Physiology Revision Guide

• Aerobic exercise


  Uses oxygen in the process of supplying energy to the body, low-intensity, allows talking (e.g. walking, jogging, cycling, swimming)
• Anaerobic exercise


  Does not use oxygen in the process of supplying energy to the body, high-intensity, does not allow talking (e.g. sprinting, high jump, speed swimming, 400m running)
• Cardiovascular system


  • Consists of the heart and the blood vessels through which the heart pumps blood around the body
• Cardiovascular system's initial response to exercise

  1. Heart rate increases to ensure working muscles receive adequate oxygen and nutrients, and waste products are removed

  2. Anticipatory rise in heart rate before exercise starts due to adrenaline release

  3. Increase in carbon dioxide and lactic acid detected by chemoreceptors triggers sympathetic nervous system to increase adrenaline release

  4. Increase in temperature increases conduction of nerve impulses across the heart
• Cardiac output


  Amount of blood pumped from the heart every minute, calculated as heart rate x stroke volume
• Blood pressure


  Necessary for blood to flow around the body, determined by cardiac output and resistance to blood flow
• Exercise increases heart rate


  Increases cardiac output
• Increased cardiac output and unchanged resistance

  Increases blood pressure
• Pulmonary ventilation


  Amount of air breathed in and out per minute, calculated as breathing frequency x tidal volume
• Respiratory system's initial response to exercise

  1. Breathing rate and tidal volume increase to meet increased oxygen demand

  2. Intercostal muscles aid breathing

  3. Valsalva manoeuvre used in anaerobic exercise to stabilise shoulder girdle and torso
• Neuromuscular system


  Communication between brain and muscles via nerve impulses (action potentials) through motor neurones
• Motor unit


  Group of muscle fibres stimulated by one nerve
• Muscle spindle


  Organ within muscle that detects muscle contraction and communicates this to the central nervous system
• ATP


  Adenosine triphosphate, protein with three phosphates attached, energy released when phosphate is broken off
• Phosphocreatine (PC) energy system

  Anaerobic system that supplies ATP quickly at the onset of exercise
• Lactic acid energy system

  Anaerobic glycolysis, breakdown of glucose to pyruvate and then lactic acid, produces ATP quickly but not as fast as PC system, used for high-intensity exercise 30 seconds to 3 minutes
• Lactic acid energy system


  The energy system that produces the majority of ATP during high-intensity exercise lasting between 30 seconds and three minutes, such as an 800m race
• Lactic acid energy system

  • It has to be continually made from ADP for our muscles to continue contracting
  • There are three energy systems that the body uses to make ATP, they differ in the rate at which they make ATP
• Phosphocreatine energy system


  1. Supplies ATP much quicker than any other energy system

  2. Produces ATP in the absence of oxygen, and is therefore an anaerobic energy system

  3. PC stores are used for rapid, high-intensity contractions, such as in sprinting or jumping

  4. PC stores only last for about ten seconds
• At the onset of exercise, the various systems respond to try to increase oxygen delivery, energy production and carbon dioxide removal
• Responses at onset of exercise

  • Cardiovascular system: increased heart rate, increased blood pressure, increased cardiac output
  • Respiratory system: increased pulmonary ventilation, increased breathing rate, increased tidal volume
  • Neuromuscular system: increased number of nerve transmissions, skeletal muscular contraction
  • Energy system: ATP production through phosphocreatine energy system and lactic acid energy system
• Venous return


  The amount of blood returned to the heart after circulating around the body
• During exercise, there is an increase in venous return

  This has the effect of stretching the cardiac muscle to a greater degree than normal, making the heart contract much more forcibly and thereby pumping out more blood during each contraction
• Starling's law


  The effect of increased stroke volume during exercise
• Vasoconstriction


  The process of blood vessels becoming smaller
• Vasodilation


  The process of blood vessels becoming larger
• Dilation of the blood vessels feeding the working muscle

  Acts to reduce blood pressure, but this is counteracted by the increase in blood pressure caused by increased cardiac output
• Exercise raises systolic pressure, but there is only a slight change in diastolic pressure
• Immediately after exercise there is a fall in systolic pressure, as the skeletal muscular pump is no longer pumping blood from the muscles to the heart. This can lead to blood pooling in the muscles and cause the athlete to faint, as not enough blood is being pumped to the brain
• Thermoregulation


  The process of maintaining a constant body core temperature
• When exercising, we produce a great deal of excess heat. The cardiovascular system is vitally important in ensuring that we are able to lose this excess heat so that our core temperature does not increase
• Excess heat is lost through sweating and dilatation of peripheral blood vessels, so that blood passes close to the surface of the skin. As the sweat evaporates, it cools down the skin surface
• When we are exercising at a high intensity in hot conditions, between 15 and 25 per cent of the cardiac output is directed to the skin
• After having peaked in the first few minutes, if exercise remains at the same intensity, tidal volume and breathing rate level off and remain the same until exercise is terminated
• Oxygen dissociation curve


  An S-shaped curve that represents the ease with which haemoglobin releases oxygen when it is exposed to tissues of different concentrations of oxygen
• Only 1.5 per cent of oxygen is carried in the blood plasma. The majority of oxygen is transported in the blood by haemoglobin
• Oxygen reacts with haemoglobin to make oxyhaemoglobin. The reaction of oxygen with haemoglobin is temporary and completely reversible
• Changes in blood carbon dioxide level and hydrogen ion concentration (pH) cause shifts in the oxygen dissociation curve. These shifts enhance oxygen release in tissues and increase oxygen uptake in the lungs
• Bohr effect


  The shift in the oxygen dissociation curve caused by changes in blood carbon dioxide level and pH, named after the Danish physiologist Christian Bohr who discovered it
• During exercise, the blood becomes more acidic because of the increased production of carbon dioxide