respiration

Question 1

explain the arrangement of function of the zones of the respiratory system

Answer 1

conducting zone = first 16 generations (gen 0 is the trachea as air enters here first), includes the nose, nasopharynx, oropharynx, pharynx, larynx, trachea, bronchial tree
responsible for filtering, warming and humidifying the air

respiratory zone - where gas exchange occurs, gen 17 and onwards, alveoli are present

Question 2

what is the importance of 1) warming and 2) humidifying the air as it enters the lungs

Answer 2

1) gases are more soluble when cold, if the air is cold upon entering the blood and warms up there, decreasing it’s solubility, bubbles may form

2) addition of water vapour helps not to dry out the airways

Question 3

describe the structure of the bronchi walls

Answer 3

Cartlidge rings
smooth muscle to control airway diameter
epithelial cells (ciliated) to remove particles out of the lings
goblet cells in the epithelia to produce mucus (at a closely moderated amount)
elastic tissue

Question 4

respiratory peithelium - what properties do they have?

Answer 4

they are ciliated and are interspersed with goblet cells
there are nerve endings that sense noxious substances

Question 5

how do bronchioles differ from bronchi?

Answer 5

they have no cartilage (but still have the epithelial lining)
they have proportionally more smooth muscle

Question 6

explain the specialisations of alveoli and their cell types

Answer 6

thin walled, very close to surrounding capillaries - short diffusion pathway etc…

gas exchange takes place across epithelium type 1/ type 1 pneumocytes which have a flattened cytoplasm, everything is squished close together to speed up diffusion

type 2 epithelia produce surfactant

they increase SA - 50-100m^2

Question 7

explain how quiet inspiration works and whose law this follows

Answer 7

Atmos. Pressure is greater than alveolar pressure
Diaphragm contracts and flattens,
External intercostal muscles contract lifting rib cage up and out,
Thoracic cavity and lungs inc. in volume, pressure decreases below atmospheric pressure

Boyle’s law

Question 8

explain how forced inspiration works

Answer 8

same as quiet but with some added help -
scalene (neck muscles) and back muscles assist in pulling rib cage up
upper respiratory tract reduces resistance to flow

Question 9

explain how quiet expiration works

Answer 9

passive process
no contraction of muscle contributes, instead elastic recoil is used
the muscles form quiet inspiration (diaphragm, external intercostal), ribcage lowers back, diaphragm domes up thoracic cavity and lung volume decrease, pressure inside exceeds atmospheric, air is forced out

Question 10

what additional things happen in forced expiration?

Answer 10

abdominal muscles contract to push diaphragm up
neck and back muscles do something
internal intercostal muscle pulls ribcage in

Question 11

explain the structure and function of the pleura

Answer 11

there’s one pleural membrane on the outside of the lungs, an interpleural space filled with fluid (allows for movement between lungs and chest as one) and then a membrane on the chest wall

at resting the lungs would collapse inwards due to their elastic nature, while the chest wall would tend to expand

these forces act in opposition on the pleural membranes and find a balance

this creates a sub atmospheric (below atmospheric) pressure between the two membranes

Question 12

explain what happens in a pneumothorax

Answer 12

a collapsed lung
interpleural space is pierced, you lose the outer force of the chest, the inward force of the lungs due to the elastic nature wins, and the lung collapses

Question 13

define compliance (lungs) and what it means to have high/low compliance

Answer 13

the ease with which the lung and thorax expands during a pressure change

low compliance = more effort required to breathe in and get the necessary volume change

high compliance = expiration is difficult, lack of elastic recoil (emphysema)

Question 14

explain what surface tension is

Answer 14

attractive forces occur between water molecules
this means, at the surface, there are sideways and downwards forces toward other water molecules, but no upwards force, resulting in tightly packed water molecules at the surface with a tendency to dive down into the bulk of the solution

Question 15

explain the forces in a bubble and the equation involved (Lapalace’s equation)

do small or larger bubbles have the greater pressure?

Answer 15

the pressure of the gas inside the bubble balances with the surface tension of the surrounding water

P = 2T / r

so the smaller the bubble (smaller radius), the higher the pressure

Question 16

smaller bubbles have a greater pressure than larger ones
pressure moves from high to low
what problem does this present in the lungs?

how is this problem solved?

Answer 16

alveoli are like bubbles, and so gas would move from small alveoli at high pressure to larger ones and the small ones would just deflate which is pointless

surfactant produced by type 2 pneumocytes
it’s made of lipids mostly, plus some proteins, and acts like a detergent to reduce surface tension
hydrophilic head in the water with the hydrophobic tail sticking out provides an upward force to reduce surface tension, making it easier for expansion

Question 17

surfactant ensures all alveoli inflate, but what else does it do?

