All human physiology

• Antibody production


  1. Pathogen enters bloodstream

  2. Macrophage consumes and presents antigen

  3. Helper T-cells bind and activate

  4. Helper T-cells divide into active and memory cells

  5. B-cells process antigen and are activated by helper T-cells

  6. B-cells divide into active plasma cells and memory cells

  7. Antibodies in bloodstream destroy pathogens
• Vaccination


  Providing a safe first exposure to a pathogen so that a vaccinated person will develop immunity but not the disease

  
• Smallpox was the first infectious disease of humans to have been eradicated by vaccination

  
• Production of monoclonal antibodies

  1. B-cells are short-lived

  2. Hybridoma cells have characteristics of B-cells and cancer cells

  3. Monoclonal antibodies are produced by clones and are highly specific
• Use of monoclonal antibodies


  Diagnosis - detect presence of pathogens

  Treatment - target cancer cells
• Monoclonal antibodies are used in pregnancy testing kits
• Antigens on the surface of red blood cells stimulate antibody production in a person with a different blood group
• Elbow joint


  • Hinge joint
  • Synovial joint
  • Capsule lined with membrane that secretes synovial fluid
  • Smooth cartilage covers bone ends

  
• Biceps and triceps


  Antagonistic muscles - biceps bends the arm, triceps straightens the arm
• Joint


  Lined by a membrane that secretes lubricating synovial fluid so that the bones move smoothly against one another and friction is reduced
• Cartilage


  Covers the ends of the bones at the joint and also helps to reduce friction and absorb pressure as the joint moves

  
• Elbow joint


  • Formed of three bones - the radius and ulna in the lower arm and the humerus in the upper arm
  • Tendons attach the biceps and triceps muscles to these bones
  • The biceps is attached to the radius and the shoulder blade, when it contracts the arm bends
  • The triceps are attached to the ulna, humerus and shoulder blade and it contracts to straighten the arm
  • The biceps and triceps are an example of an antagonistic pair of muscles

  
• Skeletal/striated muscle


  • Muscle that causes the movement of our joints
  • Viewed under the light microscope it has a striped appearance made up of multinucleate cells known as muscle fibres
  • Surrounding the muscle fibre is a plasma membrane called the sarcolemma
  • Each fibre is made up of many myofibrils running parallel to one another
  • Surrounding each myofibril is a system of membranes called the sarcoplasmic reticulum and between the closely packed myofibrils are many mitochondria
  • Myofibrils are made up of repeating subunits called sarcomeres, which produce the striped appearance of a muscle fibre and are responsible for muscle contraction
  • The ends of a sarcomere are called the Z lines
  • There are two types of filament that form the striped pattern of a muscle - actin and myosin
• Skeletal muscle contraction


  1. Nerve impulses travel along the muscle fibre membrane and are carried down into the fibre through T-tubules

  2. Impulses spread along the membrane of the sarcoplasmic reticulum, causing Ca2+ ions to be released

  3. Before contraction, binding sites for myosin heads on the actin filaments are covered by troponin and tropomyosin

  4. Ca2+ ions bind to the actin filaments, causing the troponin and tropomyosin to change shape and expose the myosin binding sites

  5. Myosin heads bind to the actin filaments at the exposed binding sites, forming cross-bridges

  6. Inorganic phosphate (Pi) is released and ADP is also released

  7. The myosin heads bend towards the centre of the sarcomere, pulling the actin filaments inward past the myosin filaments, producing a 'power stroke'

  8. New ATP molecules bind to the myosin heads, breaking the cross-bridges and detaching them from the actin filaments
• Although the actin and myosin filaments do not change in length when a muscle contracts, the appearance of the banding patterns in the sarcomere is changed

  
• The type of nitrogenous waste in animals is correlated with evolutionary history and habitat
• Ammonia


  Highly basic and can alter the pH balance, also toxic as it is a highly reactive chemical
• Urea


  Less toxic form of nitrogenous waste than ammonia, requires less energy to produce than uric acid
• Uric acid


  Least toxic form of nitrogenous waste, requires the most energy to produce but is not water-soluble so less water is lost when excreted
• Vertebrates produce either uric acid or urea as these substances require less water to excrete from the body
• Ultrafiltration


  1. Occurs in the glomerulus as various small molecules leave the blood

  2. Blood pressure in the glomerulus capillaries is very high, causing about 20% of the blood plasma to pass into the Bowman's capsule

  3. The filtrate passes through three layers - the capillary wall, the basement membrane, and the epithelium of the Bowman's capsule

  4. The basement membrane acts as a molecular filter, allowing only molecules with a molecular mass smaller than 68,000 to pass through

  
• Reabsorption in proximal convoluted tubule

  1. 80-90% of the filtrate is reabsorbed, including water, glucose and ions

  2. The cells have many mitochondria fuelling active transport to selectively reabsorb ions and glucose

  3. Chloride ions are absorbed passively and water follows by osmosis as the solute concentration rises

  
• Role of loop of Henle, medulla, and collecting duct

  1. The descending limb of the loop is permeable to water but impermeable to salts, while the ascending limb is impermeable to water but allows salt to be passed out

  2. This creates a hypertonic environment in the medulla, causing water to leave the filtrate by osmosis and enter the surrounding blood capillaries

  3. The length of the loop of Henle is related to an animal's need to conserve water, with terrestrial animals having a longer loop

  
• Osmoregulation

  1. When filtrate enters the distal convoluted tubule from the loop of Henle, it is hypotonic

  2. The wall of the distal convoluted tubule and collecting duct can have low permeability to water, allowing less water to be reabsorbed if the blood solute concentration is too low

  3. ADH increases the permeability of these regions, allowing more water to be reabsorbed and the blood solute concentration to be maintained

  
• Animals that live in dry environments and need to conserve water

  • Produce small volumes of very concentrated urine
  • Have a longer loop of Henle than species that live in wet environments
• Animals that live in wet environments

  • Have very short loops of Henle
  • Excrete dilute urine
• Osmoregulation


  1. Role of loop of Henle

  2. Role of medulla

  3. Role of collecting duct

  4. Role of ADH
• When filtrate enters the distal convoluted tubule from the loop of Henle, it's solute concentration is lower than that of normal body fluids - it is hypotonic
• If the solute concentration of the blood is too low, relatively little water is reabsorbed as the filtrate passes on through the distal convoluted tubule and the collecting duct
• The wall of the distal convoluted tubule and collecting duct can have an unusually low permeability to water
• A large volume of urine is therefore produced, with a low solute concentration, and as a result, the solute concentration of the blood is increased
• If the solute concentration of the blood is too high, the hypothalamus of the brain detects this and causes the pituitary gland to secrete a hormone - antidiuretic hormone or ADH
• ADH causes the walls of the distal convoluted tubule and collecting duct to become much more permeable to water, and most of the water in the filtrate is reabsorbed
• As the filtrate passes down the collecting duct, it flows deep into the medulla, where the solute concentration of the interstitial fluid is high

  
• Water continues to be reabsorbed along the whole length of the collecting duct and the kidney produces a small volume of concentrated urine

  
• The action of the kidney helps to keep the relative amounts of water and solutes in balance at an appropriate level
• Osmoregulation


  The process of keeping the relative amounts of water and solutes in balance at an appropriate level
• Dehydration


  • Occurs if the body loses more fluid than it takes in
  • Upsets the balance of salts and sugar in the blood
  • Metabolic processes will not take place efficiently
• Early signs of dehydration

  • Extreme thirst
  • Light-headedness
  • Concentrated, dark urine
• Dehydration may occur as a result of excessive sweating, or due to the loss of water in cases of diarrhoea and vomiting