test 2

Question 1

pulmonary ventilation

Answer 1

• first of 4 respiratory processes which consists of 2 phases.
  1. inspiration - gases flow into the lungs
  2. expiration - gases exit the lungs
• movement of air during breathing is reliant on pressure and volume changes

Question 2

process 1 - inspiration

physics and muscles cause pressure relationships

Answer 2

• dependant on thoracic cavity volume changes
• volume changes lead to pressurre changes and pressure changes lead to the flow of gases
• volume changes - pressure changes - flow of gases
• boyles law = P1V1 = P2V2
• if you decrease volume the pressure goes up!!

Question 3

process 1 - physical factors influencing ventilation

Answer 3

• inspiratory muscles consume energy to overcome three factors:
  1. airway resistance to gas flow (friction and diameter, as in blood vessels) - COPD
  2. alveolar surface tension (attraction between liquid molecules at a gas liquid interface) alevoli surfactant
  3. lung compliance (distensibility or stretchiness - high in healthy lungs)

Question 4

process 1 inspiration an expiration

Answer 4

• inspiration is active, inspiratory muscles (diaphragm and external intercostals) contract:
• lungs stretch, intrapulmonary volume increases, intrapulmonary pressure decreases, air flows into the lungs down its pressure gradient = you suck air in!
• quiet expiration is normally passive, inspiratory muscles relax:
• lungs recoil, intrapulmonary volume decreases, intrapulmonary pressure increases, air flows out down its pressure gradient
• forced expiration however is an active process that uses abdominal and internal intercostal muscles

Question 5

respiratory volumes and spirometry

Answer 5

• several volumes and capacities can be described relating to the anatomy of lungs and also the movement of air in and out of lungs
• the study of lung volumes and capacities is called spirometry
• they can distinguish between obstructive pulmonary diseases such as bronchitis and restrictive disorders such as fibrosis

Question 6

process 1 - alveolar ventilation

Answer 6

• the flow of gases into and out of the alveoli during a particular time
• AVR mL/min = frequency x (Vt minus dead space)
• dead space is the volume of air in conducting zone that doesnt reach alveoli
• rapid shallow breathing decreases AVR, slow deep breaths increasing AVR

Question 7

process 2 - external respiration

Answer 7

• exchange of O2 and CO2 across the respiratory membrane from the alveolus into the blood is influenced by a number of chemical and physcial parameters
• first is partial pressure gradients (P= how much gas is around) and gas solubilities (how well it dissolves in blood)
• next is ventilation-perfusion coupling - air movement in alveoli and blood flow around the alveoli must be matched (coupled) for efficient gas exchange
• too little air movement of blood flow can compromise external respiration
• lastly, its influenced by structural characteristics of respiratory membrane- have to be very thin and moist for gas exchange
• ability of lungs and blood to exchange gases depends on amount and solubility of gases, how well air and blood flows match and thickness of the membrane

Question 8

process 3 - transport of respiratory gases

Answer 8

• gases are transported by blood (role of haemoglobin)

Question 9

process 3 - transport of O2 by Hb

Answer 9

98. 5% of molecular O2 is carried in blood by Hb
    - haemoglobin can both bind and unbind O2
    - regulated by many biochemical factors such as temperature
    - we can recall this on a curve called the oxygen-haemoglobin dissociation curve

Question 10

process 3 - transport and exchange of CO2

Answer 10

• CO2 is very soluble in water, so most (80%) is dissolved and transported differently
• about 7-10% dissolves in plasma and 20% is bound to Hb (carbaminohaemoglobin HbCO2)
• majority (70%) is transported as bicarbonate ions (HCO3-) in plasma
• in water CO2 combines to form carbonic acid

Question 11

process 3 - transport and exchange of CO2

Answer 11

• in the systemic capillaries at tissues, CO2 produced by cells changes into HCO3-
• HCO3- is carried by the plasma back to lungs
• in pulmonary capillaries at lung, HCO3- binds with H+ to form H2CO3, which is then split back into CO2 and H2O
• CO2 diffuses into the alveoli and is breathed out

Question 12

process 4 - internal respiration

Answer 12

• movement of gases from blood into body
• partial pressures and diffusion gradients are reversed:
• Po2 in tissue is always lower than in systemic arterial blood , O2 diffuses from blood to cells
• Pco2 at tissue is higher than in blood, CO2 moves from cells to blood

Question 13

neural control of respiration

Answer 13

• regulated in neurons by brain stem

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