Unit 4- Respiratory Phys. Flashcards
VC
vital capacity (4,500 ml) - maximum amount of air a person can exhale after taking the deepest breath possible
VC = TV + ERV + IRV
= tidal volume + expiratory reserve vol. + inspiratory reserve volume
TLC
Total Lung Capacity 5,700 ml) -
TLC = VC + RV
= vital capacity + residual volume
TV
Tidal Volume (500 ml) - amount of air that enters lungs during a normal, quiet inspiration.
TV = VC - (IRV + ERV)
= vital capacity - (inspiratory reserve vol + expiratory reserve vol)
RV
Residual Volume (1,200 ml) - even after a forceful expiration, some air remains in the lungs. Prevents lungs from collapsing.
RV = FRC - ERV
= functional residual capacity - expiratory reserve vol
Dead space
About 150 ml - air entering the respiratory tract that fails to reach the alveoli. Air remains in trachea, bronchi & bronchioles where gas exchange cannot take place.
How is Carbon Dioxide transported in the body?
~60% as bicarbonate ion (HCO3-) in the plasma
~30% as bound to the protein portion of Hb in RBC (cabaminohemoglobin, HbCo2)
~10% dissolved in plasma
What is the OD Curve?
- oxygen dissociation (sigmoid) curve
- shows the relationship between Po2 and % Hb saturation
What is the significance of the Plateau Portion of the OD curve?
- Top part of the curve (on the right)
- Where the P02 is high (lungs)
- Even with a 40% decrease in P02, O2 content of blood is only slightly reduced (from 97.5% to 90%)
What is the significance of the Steep Portion of the OD curve?
- left side of curve
- only a small drop in blood PO2 can make large amounts of O2 available to active tissues
A right shift of the OD curve indicates higher oxygen……
unloading (reduced affinity)
carbonic anhydrase
- causes C02 to combine with H20 to make bicarbonate ions w/in red blood cells
- in this version is how 60% of C02 travels in RBC
Chloride Shift
- Diffusion of bicarbonate ions (HCO3-) out of RBC into plasma & Cl- ions into the RBC
- important to keep the charge of the cell stable
Haldane Effect
- Deoxygenated Hb has a greater affinity to CO2 than oxygenated Hb
- overall effect:
- O2 unloading in tissues causes CO2 loading to Hb
- O2 loading in lungs causes CO2 unloading from Hb
hypoxia
insufficient oxygen at cellular level
- hypoxic hypoxia: due to a low Po2 in arterial blood
- anemic hypoxia: due to reducted O2-carrying capacity in blood
- stagnant hypoxia: inadequate oxygen delivered to tissues
hyperoxia
an above-normal partial pressure of Po2
hypercapnia
an excess of CO2 in blood caused by hypoventilation
hypocapnia
below-normal level of CO2 in the blood due to hyperventilation
respiratory acidosis
decrease in pH due to increased H+ produced when CO2 accumulates b/c of hypoventilation
What are the PHYSICAL factors influencing ventilation?
- Airway resistance: relationship between Flow, pressure & resistance
- Elastic behavior of lungs: compliance (expand) & elastic recoil
- Alveolar surface tension: influences elastic behavior of lungs
compliance
- ability to stretch; ease with which lungs can be expanded
- determined by (1) distensibility of lung tissue _ thoracic cage, and (2) surface tension of alveoli
- High compliance = stretches easily
- Low compliance = requires more force
elastic recoil
- returning to its resting volume when stretching force is released
- surface tension of alveolar fluid draws alveoli to their smallest possible size
- ELASTANCE: measure of how readily the lungs rebound after being stretched.
Neural control of respiration
- Medullary respiratory centers
2. Pons respiratory centers
Medullary Respiratory center
- dorsal respiratory group (DRG)
2. ventral respiratory group (VRG)
Dorsal Respiratory group (DRG)
- Part of Medullary Respiratory center
- Excites inspiratory muscles
Ventral respiratory group (VRG)
- Part of Medullary Respiratory center
- Active when ventilation demands increase
Pre-Botzinger complex
- Neurons show pacemaker activity: sends signals to DRG
Pontine respiratory group (PRG) [aka Pons Respiratory centers]
Has greater influence on respiration than the medulla
- pneumotaxic center
- apneustic center
pneumotaxic center
sends impulses to DRG that help “switch off” inspiratory neurons, limiting the duration of inspiration
apneustic center
prevents inspiratory neurons from being switched off
Hering-Breuer (inflation) reflex
- triggered to prevent overinflation of lungs
- pulmonary stretch receptors
Where are the peripheral chemoreceptors located and what do they do?
- Located in the carotid & aortic bodies
- respond to low levels of Po2
- used only in dire situations; as will only respond when Po2 goes below 60 mmHg
- stimulate the medullary centers - increase ventilation
Where are the central chemoreceptors located & what do they do?
- in the brain (medullary center)
- sensitive to CO2-induced H+ concentration in the brain ECF that bathes them.
- increased H+ increases ventilation
What 3 pressures are involved in ventilation?
- atmospheric
- intra-alveolar
- intra-plueral pressure
