Topic 14: Homeostasis Flashcards
Definitions I:
(a) Homeostasis
(b) Nephron
(c) Stomata
(a) Homeostasis: Maintaining stable internal conditions. (1 mark)
(b) Nephron: Kidney unit forming urine. (1 mark)
(c) Stomata: Leaf pores for gas exchange. (1 mark)
Explain homeostasis and its importance in a human athlete. [2 Marks]
Homeostasis keeps conditions optimal (1 mark); Vital for athlete’s performance, recovery (1 mark). (2 marks)
In a dog, outline the principles of homeostasis with negative feedback. [3 Marks]
Receptors detect heat (1 mark); Nervous/endocrine systems signal effectors (1 mark); Negative feedback restores norm (1 mark). (3 marks)
State how urea is formed in a human liver. [1 Mark]
Urea from deamination of excess amino acids. (1 mark)
Describe the structure of a human kidney from a dissection. [2 Marks]
Fibrous capsule, cortex outside (1 mark); Medulla, pelvis, ureter, vessels inside (1 mark). (2 marks)
Identify glomerulus and loop of Henle in a kidney photomicrograph. [2 Marks]
Glomerulus: Capillary knot (1 mark); Loop of Henle: U-shaped tubule (1 mark). (2 marks)
In a nephron, explain urine formation in Bowman’s capsule and PCT. [3 Marks]
Ultrafiltration in capsule forms filtrate (1 mark); PCT reabsorbs glucose, ions (1 mark); Water follows osmosis (1 mark). (3 marks)
Relate Bowman’s capsule structure to its function in a rat kidney. [2 Marks]
Podocytes filter blood (1 mark); Large surface speeds ultrafiltration (1 mark). (2 marks)
In a dehydrated person, describe osmoregulation via ADH and aquaporins. [4 Marks]
Hypothalamus signals pituitary (1 mark); ADH released, aquaporins insert (1 mark); Collecting duct reabsorbs water (1 mark); Urine concentrated (1 mark). (4 marks)
In a diabetic, explain glucagon’s role in blood glucose control. [4 Marks]
Glucagon binds receptors, G-protein activates (1 mark); cAMP forms, kinase cascade (1 mark); Glycogen breaks down (1 mark); Glucose rises (1 mark). (4 marks)
Explain negative feedback in blood glucose regulation in a liver cell. [3 Marks]
Insulin lowers glucose, uptake by cells (1 mark); Glucagon raises it, liver release (1 mark); Feedback balances levels (1 mark). (3 marks)
Outline how test strips measure blood glucose in a patient. [2 Marks]
Glucose oxidase reacts with glucose (1 mark); Peroxidase signals colour change (1 mark). (2 marks)
In a desert plant, explain how stomata balance CO₂ uptake and water loss. [3 Marks]
Stomata open for CO₂, photosynthesis (1 mark); Close to limit transpiration (1 mark); Balance via guard cells (1 mark). (3 marks)
State the daily rhythm of stomata in a sunflower leaf. [1 Mark]
Stomata open day, close night. (1 mark)
Describe guard cell structure and their role in stomatal opening in a pea plant. [3 Marks]
Guard cells: Thick inner walls (1 mark); Pump ions, swell to open (1 mark); Allow CO₂ entry (1 mark). (3 marks)
In a drought, explain abscisic acid’s role in stomatal closure in a cactus. [4 Marks]
Abscisic acid binds receptors (1 mark); Calcium signals closure (1 mark); Guard cells deflate (1 mark); Conserves water (1 mark). (4 marks)
