JR

Lecture 5 – Sexual Arousal, Response, Behaviors & Alternative Sexuality

Disclaimer on Gendered Language

  • The original research and many cited studies employ strictly binary, gendered terminology ("men" vs. "women").
  • Such usage excludes non-binary, trans, and gender-diverse populations, rendering these traditions inherently homo- and trans-phobic.
  • Ongoing reform in STEM methodology is needed to develop inclusive, representative science; students are encouraged to pursue and design such approaches.

Definition & Core Features of Sexual Arousal

  • Sexual arousal = activation of an intricate reflex network involving sexual organs, hormones, the peripheral & central nervous systems, and—crucially—the brain.
    • Not solely sensory; may arise from fantasy or erotic imagery with no tactile stimulation.
    • Some individuals can reach orgasm from fantasy alone (Komisaruk et al., 2006).
  • Modulating factors:
    • Emotional state, intimacy level, memory, cultural scripts.
    • Illustrative variability: explicit sexual language is highly arousing for some, threatening for others.

Individual & Cultural Variability in Erotic Triggers

  • No universal response to any given stimulus.
  • Cultural examples:
    • Uncircumcised penises = normative in Europe; perceived as a turn-off by some Americans.
  • The brain—as repository of memories & values—dominates individual “arousability.”

Neural Basis of Sexual Arousal

Cerebral Cortex
  • Outer layer of cerebral hemispheres; governs higher mental processes (memory, language, imagination, reasoning).
  • Purely mental events (fantasy) originate here.
  • Can both amplify and inhibit arousal.
Limbic System
  • Emotion- & motivation-centered network critical for human sexuality.
  • Key components:
    • Cingulate gyrus
    • Portions of the hypothalamus (incl. Medial Preoptic Area, MPOA) – regulates hormone release, biological rhythms, sex drive.
    • Amygdala – emotional salience, threat evaluation.
    • Hippocampus – memory integration.
Neuroimaging Evidence (fMRI)
  • Functional Magnetic Resonance Imaging maps blood-flow (neural activation) in real time.
  • Parada et al. 2016 study:
    • Participants: 20 males + 20 females viewed erotic video clips.
    • Result: significant subjective arousal in both groups.
    • Intensity correlated with activation in specific parietal-lobe regions.
    • Females exhibited additional activation in the lateral occipital cortex.
Neurotransmitters
  • Dopamine
    • Facilitates sexual arousal/activity; stimulates MPOA; central to reward circuitry.
  • Serotonin
    • Inhibits arousal/activity; implicated in sexual satiety.

Sensory Contributions to Sexual Arousal

Touch (Primary Trigger)
  • Sense most frequently initiating arousal.
  • Erogenous zones = areas where tactile stimulation → intense arousal.
    • Primary: densely innervated, typically near body openings (genitals, mouth, ears, anus).
    • Secondary: become sensitive through personal experience; idiosyncratic.
  • Commonly reported zones (all genders):
    • Mouth/lips, ears, back & nape of neck, inner thigh, lower back, nipples/breasts, clitoris & vagina, penis & scrotum, perineum, pubic hairline.
Vision
  • Kinsey’s early work: men reported more visual excitability than women—likely influenced by social norms/opportunities.
  • Contemporary data: physiological genital responses to erotica are similar across genders, yet self-reports may diverge (women may under-report due to social pressures).
  • Genital arousal ≠ automatic indication of sexual desire.
Smell (Olfaction)
  • Olfactory signals project directly to the limbic system.
  • Swedish 2005 study isolated possible human pheromones:
    • Estratetraenol (EST) – estrogen-like; activates hypothalamus of those attracted to women.
    • Androstadienone (AND) – testosterone derivative; activates hypothalamus of those attracted to men.
  • Evidence for pheromonal sexual attraction in humans remains inconclusive.
Taste
  • Least studied; appears minor but intimate because substances enter the body.
  • Bodily secretions (semen, vaginal fluids) can be experienced; preferences vary with secretion type & arousal state.
  • Marketing (breath mints, flavored lubricants/douches) can create insecurity or mask natural tastes/smells.
Hearing
  • Erotic conversation, moans, orgasmic cries may be arousing or distracting depending on individual and social conditioning.
  • Open verbal feedback guides partners (e.g., “slower,” “just like that”), enhancing pleasure and reducing ambiguity.

