Control of Sexual Behavior

Appetitive vs. Consummatory Behaviors

Appetitive Behaviors:
- Behaviors aimed at getting into the right condition to find the right target.
- Example (Food): Foraging.
- Example (Sex): Motivation to have sex.
Consummatory Behaviors:
- Behaviors aimed at carrying out the motivated behavior.
- Example (Food): Eating.
- Example (Sex): Actually having sex.

Pheromones:
- Species-typical molecules that work across organisms.
- In insects, a single molecule released by one sex triggers a behavior in the other, leading to copulation.
- In mammals, pheromones are usually a mix of molecules.
Vomeronasal Organ:
- Organ within the nose that detects pheromones in most mammals.
- Well-established in rodents.
- In humans, the existence of a functional vomeronasal organ is debated.
Human Pheromones?
- T-shirt smelling studies suggest that women's T-shirts worn during the fertile phase of their menstrual cycle smell sexier to heterosexual men.
Androstenone:
- A molecule found in male sweat that may act as a human pheromone.
- Applying Androstenone to women's upper lips may improve their mood and increase sexual arousal.
- In males, it might worsen mood.
MHC Genes and Attraction:
- Women may find men's T-shirts sexier if they share fewer MHC (major histocompatibility complex) genes with that man.
- This could be related to offspring having a wider range of immune molecules.
Androstenone Debate:
- Reduction in Androstenone is found in female urine only during the third trimester of pregnancy, making it unlikely to be a pheromone.
Skepticism towards Pheromone Perfumes:
- Be cautious of advertisements claiming that certain perfumes will make you sexier.

Pheromones and Innate Responses:
- Pheromones are thought to trigger innate, automatic responses.
Learned Aspects of Sexual Motivation:
- Attraction can be learned through associations (e.g., liking a partner's smell after being in a relationship).
- Fetishes are learned sexual motivations.
Sexual Orientation:
- There is no evidence that sexual orientation is a learned thing.

Testosterone in Males:
- Higher testosterone levels increase sexual motivation within an individual.
- Lower testosterone levels decrease sexual motivation.
- Testosterone is not about the comparison between individuals, it's only about changes in an individuals levels of testosterone that make changes in interest and motivation.
- Anti-androgen drugs reduce testosterone levels and sexual motivation.
- Testosterone levels increase when presented with the opportunity to have sex.
Sexual Interest in Women and the Menstrual Cycle:
- Women may be more likely to initiate sex during ovulation.
- Estradiol and testosterone contribute to sexual motivation in women.
- Increase in testosterone with an increase in estradiol will increase the effect of estradiol on sexual motivation.
- Anticipation of sexual activity can increase testosterone levels in women.

Masters and Johnson's Four Stages of Arousal:
- Excitement
- Plateau
- Orgasm
- Resolution
Excitement and Plateau:
- Involve erection in men and vaginal lubrication and swelling of the clitoris and labia in women.
- Controlled by the parasympathetic nervous system.
Autonomic Nervous System:
- Controls bodily functions (involuntary).
  - Parasympathetic nervous system.
  - Sympathetic nervous system.
Parasympathetic Nervous System:
- Two-stage organization: pre-ganglion and post-ganglion neurons.
- Ganglion: Group of neuronal cell bodies located near the target organs.
- Both sets of neurons use acetylcholine as their neurotransmitter.
- Pre-ganglion neurons release acetylcholine onto post-ganglion neurons, which use nicotinic receptors.
- Post-ganglion neurons release acetylcholine onto organs, which use muscarinic receptors.
- Increases somatic function, relaxation, and digestion.
Physiological Mechanisms of Arousal:
- Parasympathetic nervous system releases acetylcholine, causing relaxation of smooth muscle in blood vessels.
- This allows blood to flow into the penis, clitoris, and labia, causing them to swell up.
- More blood results in more lubrication.
Viagra and Cyclic GMP:
- Viagra blocks PDE5, an enzyme that breaks down cyclic GMP, which is responsible for relaxation of the muscles.
- This maintains an existing erection but does not cause one.

Sensory Stimulation:
- Stimulation of sensory neurons in the genitals activates a first-order neuron in the spinal cord.
- This neuron sends information to the brain and to an interneuron in the spinal cord.
Interneuron Influence:
- The interneuron (neuron number three) gets input from sensory neurons and the brain.
- It influences the pre-ganglion neuron (number four) to release acetylcholine.
Brain Input:
- The brain provides excitatory and inhibitory input to the interneuron.
- This input can enhance or suppress the reflex arc.
Spinal Cord Damage:
- People with spinal cord damage above a certain level may not feel genital stimulation but can still have an erection due to the local circuit.
Psychological vs. Physical Erectile Dysfunction:
- Psychological erectile dysfunction is still physical (nervous system-based).
- It may involve the brain sending inhibitory signals that stop the circuit from working.
- Stress and low self-confidence can contribute to erectile dysfunction.

Triggered after excitement and plateau when erection is complete.
Involves the sympathetic nervous system (opposite of the parasympathetic nervous system).

Smooth Muscle:
- Smooth muscles are muscles of organs that we can't control voluntarily.
- They surround blood vessels and contract or relax to control blood pressure.
Women and Erectile Dysfunction:
- Women may experience similar issues with clitoral engorgement and lubrication, but it is less well-known than in men.
Puberty and Sexual Motivation:
- During puberty, higher motivation toward sex may occur due to rising testosterone levels.
Asexuality:
- Asexuality may involve different motivational mechanisms related to sexual interest. People who are asexual may experience an orgasm.