Term Test 2 Flashcards
What are the two glands that make up the pituitary gland?
Posterior Pituitary and Anterior Pituitary
What is the posterior pituitary gland? What does it excrete?
Neural Tissue that secretes two hormones: Vasopressin (ADH) and Oxytocin
What is the anterior pituitary? What does it excrete?
Endocrine tissue: prolactin, thyrotropin, adrenocorticotropin, growth hormone, follicle-stimulating hormone, luteinizing hormone
What is the pathway of secretion of posterior hormones?
- neurohormone made and packaged in the hypothalamus
- vesicles transported down the cell
- Vesicles are stored in the posterior pituitary
- neurohormones are released into the blood
* first goes to posterior then blood
What is the pathway of anterior hormone secretion?
- neurons synthesizing trophic neurohormones release them into the capillaries of the portal system (hypothalamic hormones that tell the anterior pituitary when to release hormones)
- Portal veins carry the trophic neurohormones directly to the anterior pituitary, where they act on the endocrine cells
- Endocrine cells release their peptide hormones into the second set of capillaries for distribution to the rest of the body
*hypothalamus–>portal veins–>endocrine cells–> blood
What are the hypothalamic hormones?
Dopamine, Thyrtropin-releasing hormone (TRH), Corticotropin-releasing hormone (CRH), GHRH, Gonadotropin-releasing hormone (GnRH), Somatostatin (GHIH)
What does Dopamine do? What is its target?
Inhibit prolactin, breast
What does TRH do? Target? Further hormones?
Stimulate the release of Thyrotropin, or Thyroid-stimulating hormone (TSH), Thyroid gland –> thyroid hormones (T3/4)
What does CRH do? Target? Further hormones?
Simulate the release of Adrenocorticotropin, Adrenocorticotrophic hormone (ACTH), Adrenal Cortex–>Cortisol
what does GHRH do? Target? Further hormones?
stimulate GH (Somatotropin) release, liver–> Insulin like growth factor
What does GnRH do? Target? Further?
Stimulate the release of FSH and LH, Endocrine cells on the gonands–>androgens, estrogens, progesterones–>germ cells on the gonands
What are bones like in utero?
they are soft, cartilage is not fully ossified, active growth plates
What are adolescent bones like?
Bones are fully ossified, growth plates are closing towards the end of puberty
What are adult bones like?
Growth plates are closed, fully ossified, bone loss occurs around 35-40
What are the epiphyseal growth plates?
Epiphyseal bone plate is a flat bony structure located between the epiphysis and the metaphysis of the long bones. It holds the growth plate cartilage, providing the weakest area of the growing bone with strength and stability. It is the blue that contains chondrocytes
What is ossification and what is required for it?
Bone formation, needs osteoblasts
What direction does bone growth take place?
The growth plates are growing towards the compact bone
What is a chondrocyte?
produce new cartilage
How does bone growth work?
- Closest to the newly calcified growth plate osteoblasts lay down new bone on top of cartilage (foundation for bone from Ca2+) from the chondrocytes
- Old chondrocytes disintegrate and are replaced by bone as the bone grows
- Chondrocytes (from media) produce cartilage
- Dividing chondrocytes add length to the bone
*compact bone is the walls, the epiphyseal growth plate is chondrocytes, cartilage, and dying chondrocytes (it is a layer)
What is the stimulatory growth hormone pathway?
- Circadian rhythm, stress and cortisol, and fasting signal the hypothalamus to produce GHRH
- GHRH increases GH release from the anterior pituitary to signal on the the liver
- IGF is secreted from the liber signaling for cartilage growth (inc. in chondrocytes)
- IGF also signals a negative feedback mechanism on the anterior pituitary and hypothalamus to stop GH and GHRH production
What is the inhibitory growth hormone pathway?
- Circadian rhythm, stress and cortisol, and fasting signal the hypothalamus to produce Somatostatin (GHIH)
- Stops GH release from the anterior pituitary
- Blood glucose increases and bone and tissues grow
What is IGF-1
Insulin-Like Growth Factor
- growth-promoting effects on almost every cell in the body
- anabolic effects (growth)
How does GH stimulate bone growth?
