PSYC/NEUR 2P37 Hormones and Sex Midterm

• PSYC/NEUR 2P37, Hormones and Sex, Charlis Raineki, PhD, February 6, 2025

Midterm Exam Information

• Midterm Exam is on February 13
• It will be in the regular classroom from 8:00 AM to 9:50 AM
• The exam will be a format of true/false, multiple choice, fill in the blank, short answer, and short essay questions
• All required readings and lecture 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

Endocrine Glands

• Endocrine glands featured: Pineal, Hypothalamus, Pituitary, Thyroid, Parathyroid, Thymus, Adrenal, Pancreas, Ovary, and Testis

Hormones Defined

• Hormones are chemical messengers produced by and released into the bloodstream by glands and endocrine glands
• Hormones act as chemical messengers in the body to regulate body functions and brain functions, like hunger, reproduction, emotions, and mood

Classes of Hormones

• Amino Acid Derivatives
• Synthesized from a single amino acid such as tyrosine and tryptophan
• Example: epinephrine
• Peptides and Proteins
• Short and long chains of amino acids
• Example: adrenocorticotropic hormone (ACTH)
• Steroids
• Synthesized from cholesterol or fat
• Example: estradiol

Pituitary Gland

• The anterior pituitary is part of the pituitary gland

Control of the Posterior Pituitary

• The paraventricular and supraoptic nuclei controls it
• Magnocellular neurons
• Oxytocin is secreted in contraction during labor
• Contraction of the uterus/ parturition
• Contraction of the mammillary glands or lactation
• Social behavior is linked to the release of oxytocin
• Social behavior
• Vasopressin, an antidiuretic hormone (ADH)
• It controls the water balance and urine production
• Social behavior

Hypothalamus-Pituitary-Gland Axis

• Axis components includes: Hypothalamus, Pituitary, and Peripheral Glands
• There are releasing and inhibiting hormones from the Hypothalamus
• There are tropic hormones from the Pituitary

Hypothalamic-Pituitary Axis

• Neuroendocrine cells release the hormones: CRH, TRH, GnRH, and GnlH
• Anterior pituitary tropic hormones include: ACTH, TSH, LH, prolactin, FSH and GH
• Main target of tropic hormone goes to the Adrenal cortex, Kidney, Thyroid, Testes, Ovaries, Mammary glands, and Bones

Male HPG Axis

• LH stimulates testosterone production
• FSH stimulates sperm production (tropic hormone)
• GnRH (Gonadotropin-releasing hormone)
• LH (Luteinizing hormone)
• FSH (Follicle-stimulating hormone)

Testosterone Levels in Men

• Levels have daily and seasonal variations
• Morning peaks and evening nadirs
• Summer peak is evident in seasonal variations

Female HPG Axis

• Negative Feedback
• GnRH
• Pituitary Gonadotrophs
• LH / FSH
• Ovary
• Estradiol and Progesterone

Female HPG Axis Function

• LH stimulates progesterone production and ovulation
• FSH stimulates estradiol and follicular development

Rat Sexual Behaviour

• Involves Anogenital Investigation and Pursuit Activities

Rat Sexual Behaviour: Male

• Mount
• Forepaws are clasped against the female's hindquarters
• Mount with intromission
• Ejaculation

Activation of Testosterone in Males

• Castrated males lose interest because testosterone production stops when testosterone levels are low
• Behavior can be restored with testosterone treatment, known as the activation effect

Male Testosterone Drive

• Males with different sexual drives do not show different levels of testosterone
• Testosterone replacement returns the drive to their initial copulation levels

Testosterone and Male Sexual Behavior: Human

• Human castration can lead to a reduction in sexual interest/behavior
• Resulting effects range from asexual behavior, loss of erection or sexual interest, and continued copulation
• A male's sexuality is not correlated with normal amounts of testosterone levels
• Increasing healthy male testosterone levels does not increase sex drive

Male Sexual Behavior: Neural Circuitry

• Medial preoptic area (mPOA) in the male rat coordinates copulatory behavior
• The mPOA sends axons to the ventral midbrain, and then to the basal ganglia to coordinate mounting
• The mPOA also sends axons through brainstem nuclei to the spinal cord in order to coordinate reflexes of copulation
• Pheromones coordinate reproductive activities
• Vomeronasal organ (VNO) has specialized detection receptor cells
• The VNO information goes to the Medial Amygdala which then sends signals to the Accessory Olfactory Bulb and then to the mPOA

Rat Sexual Behaviour: Female

• 4-5 day Estrous Cycle
• Has 4 stages: diestrus I, diestrus II, proestrus, estrus
• Receptive around ovulation (behavioral estrus)
• Behaviour is exhibited through Lordosis

Rat Behaviour: Female Solicitations

• Full solicitations behaviour displays a female darting toward the male and runs or hops away
• Partial solicitations behaviour displays touchback as the female pauses in front of the male,
• Runby is shown when the female runs past the male
• Interception

Female rat sexual behaviour

• Estrogens increase proceptive behavior
• Subsequent progesterone production increases proceptive behavior and activates receptivity
• A female without ovaries will respond to the Estrogen/Progesterone combination

Human Female Sexual Behaviour

• Estradiol's impact 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 can rekindle sexual motivation in ovariectomized and adrenalectomized women

Neural Circuitry: Female Rat

• The ventromedial hypothalamus (VMH) is crucial for the lordosis response with steroid action through
• Estrogen increases in dendritic trees of neurons in the VMH
• Estrogen releases production of progestrone receptors.
• VMH sends axons to PG in the midbrain to medullary reticular formation.

Sensory Info and Circuits

• Sends sensory info to the spinal cord, descending info from the brain, evoking lordosis in the spinal cord.

Midterm exam information for PSYC/NEUR 2P37, Hormones and Sex, instructed by Charlis Raineki, PhD. The exam covers hormones, hypothalamic-pituitary axes and the hormonal and neural structures that regulate sexual behaviors in males and females. Endocrine glands featured include Pineal, Hypothalamus, Pituitary, and more.