The respiratory system

Question 1

what is respiration

Answer 1

the process of supplying oxygen and removing carbon dioxide from the tissues

Question 2

external, internal and cellular respiration

Answer 2

external- exchange of gases between lungs and blood
internal- exchange of gases between blood and cells
cellular- oxidation of glucose >energy

Question 3

aerobic respiration

Answer 3

requires a constant supply of oxygen

glucose+oxygen=carbon dioxide+water+atp

Question 4

what structures do the respiratory system consist of

Answer 4

the air conducting passages- nose, pharynx,larynx, bronchi and bronchioles
the respiratory surfaces (lungs)- respiratory bronchioles, alveolar ducts and alveoli

Question 5

nasal cavity functions and adaptions

Answer 5

functions- filters, warms and moistens incoming air

adaptions- ciliated epithelium, mucus producing cells and surface area contact with blood supply

Question 6

pharynx function and adaptions

Answer 6

function- continues to moisten and warm air

adaptions- mucous membrane - warm moist surface

Question 7

larynx and epiglottis function and adaptions

Answer 7

functions- larynx- conducts air snd sound production, epiglottis- protects air passage
adaptions
larynx- contains vocal cords (epithelial flaps) which vibrate as air pass over them
epiglottis- flap of tissue closes over the larynx during swallowing, it prevents passage pf fluid into lungs

Question 8

trachea, bronchi, bronchioles and terminal bronchioles functions and adaptions

Answer 8

functions- conducts air to respiratory surfaces, continues to filter air
adaptions- walls contain cartilage-maintains patency
smooth muscle- dilation of bronchioles
ciliated epithelium- continues to filter

Question 9

respiratory bronchioles, alveolar ducts and alveoli functions and adaptions

Answer 9

functions- exchange of gases
production of surfactant-maintains patency of alveoli(prevents collapse)
adaptions- epithelial layer-one cell thick- surrounded by pulmonary capillaries- also one cell thick- facilitates diffusion
other epithelial cells produce surfactant-detergent action

Question 10

structural and functional relationship with CVS

Answer 10

proximity of organs
- structural- main organs of both systems within the thoracic cavity
- functional- minimal distance for blood to travel
alveolar-capillary barrier:
-structural-capillary network wrapped closely round alveoli
-functional-adequate surface area for gaseous exchange and diffusion distance minimised

Question 11

mechanism of breathing

Answer 11

the thorax is a closed cavity- sealed off from the outside air except for the trachea
thoracic cavity- lined by pleura-suction force
elastic lung tissue
stimulation by nerves from the respiratory centre-causes contraction of the respiratory muscle simultaneously

Question 12

respiratory cycle

Answer 12

respiratory movements occur approx 12-14 times per minute. it is a cycle of events:
inspiration- active process, contraction of muscles
expiration- passive process, elastic recoil of lungs
pause

Question 13

the pleura

Answer 13

double serous membrane-2 layers continuous- double back at helium of lung
between pleura-serous fluid (potential space)
exerts a negative pressure

Question 14

inspiration

Answer 14

external intercostal muscles contract-ribs and sternum move up and put and diaphragm contracts
simultaneous action results in overall increase in capacity of thorax
pressure in pleural cavity reduced
increases suction pull on elastic lung tissue -stretched- expands to fill thoracic cavity
air pressure in alveoli- less than atmospheric pressure - air drawn in from atmosphere

Question 15

expiration

Answer 15

external intercostal muscles relax, ribs and sternum go down and in and diaphragm relaxes, ascends to dome shale
simultaneous action results in overall decrease in capacity of thorax
pressure in pleural cavity increased
decreased suction pull on lung tissue elastic tissue recoils
air pressure in alveoli- greater than atmospheric pressure- air forced out into atmosphere

Question 16

factors effecting efficiency of ventilation

Answer 16

compliance, airway resistance, surfactant
compliance-the ease which the lungs and thorax can be expanded
high compliance- expands easily (healthy tissue)
low- resistance to expansion

airway resistance
airflow depends on pressure diff between alveoli and atmosphere/ resistance of bronchi and bronchioles
degree of contraction of smooth muscle in walls of airways regulates diameter of airway-therefore resistance
increased sympathetic stimulation relaxes smooth muscle>bronchodilation (reduces resistance)
conditions causing narrowing of the airways> increased resistance

surfactant
a detergent like substance secreted by type 2 alveolar cells
a complex mixture of phospholipids and lipoproteins
reduces the surface tension in the alveoli
effort of inspiration to overcome surface tension reduced