Chondrocytes inc in:
- recruitment
- proliferation
- matrix
What are the catabolic, glucose sparing effects of GH?
Stimulates adipose cells to break down stored fat, fueling growth effects (lipolysis)
What are the catabolic growth effects of GH?
- Increases the uptake of amino acids from the blood
- Enhances cellular proliferation and reduces apoptosis (targets: bone, muscle, nervous system, and immune cells)
What are the catabolic diabetogenic effects of GH?
GH stimulates liver to break down glycogen into glucose, fueling growth effects (gluconeogenesis, glycogenolysis)
What would you expect to see in a person with too much growth hormone because of a pituitary tumor?
increased number of chondrocytes
What does growth depend on?
- Diet and Genetics
- adequate nutrition and no chronic stress - Hormones and growth factors like:
- GH and IGF-1
- Thyroid Hormones
- Insulin
- Sex steroids
- Cortisol
What is gigantism?
Too much GH in childhood (adds to the growth plates)
What is acromegaly?
Too much GH in adulthood (adds to the ends of irregularly shaped/flat bones and affects the skin and lips)
Where is the Thyroid?
By adams apple, middle of neck
What cell types and things make up the thyroid?
- Follicles (produce the hormones)
- C cells
- Follicular cells surrounding the colloid
- Capillaries
- Connective tissue
How are thyroid hormones made?
- Na+ I- symporter (transport both the same way) brings I- into the follicular cell
- The pendrin transporter moves the I- into the colloid
- Follicular cells synthesize enzymes and thyroglobulin for colloid
- Thyroid peroxidase adds iodine to tyrosine to make T3 and T4 (thyroid hormones)
- Thyroglobulin is taken back into the cell in vesicles to be recycled
- Intracellular enzymes T3 and T4 from the thyroglobulin protein
- Free T3 and T4 enter circulation
What are all the names of the thyroid hormone variants?
1 iodine: monoiodotyrosine
2 iodine: diiodotyrosine
3: triiodothyronine
4. thyroxine
What is Iodine used for in humans?
Just thyroid hormone
What is the stimulatory pathway of Thyroid hormone?
- TRH is made in and released from the hypothalamus at a constant rhythmic release without stimulation
- TSH is released from the anterior pituitary signaling for T3/4 to be made
- Thyroid hormone sends negative feedback mechanisms to the Hypothalamus for TRH and anterior pituitary for TSH
What is TSH and its function?
- Activates G-protein linked membrane receptors acting via Adenylate cyclase
- Stimulates synthesis and activity of enzymes involved in T3 and T4 synthesis
- activates TFs
What is the mechanism of action of thyroid hormones?
- T3/4 circulate in blood bound to plasma proteins
- T3 more potent than T4
- T4 converted to T3 in target tissues
- alter gene transription
What do T3 and T4 bind to?
Both bind to nuclear thyroid receptors (form dimers with retinoic acid receptor)
What are the metabolic functions of thyroid hormones?
metabolic rate, oxygen consumption, heat production, protein degradation, lipolysis
What are the nervous system functions of thyroid hormones?
enhance speech, thinking, reflexes
What are the growth and development functions of thyroid hormones?
essential in children, works with GH to promote growth
What are the cardiovascular functions of thyroid hormones?
enhances heart rate and contractility, peripheral blood flow, works in part by increasing numbers of B adrenergic receptors and other proteins
What are the muscular functions of thyroid hormones?
too much causes muscle weakness,
What is Hyperthyroidism and its causes?
Excess thyroid hormone
- causes: tumors, thyroid stimulating immunoglobulins
Symptoms of hyperthyroidism?
goiter, nervousness, insomnia, anxiety, high heart rate, graves disease, weight loss
Treatments of hyperthyroidism?
remove part of thyroid, block synthesis of T3 and T4 or block T4 conversion to T3
What is Graves disease and its symptoms?
