Hormonal Control of Growth, Development and Reproduction- 21 Flashcards
What hormones are important during pre-natal and post-natal development.
Insulin and Insulin like growth hormone.
What hormone is important for post natal development
Growth hormone
What hormone is important for pre and post natal brain development.
Thyroid hormone (T3)
What hormones are important for growth and development during puberty
Testosterone and estradiol
Where is growth hormone secreted and what controls it.
A protein hormone that is released by somatotropic cells in the anterior pituitary controlled by hypothalamus.
An increase cAMP via GHRH receptor activation leads to enhanced secretion of griwth hormone.
What are most effects of GH on growth mediated by
IGF-1 action by the liver.
What is the release of growth hormone described to be.
Pulsatile in nature meaning secretion occurs in discrete but irregular phases (maximal at night during puberty)
What is height determined by
Bone growth.
What is the mechanism of bone growth.
New bone tissue is added at the region called the epiphyseal bone plate. Once it closes no more bone growth can occur.
What do chrondrocytes do during bone growth
They add new cartlidge at the epiphyseal plate to push the bone up.
What do osteoblasts do during bone growth?
Osteoblasts convert Cartlidge to bone in the epiphyseal plate.
What does growth hormone stimulate in bone growth.
Differentiation of precursor cells in the epiphyseal plate into chondrocytes.
Which secrete IGF-1 and become respovsive to IGF-1.
IGF-1 acts in a paracrine manner to stimulate chondrocyte division.
What are other importants effects of IGF-1
Stimulates protein synthesis in muscle and other cell types.
Increases levels of circulating energy sources
Powerful mitogen, promoting cell growth and division.
What role does thyroid hormone play in growth and development
Stimulates synthesis of GH
Potentiates the effects of GH and IGF-1 on bone growth.
Promotes differentiation of chondrocytes.
What are the highest sex hormones in males.
Testosterone
Dihydrotestosterone
What sex hormones are highest in females
Estrogens(mainly estradiol)
Progesterone
What type of hormone are sex hormones.
Steroid hormones (so can pass membrane)
What is the release of sex hormones mediated by and what is the process.
Hypothalamus releases
Gonadotropin-releasing hormone which produces
gonadotrophs from the anterior pituitary. (FSH and LH)
Which act on ovaries/testes to produce sex hormones.
This can allow negative feedback of the process.
What peptide is important for the onset of puberty
Kisspeptin as it triggers release of GnRH
What effects does LH and FSH have in males.
LH acts on leydig cells to produce testosterone which promotes development of secondary sexual characteristics and accessory structure.
FSH works on sertoli cells to begin spermatogensis and inhibin (negative feedback on release)
What are the receptors for (dihydroxy)testosterone
Intracellular receptors binding to these results to translocation from the cytoplasm to the nucleus and gene transcription changes.
What are the effects of testosterone on growth
stimulate secretion of GH
Stimulate proteins synthesis in tissues such as muscles.
What do LH and FSH regulate in females
The levels of oestrogen and progesterone.
What happens during the ovarian cycle
Describes the changes occurring in follicles of the ovary ie maturation of follicle and release of egg.
What happens during the uterine cycle.
Describes the changes that occur in the endometrial lining of the uterus.
If fertlisation does not occur the corpus luteum will degenerate.
Why do hormone levels fluctuate in women.
FSH and LH stimulate oestrogen release from follicles.
One follicle becomes dominant and secretes high levels of oestrogen.
LH surge triggers ovulation.
The Corpus luteum forms and secretes a high amount of oestrogen and progesterone.
Negative feedback leads to low FSH and LH levels.
If pregnancy does not occur the corpus degrades meaning oestrogen and progesterone levels fall leading to a surge in LH and FSH again.
What is the function of human chorionic gonadotrophin hormone and where is it secreted.
HCG is released from the conceptus ie everything both embryonic and extra-embryonic that develops from the zygote
HCG prevents degrading of the corpus luteum.
When does menopause occur
around 50 years old
What causes menopause
The failure of the ovaries to respond to gonadotropins
The concentration of plasma estrogen is too low to maintain tissues
WHat can happen during menopause
Osteoporosis due to estrogen being a bone productive hormone
Loss of cardio protective tissue
What is a treatment used for menopause
Hormonal Replacement Therapy
