Lecture Notes - Control of Sexual Behavior

Overview

  • Discussion about sexual behavior on Valentine’s Day
  • Distinction between love and sex

Lecture Goals

  • Explore the connection between motivation for sex and physiological mechanisms
  • Discuss the stages of sexual behavior

Reminder from Previous Lecture

  • Hormones do not change sexual orientation
  • Low testosterone does not impede erections for men

Two Stages of Sexual Behavior

  1. Appetitive Behaviors

    • Behaviors aimed at preparing to find a target for carrying out motivational behavior
    • Example in food: Foraging (appetitive) vs. Eating (consummatory)
    • For sex: Motivation to have sex (appetitive) vs. Having sex (consummatory)

  2. Neural Circuits of Erection and Orgasm

    • Sexual motivation often stimulated by external stimuli but can also be internally driven
    • Pheromones and their significance in sexual attraction

Pheromones

  • Definition: Chemical signals that influence behavior in other individuals of the same species

  • Common in insects and some mammals, potentially present in humans (debated)

    • Example in insects: Specific molecules released to trigger mating behavior
    • In mammals: More complex interactions with multiple molecules involved

  • Human Pheromones:

    • Possible evidence of pheromones in humans, e.g., through T-shirt smelling studies
      • Findings: Men rated women’s T-shirts as more attractive during ovulation phases
    • Androstenone: Male pheromone found in sweat, studies show its impact on mood and sexual arousal in women
    • MHC (Major Histocompatibility Complex): Women prefer men with dissimilar MHC genes for better offspring immune function

Hormones and Sexual Motivation

  • Male sex hormones (testosterone) drive sexual motivation
  • Testosterone Levels:
    • Fluctuate with anticipation of sexual activity, influencing motivation levels
    • Low testosterone linked to decreased motivation but not sexual ability
    • Anabolic steroids (external testosterone) increase sexual motivation
  • Women: Also produce testosterone; influence of estrogen and testosterone on sexual motivation, particularly during the menstrual cycle

Effects of Contraceptive Pills

  • Women’s sexual attraction can change based on hormonal status (e.g., when stopping the pill)
  • Association between partner smell attractiveness and menstrual phase

Neural Mechanisms of Sexual Response

  1. Physiological Arousal Stages: Excitement and plateau discussed alongside orgasm
  2. Nervous System Control:
    • Parasympathetic Nervous System: Controls erection/lubrication through acetylcholine
    • Sympathetic Nervous System: Triggers orgasm
    • Local reflex arc possible below spinal cord injury; demonstrates interaction of psychological and physiological aspects

Erectile Dysfunction

  • Always physical; could have psychological components that interfere with sexual responsiveness.

Orgasm and Evaluation

  • Masters and Johnson’s four stages of sexual response: excitement, plateau, orgasm, resolution
  • Understanding of physiological mechanics important

Questions and Further Discussion

  • Importance of hormonal balance in attraction and sexual motivation
  • Exploring concepts of asexuality and its disconnection from sexual attraction / motivation

Summary

  • Sexual behavior involves both innate biological responses (including pheromones and hormones) and learned experiences/associations.
  • Motivation for sex is multifaceted involving complex interactions between chemicals in the body and external stimuli.