Reproduction Flashcards
1
Q
Where on or in the cell are the receptors for Steroid Hormones?
A
In the Cytoplasm
2
Q
Where on or in the cell are the receptors for Thyroid hormones
A
In the Nucleus
3
Q
Where on or in the cell are the receptors for peptide/catecholamine hormones?
A
Cell Membranes
4
Q
How are sterodial and thryoid hormones transported within the blood?
A
Bound to proteins within the plasma, this is because they are derivatives of cholesterol and therefore are lipophilic and poorly water soluble
5
Q
What is the ultimate regulator of the endocrine system?
A
THe Central Nervous System (CNS) with the Control Coordinator being the hypothalamus
6
Q
In relation to Hormones, what does downregulated mean?
A
The hormone in question decreases the number of receptors, therefor decreasing the sensitivity to that hormone
7
Q
In relation to Hormones what does upregulated mean?
A
The hormone in question increases the number of receptors which inturn increases the sensitivity to that hormone.
EG Oestrogen in ovarian cells during the menstrual cycle
8
Q
In relation to hormones what does sensitivity mean?
A
Sensitivity describes the acuity of a cells ability to recognize a hormonal signal and to respond in proportion to the intensity of that signal.
Sensitivity is defined as the concentration of hormone that will being 50% of the maximum response.
9
Q
What is a circadian rhythm? Eg how long does it take and what effects it?
A
They are endogenous rhythms that take 24hours but are effected by things like sunlight and temperature.
10
Q
Pulsatile rhythms are frequently superimposed on circadian rhythms, what is the usual pulsatile secretion period?
A
0.5 - 2 hourly
11
Q
Describe what a Primary Endocrine disorder is
A
A primary endrocrine disorder is one in which the target hald itself (eg thyroid) is not functioning normally
12
Q
Describe what a secondary endrocrine disorder is!
A
A Secondary Endrocrine Disorder occurs when the initial disorder is in the pituitary and the problem in the target organ is secondary to the pituitary disorder.
13
Q
Describe what a tertiary endrocrine disorder is
A
A Tertiary Endrocrine disorder is one in which the problems originates in the hypothalamus
14
Q
In relation to Reproductive Endrocrinology
- What does the Hypothalamus release
- How does it release it?
- What is the target tissue of this?
A
- Gonadotrophin-Releasing hormone (GnRH)
- either Pulsatile manner or a surge
- Target tissue for GnRH is the Anterior Pituitary
15
Q
- What does GnRH stimulate the Anterior Pituitary to do?
- What does the release of these gonadotrophins target and result in?
A
- The release of the gonadotrophins -
- Luteinizing Hormone (LH)
- Follicle Stimulating Hormone
- The Gonads of both male and female to stimulate gametogenesis and production of sex steroids which in turn has a feedback effect on the hypothalamus to regulate GnRH production and in some cases directly affect the anterior pituitary hormones
16
Q
- All mammalian fetuses start out as which sex?
- What causes the gonad to become a testis?
A
- Female
- The sex determining region of the Y chromosome (SRY), interacting with other genes causes the gonad to become a testis
17
Q
The foetal testis produces what Hormone to prevent the female system developing?
A
Anti-Mullerian Hormone
18
Q
Testosterone (which causes masculinisation) is produced where?
A
In the Leydig cells on the interstitial area of the testes
19
Q
Testosterone
- What regulates testosterone production?
- How does the Hormone regulate production of testosterone?
- Testosterone has a negative feedback on the production of which 2 hormones?
A
- Luteinizing Hormone
- LH targets the Leydig cells of the testes, binding with the receptors inducing cAMP second messenger, resulting int he formation of testosterone.
- GnRH and LH
20
Q
- In which cells does spermatogenesis occur?
- What hormone is required to stimulate these cells and therefore is required for spermatogenesis?
A
- Sertoli Cells
- Testosterone
21
Q
What is the Active form of Testosterone?
A
Dihydrotestosterone (DHT)
22
Q
- How is Testosterone transported around the body?
- Where is Testosterone degraded?
- How is it removed from the body?
A
- Highly bound to plasma protiens within the blood
- Testosterone is degraded in the liver
- Testosterone is excreated in the urine
23
Q
Sertoli Cells
- What do Sertoli Cells do?
- What hormone is required for Sertoli Cells to function?
- Sertoli cells are stimulated by which Gonadotrophin?
- What does Sertoli Cells Secrete?
