Physiology Flashcards
define internal respiration
mechanism that consumes oxygen and produces carbon dioxide
define external respiration
exchange of oxygen and carbon dioxide between the environment and cells
four steps in external respiration
- ventilation
- gas exchange between alveoli and pulmonary capillaries
- exchange in the blood
- systemic capillaries and cells
two forces that hold the thoracic wall and lungs in close opposition
- intrapleural fluid cohesiveness
- negative intrapleural pressure
describe intrapleural fluid cohesiveness
water molecules keep the pleural membranes together
is inspiration an active process
yes
how is the diaphragm flattened in inspiration
by the phrenic nerve (C3, 4 and 5)
is expiration a passive process
yes
two mechanisms of lung recoil in expiration
- elastic connective tissue
2. alveolar surface tension
describe alveolar surface tension
water and surfactant line the alveoli preventing collapse
describe alveolar interdependence
alveoli work together to prevent collapse
forces keeping the alveoli open
- pressure gradient
- surfactant
- alveolar interdependence
forces promoting alveoli collapse
- elastic tissue
- alveolar surface tension
accessory muscles of inspiration
sternocleidomastoid
scalenus
pectoral
muscles of active expiration
abdominal muscles
internal intercostal muscles
tidal volume
volume of air entering or leaving the lungs during a single breath
residual volume
volume of air remaining after maximal expiration
functional residual capacity
volume of air remaining after passive expiration
vital capacity
maximum volume of air that can be moved out during a single breath following maximal inspiration
spirometry result in obstructive lung disease
- reduced FEV1/FVC
- reduced FEV1
- FVC normal (not for COPD)
spirometry in restrictive lung disease
- normal FEV1/FVC
- FEV1 reduced
- FVC reduced
parasympathetic NS on the bronchi
bronchoconstriction
sympathetic NS on the bronchi
bronchodilation
define pulmonary compliance
measure of the effort that goes into stretching and distending the lungs
what decreases pulmonary compliance?
fibrosis oedema collapse pneumonia absence of surfactant
what increases pulmonary compliance
emphysema (loss of elastic recoil)
define alveolar dead space
this is ventilated alveoli that are not adequately perfused with blood
V/Q controls when CO2 increases
dilation of airways
constriction of blood vessels
difference in pulmonary arterioles and systemic arterioles in decreased oxygen
pulmonary arterioles vasoconstrict
four factors affecting the rate of gas exchange across the alveolar membrane
- partial pressure gradient
- diffusion coefficient
- surface area
- thickness of the membrane
dalton’s law
pressure one gas in a mixture would exert if it occupied the whole volume
Henry’s law
partial pressure in gas phase is the same in liquid phase
two forms of oxygen transportation around the body
- dissolved
- bound to Hb
Bohr effect
shifts the oxygen dissociation curve to the right
structure of foetal haemoglobin
2 alpha and 2 gamma subunits
does foetal Hb have a higher affinity for oxygen than adult Hb?
yes
three means of carbon dioxide transport in the blood
- solution
- bicarbonate
- carbamino compounds
what are carbamino compounds?
combination of carbon dioxide and terminal amine groups in blood proteins (especially in Hb which makes carbamino-Hb)
Haldane effect
removing oxygen from Hb increases ability to pick up CO2 and H+
rhythm generator of respiration
medulla
how is respiration initiated
pre-Botzinger complex in the top of the medulla
what does the pre-Botzinger complex excite?
dorsal respiratory group neurones
what do the dorsal respiratory group neurones do?
firing causes contraction of inspiratory muscles
in active expiration what is the second group of neurones activated called?
ventral respiratory group neurones
what does the ventral respiratory group neurones do?
excites accessory muscles of active expiration
how can the rhythm of respiration be modified
pons
role of the pneumotaxic centre
terminates inspiration
role of the apneustic centre
prolongs inspiration
four involuntary modifications of breathing
- pulmonary stretch receptors (Hernia-Breuer reflex)
- joint receptor
- stimulation by temp, adrenaline or cerebral cortex
- cough reflex
describe the Hering-Breuer reflex
in the bronchi and bronchioles and guard against hyperinflation
gas tensions are detectors
peripheral and central chemoreceptors
where are peripheral chemoreceptors located?
carotid and aortic bodies
where are central chemoreceptor located?
medulla (respond ot H+ in CSF- BBB)
hypoxic drive of respiration
peripheral chemoreceptors are stimulated when pO2 falls below 8kPa
chronic adaptions to high altitude hypoxia
- increased RBC
- increased 2, 3 BPG (offloads O2 more easily)
- increased capillaries
- increased mitochondria
H+ drive of respiration
peripheral chemoreceptors detect and adjust acidosis
