Biology GCSE Combined Science Notes

B11.4 The Role of Negative Feedback

Learning Objectives

• Understand the roles of adrenaline and thyroxine in the body.
• Recognize the importance of negative feedback systems.

Key Concepts

• Negative Feedback Systems: Work to maintain a steady state in the body.
  • If a factor decreases, changes occur to increase it back to original levels and vice versa.
  • Involves hormones like insulin, glucagon, female sex hormones, and thyroxine.

Thyroxine and Negative Feedback

• Produced by the thyroid gland using iodine.
• Controls basal metabolic rate, oxygen usage, and brain development.
• Maintained by negative feedback via thyroid stimulating hormone (TSH) from the pituitary gland.

Adrenaline

• Not controlled by negative feedback.
• Prepares body for 'fight or flight' by increasing heart and breathing rate, converting glycogen to glucose, and increasing mental awareness.

Questions

1. Describe how a negative feedback system works.
2. Compare thyroxine and adrenaline roles and control systems.
3. Explain the link between iodine deficiency and diseases caused by low thyroxine levels. Suggest solutions.

Hormones and Puberty

Learning Objectives

• Know the main human reproductive hormones.
• Understand how hormones control puberty changes.

Hormones in Puberty

• Oestrogen: Female hormone triggering secondary sexual characteristics and regulating menstrual cycle.
• Testosterone: Male hormone responsible for secondary sexual characteristics and sperm production.

The Menstrual Cycle

• Cycle Overview: Average 28 days, involves thickening of uterine lining and maturation of eggs.
  • Hormones involved: FSH, LH, oestrogen, and progesterone.

Female Fertility

• Egg production lasts until menopause, with increased risk of genetic problems in later years.

Questions

1. Why are hormones important in reproduction?
2. Compare puberty changes between boys and girls.
3. Describe hormones' roles in the menstrual cycle.

B11.6 Hormones and the Menstrual Cycle

Learning Objectives

• Understand hormone roles in reproduction.
• Comprehend hormonal control of the menstrual cycle.

Hormonal Control of Menstrual Cycle

• FSH: Stimulates egg maturation and oestrogen production.
• Oestrogen: Stimulates uterine lining growth and inhibits FSH.
• LH: Triggers ovulation and is regulated by oestrogen levels.
• Progesterone: Maintains uterine lining post-ovulation and inhibits FSH and LH.

Key Points

• FSH: From pituitary, stimulates eggs and oestrogen.
• Oestrogen: From ovaries, encourages uterine lining growth, inhibits FSH.
• LH: Stimulates ovulation.
• Progesterone: Produced post-ovulation, maintains uterine lining, inhibits FSH/LH.

Questions

1. Identify four hormones controlling the menstrual cycle.
2. Explain uterus lining buildup and hormonal changes during the cycle.
3. Describe main events of the menstrual cycle and peak fertility period.

These notes provide a comprehensive summary of the hormonal control of the body focusing on negative feedback mechanisms and reproductive hormone roles during puberty and menstruation.