Physiology Flashcards
what is internal respiration
inside cells
ATP & CO2 produced from glucose & O2
what is external respiration
exchange of O2 and CO2 with the external environment and body cells
4 steps of external respiration
1) ventilation
2) gas change between alveoli & blood in lungs
3) transport of O2 & CO2 in blood: lungs -> tissues
4) O2/CO2 exchange between blood and tissues (leads to internal respiration) in systemic capillaries & body cells
4 systems involved in external respiration
respiratory
cardiovascular
haematology
nervous
what is ventilation
gas exchange between alveoli & atmosphere
high -> low pressure
what happens during inspiration
contraction of inspiratory muscles
diaphragm moves down, dome flattens
intercostals move out
thorax & lungs expand
what happens to pressure in the lungs upon inspiration
intra-alveolar pressure is less than atmospheric pressure so air drawn into the lungs
pressure decreases
what happens as volume in which the gas is distributed in increases
pressure exerted by gas decreases
boyles law
at any constant temperature, pressure exerted by a gas varies inversely with the volume of the gas
what is pulmonary ventilation
volume of air breathed in and out per min
what increases pulmonary ventilation
exercise: increases depth (tidal volume) & increased breathing rate
calculation for pulmonary ventilation
L = tidal volume (L/breath) x respiratory rate (breath/min)
what is alveolar ventilation
volume of air exchanged by the atmosphere and alveoli per min
new air available for gas exchange
why is alveolar ventilation < pulmonary ventilation
dead space (some air not available for gas exchange)
equation for calculating alveolar ventilation
(tidal volume - dead space volume) x respiratory rate
why is alveolar ventilation more advantageous
increases depth of breathing
how is alveolar ventilation increased
deep slow breathing
how is pulmonary ventilation decreased
rapid shallow breathing
why is alveolar ventilation not completey perfused
due to dead space
hence air in alveoli not perfect match for blood in pulmonary capillaries
is dead space bad
dead space insignificant in heathy people as small
increases in disease
upon inspiration how much air is in the alveoli
150 already there as alveoli are never completely empuy
350 ml added
how are pleural membranes attached
water in intrapleural fluid attracted to each other so aren’t puled apart
what creates the pressure gradient in the lungs
sub-atmospheric intrapleaural pressure gradient
what does the intrapleaural gradient cause
lungs expand out, while chest squeezes in
what is pressure in the lung and pleura
lung = 760 mmHg (101 kPa)
pleura = 756 mmHg
lung pressure > pleura pressure
what is the transmural pressure gradient
4 mmHg
what are the 3 pressures I ventilation
intra - alveolar = 760 mmHG
atmospheric = 760 mmHg
Intrapleural = 756 mmHg
during ventilation what happens to the pressures in the lungs
intra-alveolar pressure pushes out (alveoli expand)
lower intra-pleura pressure pushes inwards
during ventilation what happens to the pressures in the thoracic cavity
atmospheric pressure pushes inwards
intrapleura pressure pushes out
what nerves keep the diaphragm alive
phrenic nerves C3,4,5
role of major inspiratory muscles
contract during normal quiet breathing
what are the major inspiratory muscles
diaphragm - increases thorax volume vertically
external intercostal muscles
how does the external intercostals increase lung volume
contracts to lift ribs, increases anterior and posterior, sternum moves out
increase thorax volume horizontally
bucket handle
role of the accessory inspiration muscles
contract only during forceful inspiration
3 types of accessory inspiration muscles
sternocleidomastoid
scalenus
pectoral
what is the role of the muscles of active expiration
only contract during forceful expiration
2 types of active expiration muscles
abdominal muscles
internal intercostal muscles
inspiration & expiration occurs against/down a pressure gradient
down
when does air enter/leave until
intra-alveolar pressure = atmospheric pressure
is inspiration active or passive
active (3% energy use)
inspiratory muscles contract
is expiration active or passive
