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Exam block 3 > Exam 2: Lecture 21: Reproductive Endocrinology > Flashcards

Exam 2: Lecture 21: Reproductive Endocrinology Flashcards

1
Q

What is a simple neural reflex?

A

-Employs nerves that release simple neurotransmitters directly onto target tissue

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2
Q

What is a neuroendocrine reflex?

A

-Requires neurohormone (released by neuron) to enter blood & act on remote target tissue

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3
Q

___ is the control center for repro hormones

A

The hypothalamus

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4
Q

Neurohormones enter

A

bloodstream

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5
Q

Explain the steps of a simple neural reflex

A
  1. Stimulus (temp. tactile, visual, etc.)
  2. Sensory neurons (afferent, recognition of stimulus)
  3. Transmission
  4. Efferent neurons
  5. Neurotransmitter
  6. Target tissue
  7. Response by target tissue
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6
Q

Explain the steps of a neuroendocrine reflex

A
  1. Stimulus (temp. tactile, visual, etc.)
  2. Sensory neurons (afferent, recognition of stimulus)
  3. Transmission
  4. Efferent neurons
  5. Hypothalamus
  6. Neurohormone
  7. Blood
  8. Target tissue
  9. Response by target tissue
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7
Q

The ____ is the neural control center for reproductive hormones

A

hypothalamus

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8
Q

What 3 things have direct effect on reproduction?

A

-Surge center
-Tonic center
-PVN (paraventricular nucleus)
note: all close to each other & 3rd ventricle

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9
Q

Where is the pituitary?

A

-Positioned in depression of sphenoid bone, the sella turcica

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10
Q

The ____ separates the lateral portions of the hypothalamus

A

Third ventricle

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11
Q

What does the Hypothalamo-Hypophyseal Portal System do?

A

-Allows minute quantities of releasing hormones to act on the anterior pituitary before they are diluted by general circulation

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12
Q

How does the HHP system work? (Hypothalamo-Hypophyseal Portal System)

A

-Axons from neurons in the surge center & tonic center extend to stalk region where they terminate on blood vessels of HHP system

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13
Q

What is the relationship between PVN & posterior pituitary?

A

-Axons from neurons originating in hypothalamus (PVN) extend into posterior lobe of pituitary where they release their neurohormones into a capillary plexus

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14
Q

____ does not have a portal system

A

posterior pituitary
-Neurohormones are deposited directly into systemic circulation

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15
Q

What is positive feedback?

A

Something influences the stimulation of another

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16
Q

What is negative feedback?

A

Something influences the suppression of another

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17
Q

What are some characteristics of reproductive hormones?

A

-Act in small quantities
-Posses short half-lives
-Bind specific receptors
-Can cause release of other hormones
-Can stimulate the gonads
-Can cause sexual promotion (ex: steroids)
-Can help maintain pregnancy
-Luteolysis

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18
Q

What would eliminate pregnancy?

A

-Luteolysis

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19
Q

What are the 3 ways a hormone is classified?

A

-Source
-Mode of action
-Biochemical classification

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20
Q

What are the hypothalamic hormones?

A

-GnRH (causes release of LH & FSH)

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21
Q

What are the pituitary hormones?

A

-Follicle Stimulating Hormons (FSH)
-Luteinizing Hormone (LH)
-Prolactin
-Oxytocin

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22
Q

What are the gonadal hormones?

A

-PGF2a (made in uterus)
-Progesterone (made in ovary, CL)
-Estrogen (made in ovary, follicle)
-Equine chorionic gonadotropin (made in placenta)
-Human chorionic gonadotropin (made in placenta)

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23
Q

Where are neurohormones synthesized & released & what are they?

A

-Synthesized by neurons
-Released directly into blood
-GnRH, FSH, LH, Oxytocin

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24
Q

Where are releasing hormones synthesized, what do they do, and what are they?

A

-Synthesized by neurons in hypothalamus & cause release of other hormones from anterior pituitary
-Can also be classified as neurohormone b/c synthesized & released by neurons
-GnRH