- And what does this do?
A
- Support the developing spermatozoa
- Testosterone
- Follicle Releasing Hormone (FSH)
- Sertoli Cells secrete Inhibin
- Inhibin has a negative feedback on FSH
24
Q
Sertoli cells produce the blood testis barrier, why is this important?
A
The Blood Testis barrier keeps the sperm seperate from the bloodstream as sperm is antigenically different and is the sperm was to get into the blood the body would see it as a foreign object and destroy it.
25
Explain what the result of administration of exogenous androgens (eg anabolic steroids) would be and why this happens.
Administration of Exogenous androgens (anabolic steroids) has a negative feedback on the production of GnRH, which in turn causes a decrease in production of LH & FSH. With a decrease of LH being produced there would then be a decrease in the males own testosterone as well as a reduced spermatogenesis (as it needs FSH and Testosterone). Therefor these drugs can impair male fertility.
26
What would be the result if LH was administered into an entire Male?
LH stimulates Testosterone Production via leydig cells therefore testosterone production would increase
27
What would the result of Casteration be on FSH and LH and why?
FSH and LH would become elevated due to the loss of the negative feedback loops due to the loss of production of Inhibin and Testosterone
28
What is Atresia
Cell Death
29
What is an Oocyte?
AN Oocyte is an immature egg which matures within a follicle
30
In a female the gonads form what, and what do they contain?
Female gonads form ovaries and contain oocytes. A female is born with all the oocytes she is ever going to have.
31
During meiosis the oocyte becomes surounded by granulosa cells which enclose the oocyte in a \_\_\_\_\_\_?
Follicle
32
Follicles develop in responce to what?
The gonadotrophins FSH and LH
33
When a follicle is stimulated by FSH and LH what happens?
Growth, multiplication and function of the surrounding granulosa cells and the theca cells around that.
These gonadotrophins also stimulate the cells to produce hormones and the granulosa cells release oestrogens and inhibin.
34
1. What is Oestrogens?
2. Where is is released from?
3. What is the most potent ovarian form?
4. What does an increase of Oestrogen do to the
1. Reproductive Tract?
2. Behaviour of the animal?
3. the Follicle its self (via a feedback loop)?
1. It is a steroid hormone made from cholesterol cia progesterone and androgen
2. Oestrogens are released from the granulosa cells of the developing follicle
3. 17-B-oestradiol is the most potent ovarian formof Oestrogens
4. Effect of Oestrogen
1. on the Reproductive tract, - Readies the reproductive tract for mating and pregnancy, increases the motility and blood supply of the repro tract.
2. Animal Behavior - Causes Oestrous behaviour "Animal comes into season, heat or oestrus" when it exhibits behaviour that allow mating to occur at a time that coincides with the presence of a fertile oocyte ready for fertilisation.
3. Oestrogen has a postive feedback on a surge of GnRH and thus LH and FSH, to cause final maturation and ovulation of the follicle.
35
1. What is the peptide hormone made by the follicle's granulosa cells?
2. What is the purpose of this hormone (in females)
1. Inhibin
2. Inhibin has a negative feedback on FSH so other follicles are not stimulated to develop once there is already a dominant follicle growing past a certain stage.
36
Explain Follicular Development - Follicular Phase
1. GnRH pulses induce pulses of FSH which stimulkate follicular development
2. Gronulosa cells multiply and produce Oestradiol which primes the reproductive system and feeds back positively to cause an ovulatory surge of LH
3. The LH surge triggers the resumption of meiosis in the oocytes, so they finish their division by the time they are ovulated (except in canines)
4. The wall of the follicle breaks down and the oocyte is released.
37
Explain Ovulation and the development of the Corpus Luteum
1. After the mature follicle reuptures and replease the oocyte the basement membrane around the follicle breaks down and allows the empty follicular cavity to fill with blood, forming the corpus hemorrhagicum (CH)
2. Granulosa and theca cells invade the area and differentiate into luteal cells.
3. LH, along with prolactin in some species stimulates this differentiation and the development ofthese cels into Corpus Luteum (CL)
4. The Corpus Luteum produces and releases progesterone
38
1. What is the "Hormone of Pregnancy"?
2. What is it made from and what kind of hormone is it?
3. How is this Hormone upregulated?
4. What does this hormone do to the uterine lining and glands and why?
5. What does it decrease?
6. How does this hormone allow follicular waves to form but not mature?
1. Progesterone
2. Made from cholersterol therefore its a Steroid Hormone
3. The number of progesterone receptors in reproductive tissue is increased by oestrogen stimulation.
4. Progesterone causes hypertrophy and vasculatisation of the uterine lining and glands to support an embryo.
5. Progesterone decreases uterine motility
6. By modulating GnRH, FSH and LH secretions back to pulses
39
How long does the Corpus Luteum last if not pregnant in most species?