passive
inspiratory muscles relax
process of inspration
diaphragm contacts, moves down, dome flattens, ribs move out
lungs increase siize/volume, intra-alveolar pressure decreases
process of expiration
diaphragm relax, dome resume, moves up
chest wall recoils, smaller volume, intra-alveolar pressure rises so airforces out
intra-alveolar and intra-pleural pressure during inspiration
intra-alveolar = 759mmHg intra-pleural = 754 mmHg
intra-alveolar and intra-pleural pressure during expiration
intra-alveolar = 761 mmHg intra-pleural = 756 mmHg
during inhalation what is the airways pulled open by
expanding thorax
intrapleural pressure falls
3 factors keeping alveoli open
transmural pressure gradient (MOST IMPORTANT) - sub-atmospheric
surfactant
alveolar interdependance
what creates the pressure gradient in the lungs
the difference between the pressure in the alveoli and the pleura
pleura pressure is always less than alveoli pressure
what is the role surfactant
reduces water surface tension
prevents lungs collapsing
prevents smaller alveoli emptying air into larger alveoli
interdespences meteen water molecules lining alveoli
what is surfactant made up of
lipids and proteins
surfactant has a bigger effect on smaller/bigger alveoli
smaller
what is surfactant secreted by
type II alveoli
define LaPlace Law
smaller alveoli = greater tendency to collape
LaPlace Law equation
P = 2T / r P = inward directed collapsing pressure T = surface tension r = alveoli radius
what is alveolar interdependence
if alveoli starts collapsing surrounding alveolar stretch then recoil expanding forces on collapsing alveolus opening it
what factors promote the alveoli to collapse
elasticity of stretched lung connective tissue (during recoiling)
alveolar surface tension (water molecules line alveoli)
what is tidal volume
0.5 L
normal quiet breathing
volume enter/leaves in 1 breath
what is inspiration residual volume
3.0 L
during laboured breath in
extra volume maximally inspired
above tidal volume
what is expiration residual volume
1.0 L
extra volume actively expired by maximal contraction after resting tidal volume
forcefully pushing air out
what is is residual volume
1.2 L
some air always remains in lungs
cannot be measured by spirometry
how is residual volume increased
when lung elastic recoil is lost eg. emohysema
what is inspiratory capacity
3.5 L
IRV + TV
max air that can be breathed in after normal quiet expiration
what is vital capacity
4.5 L
IRV + TV + ERV
max air that can be moved out during 1 breath after max inspiration
most important
what is Functional residual capacity
2.2 L
ERV + RV
air in lungs after normal passive expiration
what is total lung capacity
5.7 L
max volume lung can hold
VC + RV
cannot be measured by spirometry
what is dynamic airway compression
active expiration more difficult in patients with airway obstructions eg. asthma/COPD
what does dynamic airway compression a result of
driving pressure between alveolus and airway lost
rising pleural pressure compresses alveoli & airway
what does increased airway resistance cause
increased airway pressure = compressed airway
define pulmonary compliance
measure of the effort that goes into stretching/distending lungs
what causes decreased pulmonary compliance
pulmonary fibrosis pulmonary oedema lung collapse pneumonia absence of surfactant
why is decreased pulmonary compliance not good
more effort required to inflate lungs
greater change in pressure need to meet lung volume target
stiffer lungs
shortness of breath
what is increased pulmonary compliance
when elastic recoil of lungs is lost by emphysema (worsened COPD)
why is increased pulmonary compliance not good
have to work harder to get air out off the lungs - hyperinflation
obstructed airways
increases with age
how can breathing be increased
decreased pulmonary compliance
airway resistance increased
elastic recoil decreased
need for increased ventilation
how full are the lungs usually during normal breathing
1/2 full
define ventilation
rate at which gas is passing through the lungs
define perfusion
rate at which blood is passing through the lungs
what is the hypothetical point at which air flow rate matches perfusion
