1. PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 27 The Male Reproductive System: Hormonal Regulation

2. Copyright © 2010 Pearson Education, Inc. Male Reproductive System – Hormonal Regulation Hormonal Regulation of Male Reproductive Function – pp. 1038 – 1040

3. Copyright © 2010 Pearson Education, Inc. Hormonal Regulation of Male Reproductive Function A sequence of hormonal regulatory events involving the hypothalamus, anterior pituitary gland, and the testes The hypothalamic-pituitary-gonadal (HPG) axis

4. Copyright © 2010 Pearson Education, Inc. HPG Axis 1.Hypothalamus releases gonadotropin- releasing hormone (GnRH) 2.GnRH stimulates the anterior pituitary to secrete FSH and LH 3.FSH causes sustentacular cells to release androgen-binding protein (ABP), which makes spermatogenic cell receptive to testosterone 4.LH stimulates interstitial cells to release testosterone

5. Copyright © 2010 Pearson Education, Inc. HPG Axis 5.Testosterone is the final trigger for spermatogenesis 6.Feedback inhibition on the hypothalamus and pituitary results from Rising levels of testosterone Inhibin (released when sperm count is high)

6. Copyright © 2010 Pearson Education, Inc. Figure 27.9 Anterior pituitary Inhibin GnRH Testosterone Via portal blood Interstitial cells Sustentacular cell Spermatogenic cells Seminiferous tubule Somatic and psychological effects at other body sites LH FSH 1 2 2 3 4 5 6 78 Stimulates Inhibits

7. Copyright © 2010 Pearson Education, Inc. Mechanism and Effects of Testosterone Activity Testosterone Synthesized from cholesterol Transformed to exert its effects on some target cells Dihydrotestosterone (DHT) in the prostate Estrogen in some neurons in the brain

8. Copyright © 2010 Pearson Education, Inc. Mechanism and Effects of Testosterone Activity Prompts spermatogenesis Targets all accessory organs; deficiency leads to atrophy Has multiple anabolic effects throughout the body Is the basis of the sex drive (libido) in males

9. Copyright © 2010 Pearson Education, Inc. Male Secondary Sex Characteristics Features induced in the nonreproductive organs by male sex hormones (mainly testosterone) Appearance of pubic, axillary, and facial hair Enhanced growth of the chest and deepening of the voice Skin thickens and becomes oily Bones grow and increase in density Skeletal muscles increase in size and mass