lecture 16- intro to reproduction

Question 1

reproduction is?

Answer 1

the process by which new individuals of a species are produced and the genetic material is passed on from generation to generation.

Question 2

males?

Answer 2

constant production of spermatozeen at 300 million per day from puberty
constant fertility, declining with old age

Question 3

females?

Answer 3

cyclical fertility from puberty, 3-5 days per cycle
in utero, 7 million follicles and rapidly declining with age.
only around 400 follicles will be ovulated in a lifetime

Question 4

Hierarchical arrangement of endocrine glands?

Answer 4

allows for AMPLIFICATION of signals

Question 5

reproductive hormones?

Answer 5

1. Water soluble-(peptides and proteins)
   - Gonadotrophin releasing hormone (GnRH)– Hypothalamus
   - follicle-stimulating hormone (FSH)–APG
   - Luteininising hormone (LH)–APG
   - Oxytocin–PPG
2. Lipid soluble-(steroid hormones)
   - Androgens (testes) }
   - Oestrogen (Ovary) } all made of cholesterol
   - Progestagens (ovary) }

Question 6

Neurosecretory neurons

Answer 6

can conduct a nerve impulse and synthesize, carry and release neurosecretory peptide hormones

Question 7

Hypothalamus?

Answer 7

functions to act as a homeostatic regulator for reproductive, stress, body temp, hunger, thirst and sleep. NEUROENDOCRINE ORGAN.

Question 8

Posterior pituitary?

Answer 8

long axon tracts from nuclei of neurosecretory neurons pass from hypothalamus to posterior puituitary gland. neurosecretory peptide hormones pass through to axon terminal and are released upon stimulation, into the hypophyseal portal veins.
Oxytocin and ADH/vasopressin

Question 9

oxytocin?

Answer 9

released by the posterior pituitatary gland into the hypophyseal portal veins and acts to contract smooth muscle causing milf ejection and contraction of uterus during childbirth. secreted due to stimulation of nipples or uterine distension.

Question 10

anterior pituitary gland?

Answer 10

neurosecretory neurons synthesise releasing and inhibiting hormones. Secretion occurs into the linking hypophyseal portal vessels. These hormones act on secretory cells in clumps. Gonadotrophs produce FSH and LH.

Question 11

hormone regulation?

Answer 11

requires both positive and negative feedback loops to control hormone levels. Negatuve feedback often involves signalling between hypo-pit-target organ.

Question 12

Pulsate release

Answer 12

Hypothalamic secretions are released in discrete bursts, seperted by periods of little or no secretion. Prevents receptor desensitisation and down-regulation

Question 13

Pituitary hormones that regulate gonadal activity?

Answer 13

FSH and LH bind to receptors in the ovary and testis. Promoting the synthesis of sex hormones and gametogenesis.

Question 14

FSH and LH in males?

Answer 14

FSH- growth of spermatozoan

LH- stimulates testosterone production

Question 15

FSH and LH in females?

Answer 15

FSH- growth of ovarian follicle

LH- secretion of female sex hormones and stimulation of ovulation.

Question 16

Major Sex Steroids?

Answer 16

Androgens- mostly males
Oestrogens- mostly female
Progestagens- female

Question 17

Androgens?

Answer 17

Testosterone is the main secretory product of the testis and is involved with the maintenance of male characteristics and fertility
  -male sex dev.
  -spermatogenesis
  -sexual behavior
  -muscle dev.
5(alpha) Dihydrotestosterone

Question 18

Oestrogen?

Answer 18

Development and maintenance of female characteristics and fertility.

1. Oestradiol 2. Oestrone 3. oestriol
   - female sex development
   - growth of endometrium
   - regulation of menstrual cycle
   - bone growth

Question 19

Progestagens?

Answer 19

major steroidal hormone of the corpus leteum and of the placenta. Preparations pregnancy and maintenance (endometrium lining)

Question 20

Gonadatrophin secretion/feedback?

Answer 20

1. hypothalamus releases GnRH in a pulsatile fashion that stimulates the anterior pituitary gonadotrophs
2. both LH and FSH act to promote spermatogenesis and oogenesis.
3. FSH and LH also stimulate gonads to produce sex hormones that negatively feedback onto the hypothalamus and anterior pituitary gonadotrophs.

Question 21

two main functions of the gonads?

Answer 21

gamete production

hormone production

Question 22

difference between the anterior and posterior pituitary gland?

Answer 22

posterior = NEUROHYOPHYSIS
anterior = ADENOHYPOPHYSIS

the posterior system uses a neurosecretory neuron from the nuclei in hypothalamus to the posterior gland
the anterior systems’ neurosecretory neuron doesnt leave the hypothalamus but instead uses the humoral (portal system)