Respiratory System III Flashcards
tidal volume
inspiratory reserve volume
expiratory reserve volume
residual volume
tidal volume: volume of air entering resp system with each breath
inspiratory reserve volume: extra air entering lungs with maximal inspiration on top of TV
expiratory reserve volume: extra air expelled from lungs with maximum expiration (after passive expiration)
residual volume: volume of air left in lungs after maximum expiration
why are children at a greater risk of hypoxia under sedation
they have a smaller residual volume and faster metabolic rate
airway resistance relationship to airway diameter
decreased airway diameter leads to increased airway resistance
airways in allergic reactions
histamine causes smooth muscle contraction of airways
constricts the bronchioles and increases resistance
reduced airflow and restricted breathing
effect of epinephrine on airway resistance
epinephrine released by adrenal medulla causes smooth muscle relaxation
dilates the bronchioles and reduces resistance
increased airflow and gas exchange
lung compliance
what does it depend on
change in lung volume / change in airway pressure
ease with which the lungs can expand
depends on:
- extent of elastic fibres ability to stretch
- surface tension within alveoli
- mobility of thoracic cage
what can affect mobility of thoracic cage
arthritis
surfactant role in alveolus
prevents collapse and promotes lung expansion
increases lung compliance
respiratory minute ventilation
Ve = f x Vt
volume of air moved/min = breaths/min x tidal volume
alveolar ventilation
Va = f x (Vt - Vd)
alveolar ventilation = breaths/min x (tidal volume - dead space)
what can cause changes in tidal volume and dead space
what happens in regions of the lung with high airflow compared to blood supply
increased pO2 causes local arterioles to dilate
more blood is made available for O2 to be picked up
decreased pCO2 causes bronchioles to constrict reduced the airflow proportional to the airflow
what happens in regions of the lung with restricted airflow such as blocked by mucous
lowered pO2 causes local arterioles to constrict
blood is re-channelled t alveoli with higher airflow allowing more available O2 to be picked up
increased pCO2 causes bronchioles to dilate
to increase airflow and enhance CO2 elimination
where are respiratory control centres
what do they do
brainstem
integrate signals received from sensory receptors and other regions of the brain
what does the dorsal respiratory group consist of
what is the cycle
inspiratory neurons only
send signals for 2 secs causing resp muscle contraction
stop impulses for 3 secs causing relaxation
normal breathing rate
12 -20 breaths / min
what does the ventral respiratory group consist of
what do they innervate
inspiratory neurons and expiratory neurons
innervates lower motor neurons controlling accessory muscles
what allows smooth transition between inspiration and expiration
Pons
central chemoreceptors location and role
medulla
monitor pH - dependant on CO2 levels in the brain
signal directly to respiratory centres to regulate ventilation
peripheral chemoreceptors location and role
carotid bodies and aortic bodies
monitor pH, cCO2 and pO2 in arterial blood
signal to respiratory centres via glossopharyngeal and vagus nerves respectively
how do central chemoreceptors sense changes in pCO2
CO2 readily crosses BBB and combines with water forming carbonic acid
dissociates to H+ and bicarbonate
H+ stimulates central chemoreceptor which sends impulses
how do central chemoreceptors sense distinguish H+ from CO2 increase and metabolic changes
why are peripheral chemoreceptors indiscriminate to the cause of H+ increase
why does pH increase in hyperventilation
why does pH decrease in hypoventilation
respiratory acidosis vs alkalosis
acidosis: failure to get rid of CO2 generated by tissues
alkalosis: removal of too much CO2
metabolic acidosis vs alkalosis
acidosis: tissues generate excess acid or kidneys fail to get rid of acid (diabetic ketoacidosis)
alkalosis body has lost acid or gained alkali (prolonged vomiting)
factors affecting ventilation other than normal
voluntary control
pain and emotions
pulmonary irritants
lung hyperinflation
deflation reflex
