The Respiratory System - Function & Control

Question 1

What is the overall function of the respiratory system?

Answer 1

Exchange of O2 & CO2 between env & cells of body

Question 2

What are the 4 major functions of the respiratory system?

Answer 2

-Pulmonary ventilation – inflow & outflow of air between atm & alveoli
-Diffusion of O2 & CO2 between alveoli & blood
-Transport of O2 & CO2 in the blood & body fluids (body cells need O2 for making ATP - cellular resp -need for tissues to function)
-Regulation of ventilation

Question 3

What are the components of the upper respiratory system?

Answer 3

-Nose/nostrils
-Mouth
-Pharynx
-Larynx (voice box)

Question 4

What are the components of the lower respiratory system?

Answer 4

-Larynx (below vocal folds)
-Trachea
-Bronchi
-Lungs

Question 5

What occurs in the conducting zone (nose –> terminal bronchioles) - focus on nasal region most?

Answer 5

1 = Air is filtered, warmed (to 37oc) & humidified/moistened –> this conditioning of inspired air = for gas exchange to occur later

2 = Nose - filters, traps, clears particles bigger than 10um e.g., bact, pollen, viruses, dust - ps settle or caught on hairs & sticky mucus in nasal passages, trachea & bronchi
-Nasal resistance (due to hairs in nose & mucus) - inc w/ viral infections & inc airflow (e.g., exercise)
-Nasal secretions (1st line of defence) = immunoglobulins, inflamm cells, IFNs

Question 6

Where does the 2nd line of defence come from (if 1st = mucus)?

Answer 6

Cilia - lining upper airways

Question 7

What is the mucus ciliary escalator?

Answer 7

-Self-clearing mechanism of airways in resp system
-Removes inhaled particles e.g., pathogens before reach delicate lung tissue

Question 8

Process of mucus ciliary escalator (MCE)?

Answer 8

-Mucus secreted by ep (goblet) cells & glands
-Cilia propel/sweep mucus towards trachea - rate = 1cm/min
-Pathogens are stuck in this mucus or caught in cilia
-WBCs in MCE - on airway surfaces & alveoli - phagocytose pathogens that may have entered resp system

Question 9

What affect does smoking have on MCE?

Answer 9

Damages cilia lining airways - so mucus not expelled up = why get smoker’s cough

Question 10

Lobes of lungs?

Answer 10

-Right = 3 = sup, middle, inf
-Left = 2 = sup, inf

Question 11

How are lungs ventilated with air?

Answer 11

Air moves down tree like airways - which conduct air between atm & alveoli

Question 12

Order of dividing trachea –> bronchi –> bronchioles –> alveoli?

Answer 12

Question 13

What happens to surface area as get further down respiratory system?

Answer 13

SA increases - alveoli = huge SA for diffusion (gas exchange)

Question 14

What makes up the respiratory zone, & what happens here?

Answer 14

Respiratory bronchioles –> alveoli - gas exchange occurs here

Question 15

Pleura & pleural cavity structure?

Answer 15

-Parietal pleura = adheres to diaphragm and lining thoracic cavity (chest wall)
-Visceral pleura adheres to lungs
-Pleural cavity = small amount of fluid between pleurae (V & P)
-Pleural fluid = assists in breathing movements (creates surface tension) & acts as lubricant between pleural layers (prevents friction when move over each other)

Question 16

What does gas exchange occur across?

Answer 16

Blood-air barrier (down a pressure gradient - high PO2 –> low PO2 - grad across resp system)

Question 17

What are alveoli, what are they the site of, what do they arise from, what do they branch into?

Answer 17

-Basic functional units of lungs = acinus (clusters of alveoli)
-Site of gas exchange
-Come from single respiratory bronchioles
-Stem of bunch branches further = roughly 100 alveolar ducts (connect respiratory bronchioles to alveolar sacs)

Question 18

What surrounds alveoli?

Answer 18

Capillary beds - to help facilitate gas exchange

Question 19

Histology of alveoli walls - cell types & their roles?

