Chapters 12,14,15,16,17

• Purpose of the lungs

  Facilitate exchange of gases (oxygen and carbon dioxide) between air and blood. Average size lung= 2.3 kg with a volume of 4 to 6 L
• Components of breathing

  1. Nose/mouth: air entry

  2. Trachea: filters and humidifies air

  3. Bronchi and bronchioles: air passage that branches into lungs

  4. Alveoli: over 600 million sacs where gas exchange occurs
• Expiration

  Diaphragm relaxes and moves up, chest cavity shrinks and air is pushed out
• Surfactant

  -lipoprotein mixture of proteins, phospholipids, and calcium ions

  -reduces surface tension within alveoli, making it easier for them to expand during inhalation

  -prevents alveoli from collapsing from high pressures
• Fick’s law of diffusion 


  states that the rate of gas transfer through a membrane is proportional to the tissue area, the diffusion constant of the gas, and the difference in partial pressures of the gas across the membrane. This law explains how gases like oxygen and carbon dioxide efficiently exchange between the alveoli in the lungs and the blood in pulmonary capillaries, driven by differences in gas concentration and membrane characteristics.
• (TV)


  Tidal volume

  Amount of air inhaled or exhaled in a normal breath

  (0.4 to 1.0 L of air per breath)
• IRV & ERV

  Inspiratory reserve volume: volume of air inhaled in a normal inspiration (2.5-3.5 L)

  Expiratory reserve volume: volume of air exhaled in a normal expiration (1-1.5)
• RVL 


  Residual lung volume

  Air left in lungs after a full exhale, important for continuous gas exchange. Increases with age

  women=0.8-1.2

  men=0.9-1.4

  Temporarily increases from short or long exercise
• FVC


  Forced vital capacity

  Total volume of air moved in one maximal breath TV plus IRV plus ERV = 3-5 L
• TLC


  Total lung capacity

  RLV plus FVC
• FEV


  Forced expiratory volume

  Amount of air expelled in one second during a forceful breath out
• VE


  Minute ventilation

  Total volume of air breathed per minute
• MVV


  Maximum voluntary ventilation

  Max air volume moved in and out of the lungs during intense breathing for a short period of time
• Gender differences 


  Women have reduced lung size and airway diameter, smaller diffusion surface, and lower static/dynamic lung function than men

  This leads to limitations in expiratory flow which results in greater respiratory muscle work and greater use of ventilatory reserve during maximal exercise in women
• Anatomic dead space 


  portion of the respiratory system that is involved in air transport but does not participate in gas exchange. 150 to 200 milliliters volume don’t reach the alveoli
• Hyperventilation


  Too much oxygen consumption and not enough carbon dioxide elimination
• dyspnea 


  shortness of breath
• Pulmonary ventilation


  Adjusts breathing rate and depth to meet body’s needs, it is controlled by neural circuits that receive signals from the brain lungs and chemical sensors. Ensure stable alveolar gas pressures during exercise
• Inspiratory neurons 


  Located in the medulla

  Activate diaphragm and intercostal muscles to begin inhalation
• Expiratory neurons 


  Inhibit inspiratory neurons, controlling the duration and cessation of inspiration
• Humoral factors


  At rest, the bloods chemical state exerts greatest control on pulmonary ventilation
• Peripheral chemoreceptors 


  Located in carotid bodies

  These sensors react to decreases in arterial Po2 by increasing ventilation, modulate changes in blood acidity, CO2 and temperature
• breath holding 


  When holding breath it takes 40s for urge to breathe
• Temperature 


  Little to no effect on breathing rates except for hyperthermia
• Carbon dioxide and pH balance 


  -CO2 level increases can cause very high ventilation rates

  -blood acidity linked to CO2 levels and carbonic acid concentration directly affects breathing

  -lowering pH (increasing acidity) stimulates ventilation to expel CO2 and lower carbonic acid
• Neurogenic factors 


  Cortical influence: inputs from motor cortex that anticipate exercise

  Peripheral influence: sensory input from joints and muscles, adjusting ventilation fast at the onset and cessation of activity
• Ventilation phases in physical activity 


  Phase 1: immediate increase in ventilation due to neurogenic stimuli to medulla

  Phase2: ventilation plateaus and then increases with metabolic gas exchange needs

  Phase 3: steady-rate through peripheral sensory feedback
• Lactate threshold (LT) and OBLA 


  Indicate exercise intensities where lactate begins to accumulate significantly in blood, affecting performance and ventilation
• COPD


  chronic obstructive pulmonary disease

  Increases the energy cost of breathing and limit exercise capacity due to added resistance and impaired gas exchange
• Cigarette smoking 


  -increases airway resistance 3x at rest

  -resistance comes from: vagal reflex (cigarette particles) and parasympathetic ganglia (nicotine)
• Acid-base balance 


  Body maintains a pH between 7.35 and 7.45 through buffering systems
• Alkalosis and acidosis

  Alkalosis-decrease in H+ concentration=release H+

  Acidosis-increase in H+ concentration=weak acid
• Chemical buffers

  -Bicarbonate buffers: hydrochloric acid and sodium bicarbonate

  -Phosphate buffers: phosphoric acid and sodium phosphate

  -Protein buffers: hemoglobin
• Vagus nerve

  Bradycardia results from stimulation of vagus nerve from medulla’s cardioinhibitory center
• buffering 


  body's method of managing the pH balance in the muscles by neutralizing acids and utilizing lactate efficiently to sustain energy production under anaerobic conditions.
• the heart 


  Weighs 11 oz. for average male, 9 oz. for female

  Pumps ~70 mL for each beat (stroke volume) at rest

  At rest in 1 day, ~1900 gallons pumped through

  the heart
• myocardium 


  heart muscle, connected in latticework fashion for the heart to function as a unit. STRIATED MUSCLE
• Right and left side 


  Right side receives blood returning from body to the lungs

  Left side receives oxygenated blood from lungs and pump it into aorta for distribution throughout the body

  separated by interventricular septum
• Atrioventricular valves

  Tricuspid - one-way flow from right atrium to right ventricle

  Bicuspid - one-way blood flow from left atrium to left ventricle
• Semilunar valves


  located in arterial wall, prevent blood flow back into the heart.

  70% of blood returning to atria flows into ventricles before contraction

  After atrial contraction, ventricles contract and propel blood into arteries