6 topics with concise breakdowns: definitions, key facts, and class questions.
This section covers the physiological mechanisms responsible for human reproduction and sexual activity. Here, we examine in detail the functioning of the male and female reproductive systems, endocrine regulation (with an emphasis on female sex hormones), as well as the hemodynamics and neurophysiology of sexual intercourse, up to the process of fertilization.
Neuroendocrine regulation traditionally causes the most difficulty in classes and exams. Instructors are sure to ask you about the phases of the ovarian-menstrual cycle, the mechanisms of erection and ejaculation, and the cascade of reactions during the fusion of the spermatozoon and the oocyte. A deep understanding of these topics is not only the key to passing your medical physiology exam successfully, but also the foundation for future studies in obstetrics, gynecology, and urology.
Gonadal (true) sex reflects only the differentiation and presence of specific glands—ovaries or testes. Gametic sex is the functional capacity of these glands to successfully produce oocytes or spermatozoa.
Which hormones are required for complete spermatogenesis?
The primary stimulator is testosterone. However, the process cannot occur without the involvement of FSH, and the final stages of maturation require the presence of estrogens and LH.
Why does a sharp surge of LH occur before ovulation?
The LH surge is driven by a peak rise in estrogen levels 24–36 hours before ovulation. At this point, the hypothalamus-pituitary system responds to estrogens via positive rather than negative feedback.
What is the mechanism of estrogen synthesis in the ovaries?
In the theca cells, androgens are synthesized under the influence of LH. They are then transported to the granulosa cells, where they are converted into estrogens by the enzyme aromatase (whose activation is stimulated by FSH).
In which segments of the spinal cord are the centers of erection and ejaculation located?
The erection center is located in the III–IV sacral segments (S3–S4), while the ejaculation center is located in the II–V lumbar segments (L2–L5).
Where exactly is oxytocin, which participates in gamete transport, synthesized?
Oxytocin is produced by neurosecretory cells of the supraoptic and paraventricular nuclei of the hypothalamus, after which it regulates the release of seminal fluid and uterine contractions.
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