Answer 19

-Type 1 pneumocytes cells = ep cells that gives structural support to alveoli
-Type 2 pneumocyte cells = secrete surfactant —> stops alveoli collapsing in

Question 20

What is the epithelium of alveoli, & why?

Answer 20

Simple squamous epithelium (type 1 pneumocytes cells) –> as is thin - short pathway for diffusion
-Type 1 = perimeter barrier between alveoli & blood capillary

Question 21

Role of surfactant (secreted by type 2 pneumocyte cells)?

Answer 21

-Surfactant = forms lipid rich film covering alveolar surface - reduces surface tension of alveolar fluid @ air/liquid interface
—> prevents alveoli from collapsing inwards
-Made of = phospholipids & lipoproteins

Question 22

How is respiration controlled & what is this an example of?

Answer 22

-Central chemoreceptors
-Peripheral chemoreceptors
-Lung receptors
–> via -ve control mechanism to control blood gas tensions
-Chemorecs sense gas tension values

Question 23

What are chemoreceptors?

Answer 23

Specialised tissue - respond to changes in chemical composition of blood/or other fluids

Question 24

Where are central chemoreceptors found & what do they detect?

Answer 24

-In medulla oblongata (CNS)​
-Detects changes in pH linked to PCO2 in cerebrospinal fluid i.e., pH

Question 25

Explain how pH is governed by CO2 in cerebrospinal fluid (CSF)?

Answer 25

pH of CSF​
Regulated pCO2 : [HCO3–]​
–> because CO2 + H20 = H2CO3 splits into: H+ + HCO3- (lowers pH)​
HCO3- = acidic – lowers pH​
As blood-brain barrier = permeable to CO2 but not to H+ or HCO3- –> so H+ & HCO3- cannot diffuse

Question 26

What is the blood-brain barrier permeable to & impermeable to?

Answer 26

-Permeable to = CO2 (diffuses readily - to activate central chemoreceptors)
-Impermeable to = H+ & HCO3-

Question 27

Explain how central chemoreceptors respond to high PCO2?

Answer 27

-PCO2 increase in CSF (as blood-brain barrier = permeable to CO2 – diffuses readily) = pH decreases​
-Activates central chemoreceptors​
-Release of neurotransmitters – sent to respiratory centres to inc rate & depth of ventilation (as chemoreceptors directly synapse with respiratory centres) - i.e., inc ventilation​
-More CO2 exhaled, so pCO2 decreases – returns to optimal level

Question 28

Where are peripheral chemoreceptors & what do they detect?

Answer 28

-In aortic bodies on aortic arch & carotid bodies of common carotid arteries (where common carotid artery bifurcates)​
-Detects changes in pH, PO2 & PCO2 (so respond to dec in PO2 & inc in H+ & inc PCO2 in arterial blood)
–> MAINLY DETECT DEC IN PO2!!!

Question 29

Explain how peripheral chemoreceptors respond to low O2?

Answer 29

-Low PO2 of arterial blood (hypoxia)​
-Detected by ​peripheral chemoreceptors
-Afferent impulses sent along glossopharyngeal & vagus nerves - to medulla oblongata & the pons in brainstem = to stimulate respiratory centre​
-Inc rate & depth of ventilation - i.e., inc ventilation​
-Peripheral chemorecs = close to barrow rec in aortic arch (detect BP) - set respiratory pace

Question 30

What is hypoxia?

Answer 30

Low PO2 in blood

Question 31

Why is pH important?

Answer 31

Important in metabolic acidosis

Question 32

Outline how a glomus cell responds.

Answer 32

-Ca2+ closed (inactive)
-K+ channels open
-K+ into cell = depolarisation
-Causes Ca2+ channels to open = Ca2+ enters cell
-Causes release of neurotransmitters (exocytosis)
-Neurotransmitters signal to sensory neurones = to inc ventilation

Question 33

When are glomus cells activated?

Answer 33

-Decreased PO2
-Increased PCO2 OR pH