Biology 12

Chapter 4 Homeostatic Mechanisms • MHR 133

CHAPTER 4 REVIEW

Summary of Expectations

Briefly explain each of the following points.

• Homeostasis is the maintenance of the internal
  environment at a steady state, to ensure
  survival of a living organism; it is an example
  of dynamic equilibrium. (4.1)


• The body’s reactions to increased or decreased
  temperature are examples of negative feedback
  loops, which are made up of three parts: a
  receptor, an integrator, and an effector. (4.1)


• Negative feedback loops exist throughout the
  body to maintain homeostasis and prevent
  blood sugar, blood pressure, temperature, and
  other body constants from becoming too high
  or too low. (4.1)


• Since homeostasis is essential to keeping the
  body healthy, negative feedback loops are
  common within the human body. (4.1)


• The kidney’s principal function is to filter the
  blood to remove cellular waste products such
  as urea, creatinine, and uric acid from the
  body. (4.2)


• The kidneys control water balance, pH, and
  the levels of sodium, potassium, bicarbonate,
  and calcium ions in the blood. (4.2)


• Diabetes is a malfunction of the system that
  controls the levels of sugar (usually glucose)
  in the blood. (4.3)


• The release of insulin — a hormone that
  lowers blood sugar levels — is controlled by
  the same type of negative feedback system that
  exists elsewhere in the body. In this case, the
  receptor, integrator, and effector are all found
  in each beta cell of the pancreas. (4.3)


• Type 1 diabetes may be an autoimmune
  disease. (4.3)


• The immune system activates a variety of
  white blood cells to attack foreign invaders
  such as bacteria and viruses. It recognizes and
  destroys damaged cells and irregular growths
  such as tumours. (4.4)


• The immune system is primarily a function of
  two types of white blood cells — macrophages
  and lymphocytes. (4.4)
  
  
  • Cellular immunity is primarily a function of
    T cells. Antibody immunity is performed by
    B cells but initiated and controlled by T cells.
    (4.4)
  
  
  • An allergy is an inappropriate response by the
    body to a harmless material such as pollen,
    mould, or cat dander. (4.4)
  
  
  • Chemotherapy is the treatment of a disease
    using chemicals or drugs, but in today’s
    vocabulary its meaning has been limited to
    the treatment of cancers. (4.4)
  
  
  
  

Language of Biology

Write a sentence using each of the following words or

terms. Use any six terms in a concept map to show

your understanding of how they are related.

• homeostasis • tubular secretion


• interstital fluid • buffer


• dynamic equilibrium • antagonistic hormones


• vasoconstriction • insulin


• hypothermia • glucagon


• vasodilation • islets of Langerhans


• hyperthermia • immunity


• negative feedback loop • non-specific defence


• sensory receptor • pathogen


• integrator • phagocytosis


• effector • macrophage


• ureter • neutrophils


• sphincter • monocyte


• urethra • natural killer cell


• cortex • specific immune


• medulla system


• pelvis • lymphocyte


• nephron • cellular immunity


• Bowman’s capsule • antibody immunity


• proximal tubule • antigen


• loop of Henle • helper T cell


• distal tubule • cytotoxic T cell


• collecting duct • suppressor T cell


• glomerulus • memory T cell


• nephric filtrate • apoptosis


• re-absorption • histamines


• isotonic • differentiation

1.Which homeostatic mechanisms help prevent
hyperthermia when you exercise on a hot day?

2.Why does homeostasis normally involve
negative feedback loops rather than positive
feedback loops?

3.Describe three homeostatic mechanisms that

help prevent dehydration of the body.

4.Why do people shiver in cold weather?

UNDERSTANDING CONCEPTS