Respiratory system Flashcards
What are the four processes of respiration?
- pulmonary ventilation (breathing): air in/out of lungs
- external respiration: gas exchange btwn lung and blood
- gas transport: O2 and CO2 in the blood
- internal respiration: gas exchange btwn blood and tissue
What is the respiratory zone?
the area of gas exchange (microscopic structures that carry out gas exchange)
What is the conducting zone?
the zones that provide passages for air in and out of respiratory zones
What components make up the respiratory zone?
respiratory bronchioles, alveolar ducts, aveoli
What areas make up the conducting zone?
nose, nasal cavity and paranasal sinuses
pharynx, larynx, trachea, bronchi and their large branches.
Why do we need respiration?
Oxygen is needed for aerobic respiration:
glucose + O2 -> CO2 + ATP + heat
CO2 needs to be gotten rid of because:
CO2 + H2O -> H2CO3 -> H(+) + HCO3
the inc concentration of H+ ions causes a decrease in pH and affects the enzymes of the body
What are the functions of the nose and paranasal sinuses?
- provides an airway for respiration
- moistens and warms air
- filters and cleans
- resonating chamber for speech
- contains olfactory receptors
What is the philtrum?
the shallow vertical groove inferior to the apex of the nose
What is another name for the nostrils?
Nares
What are the alea?
the structure that flares around the lateral side of the nostrils (nares)
What structure is in the roof of the nasal cavity and what is its purpose?
the cribriform plate of the sphenoid and ethmoid bone
purpose is to allow olfactory nerves to pass through
What makes up the floor of the nasal cavity?
the hard and the soft palates
What is the vestibule?
the area superior to the nostrils.
What are vibrissae?
hairs inside the vestibule that trap debris from inspired air.
What is the olfactory mucosa?
the lining of the top of the nasal cavity that is responsible for smell
describe the structure (elements) of respiratory mucosa and there functions.
made up of pseudostratified ciliated columnar epithelium with goblet cells for mucous secretion
contain serous glands which secrete a watery fluid containing enzymes like lysozyme (antibacterial)
cilia move mucus + captured debris
inspired air is warmed by plexuses of capillaries and veins under the epithelial membrane.
contains many sensory nerve endings that triggers a sneeze reflex when it comes in contact with foreign particles
What are the superior, middle, and inferior nasal conchae and what is there purpose?
they are protrusions from the lateral walls.
-inc the mucosal area and creates air turbulence (this slows air flow)
these two factors allow it to enhance warming, humidifying, and cleaning air.
when air returns from the lung it is more moist and warm and allows nose nasal cavity to reclaim some of it.
What is the purpose of the paranasal sinuses?
lighten the skull and help to warm/moisten airf
What is rhinitis?
the inflammation of nasal mucosa (cold). This is accompanied by the overproduction of mucus
Because the nasal mucosa is interconnected with sinuses, and respiratory mucosa, the infection can spread through the throat to the chest and lungs.
What is sinusitis?
The inflammation of the sinus mucosa
What is the pharynx?
the section that connects the nasal cavity and the mouth superiorly and the larynx and esophagus inferiorly.
it is made up of skeletal muscle that allows voluntary control
What are the three regions of the pharynx?
NASOPHARYNX
OROPHARYNX
LARYNGOPHARYNX
What is the nasopharynx?
the superior section that contains air passageways only
lining is pseudostratified columnar epithelium with cilia like the nasal cavity
the soft palate and the uvula close to seal it off when swallowing.
PHARYNGEAL TONSIL or ANDENOIDS on posterior wall
PHARYNGOTYMPANIC (AUDITORY) TUBES open into lateral walls
What system do the tonsils belong to and what is there purpose?
the lymphatic system.
there purpose is to trap and destroy pathogens
What is the purpose of the pharyngotympanic (auditory) tubes?
to equalize pressure in the ear with the outside
What is the oropharynx?
the passageway for food + air
lining of stratified squamous epithelium (more protection then PSC)
ISTHMUS OF THE FAUCES: is the opening to the mouth
PALATINE TONSILS: lie in lateral walls of the fauces
LINGUIL TONSIL: covers the base of the tongue
what is the laryngopharynx
passageway for food and air
lining of stratified squamous epithelium
posterior to the upright epiglottis (epiglottis is part of larynx)
is continuous with larynx and esophagus
What are the 4 functions of the larynx?
cartilage in it provides a patent (never closing) airway
directs food and air into proper channels
voice production
VALSALVA’s maneuver: acts as a sphincter to stabilize core
What type of cartilage are the larynx cartilages made up of (excluding epiglottis)
hyaline
What type of cartilage is the epiglottis made of?
