Regulation of reproduction

Reproduction is regulated by

1. Nervous system

The response of nervous system is rapid and it is further classified into
  1. Simple neural reflex; Afferent neuron => interneuron => efferent neuron => target tissue.
  2. Neuro-endocrine reflex; Afferent neuron => interneuron => efferent neuron => endocrine organ => release of hormone => target tissue

2. Endocrine system

Its response is not rapid as that of nervous system. It works by the release of hormones.

Examples of simple neural reflex control

  • Muscle for sexual behavior and ejaculation.
  • Muscle for scrotal tone.
  • Scrotal sweat glands.

Examples of neuro-endocrine reflex control

  • Sperm movement into ductus defrens of male.
  • Milk ejection in female.
  • Parturition.

Classification of reproductive hormones

Hormones are classified on the following basis
  1. According to their source of release.
  2. According to their mechanism of action
  3. Biochemical classification.

1. Source

  • Hypothalamus
  • Pituitary gland
  • Gonads
  • Uterus
  • Placenta

2. Mode of action

  • Nuclear receptors
  • Cell surface receptors

3. Biochemical

  • Protein/peptide
  • Glycoprotein
  • Steroids
  • Eicosanoids/fatty acid derivatives/ PGS

Biochemical classification

1. Protein peptide (have cell surface receptors)

Protein;  PRL (prolactin), and PL (placental lactogen).
Peptide; GnRH (gonadotropin releasing hormone), RLN (relaxin), OT (oxytocin).

2. Glycoprotein

LH (luteinizing hormone), FSH (follicle stimulating hormone), eCG/PMSG (equine chorionic glycoprotein/ Pregnant mare serum gonadotropin), hCG (human chorionic gonadotropin), Inhibin, and activin.

3. Steroids (have nuclear receptors)

E2 (estradiol), P4 (Progesterone), and T (testosterone).

4. Prostaglandin

PGE2 (prostaglandin E2), and PGF2 a (prostaglandin f2 a).

Mechanism of hormones release and action

a. Autocrine

Hormone is released and act on the same cell.

b. Paracrine

Hormone is released and act on the adjacent cell.

c. Intracrine

Hormone is produced inside cell and not released. It works within the same cell.

d. Juxtacrine

Hormone remain in vesicle in cell membrane of producing cell but attach with receptors on adjacent cells.

e. Endocrine

Hormone is released into the blood.

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