Chapter 11 (Respiration) Flashcards
Internation Respiration/Cellular Respiration
- Refers to the metabolic processes carried out within the mitochondria
Respiratory Quotient (RQ) - Ratio of CO2 produced, to O2 consumed
- Varies depending on nutrients consumed
External Respiration
- Ventilation between the atmosphere and air sacs (alveoli) in the lungs.
- Exchange of O2 and CO2 between air in the alveoli and the blood in the pulmonary capillaries
- Transport of O2 and CO2 by the blood between the lungs and the tissues
- Exchange of O2 and CO2 between the blood in the systemic capillaries and tissue cells.
Anatomy of the Respiratory System
- Nasal passages
- Pharynx: common passageway for food and air
- Trachea
- Larynx: voice box
- Bronchi
- Bronchioles
- Pulmonary alveoli
- Trachea and larger bronchi
- Bronchioles
a. no cartilage, walls contain smooth muscle innervated by ANS
b. sensitive to certain hormones and local chemicals
Lungs
- Diaphragm
- Dome shaped sheet of skeletal muscle
- Separates thoracic cavity from the abdominal cavity - Pleural Sac
- Double-walled, closed sac that separates each lung from the thoracic cavity
- Pleural Cavity - interior of plural sac
- Intrapleural fluid
a. secreted by surfaces of the pleura
b. lubricates pleural surfaces
Conducting Zone
- Trachea
- Main bronchus
- Bronchus
- Bronchiole
- Terminal Bronchiole
Respiratory Zone
- Respiratory Bronchiole
- Alveolar Duct
- Alveolar Sac
Alveolus
- Site of gas exchange
- Walls consists of a single layer of flattened Type 1 alveolar cells
- Pulmonary capillaries encircle each alveolus
- Type 2 alveolar cells secrete pulmonary surfactant
- Alveolar macrophages
- Pores of Kohn
Boyle’s Law
- With a constant temperature, the pressure and volume will fluctuate inversely. Pressure increases, volume decreases by the same factor.
- If intra-alveolar pressure is less than atmospheric pressure, air enters the lungs. If the opposite occurs, air leaves the lungs.
Types of Pressure
- Atmospheric (barometric) pressure
- Intra-alveolar pressure (intrapulmonary)
- Intrapleural pressure (intrathoracic)
- Transmural pressure
Atmospheric Pressure
The pressure that is exerted by the weight of the air in the atmosphere.
Intra-alveolar Pressure
Pressure within the alveoli
Pleural Pressure
The pressure outside the lungs, but still within the thoracic cavity; pressure in the pleural space.
It closely approximates intrathoracic pressure.
Transmural Pressure Gradient
Always calculated as the inside pressure minus the outside pressure.
Alveolar pressure - Pleural pressure = Transpulmonary pressure
Breathing Mechanics
Muscles of Quiet Breathing
- The Diaphragm
- The external intercostal muscles
Muscles of Deeper Breathing
- The Diaphragm
- External intercostal muscles
- Accessory muscles of inspiration (sternocleidomastoid and scalenus)
Muscle Activity During Inspiration
- Contraction of external intercostal muscles causes the elevation of ribs which increases side-side dimension of the thoracic cavity
- Lowering of the diaphragm on contraction increases vertical dimension of the thoracic cavity.
- Elevation of ribs causes the sternum to move upwards and outward, which increases front-back dimensions of thoracic cavity.
Muscles of Expiration
- Internal Intercostal muscles
- Diaphragm
- Abdominal Muscles
Muscle Activity During Expiration
- Return of diaphragm, ribs, and sternum to resting position on relaxation of inspiratory muscles. Restores thoracic cavity to pre-inspiratory size.
- Contraction of internal intercostal muscles causes the flattening of the ribs and sternum, further reducing side-side and front-back dimension of thoracic cavity.
- Contraction of abdominal muscles causes the diaphragm to be pushes upwards, further reducing vertical dimension of the thoracic cavity.
Pressure Changes During Breathing
- Before inspiration, at the end of expiration:
- Intra-alveolar pressure is equal to atmospheric, no air is flowing. - Inspiration:
- Lungs increase in volume, intra-alveolar pressure decreases. Outside > inside pressure allows air to flow into the alveoli. - Expiration:
- Lungs recoil to previous size, intra-alveolar pressure increases. Inside > outside pressure allows air to flow out of the alveoli.