Question 17

eupnea, apnoea, hyperpnoea and hypopnea definitions

Answer 17

euponea- normal breathing
apnoea- absence of breathing
hyperpnoea- over breathing/ hyperventilation
hypopnoea- under breathing/ hypoventilation

Question 18

what is tidal volume

Answer 18

tidal volume is the volume of air entering or leaving the lungs with each breath
resting Vt is about 500ml male and 375ml female
increases during exercise

Question 19

vital capacity

Answer 19

max volume of air that can be moved in or out the lungs with a single breath

Question 20

residual volume

Answer 20

volume of air left in the lungs after maximal respiration

Question 21

anatomical dead space

Answer 21

includes air from regions where no has exchange occurs (airways and unperfused alveoli)
part of tidal volume, since air must flow through these dead spaces with each breath to reach alveoli

Question 22

pulmonary circulation

Answer 22

deoxygenated blood in arteries and oxygenated blood in veins
lower pressure than systemic circulation
blood vessels constrict in response to lack of oxygen
this diverts blood to better oxygenated parts of the lung
allows for ventilation/perfusion matching

Question 23

blood vessel structure and function

Answer 23

regulation of tone dependent on vasodilator /vasoconstrictor stimuli:circulating hormones, neurotransmitters, EDF, blood pressure
all help determine contractile state hence vessel diameter and hydraulic resistance
-contractility is major determinant of resistance to blood flow
-contractile state known as vascular tone
- tone helps regulate blood pressure and blood flow distribution, ion channels fundamental to this process
ion movement across the plasma membrane determines membrane potential
MP and calcium conc. regulates influx and release
influences sensitivity of contractile apparatus
calcium triggers contraction

Question 24

ion channels expressed by vascular smooth muscle

Answer 24

potassium channel(Katp, BKca, Kv, Kir)
calcium channel( l type amd t type)
chlorine channels(Clca, Clvol)
non specific cation channels

Question 25

unique features of pulmonary circulation

Answer 25

8x lower pressure, thinner walls, collapsible capillaries and very low resistance to blood flow

Question 26

gas exchange

Answer 26

gas exchange is optimal at both low and high cardiac output, takes place at alveolar level. the capillaries are densely packed in a continuous sheet of blood flow around the alveoli, giving a maximal contact surface to enhance gas exchange
each alveoli is perfused proportionally to its ventilation, when oxygen partial pressure is low in a region of the lungs, adjacent vessels contract and divert the blood away to better ventilated areas. by actively regulating local perfusion, acute HPV optimises conditions for gas exchange

Question 27

hypoxic pulmonary vasoconstriction (HPV)

Answer 27

unique feature of the pulmonary circulation (in the systemic circulation low O2 results in dilation)
HPV is an important physiological function
optimises ventilation/perfusion match. potential to increase arterial blood PO2
segmental hypoxia in some diseases e.g. pneumonia diverts blood away from hypoxic lobe.
global hypoxia results in elevated pulmonary pressure
pulmonary vein constriction resulting in oedema formation
observed at all levels (isolated lung to single cells) appears to nr intrinsic to smooth muscle
driven primarily by pulmonary arteries (but veins also important)

Question 28

ventilation/perfusion ratio

Answer 28

0.8 ideal ratio to provide optimal gas exchange

Question 29

oxygen transport

Answer 29

99% combined with haemoglobin to form oxyhemoglobin
minute amount (1%) dissolved in plasma

Question 30

haemoglobin

Answer 30

4 haem-porphyrin ring structures containing iron that binds to oxygen
4 globin polypeptide chains(2 alpha, 2 beta)
many different genetic variants, some of which have diminished oxygen biding capacity

Question 31

conditions that effect association of oxygen and hb

Answer 31

pH
temp
2,3-DPG (an intermediate in glucose breakdown)

Question 32

how is CO2 utilised around the body

Answer 32

7% dissolved in plasma
combined with haemoglobin to form carbaminohaemoglobin 23%
buffered as bicarbonate ion 70%

Question 33

carbonic anhydrase

Answer 33

important enzyme found in red blood cells (and elsewhere eg kidney)
catalyses conversion of CO2 to carbonic acid H2CO3

Question 34

how is CO2 transported around the body

Answer 34

buffering by Hb facilitates production of plasma Na HCO3. this in turn modulates CO2 dissociation in plasma. Hb therefore modulates plasma pH by modulating [HCO3]
CO2 dissociation in RBC principally affected by Hb
CO2 in plasma dependent only on PCO2

