Physiology 1 & 2 Flashcards
Internal respiration?
Intracellular mechanisms that produce O2 and use CO2
External respiration?
Sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body
4 steps of external respiration?
Ventilation (mechanical process of moving air into and out of the lungs)Gas exchange between the alveoli and bloodGas transport in blood (between lungs and tissue)Gas exchange at tissue level
Boyle’s law
At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas
Why does air move into the lungs during inspiration?
During inspiration, the inspiratory muscles contract causing the thorax and lungs to expand. This causes the intra-alveolar pressure to become less than the atmospheric pressure due to Boyle’s law causing air to flow down the concentration gradient into the lungs
What holds the thoracic wall and lungs in close proximity? (2)
Intrapleural fluid cohesivenessNegative intrapleural pressure
What is the intracellular fluid cohesiveness?
Water molecules in intrapleural fluid are attracted to each other and resist being pulled apart causing the plural membranes to stick together
Negative intrapleural pressure?
The intracellular pressure is below atmospheric pressure which creates a transmural pressure gradient forcing the lungs outwards and chest inwards
Atmospheric pressure value?
760mmHg
Intralveolar pressure value?
760mmHg
Intrapleural pressure value?
756mmHg
Is inspiration an active or passive process?Expiration?
ActivePassive
Major inspiratory muscle?
Diaphragm
Inspiratory muscles?
Diaphragm and external intercostal muscles
what gives motor innervation to the diaphragm?
Phrenic nerves formed from C3, 4, 5 nerve roots
When does air stop entering the lungs?
When intra-alveolar pressure equals atmospheric pressure
How does expiration occur?
Relaxation of the inspiratory muscles causes the chest wall and lungs to recoil to their perspiratory size due to their elastic propertiesThis causes the intra-alveolar pressure to rise due to boyle’s law forcing air out of the lungs down the pressure gradient until intra-alveolar pressure = atmospheric pressure
Pneumothorax definiton
Air in the pleural space (causes the lung to collapse)
Types of pneumothorax?
Traumatic (hole in chest wall)Spontaneous (hole in lung wall)
What causes a lung to recoil during expiration?
Elastic connective tissueAlveolar surface tension
Alveolar surface tension?
Attraction between water molecules at liquid air interface
What reduces the alveolar surface tension?
Surfactant (lowers surface tension of smaller alveoli more than larger alveoli)
La Place’s law?
P=2T /r (the smaller alveoli have a higher tendency to collapse)
What is surfactant made of?
Lipids and proteins