1
volume of blood leaving the lungs has the same PO2 as alveoli
airflow = bloodflow
if there is lots of ventilation there is more/less perfusion
more
what structures are involved in lung ventilation-perfusruin patch
airway smooth muscle + arterioles
in an area with greater perfusion than ventilation CO2 decreases/increases and O2 increases/decreases
CO2 increases
O2 decreases
in area with greater perfusion than ventilation airways dilate/constrict and local vessels constrict/dilate
airways - dilate
vessels - constrict
in area with greater perfusion than ventilation airflow increases/decreases and blood flow increases/decreases
airflow increases
blood flow decreases
in area with greater ventilation than perfusion airflow increases/decreases and blood flow increases/decreases
airflow decreases
blood flow increases
in area with greater ventilation than perfusion airways dilate/constrict and local vessels constrict/dilate
airways constrict
vessels dilate
in areas with greater ventilation than perfusion CO2 increases/decreases and O2 increases
CO2 deceases
O2 increases
when there is decreased O2 pulmonary arterioles vasodilation/vasoconstriction
vasoconstriction
when there is decreased O2 systemic arterioles vasodilation/vasoconstriction
vasodilation
when there is increased O2 pulmonary arterioles vasodilation/vasoconstriction
vasodilation
when there is increased O2 systemic arterioles vasodilation/vasoconstricition
vasoconstriction
4 factors affecting gas exchange rate
partial pressure of O2 & CO2
diffusion coefficient of O2 & CO2
alveolar membrane SA
thickness of alveolar membrane
how does pp O2 and CO2 affect gas exchange rate
high to low pp gradient
rate exchange increases when pp increases
most important factor
how does the diffusion coefficient of O2 & CO2 affect gas exchange rate
transfer increases as coefficient increases
CO2 coefficient 20x O2 coefficient
how does alveolar SA affect gas exchange rate
as SA increases gas exchange rate increases
how alveolar membrane SA be increased
by exercise
how can alveolar membrane SA be decreased
emphysema lung collapse
pneumoectomy
what affect does increasing the alveolar membrane have on gas exchange rate
decreases as thickness increases
how is the thickness of the alveolar membrane increased
by pulmonary oedema, fibrosis, pneumonia
what determines pressure gradient
partial pressure
define partial pressure
pressure one gas in a mixture would exert if occupied total volume (only gas present) at given temp
define Daltons Law
total pressure entered thy gaseous mixture = sum of partial pressures of each individual component
if atmospheric pressure = 760 mmHg what is pp N2 an pp O2
N2 = 760 x 0.79 = 600 mmHg O2 = 760 x 0.21 = 16 mmHg
what is PAO2 (ppO2 in alveolar air)
air in resp tract saturated with water
what is the water vapour pressure in the resp tract
47 mmHg (of total pressure)
calculate the pressure of inspired air
atmospheric pressure - water vapour pressure
760 - 47 = 713 mmHg
calculate the ppO2 inspired air
0.21 x 713 = 150 mmHg
what is the alveolar gas equation
PAO2 = piO2 - [PaCO2/0.8] 0.8 = resp exchange ratio
why is there a small gradient between PAO2 (alveolar PO2) and PaO2 (arterial PO2)
ventilation-perfusion is not a perfect match
if there is a big difference between alveolar PO2 and arterial PO2 what does this suggest
problems with gas exchange
right to left shunt in heart
why are alveoli suited to gas exchange
large SA
thin membrane
single layered walls
flattened type 1 alveolar. cell
factors that make the lungs suitable for gas exchange
large SA thin membrane alveoli repeated airway divisions extensive capillary network narrow interstitial space pulmonary circulation receives entire CO
7 noinrespiratory functions for the respiratory system
Route for water loss & heat elimination
Enhances venous return
maintain acid-base balance
speech, singing
Defence against pathogens
Removes, modifies, activates/inactivates materials passing though pulmonary circulation
Nose = smell
define henry’s law
Amount of gas dissolved and volume of liquid eg. Blood at constant temp is proportional to the partial pressure of the gas in equilibrium with the liquid
