cells: somatostatin
- F cells: pancreatic polypeptide
Exocrine portion (99%): acinar cells (digestive enzymes), duct cells (NaHCO3 solution).

Insulin Effects

Increases during post-digestive state, high nutrient intake.
Facilitates nutrient use and storage.
Lowers blood glucose: production and storage of glycogen in liver and muscle; increases glucose transport into cells; inhibits glycogen breakdown an gluconeogenesis in liver.
Lowers fatty acids: storage of fat, production and storage of triglycerides, increase transport fatty acids into adipose tissue, inhibits triglyceride breakdown.
Lowers amino acids: storage of protein, production and storage of protein, increase transport of amino acids into cells, inhibits protein breakdown.

Type I and Type II Diabetes Mellitus

Type I Diabetes: lack of insulin secretion from pancreas; treated with injected insulin.
Type II Diabetes: normal insulin secretion, but lack of target cell response to insulin; insulin treatment does not help, high blood glucose, need diet and/or exercise.

Glucagon

Increases blood glucose (amino-acid based).
Produced and released by pancreas.
Functions: glucose synthesis, glucose release, glycogen breakdown.
Regulation: blood (humoral): low blood glucose, neural: stimulated by SNS, hormonal: inhibited by insulin and somatostatin.

Glucagon Effects oppose Insulin

Glucagon is increased between meals, and during fasting; ensures brain receives sufficient glucose.
Increased blood glucose, decreased glycogen production and storage, increased gluconeogenesis and glycogenolysis in liver; increased fatty acids and ketones; increased lipolysis in adipose tissue; increased ketogenesis; decreased protein synthesis; inhibits liver protein synthesis and increased protein degradation in liver; no effect on muscle protein; and no increase in blood amino acids.

Regulation of insulin & glucagon

Includes how low or high blood glucose concentration stimulates and stops secretion of insulin or glucagon respectively.

Reproductive Systems

Male reproductive system: spermatogenesis, synthesis of sex hormones, storage, and transport.
Female reproductive system: oogenesis, synthesis of sex hormones, fertilization, pregnancy, birth, and lactation.

Spermatogenesis

Each day about 120 million sperm complete the process of spermatogenesis.

Sperm

Divided into two parts, head (acrosome & nucleus), tail (Neck, middle piece, principle piece, and end piece).

Male Sex Hormones

During puberty, hypothalamic neurosecretory cells increase GnRH secretion.
LH (luteinizing hormone) stimulates Leydig cells to produce testosterone.
FSH (follicle-stimulating hormone), necessary for sperm maturation; FSH and testosterone act synergistically on Sertoli cells to stimulate secretion of androgen-binding protein (ABP). ABP binds to testosterone, keeping its concentration high in the testes; when sufficient spermatogenesis is achieved, Sertoli cells secrete the hormone inhibin to inhibit the secretion of FSH.

Function of Androgens

Before birth: stimulates male pattern of development of reproductive system ducts/descent of testes
Increased muscular mass/skeletal growth
Wide shoulders, narrow hips
Growth of facial/chest hair; increased sebaceous (oil) gland in face (acne formation); enlargement of larynx/deepening of voice; anabolic action causes heavier muscle and strong bones

Function of Accessory Glands

Seminal vesicles: secrete alkaline, viscous fluid containing fructose, prostaglandins, and clotting proteins (fibrinogen); prostaglandins contribute to sperm motility, viability, and stimulate smooth muscle contraction in female reproductive tract.
Prostate gland: secrete milky, slightly acidic fluid (pH 6.5) containing citric acid, calcium, and phosphate ions; citric acid is used for ATP production in sperm; proteolytic enzymes break down clotting proteins from the seminal vesicles.
Bulbourethral glands: secrete alkaline fluid to neutralize acids from urine in the urethra; secrete mucus that lubricates the penis and the lining of the urethra.

Properties of Semen

Mixture of sperm and seminal fluid.
Volume: 2.5–5.0 ml
Sperm count: 50–150 million sperm per mL (less than 20 million is infertile)
pH: 7.2–7.7 (higher pH due to larger volume of fluid from seminal vesicles)
Prostatic secretion gives semen a milky appearance.
Bulbourethral glands give it a sticky consistency.
Semen coagulates within 5 minutes due to clotting proteins from seminal vesicles.
Semen reliquefies after 20 minutes due to proteolytic enzymes from the prostate.
Abnormal or delayed liquefaction causes complete or partial immobilization of the sperm.