Elastic cartilage
Name the 9 cartilage structures of the larynx.
epiglottis
thyroid cartilage (large superior cartilage) with the laryngeal prominence (ADAM’S APPLE)
Cricoid cartilage
paired cuneiform, corniculate, and arytenoid cartilages on the interoposterior surface
Explain the true and false vocal cords and there functions.
VESTICULAR FOLDS (false vocal cords) superior to true vocal cords no role in voice, but help close glottis during swallowing
TRUE VOCAL CORDS
fold of mucosa over vocal ligaments
vibration of air passing through here causes sound
muscles below the cords control tension
How is the voice produced?
SPEECH is the intermittent release of expired air while opening and closing the glottis
PITCH is determined by the LENGTH and TENSION of the vocal cords
LOUDNESS depends on force of air passing over vocal cords
RESONANCE is given by chambers of pharynx, oral, nasal, and sinus cavities
SOUND is shaped into language by muscles of the pharynx, tongue, soft palate, and lips
What is the trachea?
the windpipe from the larynx to the bronchi in the mediastinum
What are the three layers in the wall of the trachea?
MUCOSA: ciliated pseudostratified columnar with goblet
SUBMUCOSA: CT layer that contains seromucous glands that help produce the mucus sheets within the trachea
ADVENTITIA: The deep CT layer with C shaped hyaline cartilage rings
What is the trachealis muscle and what is its function?
it is made of smooth muscle and connects posterior parts of cartilage rings.
it contracts during cough to expel mucus
During swallowing it allows esophagus to expand
What is the Carina?
the last tracheal cartilage.
marks the point where the trachea branches into the two main bronchi.
The mucosa of the carina is highly sensitive and is what TRIGGERS THE COUGH REFLEX
What is the branching pattern in the air passages called?
the bronchial (respiratory) tree
What are the first three branches of the bronchi?
L and R bronchi -> lobar bronchi -> segmental bronchi
What is the diameter of the bronchioles?
< 1 mm
What are the structural changes that occur from the bronchi to the bronchioles?
Cartilage changes from C rings to irregular plates to none
Epithelium goes from ciliated pseudostratified columnar in the large to ciliated columnar in the medium to simple cuboidal in the bronchioles
Smooth muscle increases as tubes get smaller and the bronchioles have complete rings of smooth muscle
What does asthma cause?
the constriction of the smooth muscle in the smaller branches which causes difficulty of breathing
How many alveoli are there in the lungs?
approx. 300 million
What is the respiratory membrane and what is it composed of?
the barrier between the air and the blood.
optimal thickness Is 0.5 - 1 micrometer
comprised of alveolar and capillary walls (2 layers of squamous epithelial cells with fused basement membranes)
Describe the structure of the alveoli
Surrounded by elastic fibers and capillaries
Contain pores that connect to adjacent alveoli and allow air pressure to be equalized in the lungs
List and describe the 3 types of cells in the alveoli.
TYPE I SQUAMUS cells - gas exchange
TYPE II CUBOIDAL cells - secrete surfactant
ALVEOLAR MACROPHAGES (dust cells) - keep surfaces sterile
What is the function of surfactant?
it is a secretion that inhibits the bonding of H2O molecules to each other and therefore reduces surface tension in the alveoli.
As a result the alveoli are less likely to collapse. (fights the viscosity)
Describe the gross anatomy of the lungs and plurae
APEX - superior tip
BASE - inferior surface that rests on the diaphragm
HILIUM - attachment point for blood vessels, bronchi, lymphatic vessels and nerves (also known as the ROOT)
CARDIAC NOTCH - accommodates the heart
How many lobes does each lung have? propose an explanation for this.
left lung has only 2 lobes
right lung has 3
the heart is located slightly more to the left of the sternum and therefore the left lung is slightly smaller
describe the division of the lungs.
