physiology Flashcards
what is cellular respiration
use O2 and produce CO2
what is external respiration
the process of how O2 and CO2 are exchanged around the body
how many steps is there for external respiration
4
what is step 1 of external respiration
ventilation
what is ventilation
air moved in and out of the lungs so it can be exchanged
what is step 2 of external respiration
oxygen and CO2 are exchanged between air in the alveoli and blood
what is step 3 of external respiration
transport of O2 and CO2 between the lungs and tissues
what is step 4 of external respiration
oxygen and CO2 are exchanged between tissue cells and blood
what does the respiratory system include
- airways into lung
- lungs
- structures of thorax
what are the respiratory airways
tubes that carry air between the atmosphere and the air sacs
how does airways begin
nasal passage (nose)
is the oesophagus open or closed during inspiration
closed so air doesn’t go into stomach
what is the larynx
voice box
where are the vocal folds
two bands of elastic tissue that lie across the opening of the larynx h
how does air pass into the larynx
through the space between the vocal folds
what is the laryngeal opening
glottis
what happens to the glottis during swallowing
closed
how is the glottis closed
via the laryngeal muscles
what does the trachea branch into
the right and left bronchi
what are the smaller branches of the bronchi called
bronchioles
what are at the end of the terminal bronchioles
alveoli
do small bronchioles have cartilage
no they contain smooth muscle
what makes up the alveolar walls
type I alveolar cells
what surrounds each alevoli
network of pulmonary capillaries
what do type II alveolar cells secrete
pulmonary surfactant
what is the only muscle within the lungs
smooth muscles
what muscle is the diaphragm
skeletal muscle
what separates each lung from the thoracic wall
pleural sac
what is the interior of the pleural sac known as
pleural cavity
what is pleurisy
inflammation of pleural sac
how does air move
down a pressure gradient
what are the 3 important pressure in ventilation
- atmospheric
- intra-alveolar
- intra-pleural
what is atmospheric pressure
pressure exerted by the weight of the air in the atmosphere
value of atmospheric pressure
760mmHg
what is intra-alveolar pressure
pressure within the alveoli
what is intrapleural pressure
pressure within the pleural sac
value of intra-pleural pressure
756 mm Hg
is the pleural sac open or closed
closed
what two forces hold the lungs and thorax in close apposition
- intrapleural fluid cohesiveness
- transmural pressure gradient
what is intrapleural fluid cohesiveness
water molecules resist being pulled apart because they are polar and attracted to one another
what is the transmural pressure gradient
as alveolar pressure is larger than pleural pressure the lungs are forced to expand
what is pneumothorax
air flowing down its pressure gradient into pleural space
what must alveolar pressure be for inspiration
alveolar pressure must be less than atmospheric
Boyle’s law
at any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas
= the volume of a gas increases the pressure exerted by the gas decreases
what are the major inspiratory muscles
- diaphragm
- external intercostal muscle
what are the pressures before inspiration
intra-alveolar pressure equals atmospheric pressure
what is the major muscle of inspiration
diaphragm
what innervates the diaphragm
phrenic nerve
what happens to the diaphragm when it contracts
descends downwards enlarging the volume of the thoracic cavity
what lies on top of what between external intercostal and internal intercostal
external intercostal lie on top of internal intercostal
what direction do the fibres of external intercostal run
downward (hands in pockets)
what happens when the external intercostal contract
they elevate the ribs and the sternum up and out
what activate the intercostal muscles
intercostal nerves
what happens to intra-alveolar pressure when the lungs enlarge
it drops (because the same number of air molecules occupy a larger volume)
what happens now intra-alveolar pressure decreases
air flows into the lung down the pressure gradient
what value is the intrapleural pressure during inspiration
754 mm hg
what are the accessory muscles of inspiration
- sternocleidomastoid
- scalenus
what do the inspiratory muscles do at the end of inspiration
relax
what happens to the intra-alveolar pressure when the lungs recoil
rises because the greater number of air molecules are contained in a smaller volume
what happens to air when the intra-alveolar pressure increases
air moves out down its pressure gradient
what is the phrenic nerve
C3,4,5
is expiration active or passive
passive
is inspiration active or passive
always active
what are the muscles of expiration
- abdominal muscle
- internal intercostal muscle
what is the primary determinant of resistance of airflow
radius of the conducting airways
what does parasympathetic stimulation do to bronchial smooth muscle
bronchoconstriction
what does sympathetic stimulation do to bronchial smooth muscle
bronchodilation
what characterises COPD
increased air way resistance
what is encompassed in COPD
- chronic bronchitis
- emphysema
- asthma
what is chronic bronchitis
inflammatory condition of the lower respiratory airways
what do irritants do to ciliary mucus escalator
immobilise
why does pulmonary bacterial infection frequently occur in chronic bronchitis
the accumulated mucus serves as an excellent medium for bacterial growth
what is airway obstruction in asthma a result of
