BIO LEC

• Homeostasis

  Circulation and Respiration
• Exchanging Materials


  • Every organism must exchange materials with its environment
  • For most of the cells making up multicellular organisms, direct exchange with its environment is NOT POSSIBLE
• Circulatory Systems


  Functionally connect the organs with the body cells
• The wide range of invertebrate body size and form is paralleled by a great diversity in circulatory systems
• Simple animals (cnidarians and jellies)

  Have a body wall only two cells thick that encloses a gastrovascular cavity
• Gastrovascular Cavity


  Functions in both digestion and distribution of substances throughout the body
• Types of Circulatory Systems


  • Open
  • Closed
• Open Circulatory System


  Common to the Molluscs and Arthropods, it pumps blood into a Hemocoel with the blood diffusing back to the circulatory system between cells
• Closed Circulatory System


  Vertebrates, and a few invertebrates, have a closed circulatory system where blood is pumped by a heart through vessels, and does not normally fill body cavities
• Basic components of circulatory systems

  • A circulatory fluid (blood)
  • A set of tubes (blood vessels)
  • A muscular pump (the heart)
• In insects, other arthropods, and most molluscs, blood (hemolymph) bathes the organs directly in an open circulatory system
• In a Closed Circulatory System, blood is confined to vessels and is distinct from the interstitial fluid
• Closed systems are more efficient at transporting circulatory fluids to tissues and cells
• Vertebrate Circulation


  Humans and other vertebrates have a closed circulatory system called the cardiovascular system
• Blood flow in a closed cardiovascular system


  1. Arteries carry blood to smaller vessels called arterioles, then to the tiny capillaries – the sites of chemical exchange between the blood and interstitial fluid

  2. Blood then flows from capillaries into venules then to larger veins which return blood to the heart
• Fish heart


  • Has two main chambers: one ventricle and one atrium
• Amphibian heart


  • Has three chambers: two atria and one ventricle
• Reptile heart


  • Has double circulation with a pulmonary circuit (lungs) and a systemic circuit
  • Turtles, snakes, and lizards have a three-chambered heart with 2 atria and 1 ventricle
  • Crocodilians have a four-chambered heart
• Mammal and Bird heart


  • The ventricle is completely divided into separate right and left chambers
  • The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood
• A powerful four-chambered heart was an essential adaptation of the Endothermic way of life characteristics of mammals and birds
• Mammalian Circulatory Pathway


  1. Blood begins its flow with the right ventricle pumping blood to the lungs

  2. In the lungs, the blood loads O2 and unloads CO2

  3. Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle

  4. Blood returns to the heart through the right atrium
• Cardiac Cycle


  • The heart contracts and relaxes in a rhythmic cycle
  • The contraction, or pumping, phase of the cycle is called systole
  • The relaxation, or filling, phase of the cycle is called diastole
• Heart Rate


  The number of beats per minute
• Cardiac Output


  The volume of blood pumped into the systemic circulation per minute
• Maintaining the Heart's Rhythmic Beat


  • Some cardiac muscle cells are self-excitable, meaning they contract without any signal from the nervous system
  • A region of the heart called the sinoatrial (SA) node, or pacemaker, sets the rate and timing at which all cardiac muscle cells contract
  • Impulses from the SA node travel to the atrioventricular (AV) node
  • At the AV node, the impulses are conducted through the bundle of His and then travel to the Purkinje fibers that make the ventricles contract
  • The impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG)
  • The pacemaker is influenced by nerves, hormones, body temperature, and exercise
• Blood Vessel Structure


  • All blood vessels are built of similar tissues and have three similar layers
  • Arteries have thicker walls to accommodate the high pressure of blood pumped from the heart
  • In the thinner walled veins, blood flows back to the heart mainly as a result of muscle action
• Blood Flow Velocity


  The velocity of blood flow is slowest in the capillary beds as a result of the high resistance and large total cross-sectional area
• Blood Pressure


  • The hydrostatic pressure that blood exerts against the wall of a vessel
  • Systolic pressure is the pressure in the arteries during ventricular systole (the highest pressure in the arteries)
  • Diastolic pressure is the pressure in the arteries during diastole (lower than systolic pressure)
• Capillary Function


  1. Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel

  2. Precapillary sphincters control the flow of blood between arterioles and venules

  3. The difference between blood pressure and osmotic pressure drives fluids out of capillaries at the arteriole end and into capillaries at the venule end
• Lymphatic System


  Returns fluid to the body from the capillary beds and aids in body defense
• Blood


  A specialized connective tissue in the circulatory systems of vertebrates
• Blood Composition


  • Plasma (liquid matrix)
  • Cellular elements (red blood cells, white blood cells, platelets)
• Plasma


  About 90% water, contains inorganic salts, plasma proteins that influence blood pH, osmotic pressure, and viscosity, and function in lipid transport, immunity, and blood clotting
• Cellular Elements


  • Red blood cells (erythrocytes) which transport oxygen
  • White blood cells (leukocytes) which function in defense
  • Platelets which are involved in clotting
• Red Blood Cells


  • In mammals, the nucleus and most organelles are lost and they contain primarily hemoglobin
  • In amphibians, the nucleus is retained
• Stem Cells


  The cellular elements of blood are constantly replaced from a single population of pluripotent stem cells in the red marrow of bones
• Blood Clotting


  When the endothelium of a blood vessel is damaged, a cascade of complex reactions converts fibrinogen to fibrin, forming a clot
• Cardiovascular Disease


  Disorders of the heart and the blood vessels, including atherosclerosis, hypertension, heart attack, and stroke
• Gas Exchange


  Supplies oxygen for cellular respiration and disposes of carbon dioxide
• Respiratory Surfaces


  • Animals require large, moist respiratory surfaces for the adequate diffusion of respiratory gases between their cells and the respiratory medium, either air or water