Question 35

what regulates PCO2 and [HCO3]

Answer 35

lungs, kidney

Question 36

how may pH be maintained

Answer 36

kidney activity/respiratory activity

Question 37

what happens as Hb loses O2

Answer 37

H affinity increases

Question 38

respiratory acidosis

Answer 38

primarily increase in pCO2 (carbon dioxide retention) e.g. respiratory depression. increase in PCO2 causes decrease in pH. kidney compensates by excreting H+ producing highly acidic urine

Question 39

respiratory alkalosis

Answer 39

primarily decrease in PCO2 e.g. voluntary over-breathing, chronic oxygen decrease. decrease in PCO2 causes increase in pH. kidney compensates by excreting HCO3

Question 40

metabolic acidosis

Answer 40

primarily H level too high in the blood e.g. starvation
decreased pH blood registered by central chemoreceptors which:
stimulates respiration, more CO2 lost from lungs, dec PCO2, dec [H], inc pH
respiratory changes (hyperventilation) compensate for changes in pH

Question 41

metabolic alkalosis

Answer 41

primarily increase HCO3 in blood e.g. excessive vomiting, ingestion of HCO3:
inc HCO3, dec [H], inc H
registered in chemoreceptors
inhibits respiration, less CO2 lost in lungs, inc PCO2, inc [H], dec
pH
respiratory change (hypoventilation) compensate change in pH

Question 42

control of respiration

Answer 42

generally an involuntary automatic event but under certain conditions may become voluntary,
respiratory centre- groups of specialised neurones in the medulla oblongata and the pons, responsible for involuntary control.
areas in the cerebral cortex responsible for voluntary control
alveolar PCO2 normally held constant, effects of excess H in blood is combated, PO2 is raised when it falls to a potentially dangerous level.
breath to breath control is achieved by regulation of CO2 levels through central chemoreceptors. haemoglobin is highly saturated with oxygen- even in venous blood at rest still 75% saturated
‘alarm’ must be triggered if O2 levels fall to extent that saturation of hb is compromised- achieved through peripheral chemoreceptors.

Question 43

central chemoreceptors

Answer 43

located in the medulla of the brain, sensitive to pH and pCO2 but not PO2, actual stimulus is change in pH which results from change in pCO2

Question 44

peripheral chemoreceptors

Answer 44

aortic body- located in the wall of the aorta
, carotid bodies- located at the bifurcation of the carotid arteries (main supply to the head). sensitive to changes in PO2 (facilitated by very high blood flow to the bodies)

Question 45

effect of changes in blood oxygen level on respiration

Answer 45

INCREASE IN PO2:
registered by peripheral chemoreceptors, inhibits respiration, pO2 will fall back to normal
DECREASE IN PO2:
registered by peripheral chemoreceptors, stimulates respiration, chemoreceptors particularly sensitive when pO2 in the range of the steep portion of the oxygen: haemoglobin saturation curve, stimulation of respiration facilitates oxygen uptake in the lungs increasing PO2 back to normal.

Question 46

effect of changes in blood CO2 level on respiration

Answer 46

INCREASE IN PCO2;
registered as decrease in pH in central chemoreceptors, stimulates respiration, more CO2 lost out of lungs during expiration, so PCO2 falls back to normal
DECREASE IN PCO2;
registered as increase pH central chemoreceptors, inhibits respiration, less CO2 lost from lungs during expiration, pCO2 increases back to normal

Question 47

CNS control of respiration-medullary control centres

Answer 47

inspiratory centre: sends stimulus to inspiratory muscles, resting discharge rate approx 12/min, this occurs automatically in the inspiratory centre, does not require input from elsewhere in CNS, but firing rate can be modified by other inputs

expiratory centre: discrete area, located near inspiratory centre, not active during passive expiration, during active expiration sends impulses to expiratory muscles, reinforcing respiratory effort. neural connections exist linking inspiratory Nd expiratory centres.

cough centre (does it exist) ; receives input from the irritant receptors in the lungs, triggering cough reflex. considered a reflex essential to life aa it serves to remove foreign bodies from the airways

apnoeustic centre; stimulates the medullary inspiratory centre, prolongs inspiration, must be inhibited for inspiration to terminate and expiration to commence

pneumotaxic centre: inhibits apnoeustic centre and inspiratory centre, facilitates expiration