Question 1: Adrenaline is a hormone released by the adrenal glands in response to stress, preparing the body for 'fight or flight' responses. Thyroxine, produced by the thyroid gland, regulates metabolic rate and energy use. Explain how these hormones contribute to maintaining homeostasis during stressful situations.

Answer: Adrenaline increases heart rate, blood flow to muscles, and energy release, enabling quick responses, while thyroxine adjusts the metabolic rate to meet energy demands, both helping restore balance during stress.

Question 1: Define adrenaline and describe its mechanism of action in the body.

Answer: Adrenaline is a hormone that prepares the body for 'fight or flight' by binding to receptors on target cells, leading to increased heart rate, dilated airways, and energy release.

Question 2: Describe how thyroxine regulates the body's metabolic rate.

Answer: Thyroxine increases the rate of chemical reactions in cells by stimulating enzyme activity, thereby boosting metabolic rate and energy expenditure.

Question 1: Calculate the amount of thyroxine produced in a person who has a metabolic rate of 1500 kcal/day, if the average thyroxine production increases metabolic rate by 10%. Show your working.

Answer: Work: Increase in metabolic rate = 1500 kcal/day × 10/100 = 150 kcal/day. If 1 unit of thyroxine increases metabolic rate by 1 kcal, then thyroxine production = 150 units/day.

Question 2: Design a simple experiment to investigate the effect of adrenaline on heart rate. Include variables, safety precautions, and expected outcomes.

Answer: Students could measure resting heart rate, then administer a simulated adrenaline stimulus (e.g., caffeine). Independent variable: adrenaline presence; dependent variable: heart rate; control variables: age, activity level. Safety precautions include avoiding excessive caffeine and monitoring participants. Expected outcome: increased heart rate following stimulus.

Question 1: A patient with an overactive thyroid produces excess thyroxine. Describe the possible effects on their metabolic rate and overall health.

Answer: They may experience a high metabolic rate, leading to weight loss, increased heart rate, heat intolerance, and possible nervousness.

Question 2: Explain how adrenaline and thyroxine work together during a stressful situation to restore homeostasis.

Answer: During stress, adrenaline rapidly increases heart rate and energy availability for immediate action, while thyroxine adjusts the metabolic rate for sustained energy supply. Together, they ensure the body responds quickly and maintains energy balance, restoring homeostasis.

Question 1: How is understanding thyroxine important in treating hypothyroidism?

Answer: Understanding thyroxine allows for hormone replacement therapy to normalise metabolic rate and alleviate symptoms of hypothyroidism.

Question 2: Discuss how adrenaline is utilised in emergency medical treatments.

Answer: Adrenaline is used in emergency treatments such as anaphylactic shock to rapidly constrict blood vessels, open airways, and increase heart rate, restoring blood pressure and breathing.