Autoimmune disease: abnormal antibodies against the TSH receptor are produced
- no known cause
- most common cause of hyperthyroidism
- immune system produces antibodies that look like TSH and bind to the TSH receptor
- TSH receptor turns on mistakenly
What is hypothyroidism and its causes?
- Thyroid hormone deficiency
Causes: - under active thyroid gland
- no iodine in diet
Symtoms and treatments of hypothyroidism?
- goiter, slowed heart rate, slowed speech, fatigue, cold-intolerance, cretinism, stunted growth, weight gain
- exogenous thyroid hormone (T4) thyroxin
- the goiter is caused by parts of the thyroid trying to compensate
Iodine definiciency causes…
- no ability to make T3/4
- lack of negative feedback inc. TSH secretion
- TSH stimulates growth of thyroid gland=goiter
- causes death, retards, poor growth, stupidity
Without iodine what happens to a dude?
High TRH, TSH, low TH (no negative feedback)
what re the commonalities found between sexes?
- Gamete formation
- Hypothalamic/Pituitary control of reproduction
What is gametogensis?
- gametes with 23 chromosomes produces from cells in gonads with 46 chromosomes
- Involves meiosis
What is meiosis?
DNA replicated once and undergoes division twice
What is nonhomologous recombination?
- random assortment of genetic material
- reassortment of the genes so the products are a unique combo when fertilized
What is GnRH and how does it work?
- Gonadotropin Releasing Hormone
- Secreted in pulses from neuroendocrine cells in the hypothalamus
- stimulates synthesis and secretion of LH and FSH
- Pulsality is critical for reproductive function
What is the pulsality of GnRH
- regulated by hormonal feedback and higher brain centers
- Pulse frequency/amplitude changes during development and during periods in adult life
What happens if GnRH pulses are low?
- FSH released
What happens if GnRH pulses are high?
- LH released
Which is correct regarding the regulation of reproductive hormone secretion?
LH stimulates the release of steroid hormones from the gonads
How are sperm produced?
- in the testis
- optimally at 2-3C lower than body temp
- Takes 64 days
- 200 million produced a day
- Further mature in the epididymis
What do sertoli cells do?
- also called sustentacular cells
- Support sperm development
- filter and absorb nutrients
- provide tight junctions between early stages/initial germ cells and actual developing sperm
What do leydig cells do?
- secrete testosterone
How are the seminiferous tubules organized?
- sertoli cells inside tubule
- Leydig cells outside
- Spermatogonium (sperm precursors) inside as as the move to the center they mature to sperm
- capillaries are not in the tubule, just outside
What are the tight junctions responsible for?
blood testis barrier because immune cells would recognize sperm as novel proteins + only 1/2 genetic material and kill them
Process of Spermatogenesis
- Spermatogonia undergo mitosis, one stays behind to produce more spermatogonia
- The other is the primary spermatocyte that undergoes meiosis 1 forming the 2 secondary spermatocytes
- The secondary spermatocytes undergo meiosis 2 forming four spermatids
- These mature into spermatozoa (loss of cytoplasm, formation of the tail)
What are spermatozoa and their structure?
from the top:
- acrosome with enzymes derived from golgi apparatus
- nucleus
- centrioles
- mitochondrial spiral (for swim energy)
- microtubules
What does the acrosome contain?
- hyaluronidase and acrosin which breakdown the zona pellucida, a glycoprotein coat that covers the oocyte
What is semen?
Water
Lubricant: mucous
Buffers: neutralize acid
Nutrients: fructose, citric acid, vitamin C, Carnitine (for energy)
Enzymes
Zinc
Prostaglandins: Smooth muscle contractions (aid muscle contractions)
What are the exocrine organs in the male repro system?
seminal vesicle, prostate gland, bulbourethral gland (alkaline secretions)
What is the system of stimulatory hormonal control of gametogenesis in males?