Right and Left lung
LOBES of each lung
BRONCHOPULMONARY SEGMENTS: each is supplied by its own artery, vein, and segmental bronchus
LOBULES: each served by a large bronchiole and its branches
What is the stroma?
the tissue of the lung.
Consists mostly of elastic connective tissue
What are the two blood circuits that supply the lungs?
PULMONARY CIRCULATION: carries systemic blood to the lungs for oxygenation (low pressure, high volume)
BRONCHIAL CIRCUIT: carries oxygenated blood to the lungs itself (high pressure, low volume). This supplies all lung tissue except alveoli. MOST OF THE venous return from this system returns via pulmonary veins, but some will return via bronchial veins to the superior vena cava.
Describe how the lungs are innervated.
innervated by:
PARASYMPATHETIC fibers - constrict bronchioles
SYMPATHETIC fibers - dilate bronchioles
SENSORY fibers - detect changes
Enter at the root
What are the pleurae?
the thin double layered serous membrane (parietal and visceral membrane)
serous fluid is secreted between the membranes which lubricates and maintains surface tension between the layers.
What is pleurisy?
inflammation of the pleura causes membranes touch making it very painful to breath
What is pleural effusion?
Accumulation of fluid (could be blood or filtrate) in the pleural cavity. This fluid causes pressure to be exerted on the lungs making it more difficult to fill
CAUSES:
damaged blood vessel leaking blood into cavity
left sided heart failure - blood accumulates in vessels and excessive filtrate accumulates in the pleural cavity
pleurisy - rubbing of membranes may cause the production of more fluid to relieve pain
what are the three pressures involved in respiration?
Patm (atmospheric pressure): pressure exerted by air at sea level (760 mm Hg)
Ppul (pulmonary pressure): also called intra-alveolar pressure. pressure inside alveoli. Varies with each breath
Respiratory pressure: Ppul - Patm. if this is negative air will flow towards Ppul, if it is pos will move away and if it is 0 then there will be no movement
Pip (intrapleural pressure): pressure in the pleural cavity between membranes. Fluctuates with negative pressure (about 4 mm Hg less then Pip). Depends on the thoracic cavity remaining closed.
What is atelectasis?
lung collapse because of entry of air into thoracic cavity
Can be caused by:
chest wound
plugged bronchioles - associated alveoli will absorb their air and collapse
damage to visceral pleura that allows air to leak out into cavity
What is the presence of air in the intrapleural space referred to as?
pneumothorax
What is Boyle’s law?
at a constant temperature the pressure exerted by a gas varies inversely with its volume:
dec volume -> inc pressure
Describe the process of quiet inspiration and expiration.
inspiration is active:
diaphragm contracts and external intercostals raise the rib cage. This results in thoracic volume to increase and Ppul to dec below Patm. Air flows along the pressure gradient into the lung to equalize pressure
quiet exhalation is passive:
diaphragm and external intercostals relax causing volume to decrease and Ppul increase above Patm and air flows along its pressure gradient out of the lungs to equalize pressure
Describe the process of forced expiration and inspiration.
Forced inspiration:
additional muscles contract (pectoralis major and back muscles) to further increase thoracic volume. Occurs with vigorous exercise or with defective lungs.
Forced expiration:
uses abdominal and internal intercostals to further decrease volume
What are the 4 factors influencing pulmonary ventilation?
DIFFERENCE in pressure: greater the gradient, the greater air flow.
AIRWAY RESISTANCE: friction
ALVEOLAR SURFACE TENSION: surface tension generated by viscosity of water (result of polar interactions between H atoms and O atoms on an adjacent molecule)
LUNG COMPLIANCE: Ability for the lung to change volume with a given change in transpulmonary pressure
Why is airway resistance usually insignificant?
the diameters in the first part of the conducting zone are very large.
As tubes get smaller, cross sectional area gets larger.
Resistance in the terminal bronchioles is counteracted by diffusion driving the movement of gases
When does airway resistance become a problem?
when it is increased by a reflex response to irritants:
ASTHMA: constricts bronchioles (relieved by epinephrine)
Parasympathetic nerves constrict in response to irritants
What is IRDS?
infant respiratory distress syndrome.