Male Sexual Act

Penile erection: first effect of male sexual stimulation (degree proportional to stimulation, whether psychic or physical, visual, tactile, auditory, olfactory, or imagined).
During sexual stimulation: parasympathetic impulses promote erection, parasympathetic stimulation produce nitric oxide causing vasodilation of penile arteries, and bulbourethral glands secrete mucus.
Ejaculation: powerful release of semen from urethra to exterior by sympathetic reflex; smooth muscle sphincter at the base closes during ejaculation; entire period of ejaculation called male orgasm.

Function of Female Reproductive System

Female gonads (ovaries): produce secondary oocytes and hormones (progesterone, estrogen, inhibin, and relaxin); held by ovarian and suspensory ligaments.
Uterine/Fallopian tubes/oviducts: transport secondary oocyte to the uterus; sites where fertilization occurs.
Uterus: site of implantation, fetal development during pregnancy and labor.
Vagina: receives the penis during sexual intercourse and is a passageway for childbirth.
Mammary glands: synthesize, secrete, and eject milk for nourishment of the newborn.

Puberty

Period when secondary sexual characteristics begin to develop and potential for sexual reproduction is reached.
Onset of puberty is marked by LH and FSH pulses, triggered by a pulse of GnRH.
Hormone leptin plays a crucial role in triggering GnRH.
Puberty advances with hormone pulses during the day and night, lasting 3-4 years until the adult pattern is established in females.
Reproductive cycle occurs once monthly from menarche (first menses) to menopause (permanent cessation of menses).

Ovarian Cycle

Ovum production, occurs in monthly cycles, taking place over 28 days.
- Follicular phase (preovulatory phase - 14 days): Formation of 1°, 2°, and 3° follicles.
- Ovulation phase (Post ovulatory phase - 14 days): Formation and degeneration of corpus luteum, degradation of corpus luteum.

Uterine Cycle

Repeating series of changes in the endometrium, continues from menarche to menopause, three phases:
- Menses (menstrual phase): degeneration of endometrium, menstruation.
- Proliferative phase: restoration of endometrium
- Secretory phase: endometrial glands enlarge and accelerate the rate of secretion.

Structure of Uterus

Description/diagram of the uterus

Role of Hormones

GnRH stimulates the release of FSH and LH from the anterior pituitary.
FSH initiates follicular growth
LH stimulates further development of ovarian follicles; at mid cycle triggers ovulation and then promotes formation of the corpus luteum.
FSH and LH stimulate ovarian follicles to secrete estrogens; stimulated by LH, corpus luteum produces and secretes estrogens, progesterone, relaxin, and inhibin.

Hormones Involved in Ovarian Cycle

GnRH stimulates the release of FSH and LH from the anterior pituitary.
FSH stimulates the further development of ovarian follicles.
LH stimulates the secretion of estrogens/and inhibin, resulting in ovulation and the development of a corpus luteum.
Estrogens: promote development of female reproductive structures; Increase protein anabolism; Lower blood cholesterol; moderate levels inhibit release of GnRH, FSH, and LH.
Progesterone: works with estrogens to prepare endometrium for implantation; prepares mammary glands to secrete milk; inhibits release of GnRH and LH.
Relaxin: inhibits contractions of uterine smooth muscle, increases flexibility of pubic symphysis, and dilates uterine cervix during labor.
Inhibin: inhibits release of FSH and, to a lesser extent, LH.

Phases of Reproductive cycle

Duration of cycle is 28 days, four phases: Menstrual, Preovulatory, Ovulation, Postovulatory
Menstrual phase: influence of FSH, Primordial follicles develop into primary/secondary follicles.
Preovulatory phase/menstruation to ovulation: Secondary follicle becomes dominant mature (graafian) follicle, secretion of estrogen and inhibin decrease FSH, estrogen repairs endometrium produce new stratum functionalis
Ovulation phase: High levels of estrogens from almost mature follicle stimulate release of more GnRH and LH ; LH surge brings about ovulation, rupture of graafian follicle and expulsion of secondary oocyte into pelvic cavity, ovulated oocyte swept into uterine tube.
Postovulatory phase: The mature follicle collapses, becoming corpus hemorrhagicm; theca interna cells and granulosa cells mix and transform into corpus luteum cells under the influence of LH; corpus luteum secretes estrogens, progesterone, relaxin, and inhibin; secretory activity of the endometrial glands, which start secreting glycogen; if fertilization doesn't occur, progesterone and estrogen levels decline due to degeneration of the corpus luteum.