12-16days
40
What is the Luteal Phase?
In most species the CL lasts for about 12-16 days if the animal is not pregnant. This period of progesterone dominance is called the luteal phase. During this time ther will be waves of follicles growth but they do not mature and ovulate, because the progesterone inhibition form the CL prevends the surge of GnRH and gonadotrophins necessary for this further development. Removal of the CL is necessary for another cycle to occur.
41
Luteolysis
1. What is Luteolysis?
2. In animals which are not pregnant what is released from the non-pregnant uterus to cause Luteolysis?
3. How does this cause Luteolysis?
1. The breakdown of the Corpus Luteum
2. PGF2a
3. PGF2a interferes with the blood supply of the CL and inhibits progesterone formation. Once progesterone concentration drop the inhibition of GnRH is removed, allowing a surge of GnRH and of FSH and LH, which can act on follicles that are partially developed enough to have the appropriate receptors for the gonadotrophins. These follicles cna then matire so that they animal returns to the follicular phase and ovulation can occur.
42
What are the 5 stages of the Oestrous Cycle?
1. Proestrus
2. Oestrus
3. Metoestrus
4. Dioestrus
5. Dioestrus
6. Anoestrus
43
What is Polyoestrus?
Meaning having more than one cycle per year.
Meaning - if an animal doesnt get pregent the CL is lysed and another follicle grows and ovulates and the cycle happens again.
44
What is Proestrus?
The time when follicles are undergoing final maturation and development.
The follicular oestrogens are increasing and everything is getting ready for the time of optimal fertility. In most animlas this last for 2-3 days; in the bitch it last for over a week
45
What is Oestrus?
Oestrus is the period of sexual receptivity, with high oestrogens and LH peak.
During this time the female will allow mating, so that sperm arrives in the oviduct at the time when the mature oocyte is ready for fertilisation. in the cow, oestrus lasts for less than 24hours but in a bitch it may last over a week.
46
What is Metoestrus?
The 2 days immediately after ovulation, when the Corpus Luteum is forming.
47
What is Dioestrus?
Corresponds to the luteal phase, when the CL secretes progesterone. In polyoestrus animals there are waves of follicles that grow but do not mature. In the bitch, who only has one cycle every 6 months or so, diestrus (the luteal period) lasts for the same lenght of time, wheather they are pregnant of not. ie about 2 months. After this the bitch enters anoestrus
48
1. What is Anoestrus?
2. For a Mare when are they in anoestrus?
3. For an Ewe when are they in anoestrus?
4. What do these seasonal animals respond to, to start cycling again?
1. Period of sexual quiescence, when there is no ovarian activity at all. The bitch enters anoestrus after each cycle, for about 4 months. Seasonal animals such as horses and sheep are in anoestrus in their off season.
2. For the mare their anoestrus occurs over winter,
3. For the ewe they are in anoestrus in spring/summer
4. These seasonal animals respond to changes in daylenght to start cycling again and then have repeated cycles until they get pregnant or until they return to anoestrus
49
1. What is Induced Ovulation?
2. What are some animals that are induced ovulators?
3. If Ovulation is not induced what happens to the follicles?
1. Induced Ovulation is where ovulation and CL formation depends on the stimulation at mating, which induces an LH surge to cause final maturation and ovulation of the follicle.
2. Cat, Rabbit, Ferret, Alpaca
3. If ovulation is not induced the follicles regress and a new wave forms quickly, so that these animals can seem to be in oestrus almost continuously.
50
Most farm animals, cow, ewe, mare, sow, bitch are what kind of ovulators?
These are Spontaneous Ovulators. Ovulation occurs irrespective of mating. a CL forms and lasts for a variable amount of time, depending on the normal cycle.
51
What are the two functions of the Ovaries?
1. Formation, development and release of female gamates (Egg, Ova)
2. Synthysis and secretion of Oestrogens and progestagens, steroidial hormones that orchestrate events associated with the oestrus(or ovarian or menstral) cycle, pregnancy and partritution
52