- thickening of airway walls
- plugging of the airways by excessive secretion of thick mucus
- airway hyperresponsiveness
triggers of asthma
- allergens (dust mites, pollen)
- irritants
- infections
- exercise
characteristics of emphysema
- collapse of smaller airways
- breakdown of alveolar walls
is emphysema reversible
no
what causes emphysema
excessive release of protein digesting enzymes e.g. trpysin
what protects the lungs from enzymes like trypsin
alpha1- antitrypsin
what can happen with over production of alpha1-antitrypsin
they start to destroy lung tissue as they get overwhelmed
what is more difficult in COPD expiration or inspiration
expiration
do the smaller airways have cartilaginous rings
no
why do asthmatics have a wheeze
expiration is more difficult than inspiration so air is forced out through the narrowed airways
what in the lungs allows them to be stretched and then return to their normal size
- compliance
- elastic recoil
what is compliance
how much effort is required to stretch or distend the lung
what does it mean if compliance is high
is stretches far for little increase
what does it mean if compliance is low
more effort is taken to stretch the lungs
examples of diseases that cause decreased compliance
pulmonary fibrosis
where is pulmonary fibrosis
normal lung tissue is replaced with scar forming connective tissue
what is elastic recoil
how readily the lungs rebound after being stretched
what does the lungs elastic behaviour depend on
- high elastic connective tissue
- alveolar surface tension
what are elastin fibers
fibres that have elastic properties
how are elastin fibres arranged
meshwork that amplifies their elastic behaviour
what bonds make water attracted to each other
hydrogen
what is link between surface tension and lung compliance
the greater the surface tension the less compliant the lungs
what happens to elastic recoil in emphysema
elastic recoil is decreased
do patients with emphysema have difficulty with inspiration or expiration
expiration
what cells secrete pulmonary surfactant
type II alveolar cell
what does pulmonary surfactant do
it intersperses between the water molecules in the fluid lining the alveoli and lowers alveolar surface tension
what is the law of LaPlace
smaller alveoli have higher tendency to collapse
what size of cells is surfactant greater on
smaller
how are alveoli interconnected
by connective tissue
what happens if an alveolus starts to collapse
surrounding alveoli are stretched as their walls are pulled in the direction
= alveoler interdependence
why does newborn respiratory distress syndrome
developing foetal lungs do not produce surfactant until late in the pregnancy
what disease causes airway resistance to increase
COPD
what disease causes elastic recoil to decrease
emphysema
what causes a need for increased ventilation
exercise
tidal volume
volume of air entering or leaving the lungs during a single breath
value of tidal volume
500 ml
what is inspiratory reserve volume
extra volume of air that can be maximally inspired over and above the typical resting tidal volume
value of inspiratory reserve volume
3000ml
what is inspiratory capacity
maximum volume of air that can be inspired at the end of normal quiet expiration
value of inspiratory capacity
3500 ml
what is expiratory reserve volume
extra volume of air that can be actively expired
value of expiratory reserve volume
1000ml
what is residual volume
minimum volume of air remaining in the lungs after a maximal expiration
value of residual volume
1200 ml
what is functional residual capacity
volume of air in the lungs at the end of a normal passive expiration
what is value of functional residual capacity
2200 ml
what is vital capacity
maximum volume of air that can be moved out during a single breath following maximal inspiration
what is value vital capacity
4500 ml
what is total lung capacity
maximum volume of air that the lungs can hold
what is value of total lung capacity
5700 ml
what is FEV1
volume of air that can be expired during the first second
what is pulmonary ventilation
volume of air breathed in and out in one minute
how to calculate pulmonary ventilation
tidal volume x respiratory rate
what is anatomic dead space
parts that remain in the conducting airways that aren’t available for gas exchange
what is alveolar ventilation
the volume of air exchanged between the atmosphere and alveoli per minute
what is alveolar dead space
ventilated alveoli that are inadequately perfused
what happens to pulmonary arterioles in decreased O2
vasoconstriction
what happens to pulmonary arterioles in increased O2
vasodilation
what happens to systemic arterioles in decreased O2
vasodilation
what happens to systemic arterioles in increased O2
vasoconstriction
where are ventilation and perfusion less when someone stands up
at the top
how does the ventilation perfusion ratio differ
decreases from top to bottom
what is the blood a transport system for
CO2 and O2
what is largest portion of air
nitrogen
value of atmospheric pressure
760 mmHg
what is partial pressure
the individual pressure exerted independently by a particular gas within a mixture of gases
what does it mean if the greater the partial pressure of a gas in a liquid
the more the gas is dissolved
Fick’s law of diffusion
the diffusion rate of a gas through a sheet of tissue also depends on the surface area and thickness of a membrane
what happens to surface area during exercise
increased to enhance the rate of gas transfer
what happens to thickness when alveolus stretches
