Hormones and Sex Lecture Slides PDF - Brock University

Hormones and Sex PSYC/NEUR 2P37 Charlis Raineki, PhD (he/him) February 6, 2025 Midterm Exam – Feb 13 - Exam will be in our regular classroom - 8-9:50am - Exam Format - True / False - Multiple choice questions - Fill in the blank -...

Hormones and Sex PSYC/NEUR 2P37 Charlis Raineki, PhD (he/him) February 6, 2025 Midterm Exam – Feb 13 - Exam will be in our regular classroom - 8-9:50am - Exam Format - True / False - Multiple choice questions - Fill in the blank - Short Answer - Short Essay - All required book chapter readings and lectures content are examinable Learning Objectives - Describe hormones, hormonal classes, and their mechanisms of action - Discuss the hypothalamic-pituitary axes - Evaluate the hormonal and neural structures that regulate sexual behaviors in males and females The endocrine glands Copyright © 2021, 2018, 2014 Pearson Education, Inc. All rights reserved.  What are hormones? - Hormone – chemical messenger produced by and released into the bloodstream from endocrine glands - Act as chemical messengers in the body to regulate many body functions (e.g., hunger, reproduction) and brain functions (e.g., emotions and mood) Classes of hormones - Amino acid derivatives - Synthetized from a single amino acid (tyrosine and tryptophan) - e.g., epinephrine - Peptides and proteins - Short and long chains of amino acids - e.g., adrenocorticotropic hormone (ACTH) - Steroids - Synthesized from cholesterol (fat) - e.g., estradiol Learning Objectives - Describe hormones, hormonal classes, and their mechanisms of action - Discuss the hypothalamic-pituitary axes - Evaluate the hormonal and neural structures that regulate sexual behaviors in males and females  anterior pituarity makes up the pituitary Adenohypophysis / Neurohypophysis Control of the Posterior Pituitary - Paraventricular and supraoptic nuclei - Magnocellular neurons - Oxytocin contraction during labour - Contraction of uterus – parturition - Contraction of the mammillary glands – lactation - Social behavior - Vasopressin or antidiuretic hormone (ADH) - Controls water balance – production of urine - Social behavior Adenohypophysis / Neurohypophysis Hypothalamus- Pituitary-Gland Hypothalamus Axis Releasing or Inhibiting hormones Pituitary Tropic hormones + Peripheral Hormones Peripheral Glands Hypothalamic- Pituitary Axes  — HPG axis Hypothalamus Males POA GnRH LH stimulates the production of + testosterone — Pituitary FSH stimulates the production of sperm tropic hormone that Gonadotrophs travels thtpugh the circulatory system to LH/FSH the gonads + Testosterone Testis GnRH: Gonadotropin-releasing hormone LH: Luteinizing hormone FSH: Follicle stimulating hormone Testosterone levels in men Daily variations Season variations Morning peak Summer peak Evening nadir Bremer, 1983 Santi et al., 2020 HPG axis — Hypothalamus Females POA Negative feedback GnRH + — Pituitary Gonadotrophs LH/FSH + Estradiol Ovary Progesterone  HPG axis + Hypothalamus Females POA Positive feedback GnRH LH stimulates the production of + progesterone and ovulation + Pituitary FSH stimulates the production of Gonadotrophs estradiol and follicular development LH/FSH + Estradiol Ovary Progesterone Learning Objectives - Describe hormones, hormonal classes, and their mechanisms of action - Discuss the hypothalamic-pituitary axes - Evaluate the hormonal and neural structures that regulate sexual behaviors in males and females Rat sexual behavior Rat sexual behavior: Male - Mount - Forepaws clasped against female’s hindquarters - Mount with intromission - Ejaculation Testosterone and male sexual behavior - A castrated male rat loses interest in mating because testosterone is no longer produced - Behavior is restored with testosterone treatment - the activational effect; hormones briefly activate behavior Testosterone and male sexual behavior - Males with different sexual dive don’t show different levels of testosterone - Testosterone replacement return them to their initial levels of copulation Testosterone and male sexual behavior: Human - Castration in humans leads to reduction in sexual interest and behavior - Effects are variable: - Asexual - Loss of ability to have erection but maintain sexual interest - Continue to copulate - Level of male sexuality is not correlated with testosterone levels in healthy men - Increasing healthy male testosterone levels does not increase sex drive Neural circuitry that regulates male sexual behavior - In male rats, the medial preoptic area (mPOA) coordinates copulatory behavior - mPOA sends axons to the ventral midbrain, then to the basal ganglia to coordinate mounting - mPOA also sends axons through brainstem nuclei to the spinal cord to coordinate reflexes of copulation Neural circuitry that regulates male sexual behavior - Pheromones help coordinate reproductive activities - The vomeronasal organ (VNO) - specialized receptor cells that detect pheromones - can activate male arousal - VNO information is sent to the accessory olfactory bulb, which then projects to the medial amygdala, and in turn to the mPOA Rat sexual behavior: Female - Estrous cycle – every 4-5 days - Four stages: diestrus I, diestrus II, proestrus, estrus - Receptive around ovulation - “behavioral estrus” - Behavior: lordosis Rat sexual behavior: Female - Full solicitations - Female darts toward the male and runs or hops away - Partial solicitations - Touchback: female pauses in front of the male - Runby: female runs past the male - Interception Estrogens and progesterone and female sexual behavior - Estrogens are important for female proceptive behavior - The subsequent production of progesterone increases proceptive behavior and activates receptivity - A female without ovaries will respond to a combination of estrogen and progesterone treatments diestrus I diestrus II proestrus estrus Testosterone and female sexual behavior: Human - Estradiol’s role on female sex drive is unclear - Testosterone increases the proceptivity of ovariectomized and adrenalectomized female rhesus monkeys - Correlations are seen between sexual motivation and testosterone in healthy women - Testosterone has been found to rekindle sexual motivation in ovariectomized and adrenalectomized women Neural circuitry that regulates female sexual behavior - In female rats, the ventromedial hypothalamus (VMH) is crucial for the lordosis response through steroid actions - Estrogen increases dendritic trees of neurons in the VMH - Estrogen also stimulates production of progesterone receptors Neural circuitry that regulates female sexual behavior - VMH sends axons to the periaqueductal gray in the midbrain, which projects to the medullary reticular formation - This in turn projects to the spinal cord via the reticulospinal tract - As the male mounts, sensory information, via the spinal cord, and descending information from the brain evoke lordosis Learning Objectives - Describe hormones, hormonal classes, and their mechanisms of action - Discuss the hypothalamic-pituitary axes - Evaluate the hormonal and neural structures that regulate sexual behaviors in males and females