Pressure Gradient and Resistance
F = change of P / R
F: Flow rate
P: Difference b/w atmospheric and intra-alveolar pressure
R: resistance of airways (related to radius)
- In a healthy person, the radius of the conducting system is large and resistance remains extremely low.
- In an asthmatic person, the radius can be low and resistance can be high, so less air moves into the lungs.
Role of ANS in Flowrate
Parasympathetic:
- Promotes bronchiolar smooth muscle contraction
- Bronchoconstriction. Increases air resistance.
- Low air demand.
Sympathetic:
- Your body secretes epinephrine to promotes smooth muscle relaxation
- Bronchodilation. Decreases airway resistance
- High air demand.
Surface Tension
The attractive forces in water is responsible for surface tension. Because of this the alveoli
- Resists being stretched.
- Tends to be reduced in surface area or size.
- Tends to recoil after being stretched.
Pulmonary Surfactant
Secreted by Type 2 Alveolar Cells
- Increases the surface tension and decreases pulmonary compliance; reduces inflation of the lungs.
- Reduces the lungs capacity to recoil, preventing them from collapsing.
- Maintains the lungs stability.
Spirometer
Measures lung volume and capacity.
Spirogram
A graph that record inspiration and expiration
Lung Volumes and Capacities
- Tidal volume (TV): The volume of air entering and leaving the lungs in a single breath (~500ml)
- Inspiratory Reserve Volume (IRV): Extra volume of air that can be maximally inspired over and above the typical resting tidal volume (~3 L)
- Expiratory Reserve Volume (ERV): Extra volume that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume. (1 L)
- Residual volume (RV): the minimum volume of air remaining in the lungs even after a maximal expiration (~1.2 L)
- Vital Capacity (VC): the maximum volume of air that can be moved out in a single breath following a single breath following a maximal inspiration.
VC = IRV + VT + ERV = 4500ml - Total lung capacity: The maximum volume of air that the lungs can hold
- TLC: VC + RV (5,700ml)
Pulmonary Ventilation
The volume of air breathing in and out in 1 minute.
- Changes in lung volume are represented by:
1. Minute/pulmonary ventialation
2. Respiratory rate
Pulmonary/minute ventilation = tidal volume x respiratory rates
Alveolar Volume/Ventilation
Volume of the air exchanged between the atmosphere ad the alveoli per minute.
(TV - Dead Space Volume) x Respiratory rate = Alveolar Ventilation
Anatomic Dead Space
A portion of inspired air will remain in the conducting airways and is not available for gas exchange.
~ 150ml
- 500ml of old alveolar air is expired, only 350ml expired to atmosphere, 150ml remains in the dead space.
- 150ml of inspired air is old alveolar air that was in the dead space. A fresh 150ml will enter the dead space.
Work of Breathing
- Normally requires 3% of total energy expenditrue for quiet breathing
- Lungs normally operate at about “half full”
- Work of breathing increases when:
1. Pulmonary compliance is decreased
2. When airway resistance is increased
3. When elastic recoil is decreased
4. When there is a need for increased ventilation.
Local Control of Smooth Muscles on the Airways
- Accumulation of carbon dioxide in alveoli decreases airway resistance leading to increased airflow
- Increase in alveolar oxygen concentration brings about pulmonary vasodilation which increases blood flow to match larger airflows.
Partial Pressures
- Individual pressure exerted independently by a particular gas among the mixture of other gases
- The pressure exerted by a particular gas is directly proportional to the % of that gas in the total air mixture.
- Partial pressure exerted by each gas in a mixture equals the total pressure times the fractional composition of this gas in the mixture.
- The greater the partial pressure of a gas in a liquid, the more of that gas is dissolved in that fluid
- Partial pressure gradient exists
1. Between alveolar air and pulmonary capillary blood
2. Between systemic blood and surrounding tissue - Gases always diffuse from the are of high partial pressure to lower.
- The larger the partial pressure gradient, the more O2 and CO2 diffuses into and out of the tissue and blood.
PO2= 21 x 760 / 100 = 159.6 mm Hg
Pulmonary and Systemic Capillary Gas Exchang
- The venous blood, low in O2 and high in CO2, enters the lungs
- Alveolar O2 is high, and CO2 is low because only a portion of the alveolar air is replaced by fresh atmospheric air during each breath.
