Lecture Outline - PowerPoint PPT Presentation

Lecture outline l.jpg
Download
1 / 29

  • 256 Views
  • Updated On :
  • Presentation posted in:

Lecture Outline. Early Sexual Development Hormonal Control of Sexual Behavior Neural Control of Sexual Behavior. Markers of Sex. Genetic: XX or XY (23rd chromosome pair) Gonadal: testes or ovaries Hormonal: Estrogen/androgen Internal reproductive: presence of

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Presentation

Lecture Outline

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Lecture outline l.jpg

Lecture Outline

  • Early Sexual Development

  • Hormonal Control of Sexual Behavior

  • Neural Control of Sexual Behavior


Markers of sex l.jpg

Markers of Sex

  • Genetic: XX or XY (23rd chromosome pair)

  • Gonadal: testes or ovaries

  • Hormonal: Estrogen/androgen

  • Internal reproductive: presence of

    • Müllerian system or Wolffian system

  • External reproductive


Sexual development l.jpg

Sexual Development

  • “Nature’s Impulse is to create a female”

  • In the absence of androgen, female pattern develops:

    • Müllerian system

    • External genitalia

    • Brain


Male sexual development l.jpg

Male Sexual Development

  • Sry gene on Y chromosome induces development of testis (H-Y antigen)

    • Testes secrete:

      • Anti-Müllerian hormone (defeminizing effect)

      • Androgens: stimulate Wolffian system development

    • External male reproductive structures require dihydrotestosterone (androgen)


Alterations in development l.jpg

Androgen insensitivity

XY-females

Adrenogenital syndrome

Deficit in adrenal cortisol release

Adrenal hyperactivity

Excess adrenal androgens

Turner’s syndrome- XO, apparent female no ovaries

Sex reassignments-1975 twin’s case.

Other species- e.g. Hyena

Increasingly earlier onset of puberty in humans

No real external hermaphrodites

Alterations in Development


Female hyena pup mom l.jpg

Female Hyena Pup & Mom


Adult sexual behaviors rodent l.jpg

Male

Intromission

Pelvic thrusting

Ejaculation

Female

Lordosis response

Receptivity

Proceptivity

Attractiveness

Adult Sexual Behaviors (Rodent)


Adult sexual behavior females and hormones l.jpg

Adult Sexual Behavior: Females and Hormones

  • Organizational: Lack of exposure to androgens results in feminization

  • In humans:

    • Menstrual cycle

    • Other influences-male initiation

    • Androgens- sex drive

  • Rodent Adult sexual behavior depends on

    • Estrogen followed by progesterone: facilitates:

      • Receptivity, proceptivity, and attractiveness

    • Oxytocin: contributes to orgasm


Adult sexual behavior males and hormones l.jpg

Adult Sexual Behavior: Males and Hormones

  • Early androgen exposure promotes:

    • Behavioral defeminization as an adult

    • Behavioral masculinization

    • Due to estrogen derived from testosterone

  • Activational effects:

    • Male sexual behavior requires testosterone, estrogen

    • Oxytocin may contribute to orgasm

    • Vasopressin may mediate male sexual refractory period

  • Contrary to popular belief:

    • Levels of sexuality (macho) are not correlated with levels of testosterone.

    • Sex drive is not increased with increases in testosterone


  • Anabolic steroid abuse l.jpg

    Anabolic Steroid Abuse

    • Males-

      • increases musculature, athletic performance.

      • Used cosmetically.

      • Causes tissue damage, emotional changes, testicular atrophy, breast development ,oral-liver damage.

    • Females-

      • Causes masculinization –many symptoms.


    Sexual orientation l.jpg

    Sexual Orientation

    • Most work on males

    • Genetic factors

      • twin studies

    • Hormones

      • Early exposure to synthetic estrogens cause high rates of female bisexuality

      • Congenital adrenal hyperplasis-increases homosexuality in females (ca. 48%), normal males.

    • Brain differences-

      • size, lateralization, anatomy (SCN, ant. commisure, INAH-3).

      • Identity-(BNST)


    Pheromones l.jpg

    Pheromones

    • Rodents and most mammals:

    • Vomeronasal organ- accessory olfactory bulb

      • Lee-Boot– estrous ceases in grouped females

      • Whitten - male urine reinitiates estrous

      • Vandenberg - male urine speeds onset of puberty.

      • Bruce- new male urine aborts pregnancy.

    • In human females: olfactory stimuli

      • Synchronized menstrual cycles

      • Androstenol- increased social interaction

      • Little evidence for sex attractants


    Neural control of male sexual behavior l.jpg

    Neural Control of Male Sexual Behavior

    • Adult sexual behavior depends on sufficient plasma testosterone

      • Hormone effects activity of

        • Sensory neurons on sex organs

        • Spinal cord neurons that participate in sexual reflexes (e.g. bulbocavernous nuc.)

        • Neurons within medial preoptic area (MPA)


    Medial preoptic area l.jpg

    Medial Preoptic Area

    • MPA involvement in male sexual behavior:

      • MPA contains testosterone receptors

        • Infusions of testosterone into MPA restore copulation in castrated rats

      • MPA neurons are active during copulation

        • Both firing rate and c-fos studies

      • Electrical stimulation of MPA induces copulation

      • Lesions of the MPA disrupt copulation


    Neurotransmitters and male sexual behavior l.jpg

    Neurotransmitters and Male Sexual Behavior

    • Oxytocin: increases likelihood of penile erections, speeds latency to ejaculation

    • Vasopressin: may facilitate male sexual behavior

    • Dopamine: may facilitate male sexual behavior

      • Sexual activity increases dopamine release within the MPA

      • Intra-MPA infusion of DA antagonist impairs male copulation


    Female sexual behavior ventromedial hypothalamus l.jpg

    Female Sexual Behavior: Ventromedial Hypothalamus

    • VMH may play a critical role in modulating female sexual behavior in rats:

      • VMH lesions block lordosis in female rats after estrogen/progesterone

      • Electrical stimulation of VMH facilitates lordosis

      • Copulation is associated with fos production in the VMH (and amygdala)

      • Connections of VMH with amygdala and PAG


    Hormonal effects via the vmh l.jpg

    Hormonal Effects Via the VMH

    • Female sexual behavior is influenced by:

      • Estrogen/progesterone:

        • VMH infusions restores sexual activity in ovariectomized rats

      • Oxytocin

        • Receptors are found within the VMH

        • Oxytocin receptors depend on earlier estrogen/progesterone treatments

        • Oxytocin infusions into VMH facilitate female sexual behavior

        • VMH infusions of oxytocin antagonist decrease female sexual behavior


  • Login