phys/pharm

• Monitor the patient for adverse reactions
• Pharmacodynamics


  Terminology around the study of the effects of drugs on the body
• Antagonist


  Blocks receptor activation
• Partial Agonist


  Produces partial response
• Affinity


  Strength of drug-receptor binding
• Potency


  Concentration needed for effect
• Respiration


  Glucose + O2 → ATP + CO2 + H2O + heat
• Purposes of Respiration


  • Deliver O2 to cells for the purpose of cellular respiration (energy production!)
  • Remove CO2
• Required for Respiration


  • System of conduits (pipes)
  • Large diffusion surface area
• Respiratory Anatomy


  • Respiratory tract (passageways)
  • Lungs (diffusion surface area)

  
• Upper Respiratory Tract


  • Nasal cavities
  • Pharynx

  
• Lower Respiratory Tract


  • Trachea
  • Bronchial tree

  
• The Lungs


  • R: 3 lobes
  • L: 2 lobes
• The Bronchial Tree


  • Consists of primary bronchi and 13 generations of their branches
  • 300,000 bronchioles in each lung
• Two Zones of the Bronchial Tree

  • Conducting zone
  • Respiratory zone
• Conducting Zone


  • Extends from trachea to terminal bronchioles
  • Walls of upper regions are composed of cartilage and smooth muscle lined with pseudostratified ciliated columnar epithelium
  • Walls of smaller tubes lined with cuboidal epithelium
  • No gas exchange occurs here
• Anatomical Dead Space Volume


  Volume of gases in the upper respiratory tract and the conducting zone of the lower respiratory tract where gas exchange does not occur, approximately 150 mL

  
• Respiratory Zone


  • Extends from respiratory bronchioles to alveoli (150 million per lung)
  • Walls very thin (simple squamous epithelium)
  • Site of gas exchange

  
• Respiratory Membrane (Alveolar Wall)


  • Endothelium of pulmonary capillaries
  • Type I alveolar cells (squamous epithelium 1 cell thick)

  
• Processes Involved in Gas Exchange

  • Ventilation
  • External respiration
  • Gas transport
  • Internal respiration
  • Cellular respiration
• Ventilation


  "Breathing" or "respiration", movement of gases between the atmosphere and the alveoli
• Lungs


  • Have no means of moving by themselves, they move only in response to changes in pressure in the intrapleural and intrapulmonary spaces
• Intrapulmonary Space


  Space within the lungs
• Intrapleural Space


  Space between the parietal and visceral pleurae
• Pressure Changes Associated with Ventilation

  • Atmospheric pressure = 760 mm Hg
  • Intrapulmonary pressure changes +/- relative to atmospheric pressure
  • Intrapleural pressure is always negative (-2 to -5 mm Hg)
• Boyle's Law


  If temperature is held constant, the pressure of a gas varies inversely with its volume
• Inspiration


  1. Thorax expands

  2. Diaphragm descends

  3. Intrapleural volume increases

  4. Intrapleural pressure decreases

  5. Lung tissue is pulled outward

  6. Alveoli expand

  7. Intrapulmonary volume increases

  8. Intrapulmonary pressure decreases

  9. Air is drawn into alveoli
• Hering-Breuer Reflex


  Stretch receptors in the lungs, visceral pleura and bronchioles are stimulated by inspiration, sending impulses to the respiratory centre to terminate inspiration and initiate expiration, preventing over-inflation of the lungs
• Expiration


  1. Diaphragm relaxes

  2. Thoracic wall and lungs recoil

  3. Alveoli recoil

  4. Intrapulmonary volume decreases

  5. Intrapulmonary pressure increases

  6. Air is driven out of the lungs
• Airway Resistance


  Affected by bronchiole diameter, increased by bronchoconstriction and decreased by bronchodilation
• Gas Flow


  Gas flow = pressure gradient / resistance, increased resistance results in decreased flow
• Poiseuille's Law


  F = Pr^4/8L, when the radius is reduced to 1/2, the flow is reduced to 1/16
• Lung Expansion


  • Maintained by negative pressure in intrapleural space
  • Opposed by elastic recoil of the lungs and surface tension within alveoli (normally low due to surfactant)
• Surfactant


  Secreted by type II alveolar epithelial cells, reduces surface tension within alveoli
• Normal Lung Volumes/Capacities


  • Tidal volume (TV)
  • Inspiratory reserve volume (IRV)
  • Expiratory reserve volume (ERV)
  • Residual volume (RV)
  • Vital capacity
  • Total lung capacity (TLC)

  
• Forced Expiratory Volume (FEV1)

  Volume of air that can be forcibly exhaled in 1 sec. (after maximum inhalation), normally equal to about 80% of FVC
• Processes Involved in Gas Exchange

  • Ventilation
  • External respiration
  • Gas transport
  • Internal respiration
  • Cellular respiration
• External Respiration


  Diffusion of gases between the alveolar air and the blood, occurs in the lungs

  
• Factors Determining Diffusion (of Gases)


  • Surface area for diffusion
  • Thickness of the diffusion membrane
  • Solubility of gases
  • Partial pressure of gases
  • Ventilation-perfusion ratio
• Surface Area for Diffusion

  • Normal alveolar surface area is about 70 m2, may be reduced by disease (emphysema, pulmonectomy)