External Chemical Influences

Aphrodisiacs
  • Substances believed to heighten sexual response; actual efficacy predominantly placebo-driven.
  • Common (mis)classified agents:
    • “Poppers” (amyl nitrate) – blood-vessel dilation.
    • Alcohol – increases subjective arousal but impairs physiological performance.
Anaphrodisiacs (Sex-Drive Inhibitors)
  • Antidepressants affecting serotonin (e.g., Prozac) – delayed orgasm/erection.
  • Opioids (codeine, heroin, oxycontin, dextromethorphan) – diminish overall sexual function.
  • Nicotine – vasoconstriction; reduces genital engorgement capacity.

Hormonal Control of Sexual Function

Estrogens
  • Support general well-being, vaginal tissue elasticity, lubrication.
  • High pharmacologic doses can decrease libido.
  • Post-menopausal/Oophorectomy estrogen therapy ↑ lubrication, may modestly ↑ desire, pleasure, orgasmic capacity.
Testosterone (T)
  • Stronger link to libido than to physiological performance.
  • Castration (surgical/chemical) → drastic T reduction & corresponding libido decline.
  • Some jurisdictions administer weekly Depo-Provera injections to sex offenders to ↓ T & sexual drive (ethical debates; historical roots in eugenics, racism, ableism, classism).

Models of Sexual Response

Masters & Johnson – Human Sexual Response Cycle (HSRC)
  • Data 1957{-}1965; 694 participants; >10\,000 observed sexual acts.
  • Four phases driven by two physiologic reactions (vasocongestion & myotonia):
    1. Excitement
    • Onset: seconds to hours; genital engorgement, lubrication, sex flush, nipple erection, increased HR/BP.
    • Male specifics: penile erection, testes elevation.
    • Female specifics: clitoral swelling, labial changes, uterus elevation, breast enlargement.
    1. Plateau
    • Intensified vasocongestion; orgasmic platform (outer \frac{1}{3} vagina) forms; clitoris withdraws; testes fully elevated; pre-ejaculatory (Cowper’s) fluid may appear.
    • Sharp rise in myotonia & cardiopulmonary parameters.
    1. Orgasm
    • Duration: a few seconds; rhythmic contractions (3{-}15 pelvic spasms).
    • Emission → semen pools in urethral bulb; expulsion → ejaculation via penile root contractions.
    • Female: vaginal/uterine contractions; possible Skene’s gland expulsion.
    • Neurochemicals: prolactin (refractory), oxytocin/vasopressin (bonding, contractions), endorphins (pleasure).
    1. Resolution
    • Rapid return to baseline if orgasm occurred; slower if not.
    • Refractory period (predominantly in penis-owners) – minutes to longer; linked to prolactin surge.
Age-Related Changes
  • Diminished intensity of all phases; slower erection/lubrication; reduced orgasmic contractions; accelerated resolution.
Dual Control Model (Bancroft & Janssen 2000{-}2017)
  • Sexual output = balance of two semi-independent systems:
    • Sexual Excitation System (SES) – "gas pedal."
    • Sexual Inhibition System (SIS) – "brake pedal."
  • Individuals fall along a normal distribution for both SES & SIS sensitivity, explaining variability in behaviors and problems.

Sexual Difficulties & Remediation

  • Satisfaction is subjective; presence/absence of dysfunction does not automatically determine contentment.
  • Common problems (may or may not cause distress):
    • Excitement-phase: Inhibited desire, Erectile Disorder (ED), Persistent Genital Arousal Disorder (PGAD).
    • Orgasm-phase: Anorgasmia, rapid or delayed orgasm.
      • Solutions: self-stimulation, start-stop technique, position changes, open communication, low-dose SSRIs for rapid ejaculation.
    • Dyspareunia (painful intercourse) & Vaginismus: involuntary vaginal muscle contractions; can stem from infection, scarring (e.g., Peyronie’s in males).
General Sex-Therapy Principles
  • Self-awareness: learn personal anatomy & preferences.
  • Communication: partners collaborate openly.
  • Sensate focus: non-goal-oriented touching to reduce performance anxiety and enhance pleasure.

Ethical, Philosophical & Practical Takeaways

  • Necessity for inclusive, non-binary research frameworks.
  • Critical evaluation of pharmacologic interventions (e.g., chemical castration) within human-rights context.
  • Recognition that subjective, cultural, and physiological aspects of sexuality intertwine; holistic approaches best support sexual well-being.