becomes thinner
what condition causes surface area to decrease
emphysema
why is surface area decreased in emphysema
alveolar walls are lost
what about the thickness can cause decreased gas exchange
an increased thickness
what diseases causes thickened walls
- pulmonary oedema
- pulmonary fibrosis
- pneumonia
what is pulmonary oedema
an excess accumulation of interstitial fluid between the alveoli and capillaries
what causes pulmonary oedema
left sided heart failure
what happens in pulmonary fibrosis
replacement of delicate lung tissue with thick fibrous tissue
what is pneumonia
inflammatory fluid accumulation within or around the alveoli
what is pneumonia due to
bacterial or viral infection of the lungs
what has a greater diffusion constant CO2 or O2
CO2 twenty times more than O2
when diffusion is impeded what gas is more affected
O2
how does oxygen move
by diffusion down its partial pressure gradient
how is most O2 transported
bound to haemoglobin
by what methods is O2 transported
- solution
- haemoglobin
what is dissolved O2 related to
Po2
how much O2 is transported in solution
1.5%
where is haemoglobin
in red blood cells
is O2 binding to haemoglobin reversible or irreversible
reversible
how much O2 is transported bound to haemoglobin
98.5%
what determines haemoglobin saturation
Po2
how many iron molecules in haemoglobin
4
how many O2 molecules can haemoglobin transport
4
what can cause Po2 to fall
- high altitudes
- O2 deprived environments
does O2 in haemoglobin contribute to Po2
no only dissolved O2
what does Hb do when Po2 falls
Hb must unload some O2
other factors that affect O2 unloading in Hb
- CO2
- acidity
- temperature
- 2,3 bisphosphoglycerate
in what direction does increased Pco2 shift the O2 curve
to the right
what direction does increased acid shift the O2-Hb curve
to the right
what is increased release of O2 known as
Bohr effect
what does a rise in temperature shift the O2-Hb curve
to the right
where is 2,3 BPG
in the red blood cell
when is 2,3 BPG produced
red blood cell metabolism
when can 2,3 BPG increase
- high altitudes
- anaemia
haemoglobin has a higher affinity for O2 than CO2
true or false
FALSE
haemoglobin has a higher affinity for CO2 than O2
how is most CO2 transported in the blood
as bicarbonate
how is carbon dioxide transported in the blood
- solution
- carbamino haemoglobin
- bicarbonate
what does amount of CO2 dissolved depend on
Pco2
what is formed when CO2 combines with Hb
carbamino haemoglobin
what does reduced Hb have a higher affinity for
CO2
what does unloading of O2 from Hb facilitate
picking up of CO2 by Hb
how is CO2 transported by bicarbonate
- CO2 combines with H2O forming carbonic acid
enzyme = carbonic anhydrase
is the membrane permeable or impermeable to H+
impermeable
Haldane effect
removing O2 from Hb increases ability of Hb to pick up CO2
what does Haldane effect work with
Bohr effect
how does chloride move
into red blood cells down the electrochemical gradient
what is hypoxia
insufficient O2 at cell level
what is hyperoxia
above normal arterial Po2
what is hypercapnia
excess CO2 in arterial blood
what causes hypercapnia
hypoventilation
what can trigger hyperventilation
- anxiety
- fever
- aspirin poisoning
what type of muscle are the respiratory muscle
skeletal
what is the primary respiratory control centre
medulla
what is in the pons
- pneumotaxic centre
- apneustic centre
what is in the medulla
- dorsal respiratory centre
- ventral respiratory centre
what does dorsal neurones stimulate
inspiration
are ventral neurones activated during normal breathing
no
what stimulates ventral neurones
dorsal neurones
what is ventral neurones important in
active expiration
what generates the respiratory rhythm
pre-Botzinger complex
where is pre-Botzinger complex located
in upper end of medulla
what kind of activity does pre-Botzinger complex have
spontaneous pacemaker activity
where does pneumotactic centre send its impulses
to dorsal neurone
what does stimulation of pneumotactic centre cause
inhibits inspiration
what does apneustic centre do
prevents inspiration neurones from being switched off = prolongs inspiration
what is apneusis
prolonged breathing
when does apneusis occur
in some cases of severe brain damage
when is Hering-Breur reflex triggered
when tidal volume is large e.g. during exercise
what does Hering-Breur reflex prevent
overinflation of lungs
how is arterial Po2 monitored
peripheral chemoreceptors
where are peripheral chemoreceptors
- carotid
- aortic
are peripheral chemoreceptors sensitive
no
what is the most important magnitude of ventilation under resting conditions
Pco2
where are central chemoreceptors
in the medulla near respiratory centre
what do central chemoreceptors detect
CO2 induced H+ in ECF
how is movement of materials restricted in ECF
by blood brain barrier
what is the blood brain barrier permeable to
CO2
can H+ permeate the blood brain barrier
no
what removes H+
HCO3-
what can cause an increase in H+ concentration
diabetes mellitus
can joint and muscle movement stimulate the respiratory centre
yes
what does epinephrine release stimulate
ventilation
how does inhalation of noxious particles affect ventilation
ceases it
how does pain affect respiratory centre
stimulates it ‘gasp’
how do hiccups occur
when involuntary spasmodic contractions of diaphragm occur
when is respiratory centre inhibited
during swallowing (prevent food entering the lung)
what is dyspnoea
short of breath
when can dyspnoea be seen
- obstructive lung disease
- pulmonary oedema (assoc cardiac failure)
