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ANIMAL PRODUCTION - Reproduction > 1 – Hormonal Basis of Reproduction > Flashcards

1 – Hormonal Basis of Reproduction Flashcards

1
Q

Hormones

A
  • Chemical messengers
  • Released into circulations
  • Targets need to have specific receptors (extracellular or intracellular)
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2
Q

Hormone Transportation

A

o Free (ex. water-soluble)
o Bound (ex. lipid-soluble)

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3
Q

Hormone classification

A

o Biochemical structure
o Source
o Mode of action

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4
Q

Half-life

A
  • Determines how fast a hormone is metabolized
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5
Q

Systemic regulation

A
  • Controls processes ANYWHERE in the body (only target tissues respond)
    o Neuroendocrine
    o Endocrine
    >Travel slower, but response is longer-lasting and widespread (MULTIPLE tissues at the same time)
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6
Q

Point-to-point regulation

A
  • Controls specific processes at specific cells/tissues connected by NERVES (‘landline phone’)
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7
Q

Biochemical structure

A
  • Peptide (ex. GnRH)
    o Shorter half life (shorter the chain=shorter the half life)
  • Glycoprotein (Ex. LH, FSH)
  • Steroid (Ex. E2, P4)
  • Modified fatty-acids derived (prostaglandins)
    o Autocrine/paracrine function, so not really hormone
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8
Q

Secretion Patterns

A
  1. Pulsatile
  2. Surge
  3. Cyclic
  4. Circadian & circannual
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9
Q
  1. Pulsatile
A

a. Most hormones
b. Reach a peak, then decline to basal levels (dependant on half-life)
c. Single blood sample inadequate for diagnosis
d. Ex. LH, testosterone

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10
Q
  1. Surge
A

a. Preovulatory GnRH/LH surge
b. ONLY in females: surge centre for large pulses back-to-back to stimulate LH surge and cause ovulation

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11
Q
  1. Cyclic
A

a. Reproductive aged females: influenced by HPG axis and ovarian activity

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12
Q
  1. Circadian & circannual
A

a. Circadian: 24hrs
i. LH increases in urine of boys at night
b. Circannual: vary by season
i. Reproductive hormones in seasonal breeders
c. Melatonin: reflects length of night

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13
Q

Negative feedback

A
  • Acts to MINIMIZE deviation from setpoint
  • Leads to STABILITY
  • Main control for most hormones
  • 2 hormones keep each other within normal range
  • GnRH asks for LH, LH signals that it has been received
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14
Q

Positive feedback

A
  • Acts to INCREASE deviation from setpoint
  • Leads to INSTABILITY
  • Occurs only in a few situations
  • Increased target hormone potentiates initial hormone release
  • *cycle continues until something gives in
  • Ex. babies head against cervix, tells uterus to contract, oxytocin released=contraction of uterus (stops at parturition)
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15
Q

G protein-coupled receptors (GPCRs)

A
  • 7-pass transmembrane domains
  • Involved in link between 1st and 2nd messengers
    o Gs or GI act to get or not get cAMP
    o Gq activates PLC to get IP3+DAG to get Ca2+
  • Molecular switches
  • Can be activated by various ligands
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16
Q

Hypothalamic control of anterior pituitary

A

-Parvicellular neurosecretory cells secrete RELEASING or INHIBITORY factors
-Portal vessels: link 2 capillary networks

17
Q

Parvicellular neurosecretory cells secrete RELEASING or INHIBITORY factors

A

o Released near capillaries of HYPOPHYSEAL PORTAL SYSTEM at the median eminence
o Transported efficiently to the anterior pituitary gland to regulate the secretion of pars distalis hormones

18
Q

Hypophyseal portal system

A
  • Ensures regulatory hormones reach cells in A. pituitary before entering general circulation
19
Q

Median eminence

A
  • Swelling near attachment of infundibulum where hypothalamic neurons release regulatory hormones into interstitial fluids
    o Enter the bloodstream through fenestrated capillaries
20
Q

Gonadotropes
* Hypothalamic regulator

A

o GnRH: 10 AA, stimulatory

21
Q

Gonadotropes
* Tropic hormone secreted

A

o FSH: 213AA, 3 hr half life
o LH: 210AA, 0.5 hr half life
o Alpha subunit=common
o Beta subunit=hormone-specific subunit
o *pulsatile
o hCG works on same receptor as LH
* *GnRH pulse, FSH sluggish pulses, LH sharper pulse (due to shorter half life)

22
Q

Gonadotropes
* Target endocrine gland

A

o Ovary: granulosa & theca cells
o Testis: Sertoli & Leydig cells

23
Q

Gonadotropes
* Receptor

A

o FSH and LH receptors (Gs protein coupled)

24
Q

Gonadotropes
- Negative feedback hormone

A

-estrogen
-progesterone
-testosterone
-inhibin

25
Q

o Estrogen

A

 Low levels=negative feedback
 Increased levels=positive feedback=ovulation

26
Q

Cytoplasmic or nuclear receptors

A
  • Nuclear receptors for sex steroids
  • Alter rate of DNA transcription
  • Alter synthesis of enzymes or structural proteins
  • *DIRECTLY affect activity and structure of target cell
27
Q

Genomic action of steroids

A
  • Slow response thru intracellular receptors
    o Ex. mucous secretion by female tract, uterine gland secretion
28
Q

Nongenomic action of steroids

A
  • Fast response thru GPCRs
    o Ex. ion channel alteration->increased myometrial contraction
    o Ex. ion channel inhibition->decreased myometrial contraction
29
Q

Receptor density

A
  • 2,000 to 100,000
  • Higher density=higher potential response
    o Cell type
    o Up-regulation
    o Down-regulation
30
Q

Receptor-hormone affinity

A
  • Greater affinity=greater response
    >native hormone
    >agonists
    >antagonists
    >permissive effects
31
Q

o Agonists (additive effects)

A

 Net result from 2 hormones is greater than each acting alone
* Could have a synergistic effect
 Ex. testosterone & FSH promote sperm production

32
Q

o Antagonists

A

 Net result depends on balance between hormones
 Observed effects are weaker than those produced by either hormone UNOPPOSED
 Ex. estrogen vs. progesterone actions

33
Q

o Permissive effects

A

 One hormone need for second hormone to produce its effect
 Ex. oxytocin works best in presence of estrogen

34
Q

Hormone metabolism and clearance

A
  • Some metabolites remain biologically active in feces/urine
  • Most protein hormones are degraded by liver & kidneys
    o Others by serum proteases or target cells
  • In liver, steroids metabolized
    o Become water-soluble and inactivated to be excreted in urine or feces
35
Q

Measurement of hormone levels

A
  • Normal levels are from nanograms to picograms per mL blood
  • Immunologic methods
  • Bioassays
  • Radioisotope techniques
  • Molecular biology techniques
36
Q
  • Immunologic methods
A

o RIA
o ELISA
o IHC

37
Q
  • Bioassays
A

o In vitro, cells in culture
o In vivo, amphibians form MSH

ANIMAL PRODUCTION - Reproduction (17 decks)

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