according to henrys law what happens as pp increases
increased amount of gas dissolved in the liquid phase and proportionally increase gas concentration in gaseous phase
what is pp gas in solution
gas mixture in equilibrium
2 ways oxygen can be transported in the body
as dissolved oxygen
transported by haemoglobin
what is the amount of oxygen transported in the blood proportional to
oxygens partial pressure
at PO2 13.3kPa how much O2 is dissolved in blood
3 ml per L
not enough oxygen transported this way
O2 dissolved = 1.5%
at resting, how much oxygen is dissolved in the blood
CO = 5L/min 3x5 = 15ml/min taken into tissues
what is resting O2 body cell consumption
250 ml/min
during strenuous exercise how much oxygen is dissolved in the blood
CO = 30 L/min
3x30 = 90 ml/min into tissues
O2 consumption increases 25 fold
how is most oxygen transported in the blood
attached to Hb
what is O2 conc in arterial blood
200 ml/L
wha tis normal arterial PO2
13.3 kPa
what Is normal Hb conc in blood
150 g/L
what percent of Oxygen is usually bound to Hb in healthy individuals
98.5%
>95%
describe Hb structure and function
reversibly binds O2
4 haem groups - a & b chains and Fe
what is co-operativity
the binding of one oxygen molecule to a haem group increases the affinity of the remaining subunits for oxygen
produces a sigmoid curve
what is the primary factor determining % Hb saturation
PO2
as pO2 increases saturation inreases
why does the sigmoid curve of Hb saturation flatten out, advantage of this
all the sites are occupied
advantage: moderate fall in PO2 doesn’t affect O2 loading
advantage of a sigmoid curve steep part for Hb saturation
tissues get lots of O2 for small drop in capillary PO2
No matter the Hb conc will always reach 100% saturation of the haemoglobin present as it is dependant on pO2
More haemoglobin = more O2 carried
True or False
True
what is O2 delivery to tissues dependant on
O2 in arterial blood
CO
Oxygen delivery index equation
DO2l = CaO2 x Cl
CaO2 = oxygen content of arterial blood
Cl = cardiac index
(2.4 -4.2 L/min/metre)
what is the oxygen content of arterial blood determined by
Hb concentration
Hb saturation with O2
equation for oxygen content of arterial blood
CaO2 = 1.34 x [Hb] x SaO2 SaO2 = % Hb saturated with O2
how much O2 does 1g Hb Carry when fully saturated
1.34 ml
what is oxygen delivery to tissues impaired by
respiratory disease - affects pO2
heart failure - not enough blood carrying O2 pumped to tissues, decreased CO
Anaemia - not sufficient Hb
Decreased pp inspired O2
what happens if pO2 becomes low
less binding to Hb
decreased arterial pO2 and decreased Hb saturation
Bohr effect at tissues
Hb saturation curve shifts to the right
decreases affinity so O2 unloading at tissues
how is O2 release at tissues increased
Increased PCO2
Increased H+
Increase temp
Increased 2,3 Biphosphoglycerate
how does foetal haemoglobin differ from adult haemoglobin
2a + 2 y subunits (HbA has 2a + 2b)
interacts less with 2,3-biglycerate
higher O2 affinity curve shifted to left of HbA
why is it advantageous HbF has greater affinity for O2 than HbA
Allows O2 delivery to foetus across placental if mothers PO2 lowered
where is myoglobin in body
skeletal & cardiac muscle cells
how does myoglobin differ from haemoglobin
1:1 binding
1 haem group so no co-operativity
hyperbolic cuve
myoglobin releases O2 at very high/low pO2
low
why is myoglobin used
short term O2 storage - anaerobic conditions
what does myoglobin in blood suggest
muscle damage
how is CO2 transported in the body
10% in solution (henrys law, 20 x more soluble than O2)
60% as Bicarbonate
30% as carbamino compounds
how is CO2 transported as bicarbonate
In red blood cells
CO2 + H20 reversibly converted to H2CO3 which is reversibly converted to H+ & HCO3-
what enzyme catalyses conversion of CO2 and H2O to H2CO3
carbonic anhydrase
what are the H ions produced alongside bicarbonate used for
combine to form haemoglobin
how is CO2 transported as carbamino compounds
CO2 & terminal amine group in blood proteins
carbamino-haemoglobin
benefit of using carbamino-haemoglobin to transport CO2
rapid even without enzyme
if Hb is reduced binds more/less CO2 than HbO2
more CO2 than HbO2