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25
Where are **Gonadotropins** synthesized, what do they do, and what are they?
-Synthesized & secreted by specialized cells in anterior lobe of pituitary gland -Have stimulatory effect on gonads -FSH, LH
26
Where are **sexual promoters** secreted, what do they do, and what are they?
-Secreted by gonads to stimulate reproductive tract, regulate function of hypothalamus & anterior pituitary & regulate reproductive behavior -Estrogen, Progesterone, Testosterone, eCG, hCG
27
What are the hormones classified under the **pregnancy maintenance hormone** mode of action & what does it do?
-High concentration during pregnancy -Responsible for maintaining pregnancy & assisting female in lactation ability -Progestins, Placental Lactogen
28
What are the **general metabolic hormones** and what do they do?
-Promote metabolic well-being -Thyroxin, adrenal corticoids, growth hormone
29
What are the **lutyletic hormones** & what do they do?
-Cause destruction of the CL -PGF2a
30
What is the peptide classification of hormones and what falls under it?
-Very small protein -GnRH is a decapeptide, Prolactin, Relaxin
31
What is the glycoprotein classification of hormones and what falls under it?
-A polypeptide protein that has carbohydrate moieties -Large protein -FSH, LH, Inhibin
32
What is the steroid classification of hormones and what falls under it?
-Have a common molecular nucleus -Progesterone, Testosterone, Estradiol
33
What is the prostaglandins classification of hormones and what falls under it?
-Lipid based -PGF2a, Prostaglandin E2
34
Why does the biochemical classification of reproductive hormones matter?
-The body doesn't notice the really small hormones -So, have to give a small hormone to induce ovulation or the immune system will notice
35
_____ can be taken and through different enzymatic conversions go to pregnenolone, progesterone, testosterone, or estradiol
Cholesterol
36
Reproductive hormones are required to bind to
specific receptors on their target cells
37
What do protein hormones do?
-Bind to plasma membrane bound receptors
38
What do steroid hormones do?
-Travel freely through plasma membrane into cytoplasm & bind directly to specific nuclear receptors
39
Binding of hormones results in
**new protein** synthesis
40
Steroid hormones can bind to
-Membrane receptors & nuclear receptors
41
What is the fast response steroid hormone action?
-Binds to a membrane receptor causing protein production
42
What are examples of fast response steroid hormone action?
-Estradiol - increased myometrial contractions (period cramps) -Progesterone - decreases myometrial contractions
43
What is the slow response steroid hormone action?
-Binds to nuclear receptor inside cell causing protein production
44
What are examples of slow response steroid hormone action?
-Estradiol - mucous secretion by female tract -Progesterone - uterine gland secretion
45
____ ultimately regulates GnRH
CNS
46
The tonic center is in
Female & male
47
The surge center is in
Females only
48
Hypothalamic nuclei nerve cell bodies are found
in the hypothalamus
49
What are the clusters of specific hypothalamic nuclei?
-GnRH -TRH -CRH
50
Where do hypothalamic nuclei axons terminate
Terminate on capillaries in the H-HPS (Hypothalamo-Pituitary Gonadal Axis) -Picogram amounts released -Neurohormones released into blood
51
____ regulates reproduction primarily based upon a **positive & negative feedback system**
Hypothalamo-Pituitary Gonadal Axis
52
Hormones can have _____ feedback on different areas
both positive & negative feedback on different areas
53
What are the key players in the HPG axis?
-GnRH -Gonadotropins -Oxytocin -Gonadal hormones
54
What is GnRH and where is it?
-Gonadotropin Releasing Hormone -Hypothalmic nuclei
55
What are the gonadotrops and where are they?
-FSH, LH, Prolactin -Anterior pituitary
56
Where is oxytocin?
-Made in paraventricular nucleus & transported to posterior pituitary for release into bloodstream
57
What are the gonadal hormones?
-Testosterone, estrogen, etc.
58
The strength of hormone action depends on
-Pattern & duration of secretion -Half-life -Receptor density -Receptor-hormon affinity
59
Steroid hormones are metabolized
by the liver
60
Protein hormones are degraded
in the liver & kidneys
61
Which of the following does the pituitary secrete? A. Oxytocin, FSH, & LH B. Testosterone & Inhibin C. FSH and Progesterone D. Estrogen & Inhibin E. LH & GnRH
A. Oxytocin, FSH & LH
62
The tonic center releases ____ amounts of GnRH
small
63
The surge center releases ____ amounts of GnRH
large
64
What is the difference in the male and female hypothalamus?
-Males do not have a surge center
65
Why do males not have a surge center?
-Testosterone defeminizes hypothalamus during embryogenesis & eliminates GnRH surge center in male -Female has no testes, so does not produce testosterone
66
What is the mechanism of "defeminization"?
-Testosterone produced by testes in developing male fetus penetrate BBB (blood brain barrier) -Once testosterone is in brain, it is converted to Estradiol -So, estradiol actually defeminizes the hypothalamus and causes the surge center to not develop
67
Why does estradiol in females not defeminize the surge center?
-In female, estradiol is bound by alpha-fetoprotein which prevents the estradiol from crossing the BBB
68
____ surges just before the huge release of LH
Estrogen
69
What is puberty in domestic species?
-Process of acquiring reproductive competence
70
Most mammalian systems are functional at birth, what is the exception?
-Reproductive system
71
Puberty is a ____ and _____ maturation process
gradual and multifactorial (not a single event)
72
Onset of puberty is dependent upon
the ability of hypothalamic neurons to produce GnRH in sufficient quantities to support gametogenesis
73
What are the many female definitions of puberty?
-Age at 1st heat -Age at 1st ovulation -Age at which female can support pregnancy w/out problems
74
What are the many male definitions of pregnancy?
-Age when behavioral traits evident -Age at 1st ejaculation -Age when spermatozoa 1st appear in ejaculate or urine -Age which threshold # of spermatozoa reached in ejaculate
75
What is the physiologic definition of puberty for male & female?
Specific hypothalamic nuclei are capable of releasing adequate quantities of GnRH to -Cause gonadotropin release (FSH & LH) -Ultimately, cause ovulation & spermatogenesis
76
Development of hypothalamic nuclei are dependent on
-Threshold body size -Nutritional factors -Environmental cues -Photoperiod -Genetics
77
In the male, the physiologic onset of puberty is brought about because
of decreased hypothalamic sensitivity to negative feedback by Testosterone/Estradiol
78
What happens physiologically before puberty?
-GnRH neurons in tonic & surge centers of hypothalamus release low amplitude & low frequency pulses of GnRH
79
What happens physiologically after puberty?
-Tonic center controls basal levels of GnRH which are higher than in prepubertal females b/c the pulse frequency increases -Surge center controls the preovulatory surge of GnRH
80
What time frame is required for the pulse frequency to become high enough for puberty to be achieved?
~2 months
81
In the prepubertal female, the surge center is sensitive to ____. BUT what?
-Sensitive to estradiol -BUT surge center cannot release ovulatory quantities of GnRH b/c ovary cannot secrete high enough levels of Estradiol
82
What are possible influences of metabolic signals upon GnRH neurons?
-Blood glucose concentrations -Blood leptin -Blood fatty acids

Exam block 3 (39 decks)

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