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.