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Animal Production > Hormonal Basis of Reproduction > Flashcards

Hormonal Basis of Reproduction Flashcards

1
Q

What is a hormone?

A

A chemical messenger released from certain cells into circulation to control activity at target cells, tissues, organs

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2
Q

Specificity of hormone targets

A

Specific receptors are needed for each hormone

Target can be a few or many cells, tissues, organs

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3
Q

How can hormones be transported?

A
  1. Free (in solution)- usually for water soluble hormones
  2. Bound to binding proteins- usually lipid soluble hormones
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4
Q

Hormone Receptor locations

A

Can be either:
1. Extracellular

  1. Intracellular
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5
Q

First messenger hormone

A

The hormone that binds to extracellular receptors which results in the release of second messenger inside the cell

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6
Q

Second messenger and examples

A

Intermediate molecule that appears due to a hormone receptor interaction, and can either activate, inhibit, or act as a cofactor to result in change in metabolic reactions

Examples: cAMP, cGMP, Ca2+

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7
Q

Amplification during hormone binding

A

A single/few hormone(s) will bind to receptor, but this binding will result in thousands of second messengers being released

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8
Q

Half-life

A

time required for half of the hormone to disappear from blood/body

will determine how fast the hormone is metabolized

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9
Q

Neurohormones vs. neurotransmitters

A

Both occur when neurons cause the release of chemical messengers

In blood= neurohormones
Across synapse= neurotransmitters

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10
Q

Systemic hormone release

A

Results when neurons cause the release of chemical messengers (neurohormones) into the blood

Sends message anywhere in the body BUT only target cells can respond

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11
Q

Point to point hormone release

A

Results when neuron causes chemical messenger (neurotransmitters) release across a synapse

Sends message to specific cells connected by nerves (direct signal)

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12
Q

Endocrine message/hormone release

A

Endocrine system releases hormones directly into the blood.

Much slower travel but results in the response lasting longer and targeting multiple tissues/cells at the same time

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13
Q

Three ways in which reproductive hormones are classified

A

1.Biochemical structure
2.Source (where they came from)
3. Mode of Action

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14
Q

Types of biochemical structure of reproductive hormones

A

1.Peptide hormones
2.Glycoprotein hormones
3. Steroid hormones
4. Modified fatty acid derived = prostaglandins

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15
Q

Peptide hormones example and half life

A

Protein chains= peptide
Short half life!! *shorter the chain, shorter the half life, which make it very difficult to measure them

Eg. GnRH

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16
Q

Glycoprotein hormones half life and examples

A

LH and FSH

Usually medium half lives (hours)

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17
Q

Steroid hormone examples

A

Estradiols (E2) and progesterones (P4)

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18
Q

Modified fatty acid derived (prostaglandins)

A

-Not considered typical hormones because they are mostly autocrine/paracrine

-important for reproductive management as they help end life of corpus luteum

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19
Q

Peptide hormones structure, solubility, synthesis, storage, secretion, transport, receptors, action

A

Structure: chains of amino acids (3 to >200 aa)

Solubility: hydrophilic

Synthesis: rER, packaged in golgi

Secretion: exocytosis

Transport: mostly free hormone

Receptors: surface of target cell

Action: mostly 2nd messenger system or channel changes; may activate genes

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20
Q

Steroids structure, solubility, synthesis, storage, secretion, transport, half life, receptors, action

A

Structure: cholesterol derivative

Solubility: lipophilic (readily cross membrane)

Synthesis: modification of cholesterol

Storage: Never stored, only precursors

Secretion: diffusion

Transport: bound to plasma proteins

Half life: long

Receptors: intracellular (either cytoplasmic or nuclear)

Action: mostly direct effect on genes to produce new proteins

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21
Q

Pulsatile secretory pattern

A

**episodic or tonic

  • most common pattern of release for hormones

-quick peak, then decline (depends on half life)

-single blood samples are usually inadequate for diagnosis

-ex. LH, testosterone

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22
Q

Surge secretory pattern

A

**Sustained or phasic

-Occurs in preovulatory GnRH/LH surge. Hypothalamus tonic center will release 1-3/hr pulses. Long surges needed for ovulation

23
Q

Cyclic secretory pattern

A
  • cycle pattern
    -Occurs in female reproductive age; influenced by HPG axis and ovarian activity
24
Q

Circadian and circannual secretory pattern

A

**mainly influenced by melatonin

Circadian: release varies across 24hr cycle

Circannual: release varies by season eg. seasonal breeders

25
Q

Hormone secretion feedback control

A
  1. Negative feedback- minimizes change from set point
  2. Positive feedback-increases deviation from setpoint
26
Q

Negative feedback

A

-minimizes deviation= stability= 2 hormones keep each other in normal range

-most common control mechanism

-important in diagnosis of hormone disorders

27
Q

Positive feedback

A
  • increases deviation= instability

-cycle continues until something gives. Increased target hormone leads to hormone release which leads to more release etc.

