Transport

• An open circulatory system has no blood vessels so the blood bathes the tissues directly whilst being held in a cavity called the haemocoel.
• A closed circulatory system had blood travelling in blood vessels where the force is generated by a muscular pump such as the heart. In the process, oxygen is transported in red blood cells that conatin a pigment called haemoglobin.
• 2 Types of closed circulatory systems

  • single
  • double
• Single (closed) circulation is when the blood flows around the heart once before returing to the heart.
• Double (closed) circulation is when blood flows through the heart twice.
• What is an example of open circulation?

  • Insects
• Describe open circulation in insects

  Insects have a long dorsal tube shaped heart which spans the length of the entire insect. Blood is pumped to the haemocoel at low pressure before returing slowly back to the heart.
• Name 2 examples of single (closed) circulation

  • Fish
  • Earthworm
• Describe single (closed) circulation in fish

  Deoxygenated blood flows from the ventricles to the gills. Oxygenated blood travels to the tissues and organs. Deoxygenated blood returns to the artia via veins.
• Describe single (closed) circulation in earthworms

  Blood moves forward in the dorsal vessel an dback in the ventral vessel. Blood is pumped using 5 pairs of pseudo hearts.
• Name and example of double (closed) circulation

  • mammals
• Describe double (closed) circulation in mammals

  Pulmonary Circuit: The right side pumps deoxygenated blood from the heart to the lungs and oxygenated blood returns to the left side of the heart.

  Systemic Circuit: The left side pumps oxygenated blood from the heart to the body and deoxygenated blood returns to the right side of the heart.
• What are the 2 circuits in mammal circulation?

  • Pulmonary
  • Systemic
• Describe the pathway of deoxygenated blood

  1. Deoxygenated blood from the body enters the vena cava on the right side of the heart
  2. Passes into the right atrium
  3. Through the tricuspid valve
  4. Into the right ventricle
  5. Then it passes through the semi lunar valve
  6. Out of the pulmonary artery
  7. Blood heads to the lungs to be oxygenated
• Describe the pathway of oxygenated blood

  1. Oxygenated blood from the lungs enters the pulmonary vein on the left side of the heart
  2. Passes into the left atrium
  3. Through the bicuspid valve
  4. Into the left ventricle
  5. Then it passes through the semi lunar valve
  6. Out of the aorta
  7. Blood heads to the body where oxygen can be used in respiring tissues and becomes deoxygenated
• AVN


  Atrioventricular Node
• SAN


  Sinoatrial Node is the natural pacemaker of the heart
• The heart is myogenic which means that contractions are initiated from within the heart without interaction with the nervous system
• Name 3 stages of the cardiac cycle

  • Cardiac diastole
  • Atria systole
  • Ventricular systole
• Cardiac diastole is when the atria and ventricles are both at rest. Blood is at low pressure in the veins. Pressure increases as the atria begin to fill. Some blood trickles through the open atrioventricular valves into the relaxed ventricles.
• Atria systole is when pressure in the atria is the highest causing the atria walls to contract and push blood into the ventricles. Pressure in the ventricles begins to increases as they fill.
• Ventricular systole is when the pressure in the ventricles is the highest which causes the ventirlces to contract from the apex upwards, pushing blood aout of the heart through the aorta and pulmonary artery. Ventricular pressure increases more than the atria causing the atrioventricluar valves to shut to prevent backflow. The pressure causes the semilunar valves to open.
• Stages of controlling the heart beat

  1. SAN starts waves of depolarisation which spread to the atria causing them to contract
  2. There is al ayer of tissue between the atria and ventricles which has a high electrical resistance. This prevents the ventricles from contracting at the same time of the atria.
  3. AVN delays impulses by 0.1 seconds
  4. AVN passes the waves of excitation down the bundle of HIs and up the Purkinje fibres in the interventricular septum.
  5. This causes the ventricles to contract from the apex upwards, pushing blood out of the heart.
• What 3 layers do both veins and arteries have?

