Sex and the Neuroendocrine System Pt. 1

Glands

• Two main types of glands:
  • Exocrine Glands: Release chemicals into ducts for transport to target locations, primarily on the body surface (e.g., sweat glands).
  • Endocrine Glands: Ductless; secrete hormones directly into the circulatory system, targeting various organs (including other endocrine glands).
• Organs such as the stomach, liver, intestines, and body fat can release hormones and are part of the endocrine system despite not being classified as glands.
• Primary function of glands is hormonal release; there are 10 major endocrine glands.

Gonads

• Specific endocrine glands related to sex:
  • Male (Testes): Produce haploid sperm cells (23 chromosomes) containing half of the genetic material.
  • Female (Ovaries): Produce haploid egg cells (23 chromosomes) with similar genetic material constraints.
• A zygote forms upon fertilization of an egg by a sperm cell, resulting in a diploid cell (46 chromosomes).
• 22 of the 23 chromosome pairs are autosomal (non-sex chromosomes); the 23rd can be X or Y in sperm, always X in eggs.
• Offspring sex determination:
  • XY = male
  • XX = female

Hormones

• Three categories of vertebrate hormones:
  • Amino Acid Derivatives: Synthesized from a single amino acid (e.g., Epinephrine from adrenal medulla).
  • Peptide and Protein Hormones:
    • Peptide: Short chains (e.g., Oxytocin).
    • Protein: Long chains (e.g., Human growth hormone).
  • Steroid Hormones: Derived from cholesterol; affect sexual development and behavior.
    • Small, fat-soluble molecules that can penetrate cell membranes and influence gene expression.
• Sex steroids from gonads include:
  • Androgens: E.g., Testosterone.
  • Estrogens: E.g., Estradiol.
  • Progestins: E.g., Progesterone.
• Both male and female gonads release all three sex steroid categories, but:
  • Testes release more androgens.
  • Ovaries release more estrogens.

Adrenal Gland

• Functions as an endocrine gland.
• The adrenal cortex regulates glucose and salt levels in blood.
• Produces small quantities of sex steroid hormones released by gonads.

Pituitary Gland

• Known as the master gland; regulates hormone release from gonads.
• Distinct regions play different roles:
  • Anterior Pituitary: Originates from embryonic roof of the mouth, releases tropic hormones, and exerts master gland qualities.
  • Posterior Pituitary: Develops from hypothalamic tissue, connected to the hypothalamus.
• Tropic hormones stimulate other glands to release hormones (e.g., gonadotropic hormone stimulates gonads).
• Hormonal release patterns:
  • Males: Constant levels of gonadotropic and gonadal hormones.
  • Females: Cyclical release every 28 days.

Research Findings

• Anterior pituitary glands switched between male and female rats showed hormonal changes:
  • Cyclical function in female rats became consistent in males.
  • Steady function in male rats became cyclical in females.
• Concludes that the pituitary gland is controlled by another structure in the nervous system.

Explore the differences between exocrine and endocrine glands in this quiz. Learn how these glands function in the neuroendocrine system, focusing on their roles and the types of chemicals they release. This foundational knowledge is crucial for understanding hormonal interactions in the body.