Module 3: Circulation and Gas Exchange
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Questions and Answers

What is the primary function of the valves in the heart?

  • To prevent back flow of blood (correct)
  • To set the rate and timing of cardiac muscle cell contraction
  • To divide the ventricle into pulmonary and systemic circuits
  • To regulate blood pressure

Which part of the heart generates electrical impulses to regulate heartbeat?

  • Sinoatrial (SA) node (correct)
  • Ventricles
  • Pulmonary artery
  • Atrioventricular (AV) node

What is the primary reason why diffusion alone is not sufficient for larger organisms?

  • Because it is a slow process
  • Because it is only effective over short distances (correct)
  • Because it is unable to transport large molecules
  • Because it is not able to transport nutrients and oxygen to cells

During exercise, blood flow is primarily directed to which part of the body?

<p>Muscles (D)</p> Signup and view all the answers

What is the main advantage of a closed circulatory system?

<p>It separates blood from interstitial fluid (D)</p> Signup and view all the answers

What determines the flow of blood in capillaries?

<p>Muscle contraction and sphincters (B)</p> Signup and view all the answers

What is the term for the contraction of the heart muscle?

<p>Systole (B)</p> Signup and view all the answers

Which of the following animals has a 2-chambered heart?

<p>Fish (A)</p> Signup and view all the answers

What is the function of a circulatory system in maintaining homeostasis?

<p>Maintaining a stable internal environment (D)</p> Signup and view all the answers

What is the term for the fluid that combines blood and interstitial fluid in open circulatory systems?

<p>Haemolymph (C)</p> Signup and view all the answers

Study Notes

Diffusion in Small Organisms

  • Occurs across the surface of the organism
  • Diffusion time is proportional to distance^2
  • Surface area to volume ratio decreases with increased body size, making diffusion less efficient in larger organisms

Circulation Systems

  • Transport nutrients, oxygen, and waste products to and from cells
  • Facilitates movement of nutrients and oxygen to and from cells
  • Allows for faster transport of substances over long distances

Animals Without a Circulatory System

  • Turbellarians (flatworms): flat shape increases surface area and decreases diffusion distance
  • Cnidarians: central gastrovascular cavity for digestion and transport, with a body wall only 2 cells thick

Functions of Circulatory Systems

  • Transport: nutrients, wastes, respiratory gases, heat, and hormones
  • Homeostasis: maintains a stable internal state despite changes in the external environment

Animals with Circulatory Systems

  • Two types of systems: open and closed
  • Open systems: arthropods and most molluscs, with no distinction between blood and interstitial fluid (haemolymph)
  • Closed systems: annelids, echinoderms, cephalopods, and chordates, with blood distinct from interstitial fluid

Evolution of Vertebrate Circulatory System

  • Adaptations of cardiovascular system in vertebrates through natural selection
  • Common features: heart, blood vessels, and double circulation
  • Fish: 2-chambered heart, 2 capillary beds
  • Amphibians: 3-chambered heart, double circulation, and some mixing of oxygenated and deoxygenated blood
  • Reptiles: 4-chambered heart, double circulation, and less mixing of oxygenated and deoxygenated blood
  • Mammals and birds: 4-chambered heart, double circulation, and complete separation of oxygenated and deoxygenated blood

Mammalian Heart

  • Sequential contractions of atria and ventricles
  • Valves between atria, ventricles, and major arteries prevent backflow
  • Contraction = systole, relaxation = diastole

How do the Heart Muscles Contract?

  • Sinoatrial (SA) node or "pacemaker" sets the rate and timing of cardiac muscle cell contraction
  • Generates electrical impulses relayed through atrioventricular (AV) node

Structure of Blood Vessels

  • Blood flow in veins: interrelationship between blood flow velocity, cross-sectional area, and blood pressure

Blood Flow and Distribution

  • Distribution of blood varies depending on the situation
  • Always prioritizes the brain, kidneys, liver, and heart
  • Also supplies the alimentary canal after a meal, and muscles during exercise
  • Capillary flow controlled by muscle contraction and sphincters

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Description

The learning content this week will help you to:

Interrelate biological structure, process and function in animals at organismal and organ levels Outline the structural systems of animals.

As you work through the activities and information in this module, think about how your own body achieves these tasks.

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