Ovulation Phase

High levels of estrogens from almost mature follicle stimulate release of more GnRH and LH.
LH surge brings about ovulation, rupturing of graafian follicle and expulsion of secondary oocyte into pelvic cavity.
Ovulated oocyte usually swept into uterine tube.

Postovulatory Phase

Time between ovulation and onset of next menses; mature follicle collapses becoming corpus hemorrhagicum.
Theca interna and granulosa cells mix and transform into corpus luteum cells under LH influence.
Corpus luteum secretes estrogens, progesterone, relaxin, and inhibin.
In uterus: secretory activity of endometrial glands, secreting glycogen; if fertilization doesn't occur, progesterone and estrogen levels decline.

Menstrual cycle

Description/diagram of the hormonal regulation of changes in the ovary and uterus, showing menstruation/menstrual, ovulation, follicular, and luteal phases on a graph with hormone levels throughout the cycle.

Pregnancy

Sequence of events starting with fertilization, proceeding to implantation, embryonic and fetal development.
Ends with birth about 38-40 weeks after last period.
Prenatal development: fertilization to birth, embryological & fetal developments, divided into 3 calendar months
- First trimester: rudiments of all major organ systems appear
- Second trimester: nearly complete development of organ systems
- Third trimester: rapid fetal growth

Hormones of Pregnancy

Human chorionic gonadotropin (hCG) rescues corpus luteum from degeneration.
Progesterone: maintains endometrium, prepares mammary glands.
Estrogen: prepares mother's body for birth; helps prepare mammary glands.
Relaxin: increases flexibility of pubic symphysis, helps to dilate uterine cervix during labor.
Human chorionic somatomammotropin (hCS): increases growth hormone by increase protein synthesis, decreases glucose use, increase fatty acid use; establishes timing of birth/increases secretion of cortisol.

Labor or Giving Birth/Parturition

Process by which the fetus is expelled from the uterus through the vagina.
End of gestation, high estrogen levels in mother's blood stimulate oxytocin and relaxin and prostaglandins from placenta.
Oxytocin stimulates uterine contractions; Contract myometrium forcefully.
Relaxin increase the flexibility of pubic symphysis, and dilates uterine cervix.
Prostaglandins, induce production of enzymes that digest collagen fibers in cervix, causing it to soften; True labor is divided into three stages.

Three Stages of Labor

Stage of Dilation (6–12 hrs): contractions of uterus, rupturing of amniotic sac, complete dilation (to 10 cm) of the cervix.
Stage of Expulsion (10 minutes to several hours): time from complete cervical dilation to delivery of baby.
Placental Stage (5–30 minutes): time after delivery until the placenta/”afterbirth” is expelled by powerful uterine contractions.

Lactation

Secretion and ejection of milk from mammary glands.
Prolactin levels increase as pregnancy progresses; no milk secretion occurs because progesterone inhibits prolactin effects.
After delivery, estrogen and progesterone levels decrease; suckling initiates nerve impulses from stretch receptors in the nipples to hypothalamus to release of prolactin; first few days after birth, mammary glands secrete cloudy fluid called colostrum (less lactose, no fat, and maternal IgA antibodies).
Lactation often blocks ovarian cycles for the first few months following delivery.

Regulation of Lactation

Suckling of baby on nipple causes increasing touch sensations.
Touch-sensitive sensory neurons in nipple produce nerve impulses
Hypothalamus and posterior pituitary are the control centers, resulting in positive feedback for milk availability.
Interruption of cycle: baby ceases to suckle, breaking the positive feedback cycle.

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Test your knowledge on the primary roles of hormones and their functions within the endocrine system. This quiz covers key concepts like gland functions and the study of hormones. Assess your understanding of this vital aspect of human biology.