- The partial pressure gradients between the alveoli and pulmonary capillary blood cause O2 to diffuse into the blood, and CO2 out. This stops when partial pressures are equal.
- Blood leaving the lungs has a high partial pressure and O2 content, and low CO2 content.
- Partial pressure of O2 is higher, and CO2 is lower in O2 consuming and CO2 producing tissue cells.
- O2 diffuse from the arterial blood into cells, and CO2 from the cells to the blood.
- After the exchange, blood is low in O2 and high in CO2.
Factors that Affects Gas Exchange
- An increase in surface area = increase in gas transfer.
- Increase in thickness of the barrier separating air and blood decreases the rate of gas transfer.
- Rate of gas exchange is directly proportional to the diffusion coefficient for a gas.
Oxygen Transport
- Most oxygen in the blood is transported bound to RBC hemoglobin.
- O2 can be physically dissolved. 1.5% because O2 is a poor plasma soluble.
- Chemically bound to hemoglobin 98.5%.
- Hb + O2 = HbO2 (oxyhemoglobin) - plasma
- HbO2 = O2 + Hb (in the tissue)
The amount dissolved is directly proportional to the PO2 of the blood; the higher the PO2, the more O2 dissolved in the plasma.
Gas Transport
- The percent saturation is high where the partial pressure of O2 is high
- The relationship is shown in the oxygen-hemoglobin dissociation curve.
- The plateau part of the curve is where the partial pressure of oxygen is high
- The steep part of the curve exists at the systemic capillaries.
Haldane Effect
Hemoglobin promotes the net transfer of CO2 and H+ at both the alveolar and tissue levels.
- H2CO3 in RBC’s dissociate into H2O and CO2
- H2O then dissociates into H+
- Unloading O2 allows Hb to pick up H+
- Hb has a greater affinity for H+ than CO2.
Bohr Effect
The decrease in the amount of oxygen associated with hemoglobin in response to a lowered blood pH (typically caused by increased CO2 concentration).
Both the Bohr and Haldene effect work together to facilitate O2 liberation and the collection of CO2 and CO2 generated H+
CO2 Transportation in the Blood
- Physically dissolved 5-10%
- Bound to hemoglobin 5-10%
- CO2 + Hb = HBCO2 (carbamino hemoglobin)
- CO2 binds with globulin of Hb - As bicarbonate ion 80-90%
- CO2 + H2O = H2CO3 (carbonic acid)
- H2CO3 = H+ + HCO3 (bicarbonate)
- H+ + HCO3 = H20 + CO2 (blood)
Hypoxia
- Having insufficient O2 at the cell level
1. Hypoxic hypoxia (high altitudes)
2. Anemic hypoxia: related to reduced O2 capacity of the blood
3. Circulatory hypoxia: related to too little blood delivery to the tissue (heart failures)
4. Histotoxic hypoxia: the cells can’t use the O2 provided.
Hyperoxia
- Condition of having an above-normal arterial PO2
1. Can only occur when breathing supplemental O2
Hypercapnia
- Condition of having excess CO2 in arterial blood
1. Caused by hypoventilation
Hypocapnia
- Below normal arterial PCO2 levels
1. Caused by hyperventilation - Can be caused by anxiety, ever or aspirin poisoning.
Medullary Respiratory Centre
- Dorsal respiratory group - mostly inspiratory neurons.
- On = inspiration
- Off = expiration - Ventral respiratory group - both inspiratory and expiratory neurons
- Only activates during increased ventilation (exercise) - Pre-botzinger complex - widely believed to generate respiratory rhythm.
Pneumotaxic Centre
Pons
- Sends impulses to DRG to help “switch off” inspiratory neurons
- Dominates of apneustic centre
Apneustic Centre
Pons
- Prevents inspiratory neurons from being switched off
- Provides an extra boost to inspiratory drive
Hering-Breuer reflex
- Triggered to prevent overinflation of the lungs
- Chemical factors that play a role in determining magnitude of ventilation
- PO2
- PCO2
- H+
Ventilation Factors Unrelated to Gas Exchange
- Sneezing and coughing
- Noxious agents that cause you to stop breathing
- Pain
- Various emotional states
- Swallowing
Hearing-Breuer Reflex
- Exercise causes high tidal volume
- Pulmonary stretch receptors intiate the H-B reflex (medullary centre).
- This prevents the lungs from over inflation by inhibiting the inspiratory neurons.
