Topic 2 ~ SEHS

• Principal structures of the ventilatory system:

  • Nose
  • Mouth
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Bronchioles
  • Lungs
  • Alveoli
• Function of the conduction airways:

  • Low resistance pathway for airflow through structural supports like nasal passages and ridges on the pharynx
  • Defence against harmful substances by trapping particles in nasal hair, saliva, and mucus
  • Warming and moistening the air due to core temperature and air chamber in the nose and mouth
• Definitions:

  • Pulmonary ventilation: inflow and outflow of air between the atmosphere and the lungs
  • Total lung capacity: volume of air in the lungs after maximum inhalation
  • Vital capacity: maximum volume of air exhaled after maximum inhalation
  • Tidal volume: volume of air breathed in and out in one breath
  • Expiratory reserve volume: volume of air in excess of tidal volume that can be exhaled forcibly
  • Inspiratory reserve volume: additional inspired air over and above tidal volume
  • Residual volume: volume of air still contained in the lungs after maximum exhalation
• Mechanics of ventilation in the human lungs:

  • Inspiration:
  • External intercostal muscles contract
  • Diaphragm contracts and becomes flatter
  • Ribs and sternum move upwards and outwards
  • Increase in thoracic volume which decreases thoracic pressure
  • Expiration:
  • External intercostal muscles relax
  • Diaphragm relaxes and domes upwards
  • Ribs and sternum move downwards and inwards
  • Decrease in thoracic volume which increases thoracic pressure
• Nervous and chemical control of ventilation during exercise:

  • Nervous control:
  • Breathing rate increases due to proprioceptors in muscles and joint receptors
  • Information sent to the Respiratory Control Centre (RCC) in the medulla oblongata
  • Impulse sent to respiratory muscles via phrenic nerves
  • Chemical control:
  • Increase in blood acidity levels due to CO2 and H+ ions
  • Detected by chemoreceptors in the carotid artery
  • Information sent to RCC to increase rate and depth of ventilation
• Role of haemoglobin in oxygen transportation:

  • Haemoglobin transports oxygen from lungs to tissues
  • Most oxygen in blood is transported by haemoglobin as oxyhemoglobin
  • Haemoglobin carries oxygen and carbon dioxide in red blood cells
  • Has high affinity for oxygen and is an iron compound
• Process of gaseous exchange at the alveoli:

  • Gaseous exchange is inspiring oxygen into the body and expelling carbon dioxide out
  • Occurs across the respiratory membrane in pulmonary diffusion
  • Oxygen diffuses from alveoli to capillaries to oxygenate blood
  • Carbon dioxide diffuses from capillaries to alveoli to be expelled
• Composition of blood:

  • Cells: Erythrocytes, Leucocytes, Platelets
  • Plasma: formed from water, dissolved gases, and nutrients
  • Blood is transport vehicle for electrolytes, proteins, gases, nutrients, waste products, and hormones
• Functions of erythrocytes, leucocytes, and platelets:

  • Erythrocytes: carry oxygen, contain haemoglobin, produced in flat bones and red blood cells
  • Leucocytes: fight infection, involved in immune function, produced in bone marrow
  • Platelets: help form blood clots, assist in repair following injury, produced in bone marrow
• Blood clotting:

  • Helps to stop bleeding and prevent loss of body fluids
  • Assists in the process of repair following injury
  • Produced in bone marrow
• Anatomy of the heart:

  • Four chambers: Left atrium, Right atrium, Left ventricle, Right ventricle
  • Both ventricles have thicker walls than the atria
  • Left ventricle is the thickest
  • Four valves: Bicuspid, Tricuspid, Aortic valve, Pulmonary valve
  • Four major blood vessels: Vena cava, Pulmonary vein, Aorta, Pulmonary artery
• Blood flow through the heart:

  1. Deoxygenated blood travels from the body to the right side of the heart via superior and inferior vena cava

  2. Deoxygenated blood enters right atrium and goes through tricuspid valve to right ventricle

  3. Deoxygenated blood travels through pulmonary valve and out of pulmonary artery to the lungs

  4. Blood becomes oxygenated and taken to the heart via pulmonary veins into left atrium

  5. Blood goes through bicuspid valve to left ventricle

  6. Travels through aortic valve and aorta to the rest of the body

  7. Body uses oxygen and blood becomes deoxygenated
• Intrinsic regulation of heart rate:

  • Sinoatrial Node (SA) acts as an internal pacemaker
  • SA node generates electrical impulses
  • Atrioventricular Node (AV) creates a delay between atrial and ventricular contractions
  • Parasympathetic system slows down heart rate
  • Sympathetic system increases heart rate
• Extrinsic regulation of heart rate:

  • Controlled by external factors besides the SA node
  • Receptors like proprioceptors, baroreceptors, and chemoreceptors send impulses to the cardiac control center in the medulla oblongata
  • Parasympathetic nerves slow heart rate
  • Sympathetic nerves increase heart rate
• Relationship between pulmonary and systemic circulation:

  • Pulmonary circulation delivers deoxygenated blood from the heart to the lungs
  • Systemic circulation delivers deoxygenated blood from the heart to the body
  • Both systems are essential for oxygen transfer and bodily functions
  • Pulmonary circulation has lower blood pressure than systemic circulation
• Relationship between heart rate, cardiac output, and stroke volume during exercise:

  • Cardiac output increases with exercise due to increased stroke volume and heart rate
  • Heart rate increases in direct proportion to exercise intensity
  • Max stroke volume is achieved during sub-maximal exercise
• Cardiovascular drift:

  • Gradual increase in heart rate during prolonged sub-maximal exercise
  • Core body temperature increases, leading to dehydration and redistribution of blood
  • Blood becomes more viscous, decreasing venous return and stroke volume
  • Heart rate increases to maintain cardiac output
• Systolic and diastolic blood pressure:

  • Systolic: Highest pressure during ventricular contraction
  • Diastolic: Lowest pressure during ventricular relaxation
• Systolic and diastolic blood pressure data:

  • Normal range at rest: 120/80 mmHg
  • Diastolic pressure remains constant during exercise
  • Systolic pressure increases during exercise
• Systolic blood pressure:

  • At rest, approximately 120mmHg
  • Increases during exercise due to the increase in muscular tissues needed for oxygen
  • Both stroke volume (SV) and heart rate (HR) increase during exercise
  • More forceful and frequent contractions of the heart lead to a higher cardiac output affecting systolic pressure
• Diastolic blood pressure:

  • At rest, 80mmHg
  • Remains constant during exercise due to dilation of arterial walls to increase venous return to the heart
  • Can slightly decrease in trained athletes in some cases
• Dynamic exercise:

  • Involves vigorous rhythmic exercise
  • Venous return is bigger and blood flow is higher due to dilation of blood vessels in active muscles
  • Heart pumps harder and more frequently, increasing blood pressure
  • Systolic blood pressure increases rapidly at the start of exercise and levels off
  • Diastolic pressure remains constant
  • Increase in systolic pressure helps increase blood flow to working muscles
• Static exercise:

  • Involves high resistance exercise focusing on muscle tension
  • Big increases in both systolic and diastolic pressure due to mechanical compression of the peripheral arterial system
  • Blood pressure is much higher than in dynamic exercise
  • Not advised for people with coronary heart disease
• During rest:

  • Blood is distributed at a slower rate, around 20% of total blood flow
  • Blood is directed to all organs evenly
  • Skin has minimal blood flow at rest
• During exercise:

  • Blood is distributed at a faster rate, active muscles can demand 85-90% of total blood flow
  • Increased cardiac output directs more blood to active muscles
  • Blood flow increases to heart and lungs
  • Increased acidity/CO2/temperature trigger vasodilation and vasoconstriction
  • Blood moves to working muscles due to vasodilation
• Cardiovascular adaptations from endurance exercise training:

  • Increased left ventricle volume leads to increased stroke volume
  • Lower resting and exercise heart rate
  • Increased arterio-venous oxygen difference
  • Larger and more numerous mitochondria in trained skeletal muscle
  • Increased aerobic system enzyme activity
  • Increased glycogen storage in muscle
  • Slight cardiac hypertrophy
  • Increase in blood plasma volume
  • Increase in cardiac output
  • Increase in blood volume and red blood cells
• Maximal oxygen consumption (VO2max):

  • Represents the maximum rate an individual can take in and use oxygen
  • Determined by maximal HR, SV, and arteriovenous oxygen difference
  • Often expressed in ml per kg of body weight per minute
  • Indicator of aerobic potential
  • Can be measured using tests like treadmill test or beep test
  • Varies depending on mode of exercise
  • Aerobic training improves physiological features
• Variability of maximal oxygen consumption in selected groups:

  • Males typically have 40-60% higher VO2max than females
  • Trained individuals have higher VO2max due to physiological adaptations
  • VO2max increases from childhood to young adulthood and decreases with age
  • Regular exercise can slow the decline in VO2max with age
• Variability of maximal oxygen consumption with different modes of exercise:

  • Treadmill running produces higher VO2max values compared to cycling or arm ergometry
  • Competitive cyclists achieve scores equal to their treadmill VO2max scores
  • Arm ergometry aerobic capacity reaches only about 70% of treadmill VO2max scores