Respiratory System III

Question 1

tidal volume
inspiratory reserve volume
expiratory reserve volume
residual volume

Answer 1

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

Question 2

why are children at a greater risk of hypoxia under sedation

Answer 2

they have a smaller residual volume and faster metabolic rate

Question 3

airway resistance relationship to airway diameter

Answer 3

decreased airway diameter leads to increased airway resistance

Question 4

airways in allergic reactions

Answer 4

histamine causes smooth muscle contraction of airways
constricts the bronchioles and increases resistance
reduced airflow and restricted breathing

Question 5

effect of epinephrine on airway resistance

Answer 5

epinephrine released by adrenal medulla causes smooth muscle relaxation
dilates the bronchioles and reduces resistance
increased airflow and gas exchange

Question 6

lung compliance
what does it depend on

Answer 6

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

Question 7

what can affect mobility of thoracic cage

Answer 7

arthritis

Question 8

surfactant role in alveolus

Answer 8

prevents collapse and promotes lung expansion
increases lung compliance

Question 9

respiratory minute ventilation

Answer 9

Ve = f x Vt

volume of air moved/min = breaths/min x tidal volume

Question 10

alveolar ventilation

Answer 10

Va = f x (Vt - Vd)

alveolar ventilation = breaths/min x (tidal volume - dead space)

Question 11

what can cause changes in tidal volume and dead space

Question 12

what happens in regions of the lung with high airflow compared to blood supply

Answer 12

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

Question 13

what happens in regions of the lung with restricted airflow such as blocked by mucous

Answer 13

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

Question 14

where are respiratory control centres
what do they do

Answer 14

brainstem
integrate signals received from sensory receptors and other regions of the brain

Question 15

what does the dorsal respiratory group consist of
what is the cycle

Answer 15

inspiratory neurons only

send signals for 2 secs causing resp muscle contraction
stop impulses for 3 secs causing relaxation

Question 16

normal breathing rate

Answer 16

12 -20 breaths / min

Question 17

what does the ventral respiratory group consist of
what do they innervate

Answer 17

inspiratory neurons and expiratory neurons
innervates lower motor neurons controlling accessory muscles

Question 18

what allows smooth transition between inspiration and expiration

Answer 18

Pons

Question 19

central chemoreceptors location and role

Answer 19

medulla
monitor pH - dependant on CO2 levels in the brain
signal directly to respiratory centres to regulate ventilation

Question 20

peripheral chemoreceptors location and role

Answer 20

carotid bodies and aortic bodies
monitor pH, cCO2 and pO2 in arterial blood
signal to respiratory centres via glossopharyngeal and vagus nerves respectively

Question 21

how do central chemoreceptors sense changes in pCO2

Answer 21

CO2 readily crosses BBB and combines with water forming carbonic acid
dissociates to H+ and bicarbonate
H+ stimulates central chemoreceptor which sends impulses

Question 22

how do central chemoreceptors sense distinguish H+ from CO2 increase and metabolic changes

Question 23

why are peripheral chemoreceptors indiscriminate to the cause of H+ increase

Question 24

why does pH increase in hyperventilation

Question 25

why does pH decrease in hypoventilation

Question 26

respiratory acidosis vs alkalosis

Answer 26

acidosis: failure to get rid of CO2 generated by tissues
alkalosis: removal of too much CO2

Question 27

metabolic acidosis vs alkalosis

Answer 27

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)

Question 28

factors affecting ventilation other than normal

Answer 28

voluntary control
pain and emotions
pulmonary irritants
lung hyperinflation
deflation reflex