- GnRH from hypo stimulates FSH and LH in anterior
- FSH signals for secondary messengers to make cell products
- The cell products make androgen-binding protein (ABP)
- ABP interacts with testosterone from LH stimulating Leydig cells to support sperm development
What in the inhibitory control of male gametogenesis?
- Cell products produced by FSH’s secondary messengers signals for Inhibin, which stops FSH production
- LH production and GnRH production are stopped by Testosterone production
FSH role
stimulates sertoli cells
- support sperm development
- secrete inhibin (inhibits FSH release)
- Secrete androgen-binding protein (helps to concentrate androgens in testis)
LH role
Stimulates Leydig cells to secrete testosterone
Testosterone secretion throughout life
- burst in fetus
- burst in neo-natal
- nothing pre-puberty
- HUGE burst in puberty to adult then steady decline
Hormone levels of men throughout their life…
LH, T, FSH, and INSL3:
- high-second and third trimester, 0-6 months, puberty
- low/rising: first trimester, childhood
AMH:
- high: first, second, third trimester, childhood
- low: steep drop at puberty
Inhibin:
- high: first, second, third trimester, childhood (first half), rises at puberty
- low: second half of childhood
What is hypogonadism?
- decreased function of the testis
- decreased production of androgens, inhibin B, AMH, and/or impaired sperm production
What is primary hypogonadism’s pathway?
- Inc in GnRH
- Inc. FSH and LH
- Dec. testosteron b/c testis damaged
- no negative feedback lots of GnRH, FSH, and LH still
What is secondary hypogonadism?
- damaged hypothalamus
- low GnRH
- affects anterior pituitary
- low FSH and LH
- low testosterone
* one can be given supplementary testosterone
What does testosterone do in sex-specific tissues?
- promotes spermatogenesis
- maintains and stimulates secretion from prostate and seminal vesicles
- Maintains reproductive tract
Other reproductive effects of testosterone?
- Inc. sex drive
- negative feedback on LH, FSH, GnRH
Secondary sex characteristics of testosterone?
- male pattern hair growth, baldness
- promotes muscle growth
- Increases sebaceous gland secretion (odors)
Non-reproductive effects of testosterone
- promotes protein synthesis
- Increases aggression (side effects of steroids)
- Stimulates erythropoiesis (make new blood)
What else can testosterone make?
cholesterol–>testosterone–>+5a-reductase–>DHT–>important for prostate, external male genitalia, and baldness
What happens when you inhibit 5a-reductase
- treatment for benign prostate enlargement
- increased hair growth
How are oocytes produced?
Oogenesis:
1. Before birth: oogonia undergo meiosis 1, duplicate their DNA then STOP resulting in primary oocytes
2. at puberty 300,00 primary oocytes remain
3. After puberty, one primary oocyte completes meiosis 1 and enters meiosis 2 to become a secondary oocyte every 28 days
4. Secondary oocyte released at ovulation
5. Secondary oocyte completes meiosis 2 only if fertilized, dies if not
What are the differences between oogenesis and spermatogenesis?
- asymmetric cell division (only one secondary oocyte produced from each oogonium), remove polar bodies
- Limited duration (menopause)
- Limited number of primary oocytes
What is the process of oocyte maturation?
- primary oocytes are surrounded by granulosa and theca cells in what is called primary follicles
- Maturation recruits 5-10 follicles in each ovary, only one will fully mature
- remaining oocytes die (atresia)
What is the structure of the primary follicle?
- Theca externa
- Theca interna
- basement membrane
- granulosa cells
- atrium is also in the primary follicle
What are theca cells for?
- secrete steroid hormone precursors
What are granulosa cells for?
support oocyte development
Explain the ovarian cycle, follicular phase…
Days 1-14:
1. 5-10 follicles per ovary are selected to mature
2. The granulosa cells surrounding the primary oocyte proliferate
3. the theca cell proliferate and produce androgens–>estrogens as well and the atrium forms
4. All cells have proliferated a ton and the atrium is a huge fluid filled cavity with estrogen and enzymes (now a tertiary follicle)
5. the oocyte is now secondary and a dominant follicle is selected
What is the LH surge and what does it do?