A result of too little surfactant being secreted into the alveoli causing increased surface tension. This abnormally high surface tension causes the alveoli to collapse after each expiration and then they have to be completely reinflated after each breath which causes tremendous energy.
Common in premature babies because the ability to produce adequate surfactant is developed in the last 2 months of pregnancy.
Treated with a mist of synthetic surfactant
What is lung compliance.
It is the ability for the lung to change volume that occurs with a given change in the transpulmonary pressure
the higher the compliance the less effort needed to expand the lungs.
What are the two main factors that determine lung compliance?
DISTENSIBILITY of the lung (stretchiness)
SURFACE tension in the alveoli
in healthy people the lung distensibility is high because of the large amount of elastic CT and surface tension is low because of surfactant.
What diminishes lung compliance? (4)
DIMINISHED BY:
FIBROSIS - non elastic scar tissue replacing normal elastic tissue (caused by inflammations and infections)
REDUCED production of surfactant
DECREASED flexibility of the thoracic cage (deformities of thorax, ossification of the costal cartilages, paralysis of intercostal muscles)
BLOCKAGE of smaller respiratory passages
What is tidal volume (TV) and its normal value?
air moved in and out with each quiet normal breath
500 mL
What is the inspiratory reserve volume (IRV) and its normal value?
max amount that can be inhaled in addition to tidal volume.
1900 mL female
3100 mL male
What is the expiratory reserve volume (ERV) and its normal value?
max amount of air that can be expired forcefully after a tidal exhalation.
700 mL female
1200 mL male
What is the residual volume (RV) and what is its normal value?
the amount of air that remains in the lungs after forceful expiration (prevents collapse)
1100-1200 mL for both sexes
What is total lung capacity (TLC)? and its normal values
TLC = TV + IRV + ERV + RV
about 4200 mL female
about 6000 mL male
What is the vital capacity (VC) and its normal values?
total air moved in and out with as deep a breath as possible:
VC = ERV + IC + TV
approx. 80% of TLC
3100 mL female
4400 mL male
What is inspiratory capacity (IC) and its normal values?
total amount of air that can be inspired after tidal expiration
IC = IRV + TV
2400 mL female
3600 mL male
What is functional residual capacity (FRC) and its normal values?
the amount of air left in the lungs after a tidal expiration
FRC = ERV + RV
1800 mL female
2400 mL male
What does the dead space in the lungs refer to?
the volume where gas exchange does not occur
2 types:
ANATOMICAL dead space: volume of the conducting zone (150 mL)
ALVEOLAR dead space: volume of alveoli that cease to act in gas exchange to collapse or obstruction
Total dead space is the sum of the above non-useful volumes
What is the normal volume of the anatomical dead space?
150 mL
What is a pulmonary function test?
conducted by using a spirometer (measures volumes)
What changes in pulmonary volumes might occur with obstructive pulmonary diseases. List some of these diseases
chronic bronchitis, asthma, emphysema
inc resistance -> hyperinflation of the lungs -> inc TLC, FRC, and RV
the inc resistance means it is harder to expel air resulting in hyperinflation
What changes in pulmonary volumes occur with restrictive pulmonary diseases. List a few disease that cause this.
TB, polio, fibrosis
Reduction in total lung function because of inhibited lung expansion.
dec VC, TLC<, FRC, and RV
Explain alveolar ventilation rate.
AVR = frequency of breaths x TV - deadspace
Increases with the long deep breaths
decreases with short shallow breaths (most of the air doesn’t reach the alveoli)
What are non-respiratory air movements?
air movements that are not related to breathing but move air in and out of the lungs
eg coughing, yawning, sneezing.
What is Dalton’s law of partial pressures?
total pressure exerted by a mixture of gases is the sum of the pressures exerted by each gas.
the partial pressure is proportional to its percentage in the mixture
at high altitudes the pressure exerted by each gas is proportionally less
What is Henry’s law?