  • Tunica Intima
  • Tunica Media
  • Tunica Externa
• Tunica Intima

  • Innermost layer
  • Single layer of endothelium
  • Has a smooth lining to reduce friction
  • In arteries it is supported by elastin rich collagen
• Tunica Media

  • Middle layer
  • Has elastic fibres and smooth muscle
  • Thicker in the arteries
  • A pulse can be felt in the arteries due to the elastic fibres recoiling and pushing blood through the vessel
  • Contraction of muscle helps to regulate blood flow and blood pressure as blood flows further from the heart
• Tunica Externa

  • Outermost layer
  • Contains collagen fibres that resist overstretching
• Arteries

  • Carries blood AWAY from the heart
  • has thick muscular walls to withstand high pressure
  • Arteries - Arterioles - Capillaries
• Veins

  • Carries blood TO the heart
  • For veins above the heart, blood returns by gravity
  • For veins below the heart, blood returns by pressure from surrounding muscles
  • Has a larger lumen and thinner walls with less muscle
  • Conatin semi lunar valves which resist backflow of blood
  • Blood is at low pressure and travels at a slow rate
• Faulty valves in veins can cause blood to flow backwards. This can cause varicose veins and heart failure.
• Capillaries

  • Penetrate all tissues and organs
  • 1 Cell thick which is made of endothelium that sits on a basement membrane
  • has pores that are permeable to water and solutes
  • A small diameter leads to slow blood flow which allows enough time for exchanging materials
  • Capillaries - venules - veins
• What is a red blood cell called?

  Erythrocyte
• Erythrocytes

  • Has a bioconcave shape which increases the surface area for gas exchange
  • Small and flexible to be able to move through capillaries
  • No nucleus so there is more room to carry oxygen
  • Contain a pigment called haemoglobin
• Haemoglobin

  • 4 Globular proteins
  • Contain haem groups which each contain 1 iron ion
  • Allows erythocytes to carry oxygen
  • Has a high affinity for oxygen
  • Combines with oxygen to form oxyhaemoglobin
• How does oxygen get from the lungs into the blood and to respiring tissues?

  1. Oxygen diffuses from the lungs and into the blood plasma
  2. It passes down a concentration gradient into the erythrocyte
  3. Oxygen binds to haemoglobin to maintain concentration gradients
  4. Oxygen binds to the haem groups of haemoglobin
  5. In respiring tissues oxygen dissociates from oxyhaemoglobin
  6. Oxygen diffues into respiring tissue
• What shape is an oxygen dissociation curve?

  Sigmoid
• What binding is found in the oxygen dissociation curve?

  Cooperative Binding
• Decsribe the 3 stages in the oxygen dissociation curve

  1. At low partial pressures of oxygen, the first oxygen molecule is more difficult to bind. When it does it changes the shape of the haemoglobin.
  2. The change in shape makes it easier for the second and third oxygen molecule to bind
  3. At higher partial pressures of oxygen, it become more difficult for the fouth oxygen molecule to bind due to less frequent successful collisions. This makes it difficult to reach 100% saturation
• Name 3 ways that carbon dioxide can be transported

  • Dissolved in plasma
  • Associates with haemoglobin to form carbamino haemoglobin
  • As hydrogen carbonate ions
• How carbon dioxide travels as hydrogen carbonate ions

  1. Carbon dioxide diffuses into the erythrocyte

  2. It dissolves in water causing it to form carbonic acid

  3. Carbonic acid dissociates to form hydrogen ions and hydrogen carbonate ions

  4. Hydrogen carbonate ions diffuse out the cell by facilitated diffusion

  5. To balance out the negative outflow of charge, chloride ions diffuse into the cell. This is known as the chloride shift

  6. Hydrogen ions cause the oxyhaemoglobin to dissociate into oxygen and haemoglobin. Hydrogen ions bind to the haemoglobin forming haemoglobinic acid

  7. Oxygen diffuses into respiring tissues