Answer 17

prevents overexpansion - the surfactant’s density decreases as the alveoli stretches, reducing it’s effects so surface tension increases, assisting alveoli in recoiling/not overexpanding

Question 18

define anatomical and physiological dead space

Answer 18

anatomical = volume of conducting airways

physiological = volume of lungs not participating in gas exchange, so conducting airways + non functioning

Question 19

there are 8 things to know from a spirometer - what are they?

Answer 19

IRV = inspiratory reserve volume (from peak of normal breath to peak of max breath)
FEV = forced expiratory volume (fill lungs AMAP, blow out as hard as possible in 1 sec)
VC = vital capacity - deep breath in then breath out as much as you can
RV = residual volume, volume of air left in lungs you cannot breath out
TLC = total lung capacity RV + VC
TV = tidal volume = volume breathe in after 1 sec
ERV = expiratory reserve volume, how much you can force out after a normal exhale
FRC = functional residual capacity RV + ERV

Question 20

in exercise tidal volume increases, but our lung’s capacity doesn’t change - how so?

Answer 20

residual volume decreases so the sum of TV and RV remains the same

Question 21

how do you calculate residual volume?

Answer 21

put known volume of helium in the air chamber as this isn’t able to cross the alveoli
measure the concentration of helium before and after the experiment, use V1C1 = V2C2

Question 22

what is the relationship between air flow in/otu of the lungs and 1) the pressure gradient
2) the resistance

Answer 22

1) proportional
2) inversely proportional

Question 23

what is poiseuille’s law? what does this mean for airflow?

Answer 23

resistance is inversely proportional to the fourth power of the radius, meaning it only takes a small change in radius to massively impact resistance (and therefore flow rate)

Question 24

resistance - how is it shared between airways?
smaller radii = greater resistance so why do these proportions not follow that?

Answer 24

pharynx to larynx is responsible for 40% of resistance
airways bigger than 2mm are collectively responsible for 40%
airways less than 2mm = 20%

bigger aways are in series - you add resistance

smaller airways are in parallel so total resistance is 1/R + 1/R etc…)

Question 25

things that affect airway diameter increase resistance, so they also...

Answer 25

reduce airflow, like mucus or oedema

Question 26

how does smooth muscle control work in the lungs?

Answer 26

constriction = parasympathetic system, ACh released from vagus nerve, acts on muscarinic receptors (GPCRs) dilation = sympathetic, release of noradrenaline = weak agonist of adrenergic receptors leads to dilation

Question 27

humoral factors - two molecules that effect constriction dilation?

Answer 27

epinephrine circulating blood = strong agonist causes dilation histamine - released in inflammatory response = constriction

Question 28

what are the proportions and partial pressures of gas in dry (atmospheric) vs wet (trachea) air?

Answer 28

nitrogen - dry = 80% 590 mmHg wet = 73% 560 mmHg oxygen - dry = 21% 160 wet = 20% 150 carbon dioxide - dry = 0.03% 0.2 wet = same Ar - around 1% and 7 in both water - dry = 0, 0 wet = 6% and 47

Question 29

what is Dalton's law?

Answer 29

total pressure = sum of partial pressures

Question 30

what is Henry's law?

Answer 30

determines the concentration of gas dissolved in a solution [dissolved oxygen] = S X P S = solubility coefficient in mM/mmHg P = partial pressure

Question 31

why do we need RBCs and haemoglobin?

Answer 31

plasma cannot deliver enough O2 alone: where PP of oxygen is around 100 mmHg and its solubility in saline is low, around 0.003ml of O2 per 100ml blood per mmHg at rest, cardiac output of of 5000ml/min the plasma can provide at most 15ml/min O2 to body, when it needs 250

Question 32

describe the structure of haemoglobin and the role of methaemoglobin reductase

Answer 32

tetrameric (four subunits) each of the four subunits has a haem and a globin chain in middle there's a porphyrin ring with a single iron atom that must be 2+ methaemoglobin helps to convert Fe3+ back to Fe2+

Question 33

explain the difference between adult and foetal haemoglobin structure what are the two states haemoglobin occupies? what happens when one oxygen binds to a subunit of haemoglobin?

Answer 33

adult has two alpha and two beta chains while foetal has two gamma instead of the beta two states = tensed (low affinity for oxygen) relaxed = high affinity for oxygen all the subunits will then change to relax, making it easier for more oxygen o bind (hence the steep rise of the dissociation curve)

Question 34

what proportion of oxygen is actually Hb bound?

Answer 34

most of it in arterial blood 97.5%, in venous blood 75%

Question 35

what are the effects of 1) temperature, 2) pH, 3) 2,3 - diphosphoglycerate on the Hb dissociation curve?

Answer 35

temperature = if high curve shifts right (lower affinity) pH = if low curve shifts right (Bohr effect) 2,3-DPG = if increases curve shifts right, it indicates metabolic activity

Question 36

how are the sifts in Hb affinity due to temperature/pH/2,3-diphosphogycerate changes useful?