When a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure
moves towards equilibrium of partial pressure between the two phases
Amount of gas that will dissolve also depends upon its solubility (CO2 is 20x more soluble than O2) and the temp of the liquid (dec temp more gas will dissolve)
What is a hyperbaric oxygen chamber and what principle does it operate on?
operates on henry’s law
contain O2 gas at pressures greater than atmospheric levels and are used to force greater than normal amounts of O2 into blood of patients suffering from carbon monoxide poisoning or tissue damage
What are the three factors that affect external respiration?
Degree of partial pressure gradients and gas solubility
ventilation-perfusion coupling
condition of the respiratory membrane
Explain the characteristics of partial pressure gradient and gas solubility in external respiration.
PO2 gradient in the lungs is steep
venous blood PO2 = 40 mm Hg
alveolar PO2 = 104 mm Hg
REACHES equilibrium in 0.25 secs (1/3 of the total time a RBC is in a pulmonary capillary
PCO2 is less steep:
venous PCO2 = 45 mm Hg
alveolar PCO2 = 40 mm Hg
CO2 diffuses in equal amounts of O2 because CO2 is 20x more soluble than O2
Explain ventilation-perfusion coupling in external repiration
Ventilation: amount of gas reaching the alveoli
Perfusion: amount of blood reaching the alveoli
These two factors must be matched for effective gas exchange
Explain the bodies reaction to PO2 levels in the alveoli
where alveolar PO2 is high, arterioles dilate -> inc in blood flow
Where alveolar PO2 is low, arterioles constrict -> dec in blood flow
this is opposite of other tissues. in the lungs, blood is directed to area that is having efficient O2 exchange
Explain the lungs reaching to PCO2 levels in the alveoli
Where PCO2 is high, bronchioles dilate -> inc in air flow
visa versa
allows the areas of high CO2 to be eliminated faster
Explain how the condition of the respiratory membrane affects external respiration.
Efficient gas exchange requires:
- a thin membrane (.5 - 1 micrometer)
- a large surface area (lungs are 40x SA of skin)
- a moist surface (gases must first be dissolved in water before they can diffuse across a membrane)
What conditions reduce the effectiveness of the respiratory membrane?
thickening of the membrane - pulmonary edema (water logged lungs)
reduced SA eg emphysema, tumors, excess mucus
What percent of O2 in the blood is carried in the plasma and what percent is carried by the hemoglobin?
- 5% in the plasma
98. 5% in the hemoglobin
what is hemoglobin called when it is saturated and when it is reduced (missing O2)
oxyhemoglobin - HbO2
deoxyhemoglobin - HHb
Explain the chemical process for loading and unloading of O2 from hemoglobin
HHb + O2 HbO2 + H
As O2 binds, Hb changes shape and its affinity increases
As O2 is released, Hb changes shape and its affinity decreases
This causes the loading and offloading of O2 to be very efficient
What conditions affect the rate of loading and unloading of O2?
PO2, temperature, blood pH, PCO2, and concentration of BPG
Explain the relationship between % saturation of hemoglobin in the blood and PO2 dissolved in the blood.
% saturation vs PO2 is not linear. (s-shaped
small drops in PO2 from norm result in large drops in % sat
in blood leaving lungs % sat = 100%
in venous blood % sat = 75%
only 20-25% of bound O2 is unloaded during one circuit
Remainder is called the VENOUS RESERVE: can be used to adapt to more strenuous conditions without inc CO or respiratory rate (exercise, altitude)
Explain the influences of PCO2, temp, H+ and BPG on offloading
PCO2 and pH: inc CO2 -> inc [H+] -> dec in pH
BOHR EFFECT: acidosis weakens the hemoglobin-O2 bond
[BPG] is an intermediate in anaerobic metabolism
inc in [BPG] hemoglobin releases O2 easier
if [BPG] too low O2 is irreversibly bonded to hemoglobin
TEMPERATURE: inc in temp results in inc release from hemoglobin because of direct effect of enzymes and by increasing BPG synthesis
All of these factors see an increase in active tissue, so the graph of % saturation of hemoglobin and PO2 will see a shift to the right in active tissues
What role does NO (nitric oxide) play in gas exchange.
