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Questions and Answers
Which nerves regulate the activity of the respiratory muscles?
Which nerves regulate the activity of the respiratory muscles?
Where are the neural centers that control respiratory rhythm and depth primarily located?
Where are the neural centers that control respiratory rhythm and depth primarily located?
What role does the medulla play in the control of respiration?
What role does the medulla play in the control of respiration?
How do the pons centers contribute to respiration?
How do the pons centers contribute to respiration?
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Which physical factor can increase the rate of breathing?
Which physical factor can increase the rate of breathing?
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What limits voluntary control of breathing?
What limits voluntary control of breathing?
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How do emotional factors influence respiratory rate and depth?
How do emotional factors influence respiratory rate and depth?
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What happens when the respiratory centers in the medulla ignore messages from the cortex?
What happens when the respiratory centers in the medulla ignore messages from the cortex?
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What is the function of the expiratory center in the medulla?
What is the function of the expiratory center in the medulla?
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Which nerve is NOT involved in the regulation of respiratory muscles?
Which nerve is NOT involved in the regulation of respiratory muscles?
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Study Notes
Respiratory Gas Transport
- Oxygen and carbon dioxide must be transported to and from the lungs and tissue cells of the body via the bloodstream.
- Internal Respiration: gas exchanges occur between the blood and tissue cells at systemic capillaries.
Mechanics of Breathing
- Rule: volume changes lead to pressure changes, which equalize pressure, leading to the flow of gases to equalize pressure.
- Inspiration:
- Air flows into the lungs, chest expands laterally, rib cage elevates, and diaphragm depresses and flattens.
- Lungs stretch to a larger thoracic volume, causing intrapulmonary pressure to fall, and air flows into the lungs.
- Expiration:
- Air leaves the lungs, chest depresses, rib cage descends, and diaphragm elevates and becomes dome-shaped.
- Lungs recoil to a smaller volume, intrapulmonary pressure rises, and air flows out of the lung.
Volumes within the Lungs
- Intrapulmonary Volume: volume within the lungs.
- Intrapleural Pressure: normal pressure within the pleural space, always negative, preventing lung collapse.
Nonrespiratory Air Movements
- Result from reflex activity, but some may be produced voluntarily (e.g. coughing, sneezing, crying, laughing, hiccups, yawning).
Respiratory Volumes and Capacities
- Tidal Volume: approximately 500 ml of air moved in and out of the lungs with each breath.
- Inspiratory Reserve Volume: amount of air that can be forcibly taken in over the tidal volume (2100-3200 ml).
- Expiratory Reserve Volume: amount of air that can be forcibly exhaled after a tidal expiration (approximately 1200 ml).
- Residual Volume: air remaining in the lungs even after the most strenuous expiration (approximately 1200 ml), allowing gas exchange to continue between breaths.
- Vital Capacity: total amount of exchangeable air (typically around 4800 ml in healthy young men), sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume.
Calculations
- ERV: 1200 ml
- IRV: 2100 ml
- IRV - Tidal Volume: 1600 ml
- Vital Capacity: 4800 ml
Dead Space and Functional Volume
- Dead Space Volume: air that enters conducting zone passageways and never reaches alveoli.
- Functional Volume: air that reaches respiratory zone and contributes to gas exchange (approximately 350 ml).
Gas Transport
- Oxygen is transported in the blood in two ways:
- Most attaches to hemoglobin molecules inside RBCs to form oxyhemoglobin.
- A small amount is carried dissolved in the plasma.
- Carbon dioxide is transported in the plasma as bicarbonate ion or inside RBCs bound to hemoglobin.
Control of Respiration
Neural Regulation
- Phrenic and intercostal nerves regulate respiratory muscles (diaphragm and external intercostals).
- Medulla and pons: neural centers controlling respiratory rhythm and depth.
- Medulla: sets basic rhythm of breathing, contains pacemaker (inspiratory center) and expiratory center.
- Pons: smooths out basic rhythm of inspiration and expiration set by medulla.
Non-neural Factors Influencing Respiratory Rate and Depth
- Physical factors: modify rate and depth of breathing (e.g. talking, coughing, exercising, increased body temperature).
- Volition (conscious control): limited, respiratory centers ignore cortex messages when oxygen supply in blood is low or blood pH is falling.
- Emotional factors: modify rate and depth of breathing through reflexes initiated by emotional stimuli acting through centers in the hypothalamus.
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Description
Learn about the different volumes of air in the lungs, including tidal volume, inspiratory reserve volume, and expiratory reserve volume.
