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4.7.8Additional lessons

Hormones and Puberty — IB Biology HL Revision Notes & Topical Questions

5 min read 5 parts Lesson 62 of 101

📚 IB Biology HL Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Section 1 of 5The Hormone Chain

Puberty is the period when sexual maturity is reached, usually between about 9 and 16 years of age.

Hypothalamus
  • Hypothalamus At the start of puberty it increases the release of gonadotrophin-releasing hormone (GnRH) in pulses.
Anterior pituitary
  • Anterior pituitary GnRH stimulates it to secrete follicle-stimulating hormone (FSH) and luteinising hormone (LH).
Testes
  • Testes LH stimulates interstitial cells to make testosterone, and FSH with testosterone supports sperm production.
Ovaries
  • Ovaries FSH and LH stimulate follicle development and secretion of oestradiol and progesterone.

Section 2 of 5Male Changes

Testosterone
  • Testosterone The main male sex hormone, produced in the testes and responsible for the changes of puberty.
Reproductive organs
  • Reproductive organs The testes and penis enlarge and sperm production begins.
Secondary characteristics
  • Secondary characteristics Pubic and facial hair, deeper voice and increased muscle growth develop.
Growth
  • Growth A growth spurt occurs and body shape changes.
HormoneProduced byMain effects at puberty
GnRHHypothalamusStimulates FSH and LH release
FSH, LHAnterior pituitaryStimulate the gonads
TestosteroneTestesMale characteristics, sperm production
OestradiolOvariesFemale characteristics, cycle

Section 3 of 5Female Changes

Oestradiol
  • Oestradiol The main female sex hormone from the ovary, controlling the changes of puberty.
Breast and hips
  • Breast and hips Breast tissue develops and the pelvis widens, changing body shape.
Body hair
  • Body hair Pubic and underarm hair begins to grow at this stage of puberty.
Menstrual cycle
  • Menstrual cycle The first menstruation, called menarche, begins the cycle of ovulation and menstruation.

Section 4 of 5Control and Variation

Timing
  • Timing The age of puberty varies with genes, nutrition and body fat, and the process takes several years.
Primary versus secondary
  • Primary versus secondary Primary characteristics are present from birth, whereas secondary characteristics develop at puberty.
Negative feedback
  • Negative feedback Once sex hormones rise, they exert feedback on the hypothalamus and pituitary to regulate their own secretion.

Section 5 of 5Exam Checklist & Tips

4.7.8 – Key Points for the Exam

  • Puberty The stage of development when sexual maturity is reached.
  • GnRH A hypothalamic hormone that stimulates the release of FSH and LH.
  • Testosterone The male sex hormone made in the testes.
  • Secondary sexual characteristic A feature that develops at puberty and distinguishes the sexes, but is not directly involved in gametes.

Common Mistakes

  • Saying the pituitary produces testosterone; the testes do.
  • Stating that boys and girls have no oestradiol or testosterone.
  • Confusing menarche (first menstruation) with ovulation.
  • Thinking the hormone sequence begins in the gonads.

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