28
Q

Positive feedback examples

A
  1. Partuition- babys head pushes= receptors receive signal= oxytocin release= contraction= babys head pushes= more oxytocin
  2. Milk letdown- suckling/crying= release of oxytocin= letdown of milk= more suckling
29
Q

Negative feedback loop example

A

Follicle production will result in release of inhibin which will inhibit release of LH and FSH which will decrease follicle production

30
Q

G protein coupled receptors

A

Receptors with 7-pass transmembrane domains

-Act as molecular switches (GTP=on; GDP= off)

31
Q

Hypothalamus control of anterior pituitary

A
  1. Neurosecretory cells secrete releasing or inhibiting factors at the median eminence
  2. Releasing or inhibitory factors taken up by fenestrated capillaries of hypophyseal portal system
  3. Factors transported to anterior pituitary gland to regulate the secretion of hormones at the pars distalis
32
Q

Hypothalamic regulator hormone

A

Gonadotropic releasing hormone (GnRH) released by hypothalamus and transported to anterior pituitary!

33
Q

GnRH

A

-10 aa peptide
- stimulatory

34
Q

What tropic hormones are secreted by anterior pituitary when activated by GnRH?

A

-Follicle stimulating hormone and Luteinizing Hormone

35
Q

FSH

A
  • 213 aa; 33 kDa glycoprotein
    -has both alpha and beta subunits
    -3hr half life
  • pulsatile
36
Q

LH

A
  • 210 aa; 28 kDa glycoprotein
    -has both alpha and beta subunits
    -0.5hr half life
  • pulsatile
37
Q

Molecule size for threshold for filtration of kidneys

A

30-40 kDa threshold to be passed into kidneys

38
Q

FSH and LH receptors and targets

A

-Have FSH and LH G-protein coupled receptors

-Target Ovary (FSH=granulosa cells, LH=theca cells) and Testis (FSH= sertoli cells, LH= Leydig cells)

39
Q

Negative feedback of FSH and LH

A

-estrogen= at low levels is negative, but becomes positive feedback at high levels
-inhibin= selective negative feedback on FSH and plays a role in pulse speed
-progesterone
- testosterone

40
Q

Glycoprotein structure of LH and FSH

A
  • alpha subunit which is common with all and beta subunits which are hormone specific
41
Q

LH and hCG receptors

A

both use the LH receptor. Makes sense because hCG will promote CL

42
Q

Intracellular receptors

A
  • Steroids are lipophilic and will diffuse across cell membrane
    > sex steroids= nuclear receptors
    >other steroids= cytoplasmic

-can alter the rate of DNA transcription in nucleus/alter synthesis of enzymes or structural proteins which will directly impact the activity and structure of the target cell

43
Q

Steroid receptors and their action

A
  1. Intracellular receptors= genomic action; slow response
  2. GPCRs= nongenomic action; fast response
44
Q

Receptor density

A

From 2000- >100000

higher density= higher potential response

45
Q

Receptor- hormone affinity

A

greater affinity= greater response

46
Q

Antagonist interactions at receptors

A

bind the same receptors but cause no or a weak response

47
Q

Agonist interaction at receptor

A

bind the same receptors and cause the same or higher response

48
Q

Additive interaction at receptor

A

The net result from two hormones is greater than each acting alone

49
Q

Synergist interaction at receptors

A

Two hormones binding result in greater effect than the sum of the hormones individually

50
Q

Permissive effects at receptors

A

one hormone is needed for the second hormone to produce its effect

51
Q

Hormone clearance

A

-hormones may or may not be degraded (liver or kidney; or serum proteases or target cells) before elimination in bile and urine
>some can remain biologically active in environment

52
Q

How does liver metabolize hormones?

A

-liver makes hormones water soluble for clearance by glucuronide conjugation or sulfate residues

53
Q

Normal hormone levels

A

-extremely low
-from nanograms (10^-9) to picograms (10^-12)

54
Q

How are hormone levels measured?

A

-Radio immunoassays (RIA)
-Enzyme-linked immunosorbant assay (ELISA)
-immunohistochemistry (IHC)

-Bioassays (in vitro-cells in culture; in vivo-use amphibians)
-radioisotope techniques
-molecular biology techniques

Animal Production (17 decks)

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