Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts ( M).
The Hypothalamus is the basal part of the diencephalon and regulates the pituitary gland via releasing hormones (e.g., ) and inhibiting hormones (e.g., Somatostatin).
The Pituitary Gland (Hypophysis) consists of the Adenohypophysis () and Neurohypophysis (Oxytocin and Vasopressin/).
Thyroid Gland: Secretes Thyroxine () and Triiodothyronine (), which require Iodine for synthesis. It also secretes Thyrocalcitonin () to lower blood levels.
Parathyroid Hormone () increases blood levels by acting on bones (resorption), renal tubules, and absorption from digested food.
Adrenal Gland: The Medulla secretes Catecholamines (Adrenaline and Noradrenaline) for 'fight or flight' responses. The Cortex secretes Glucocorticoids (e.g., Cortisol) and Mineralocorticoids (e.g., Aldosterone).
Pancreas (Islets of Langerhans): -cells secrete Glucagon (Hyperglycemic hormone) and -cells secrete Insulin (Hypoglycemic hormone).
Mechanism of Hormone Action: Water-soluble hormones (Proteins, Peptides) bind to membrane-bound receptors and generate secondary messengers like , , or . Lipid-soluble hormones (Steroids, Iodothyronines) enter the cell and bind to intracellular/nuclear receptors to regulate gene expression.
📐Formulae
💡Examples
Problem 1:
A patient exhibits an enlargement of the thyroid gland, a low metabolic rate, and weight gain. Identify the condition and the primary cause.
Solution:
The condition is Hypothyroidism (Goitre).
Explanation:
Hypothyroidism is caused by a deficiency of Iodine in the diet, leading to low levels of and . Since these hormones regulate the Basal Metabolic Rate (BMR), their deficiency causes a decrease in consumption and energy production, leading to weight gain and lethargy.
Problem 2:
Contrast the mechanism of action between Follicle Stimulating Hormone () and Estrogen.
Solution:
uses extracellular receptors and secondary messengers, while Estrogen uses intracellular receptors.
Explanation:
is a peptide hormone (water-soluble) and cannot cross the lipid bilayer; it generates secondary messengers like . Estrogen is a steroid hormone (lipid-soluble) which passes through the cell membrane to form a hormone-receptor complex directly with the genome in the nucleus.
Problem 3:
How does (Vasopressin) affect the concentration of urine?
Solution:
increases water reabsorption in the distal tubules, resulting in concentrated urine.
Explanation:
acts on the distal convoluted tubule () and collecting ducts of the kidney, increasing their permeability to water. This prevents diuresis (excess water loss) and helps maintain body fluid volume.