Hormonal Control of Growth, Development and Reproduction

Question 1

at what stage of development is insulin and insulin like growth hormones important?

Answer 1

during prenatal and postanatal development

Question 2

at what stage of development is growth hormone important?

Answer 2

post natal development

Question 3

at what stage of development is thyroid hormone important ?

Answer 3

for prenatal brain development and postnatal development

Question 4

at what stage of develpoment is sex hormones(testosterone and estradiol) important?

Answer 4

during puberty

Question 5

where is growth hormone secreted?

Answer 5

by somatotropic cells in the anterior pituitary

Question 6

describe the release of growth hormone?

Answer 6

pulsitile- secretion occurs in discrete but irregular pulses between pulses GH levels can be undetectable.

Question 7

when is the amplitude of GH secretory pulses maximal?

Answer 7

at night

Question 8

what determines height

Answer 8

bone growth

Question 9

where is new bone tissue added

Answer 9

epiphyseal growth plate

Question 10

when does bone growth stop?

Answer 10

once the epiphyseal growth plate closes(it is converted to bone), no more bone growth can occur

Question 11

what do osteoblasts do at the epiphyseal plate?

Answer 11

convert Cartlidge to bone

Question 12

what do chondrocytes do at the epiphyseal plate?

Answer 12

add new Cartlidge here, pushing the bone up

Question 13

what hormones stimulate bone growth?

Answer 13

insulin like growth factor and growth hormone

Question 14

what does growth hormone do?

Answer 14

stimulates differentiation of precursour cells in the epiphyseal plate into chondrocytes

Question 15

what do differentiated chondrocytes do?

Answer 15

secrete IGF-1 and become responsive to IGF-1.

Question 16

what does IGF-1 do?

Answer 16

stimulates chondrocyte cell division

Question 17

other important effects og GH/IGF-1?

Answer 17

• stimulate protein synthesis in the muscles and other cell types
• increases levels of circulating energy sources
• IGF-1 is a powerful mitogen, promoting cell growth and division throughout the body.

Question 18

what is the role of thyroid hormone in growth and development?

Answer 18

stimulates synthesis of GH, potentiates the effects of GH and IGF-1 on bone growth, promotes the differentiation of chondrocytes.

Question 19

what are gonads?

Answer 19

testes and ovarys (the reproductive organs in male and females

Question 20

what do the gonads do?

Answer 20

they produce gametes and secrete steroid hormones(sex hormones)

Question 21

what are the highest sex hormones in males?

Answer 21

testosterone and dihydrotestosterone

Question 22

what are the highest sex hormones in females?

Answer 22

oestrogen (mainly estradiol) and progesterone

Question 23

what are gonadotrophins?

Answer 23

any of a group of hormones secreted by the pituitary which stimulate the activity of the gonads (FSH/LH)

Question 24

what are gonadotrophs

Answer 24

endocrine cells in the anterior pituitary that produce the gonadotropins

Question 25

how are sex hormones synthesized?

Answer 25

the hypothalamus releases gonadotropin releasing hormone(GnRH) which causes the gonadotrophs in the pituitary to release FSH and LH (gonadotrophins) which cause the release of sex hormones at the ovaries/testes

Question 26

what is the event that causes an onset of puberty?

Answer 26

increase in pulsatile GnRH (gonadotropin releasing hormone)

Question 27

what important role does kisspeptin do for the onset of puberty?

Answer 27

The peptide kisspeptin is important for the onset of puberty. this peptide triggers GnRH release from GnHR neurons in the hypothalamus

Question 28

what does LH do in males?

Answer 28

causes the leydig cells to release testosterone

Question 29

what does FSH do in males?

Answer 29

causes the Sertoli cells to secrete inhibin and in the presence of testosterone causes spermatogenesis

Question 30

what can testosterone be converted to in males?

Answer 30

dihydrotestosterone and estradiol, which also have important functions in male development

Question 31

what is the Main effects of testosterone on growth ?

Answer 31

Stimulate secretion of GH Stimulate protein synthesis in many tissues (e.g. muscle)

Question 32

what does the ovarian cycle describe?

Answer 32

The ovarian cycle describes changes occurring in the follicles of the ovary (follicles contain a single oocyte (immature ovum))

Question 33

what does the uterine cycle describe?

Answer 33

The uterine cycle describes changes that occur in the endometrial lining of the uterus

Question 34

what is the menopause caused by?

Answer 34

failure of the ovaries to respond to gonadotropins

Question 35

what happens during menopause?

Answer 35

Concentration of plasma estrogen is too low to maintain tissues that are dependent on this hormone

Question 36

why may osteoporosis occur during the menopause?

Answer 36

because oestrogen is a bone-protective hormone

Question 37

What does HRT involve?

Answer 37

administering oestrogen/progesterone

Question 38

what does FSH and LH do at the beginning of the cycle?

Answer 38

FSH and LH stimulate the release of oestrogen from the ovarian follicles. One follicle becomes dominant and secretes high levels of oestrogen. This surge in oestrogen exerts a positive feedback effect leading to a surge in LH and FSH LEVELS. LH surge triggers ovulation.

Question 39

in what does the corpus luteum do?

Answer 39

corpus luteum secretes high amounts of oestrogen and progesterone.

Question 40

what does the oestrogen and progesterone secreted by the corpus luteum cause?

Answer 40

negative feedback of oestrogen and progesterone leads to low FSH and LH levels.

Question 41

what happens to the corpus luteum if pregnancy doesn't occur?

Answer 41

the corpus luteum degrades, leading to a fall in oestrogen and progesterone.... as a result FSH and LH levels start to rise.

Question 42

what do oestrogen and progesterone do to the endometrium?

Answer 42

estrogen and progesterone stimulate the thickening and development of the endometrium in preparation for possible pregnancy.

Question 43

what causes menestration?

Answer 43

As levels of oestrogen and progesterone fall (as corpus luteum degenerates) this leads to degeneration of the endometrium and menstruation

Question 44

what is Human chorionic gonadotrophin (HCG)

Answer 44

HCG prevents degeneration of the corpus luteum if pregnancy occurs The corpus luteum regresses after ~ 3 months after which estrogen/progesterone secretion is from placenta