what is the Haldane effect
Removing O2 from Hb increases the ability of Hb to pick-up CO2 and CO2 generated H+
Haldane + Bohr effect facilitate:
O2 liberation
CO2 uptake & CO2 generated H+ at tissues
Curve in tissues shifted to the right and the amount of O2 given up is calculated by the difference in curves of arterial and tissue conditions
in the Haldane effect what O2 shifts CO2 dissociation curve to the left/right
right
what is PO2 venous blood
5.3
at the lungs when Hb picks up O2 what happens to CO2 and H+ binding
binding weakens
how is respiration controlled
neural control
Chemical control
where is the centre of control for respiration
Medulla
normal ventilation above - Pons, ventilation ceases below
what is the neural network that creates the rhythm of breathing located in the medulla
Pre-botzinger complex
where is the pre-botzinger complex located
upper end of medullary resp tract
how does the pre-botzinger complex create a breathing rhythm
excites dorsal neutrons (inspiratory) which fire in bursts causing contraction of inspiratory muscles when firing stops passive expiration
What neurones are responsible for hyerventilation (active expiration) by exciting internal intercostals
increased dorsal firing excites VENTRAL neurones
contraction of abdomen, forceful expiration
role of the Pons in breathing
modifies rhythm
what is located in the pons and what is its role
Pneumotaxic centre: terminates inspiration
how is the pneumotaxic centre stimulated
when dorsal resp neurones fire, inhibiting inspiration
What does do no pneumotaxic centre result in
Apneusis: prolonged breathing inspiratory gaps brief expiration
role of the apneustic centre
impulses from these neurones excite inspiratory are of medulla, prolonged inspiration
4 centres in the medulla
Pneumotaxic centre
Dorsal neurones (inspiratory)
Apneustic centre
Ventral resp
what higher brain centres influence resp centres
limbic system
cerebral cortex
hypothalamus
what stimuli influences respiratory centres
stretch receptors in bronchi J receptors Joint receptors Baroreceptors Central + Peripheral chemoreceptors
what is the herring-breur reflex
protects agains hyperinflation (during exercise)
Discharge inhibits inspiration, activated at large tidal volumes (1L)
new born babies
what are J receptors stimulated by
pulmonary capillary congestion
pulmonary oedema (left heart failure)
pulmonary emboli
what do J receptors cause
low shallow breathing
what effect do baroreceptors have on resp
increased ventilatory rate in response to decreased BP
what effect does the joint receptor reflex have on respiratory
during exercise, impulses from moving limbs increases breathing + ventilation
where is the cough reflex initiated
medulla
what happens during the cough reflex
short breath intake
larynx closure
abdominal muscles contract (increase alveolar pressure)
larynx opens and air expulsion at high speed
5 factors that increase ventilation In exercise
Reflexes from body movement Adrenaline release Cerebral cortex impulses Increased temp Later: CO2 & H in active muscles
what do peripheral chemoreceptors detect
sense O2 + CO2 tension
Sense [H+] in blood
where are central chemoreceptors located
medulla surface
role of central chemoreceptors
Sense [H+] of cerebrospinal fluid (CSF)
CSF less proteins than blood so less buffered
what is CSF separated from the blood by
blood brain barrier
what gasses is the bbb permeable and impermeable to
permeable to CO2
impermeable to H & HCO3
What is hypercapnia
PCO2 responsive ventilation
CO3 generates H through central chemoreceptors
what is hypoxic drive stimulated by
peripheral chemoreceptors
what happens when hypoxia is severe
neurones depressed
how is hypoxic drive stimulated
when arterial PO2 falls to low level >8 kPa
what patients is chronic CO2 retention present
COPD
when can hypoxia occur
at high altitudes as there is decreased PiO2
what is the acute response to high altitudes
hyperventilation and increased CO
what adaptations occur to combat hypoxia
increased RBC (polycythaemia)
increased 2,3 BPG in RBCS - O2 offloading easier
Increased capillaries: more diffusion
increased mitochondria
kindres conserve acid (decrease arterial pH)
