communication + homeostasis

• Why is communication essential for the survival of organisms?

  It allows organisms to detect and respond to changes in their environments.
• What systems trigger changes necessary for survival in multicellular organisms?

  The nervous and endocrine systems.
• What does cell signalling involve?

  Communication between cells through electrical signals or hormones.
• How does neuronal cell signalling differ from chemical signalling?

  Neuronal signalling is faster and short-term, while chemical signalling is slower and long-term.
• What is endocrine signalling used for?

  Long-distance signalling carried by the circulatory system.
• What is paracrine signalling?

  Signalling that occurs between cells in close proximity to each other.
• What is autocrine signalling?

  Signalling where a cell releases signals to stimulate its own receptors.
• What does homeostasis ensure?

  A constant internal environment despite external changes.
• How is homeostasis achieved?

  Through negative feedback mechanisms that counteract changes in internal conditions.
• What are the elements needed for a negative feedback pathway to work?

  • Sensory receptors (e.g., temperature receptors)
  • Effectors (e.g., muscles and glands)
  • Communication via nervous or hormonal systems
• What is positive feedback?

  A control pathway that increases the original change in conditions.
• Give an example of positive feedback.

  Dilation of the cervix during childbirth.
• What is an ectotherm?

  An organism that regulates its body temperature using external sources.
• How do ectotherms control their body temperature?

  By exchanging heat with their surroundings.
• What is an endotherm?

  An organism that maintains a constant body temperature independent of external temperature.
• What role do thermoreceptors play in endotherms?

  They monitor core body temperature changes and communicate them to the hypothalamus.
• What actions do endotherms take to control body temperature?

  • Shivering to generate heat
  • Sweating to cool down
  • Adjusting hair position for insulation
  • Dilation and constriction of arterioles for heat loss
• What is the main role of the kidneys?

  Excretion of waste products such as urea in the form of urine.
• What is the process of ultrafiltration in the kidneys?

  • Blood enters the glomerulus through the afferent arteriole.
  • Waste products are filtered out into the Bowman’s capsule.
  • Molecules less than 69,000 Mr can pass through barriers.
• What happens during selective reabsorption in the kidneys?

  Useful substances like glucose and amino acids are reabsorbed back into the blood.
• How are the cells lining the proximal convoluted tubule adapted for selective reabsorption?

  They have microvilli for a larger surface area and many mitochondria for ATP production.
• What is the main function of the Loop of Henle?

  To produce a low water potential in the medulla of the kidney.
• How does the Loop of Henle create concentration gradients?

  By acting as a countercurrent multiplier.
• What happens to the filtrate in the descending limb of the Loop of Henle?

  It becomes more concentrated as water is reabsorbed.
• What is the role of hormones in controlling water potential of the blood?

  They regulate the reabsorption of water in the kidneys.
• What is the function of antidiuretic hormone (ADH)?

  To increase the permeability of the collecting duct to water.
• How does ADH affect the collecting duct cells?

  It activates enzymes to produce cAMP, leading to the insertion of aquaporins into the membrane.
• What can trigger kidney failure?

  Kidney infections and high blood pressure.
• What are the consequences of kidney failure?

  Build-up of toxic waste products and fluid accumulation leading to swelling.
• What is renal dialysis?

  A treatment that filters blood to remove waste products and excess water.
• What are the two types of dialysis?

  • Haemodialysis: Blood is filtered through a machine.
  • Peritoneal dialysis: Dialysis fluid is exchanged in the body cavity.
• What is the purpose of a kidney transplant?

  To replace the damaged kidney and reverse kidney failure symptoms.
• What is the role of urine samples in medical diagnosis?

  They can be used to test for pregnancy and the presence of anabolic steroids.
• How are anabolic steroids detected in urine samples?

  Through gas chromatography by measuring the time taken for the sample to pass through a column.
• What is human chorionic gonadotropin?

  A hormone found in the urine of pregnant women.
• What is the significance of monoclonal antibodies in pregnancy testing?

  They test for the presence of human chorionic gonadotropin in urine.
• What is the main function of the liver in excretion?

  To break down harmful substances and convert them into less harmful forms.
• What are liver lobules composed of?

  Cylinders made of hepatocytes arranged in rows.
• What is the role of Kupffer cells in the liver?

  They break down old red blood cells and remove bacteria.
• What is deamination in the context of amino acid excretion?

  The removal of the amino group from excess amino acids.