Overview
This lesson covered key concepts of the endocrine system, focusing on the main glands, hormone functions, negative feedback, and how to approach relevant exam questions and past papers.
Major Endocrine Glands and Hormones
- The hypothalamus produces hormones, including ADH (antidiuretic hormone), and signals the pituitary gland.
- The pituitary gland, also called "The Master gland," secretes multiple hormones: FSH, LH, TSH, among others.
- ADH is produced in the hypothalamus but secreted by the pituitary gland; mention both for exams.
- The thyroid gland produces thyroxin, which regulates metabolism (cellular respiration).
- The pancreas is both endocrine (insulin and glucagon into blood) and exocrine (pancreatic juice via ducts).
- The adrenal glands produce aldosterone, cortisol, and adrenaline; aldosterone and ADH regulate salt and water.
- Ovaries and testes are also endocrine glands; the placenta is an endocrine gland only during pregnancy.
Endocrine vs Exocrine Glands
- Endocrine glands are ductless and secrete hormones directly into the bloodstream.
- Exocrine glands have ducts and secrete substances into target organs (not into blood).
- The pancreas functions as both types: endocrine (insulin, glucagon) and exocrine (pancreatic juice).
Hormone Regulation and Negative Feedback
- Thyroxin production is regulated by TSH (thyroid stimulating hormone) from the pituitary gland.
- Negative feedback: High thyroxin lowers TSH, and low thyroxin increases TSH.
- Negative feedback involves: stimulus, receptor, control center, corrective measure, effector, and response.
Approach to Exam Questions
- Use template answers (stimulus, receptor, control center, effector, result) for endocrine system short answers.
- For experiment-based questions, identify dependent variable from the aim, not just the table.
- Planning steps: always start with "decide" (e.g., decide on amount/type of substance, sample size).
- Factors to keep constant: any condition not already mentioned in the question (e.g., other fluids, timing).
- Reliability: mention calculating averages and using a large sample size.
Example: Alcohol and ADH Past Paper Question
- Alcohol reduces ADH secretion, making renal tubules less permeable and leading to more urine output.
- Answer such questions by applying the negative pathway to your template.
Key Terms & Definitions
- Endocrine gland — ductless gland that secretes hormones directly into the bloodstream.
- Exocrine gland — gland that secretes substances via ducts to target locations.
- Hormone — chemical messenger produced by glands, affecting specific organs/tissues.
- Negative feedback — process where a change in a system triggers a response to reverse that change.
- ADH (antidiuretic hormone) — hormone that reduces urine output by increasing water reabsorption.
- TSH (thyroid stimulating hormone) — hormone from the pituitary gland that stimulates the thyroid to produce thyroxin.
Action Items / Next Steps
- Practice past exam papers, especially from the last four years.
- Review negative feedback diagrams and processes for key hormones (e.g., thyroxin, aldosterone, ADH).
- Write template answers for endocrine/hormone questions using the provided structure.
- Prepare for Paper 1 by revising gland locations, hormones, and regulatory mechanisms.