The release of the tertiary dominant follicle (secondary oocyte and cumulus) to the fimbria of the fallopian tubes to be picked up and ovulated
1. Follicular cells (granulosa/theca) release collagenase: connective tissue to the ovary is digested
2. Progesterone is release aiding in smooth muscle contractions
Explain the luteal phase of the ovarian cycle…
- Follicular cells left behind in the ovary become corpus luteum
- This releases progesterone and estrogen
IF NOT FERTILIZED: - corpus luteum degenerates into the corpus albicans
IF FERTILIZED: - the corpus luteum continues to make progesterone and estrogen until the end of the first trimester
Describe the Menses phase of the uterine cycle
Blood vessels supplying the endometrium undergo constriction causing shedding of the endometrial lining because of declining levels of progesterone and estrogen
Describe the proliferative phase of the uterine cycle…
Endometrium develops in response to estrogen. The endometrial lining thickens as the blood supply to the tissue is re-established and cells proliferate
Describe the secretory phase of the uterine cycle…
Glands in the endometrium secrete more viscous fluid. Endometrial cells deposit lipid and glycogen in cytoplasm under the influence of progesterone and estrogen
Estrogen and Progesterone levels during the menstrual cycle
High during luteal/secretory phase, and estrogen high at the end of the follicular phase/proliferative because of atrium
Hypothalamic/Pituitary control of Early-mid follicular phase…
This is during the menses/proliferative phase of uterine
1. GnRH in hypothalamus turns on LH and FSH which begin to RISE, system still at a low
2. LH stimulates the release of androgens from theca cells
3. FSH stimulates conversion to estrogen by granulosa cells
4. Granulosa cells also secrete AMH which prevents recruitment of additional follicles
5. Estrogens exert positive feedback on granulosa cells increasing proliferation and estrogen
6. Estrogens exert negative feedback on ant pituitary and hypo to shut down LH and FSH
Hypothalamic/Pituitary control of late follicular phase and ovulation…
This is during the uterine proliferative phase
1. The tertiary follicle is now present
2. follicular cells secrete inhibin (inhibits FSH), progesterone, and estrogen
3. Progesterone increases pituitary sensitivity to GnRH (positive feedback for GnRH and LH)
4. High estrogens increase frequency of GnRH pulses to one every 65 min (positive feedback)
5. FSH being inhibited, LH surge occurs triggering meiosis 1 and ovulation
Hypothalamic/Pituitary control of Early-mid luteal phase…
This is during the beginning of the secretory phase of the uterine cycle
1. After ovulation the corpus luteum, under the influence of LH and FSH releases progesterone, inhibin, and estrogen
2. These hormones exert negative feedback at the hypothalamus and pituitary stopping LH and FSH production
3. Progesterone and Estrogen inhibits GnRH pulses (now once every 3-4 hours)
Hypothalamic/Pituitary control of late luteal phase…
This is during the end of he secretory phase of the uterine cycle:
1. The intrinsic life-span of the corpus luteum is 12 days
2. If not fertilization, the corpus luteum undergoes apoptosis
THE CYCLE REPEATS: This is during the menses phase of the uterine cycle
- FSH begins to rise to recruit new follicles
- Estrogen and progesterone are low so GnRH turns back on to make more
What is the process of estrogen regulation?
- In the theca cell LH signals for the conversion of cholesterol to androstenedione
- In the granulosa cell the FSH signals for the conversion of androstenedione to estrone via aromatase
- Estrone is converted to estradiol and then estrogens to be secreted
What are the sex-specific tissue actions of estrogen?
- promote follicular development and ovulation
- stimulates growth of the endometrium
- maintains reproductive tract
What are the other reproductive actions of estrogen?
Negative feedback effects on GnRH, LH and FSH secretion
What are the secondary sex characteristics actions of estrogen?
- stimulates development and growth of breast tissue
- increase sebaceous gland secretion