Answer 36

in respiring tissue both temperature, CO2 and decreased pH all occur a shift to the right causes a decrease in affinity making oxygen easier to unload to meet increased demands as respiration rate increases

Question 37

why is foetal haemoglobin not effected by 2,3-DPG and how is this beneficial?

Answer 37

2,3-DPG effects haemoglobin by interacting with the beta subunits, of which foetal haemoglobin has none, gamma ones in their place, so has is more leftward in it's curve compared to adult haemoglobin when 2,3-DPG is high this means the foetal haemoglobin is better at grabbing O2 at the placenta from the mother

Question 38

what is the total CO2 describing?

Answer 38

all forms of CO2 the blood carries: dissolved CO2 carbonic acid bicarbonate carbonate carbamino compounds

Question 39

how is carbon dioxide transported in the blood?

Answer 39

several different ways majority goes into RBC via aquaporins 4% of that dissolves in plasma 20% binds to haemoglobin (its amino acids) to form those carbamino compounds the rest will be converted to bicarbonate by carbonic anhydrase, then to be exchanged with chloride via a band three protein, known as hamburger explain then at the lungs the bicarbonate goes back into the RBC via the chloride exchange to be converted back to CO2 and diffuse back out to be removed

Question 40

obstructive lung disease - what is it and what are some reasons for the narrowing?

Answer 40

any narrowing of the airways, resulting in a decrease in diameter and therefore an increase in resistance, meaning reduced air flow reasons for narrowing - excess secretions asthma (bronchoconstriction) inflammation

Question 41

how odes obstructive lung disease look in spirometry? - FEV - volume time curves - flow-volume loops

Answer 41

decreased FEV, less than 80% of VC volume time curves - vital capacity is the same, takes much longer to get to the vital capacity when exhaling though flow volume loops - (above axis is exhaling, below is inhaling) concave shape indicates obstructive lung disease, like if it's just a fatter shape

Question 42

give some examples of obstructive lung diseases

Answer 42

asthma chronic bronchitis (mucus excretion) chronic obstructive pulmonary disease (structural changes) emphysema - loss of elastin means airways collapse easier in exhalation

Question 43

what causes asthma - what is it?

Answer 43

hyperactive airways in response to atopic triggers - allergies etc.. and non-atopic triggers - infections, cold air, stress, exercise etc... its an inflammatory cells move into the airways and mediators like histamines cause bronchoconstriction

Question 44

how is asthma treated?

Answer 44

salbutamol = a B2 adrenoreceptor agonist, a bronchodilator (blue inhaler) longer acting treatments = inhaled steroids (glucocorticoids) reduce inflammatory response, or long acting B-adrenoreceptor agonist (brown inhaler)

Question 45

restrictive lung disease - what is it and what are some symptoms?

Answer 45

reduced chest expansion symptoms/causes include - chest wall abnormalities/muscle contraction deficiencies loss of compliance increase in collagen response to environmental factors

Question 46

what does restrictive lung disease look like in spirometry? - VC - volume-time curves - flow volume loop

Answer 46

reduced VC compared to predicted values volume-time curves - reduced vital capacity and FEV (but FEV as a percentage can still be high) flow-volume loops - appears normal (rapid increase in flow, then linear decrease)

Question 47

what happens in asbestosis?

Answer 47

breathed in asbestos, macrophages identify and attack foreign particles, but the body cannot break down these asbestos particles so there is a build up of fibrous tissue around these particles the result can be a bit of both obstructive and restrictive lung disease

Question 48

central control of respiration - what area of the brain what neurons control quiet inspiration what is spontaneous activity what is the ventral respiratory group?

Answer 48

medulla - the pre botzinger complex is what controls the automatic but overridable breathing process dorsal respiratory neurons in the DRG control quiet inspiration spontaneous activity is the triggering of the phrenic nerve to cause inspiration, shutting it off to allow for expiration, firing it up again for another inspiration etc... the ventral respiratory group - neurons in the medulla used for forced inspiration/expiration

Question 49

Pons - what two things does it do effecting respiration?

Answer 49

it inhibits/stimulates the inspiratory centre in order to modulate basic breathing pattern the pneumotaxic centre can send signals down to inhibit inspiratory centre to shorten inspiration and increase breathing rate apneustic centre increases the depth of breathing, slows it down by prolonging inspirations, so stimulates the inspiratory centre

Question 50

what do 1) stretch receptors 2) central chemoreceptors 3) peripheral chemoreceptors do to effect breathing?

Answer 50

1) prevent overinflation using a negative feedback loop 2) monitor cerebral spinal fluid for CO2 and pH, if CO2 too high or pH too low these receptors stimulate inhalation and increase ventilation to remove more CO2 3) in carotid arteries and aorta, respond to increase in CO2, decrease in pH, or decrease in O2