unit 5

• Respiration


  1. Glycolysis

  2. Link reaction

  3. Krebs cycle

  4. Oxidative phosphorylation
• Aerobic respiration


  Respiration in the presence of oxygen
• Anaerobic respiration


  Respiration in the absence of oxygen
• Glycolysis


  1. 6-carbon glucose molecule is phosphorylated and produces two 3-carbon pyruvates

  2. 2 ATP are used and 4 produced, so there is a net gain of 2 ATP
• Link reaction


  1. 3-carbon pyruvate is oxidised

  2. NAD molecule reduced to NADH

  3. Decarboxylation as CO2 is released

  4. Coenzyme A + pyruvate → acetyl coenzyme A
• Krebs cycle


  1. Also known as the citric acid cycle

  2. Takes place in the mitochondria
• Oxidative phosphorylation


  1. Electrons transferred from NADH and FADH2 to protein complexes and electron carriers

  2. Electrons used to create an electrochemical gradient as they are pumped across the intermembrane space

  3. H+ travels to ATP synthase, powering it to make ATP
• Substrate-level phosphorylation


  A phosphate group is transferred from the substrate to ADP
• Oxidative phosphorylation


  Uses energy released from electron transfer in the transport chain to generate ATP in the mitochondrial matrix in the inner mitochondrial membrane
• Anaerobic respiration


  1. Pyruvate from glycolysis converted into lactic acid

  2. Lactic acid dissociates to form lactate and H+

  3. Produces 2 ATP per glucose molecule respired
• Respiratory quotient


  Volume of CO2 produced / volume of O2 used
• Tendons


  Inflexible and connect muscle to bone
• Ligaments


  Flexible and connect bone to bone
• Bones


  • Compact (dense and heavy, long bones, RBCs are made here)
  • Spongy (open structure)
  • Made of collagen and calcium salts in a matrix
• Joints


  • Allow movement and locomotion
  • Produce synovial fluid to reduce friction
• Ball and socket joints


  Allow movement in 3 planes (e.g. shoulder and hip)
• Hinge joints


  Allow movement up and down (e.g. knee and elbow)
• Antagonistic muscle pairs


  Consist of a flexor and extensor working in opposite directions, so when one contracts, the other relaxes
• Cardiac muscle


  • Myogenic - electrical impulses sent from cardiac control centre in medulla
  • Sinoatrial node in right atrium establishes wave of electrical excitation/depolarization
  • Atria begin contracting
  • Atrioventricular node excited
  • Slight delay before depolarization passes into bundle of His in septum
  • Bundle of His splits and carries excitation to Purkyne fibres, which distribute excitation throughout the heart
• Cardiac output


  Volume of blood pumped in a single unit of time
• Tidal volume


  Volume of air that enters and leaves the lungs at each natural resting breath
• Residual volume


  Volume of blood left in lungs after strongest possible exhalation
• Vital capacity


  Maximum volume of air that can be discharged from the lungs following maximum inhalation
• Stroke volume


  Volume of blood per beat
• Respiration minute ventilation


  Volume of gas inhaled (inhaled minute vol) or exhaled from lungs per minute
• Breathing rate


  Number of breaths taken in one minute
• Sliding filament theory


  1. Depolarization triggers release of acetylcholine

  2. Calcium ions bind to troponin and change its shape

  3. Shifts tropomyosin away and exposes myosin binding sites

  4. Actomyosin cross-bridges formed

  5. Hydrolyzed ATP on myosin head released

  6. Another ATP binds to myosin head, and cross-bridge breaks

  7. Repeated reorientation of myosin heads drags actin filaments along myosin, shortening sarcomere
• Adrenaline in fight or flight response

  • Baroreceptors in carotid arteries detect pressure changes and adrenaline needed
  • Sympathetic nerves stimulate adrenal gland to release adrenaline
  • Adrenaline stimulates cardiac control centre in brain
  • Increases heart and breathing rate, vasodilation, blood flow, decreases insulin production
• Positive feedback


  Effectors work to increase the effect/change that triggered the stimulus
• Negative feedback


  Results in a decrease in the change of the variable that triggered the response and maintains systems within narrow limits
• Homeostasis


  The process of maintaining a stable internal environment despite changes in the external environment (e.g. insulin, glycogen, blood glucose)
• Hormones


  Organic chemicals produced in endocrine glands and released into the blood, which travel to target organs to cause changes
• Exocrine gland


  Group of cells that release a substance (e.g. enzymes) into a duct that carries it to where it is needed
• Endocrine gland


  Ductless, releases hormones directly into the blood (e.g. pituitary, thyroid)
• Control of heart rate

  1. Chemoreceptors detect changes in blood pH due to CO2 concentration

  2. Baroreceptors in carotid artery detect changes in blood pressure

  3. Impulses sent to cardiovascular control centre in medulla

  4. Cardiac control centre increases/decreases frequency of impulses to heart via sympathetic nerves

  5. Sinoatrial node stimulated to generate more impulses

  6. Heart rate increases, blood flow to lungs increases, shorter cardiac cycle, more CO2 removed

  7. Parasympathetic nervous system then decreases heart rate if it goes too high
• Control of breathing rate

  1. Chemoreceptors in blood detect pH increase or decrease

  2. Impulses sent to ventilation centre in medulla

  3. Impulses travel along sympathetic nerves

  4. Intercostal muscles and diaphragm contract, lungs inflate, more impulses sent

  5. Respiratory centre inhibited, breathing muscles relax, exhalation, resting rhythm
• Loop of Henle


  1. Freely permeable to water, not permeable to NaCl, no active transport, water moves out through osmosis, hypertonic solution, only this step happens in the descending limb

  2. Very permeable to NaCl, not permeable to water, Na+ and Cl- move out through facilitated diffusion

  3. Impermeable to water, NaCl pumped out through active transport, more dilute/possibly hypotonic solution
• Control of mammalian plasma concentration and blood volume

  1. Osmoreceptors in hypothalamus send impulses to pituitary

  2. Pituitary gland releases ADH

  3. ADH binds to receptors in distal convoluted tubule and collecting duct

  4. Cyclic AMP produced as 2nd messenger, aquaporins move into cell

  5. Distal tubule and collecting duct become more permeable to water

  6. More water reabsorbed

  7. Urea produced by deamination of excess amino acids, removed through ornithine cycle
• Selective reabsorption


  1. Takes place in proximal convoluted tubule

  2. 80% of filtrate reabsorbed

  3. Necessary substances (e.g. Na+) reabsorbed through active transport

  4. Water and Cl- reabsorbed through facilitated diffusion and osmosis down concentration gradient

  5. Only urea, salt, and some water not reabsorbed

  6. Adaptations: microvilli to increase surface area, many mitochondria for ATP, constant blood supply to maintain concentration gradient
• Loop of Henle as countercurrent multiplier

  • Flow of filtrate in opposite directions
  • Sodium ions actively transported out of ascending limb
  • Water moves out from descending limb and solutes move out from ascending limb due to increased concentration gradient between tubular and interstitial fluid