respiratory Flashcards
what are the two functions of the respiratory system
- pulmonary ventilation- inspiration and expiration of air
- gaseous exchange- external respiration (movement of oxygen into the blood and carbon dioxide into the lungs) and internal respiration (release of oxygen to respiring cells for energy production and collection of waste products)
structure of the respiratory system
air is drawn into the nasal cavity through the nose and travels down the pharynx, larynx and trachea. the trachea then divides into left and right bronchi as they enter the lung cavity. the bronchi subdivide into smaller bronchioles and end in alveolar ducts. this is the entrance for air to move into the alveoli- clusters of tiny air sacs covered in a dense network of capillaries which together serve as the site for gaseous exchange
outline how oxygen is transported in the blood
oxygen binds with haemoglobin to produce oxyhaemoglobin which is then transported in the blood plasma
three ways that carbon dioxide can be transported
-dissolved in water and carried as carbonic acid
-carried with haemoglobin
-dissolved in blood plasma
define breathing rate and the average value
number of inspirations or expirations taken in one minute
12-15 breaths/min
define tidal volume and the average value
volume of air inspired or expired per breath
500ml
define minute ventilation and its average value
volume of air inspired or expired per minute
6-7.5 L/min
how does breathing rate respond to exercise
breathing rate increases in proportion to the intensity of the exercise until we approach our maximum of around 50-60 breaths/min.
-in sub-max, steady-state exercise, breathing rate can plateau due to the supply of oxygen meeting the demand of the working muscles
how does tidal volume respond to exercise
tidal volume or the depth of breathing increases initially in proportion to exercise intensity at sub-maximal intensities, up to approximately 3l. tidal volume reaches a plateau during sub-maximal intensity because an increased breathing rate towards maximal intensities does not allow enough time and requires too much muscular effort for maximal inspiration or expirations
how does minute ventilation respond to sub-max intensity
during sustained sub-maximal intensity exercise, VE can plateau as we reach a comfortable steady state. this plateau represents the supply meeting the demand for oxygen delivery and waste removal.
-firstly, there is an initial anticipatory rise in VE prior to exercise due to release of adrenaline
-then a rapid increase in VE at the start of exercise due to increased breathing rate and tidal volume to increase the oxygen delivery and waste removal in line with exercise intensity
-a steady state VE throughout the sustained intensity exercise as oxygen supply meets demand
-an initially rapid and then more gradual decrease in VE to resting levels as recovery is entered and the demand for oxygen dramatically reduces
how does minute ventilation respond to maximal intensity
during maximal intensity exercise, VE does not plateau as exercise intensity continues to increase. there is a growing demand for oxygen and waste removal which VE must continuously work to meet. tidal volume will plateau and the further increase in VE is from a continued rise in breathing rate
how does minute ventilation respond during recovery
in recovery, there is a rapid decrease followed by a gradual decrease to resting levels. although, breathing rate and tidal volume will both decrease post exercise, it is important to do this gradually- using an active recovery maintains VE providing the continued need for oxygen for aerobic energy production and the removal of waste products
inspiration at rest
-external intercostal muscles contract which lifts the ribcage and sternum up and out
-diaphragm contracts and flattens
-volume inside thoracic cavity increases
-this lowers the pressure below the atmospheric pressure
-air moves from high to low pressure
-air ruses into the lungs
expiration at rest
-external intercostal muscles relax, lowering the ribcage and the sternum down and in
-diaphragm relaxes and returns to its dome shape
-volume inside thoracic cavity decreases
-this increase the pressure above the atmospheric pressure
-air moves from high to low pressure
-air rushes out of lungs
inspiration during exercise
-external intercostal, diaphragm and additional inspiratory muscles (sternocleidomastoid and pectoralis major) give a larger force of contraction which creates a greater up and outward movement of the ribcage and sternum
-the greater movement increases the volume inside the thoracic cavity
-and decreases the pressure inside the thoracic cavity below atmospheric pressure
-this increases the depth of breathing and so more air rushes into the lungs
expiration during exercise
-diaphragm and external intercostal muscles relax
-internal intercostal and additional muscles contract to create a greater down and inward movement of the ribcage and sternum
-greater decrease in thoracic cavity volume
-higher air pressure in lungs compared to atmospheric pressure
-more air is forced out of the lungs
control centre that regulates respiration
respiratory control centre
what are the two centres within the RCC
-inspiratory centre which stimulates inspiratory muscles to contract at rest and during exercise
-expiratory centre is inactive at rest but will stimulate additional expiratory muscles to contract during exercise
at rest, which centre is responsible for the rhythmic cycle of breathing
inspiratory centre
at rest nerve impulses are generated and stimulate the inspiratory muscle causing them to contract via the ? and what does this result in
-intercostal nerve to the external intercostals
-phrenic nerve to the diaphragm
results in the thoracic cavity volume increasing, lowering the lung air pressure and after approx. 2 seconds stimulation stops and the inspiratory muscles relax. the lung tissues recoil causing a passive expiration
how is respiratory regulation controlled during exercise
sensory nerves relay information to the RCC where a response is initiated by both the IC and the EC. The RCC is chemosensitive and very receptive to chemical information.
-chemoreceptors located in the aorta and carotid arteries pick up an increase in blood acidity, increase in co2 concentration and decrease in o2 concentration.
there are also neural stimuli which feed information to the RCC:
-thermoreceptors inform of an increased blood temperature
-proprioceptors inform of motor activity in the muscles and joints
-baroreceptors, located in the lung tissue and bronchioles, inform of the state of lung inflation
chemoreceptors, thermoreceptors and proprioceptors inform the IC, which increases the stimulation of the diaphragm and external intercostal muscles to contract with more force. the IC also recruits the additional inspiratory muscles, sternocleidomastoid and pectoralis major, to contract. this greater force of contraction increases the depth of inspiration.
baroreceptors inform the EC on the extent of lung inflation. If the lung tissue begins to become excessively stretched, the EC stimulates additional expiratory muscles (internal intercostal and rectus abdominus) to contract- reduces volume of the thoracic cavity, which increases the lung air pressure causing a forced expiration- reduces time available for inspiration.
as exercise intensity increases, the combination of IC and EC control leads to an increased breathing rate and decreased breathing depth to maximise efficient respiration
what is gaseous exchange
the movement of gases across a membrane from an area of high partial pressure to an area of low partial pressure achieved by diffusion
what occurs during external respiration at rest
the exchange of gases at the lungs between the deoxygenated blood that arrives in the capillaries and the oxygen-rich atmospheric air held at the alveoli
-O2 moves from high PP at the alveoli into the low PP capillary blood. haemoglobin molecules associate with the oxygen to form oxyhaemoglobin as the blood passes the alveoli- ensuring that the blood leaving the lungs is fully saturated with O2
-CO2 moves from high PP in the carbon-rich capillary blood into the low PP alveoli down the diffusion gradient
what occurs during internal respiration at rest
the exchange of gases at the muscle cells between the oxygenated blood that arrives in the capillaries and the carbon dioxide producing muscle cells
-O2 moves from high PP in the capillary blood to low PP muscle cell- haemoglobin molecule dissociates the oxygen as they pass the muscle cell
-CO2 moves from high PP in the muscle cells to low PP capillary blood- ensures that the blood that leaves the muscle cells has been saturated with waste products ready for removal