NO is secreted by the endothelial cells.
the globin will carry the NO released and when it unloads O2 the NO will also unload causing dilation of the arterioles to increase perfusion
What is hypoxia and what does it lead to?
shortage of oxygen in the tissues
leads to cyanosis (tissue turning blue)
what is anemic hypoxia?
hypoxia caused by insufficient number of RBCs or functional hemoglobin in the RBCs
What is ischemic hypoxia?
hypoxia caused by blocked blood supply to the tissues
What is histotoxic hypoxia?
hypoxia caused by cells that cannot utilize oxygen (this is the path that cyanide follows; blocks the cellular use of oxygen)
What is hypoxemic hypoxia? What are some of its causes?
hypoxia caused by insufficient amounts of oxygen reaching RBCs
problems with ventilation/perfusion functioning
lung malfunction
low PO2 in air
carbon monoxide poisoning - CO competes with oxygen and binds irreversibly to hemoglobin
What are the three ways that CO2 is transported in the blood and the percent of total CO2 in the blood for each.
7-10% dissolved in the plasma
20% as carbonaminohemoglobin (bound to the globin)
70% is carried as a bicarbonate ion (HCO3-) in the plasma
What happens to CO2 when it moves into the capillaries?
combines with water to make H2CO3 which quickly dissociates to make H+ and HCO3-
most of this occurs in the RBCs where CARBONIC ANHYDRASE rapidly catalyzes the reaction
HCO3- diffuses out of RBCs into plasma
RBC then undergoes a chloride shift, Cl- moves into RBCs to compensate for the change in charge from bicarbonate leaving
Explain what happens to CO2 when it reaches the lungs.
dissolved CO2 diffuses out of plasma into alveoli
carbaminohemoglobin gives up its CO2
HCO3- moves back into RBCs, reacts with H+ to form H2CO3 (reverse Cl shift occurs)
H2CO3 is split by carbonic anhydrase into CO2 and H2O
CO2 diffuses into alveoli
What is the haldene effect?
it reflects the greater ability of reduced hemoglobin to form carbaminohemoglobin and to buffer H+ by combining with it.
The more saturated hemoglobin is the lesser the ability to take on CO2. The less saturated the easier.
Explain how the haldene and bohr effects interact.
As CO2 enters the systemic blood stream, it causes more oxygen to dissociate from Hb (BOHR EFFECT), which allows more CO@ to combine with Hb and more HCO3- to be formed (HALDENE EFFECT)
Describe the influence of CO2 on the blood pH
HCO3- in the plasma is the alkaline reserve of the carbonic acid-bicarbonate buffer system.
If [H+] rises, excess H+ is removed by combining with HCO3
if [H+] lowers, H+ is added by dissociating H2CO3
Lungs also greatly affect pH of the blood. Ex. slow shallow breathing will cause CO2 to accumulate in the blood resulting in higher carbonic acid levels lowering blood pH
What is respiratory acidosis?
it is the lowering of blood ph as a result of lung malfunction
Where are the centers for control of respiration located and name each center.
Centers in the MEDULLA:
VENTRAL RESPIRATORY GROUP (VRG)
DORSAL RESPIRATORY GROUP (DRG)
Center in the PONS:
PONTINE RESPIRATORY GROUP (PRG)
Describe the role and function of the VENTRAL RESPIRATORY GROPU (VRG).
rhythm generating and integrative center
- sets normal breathing rate of 12-15 breaths/minute
- inspiratory neurons stimulate phrenic and intercostal nerves, diaphragm and external intercostals contract. (active inspiration takes 2 seconds)
- expiratory neurons inhibit respiratory neurons (passive expiration takes 3 secs)
What is the normal breathing rate and what is it called?
EUPNEA - 12-15 breaths/min
2 sec contraction, 3 sec relaxation
Describe the role and function of the DORSAL RESPIRATORY GROUP (DRG)
Integrates input from peripheral stretch and chemoreceptors
entire role not known
Describe the role and function of the PONTINE RESPIRATORY GROUP (PRG)
influence and modify activity of the VRG to accommodate activities like sleeping, speaking, exercising.
smooth out transitions btwn inspiration and expiration
Integrates input from higher brain centers
What happens when the PRG becomes damaged?
Apneustic breathing occurs (prolonged inspiration)
How is the respiratory rhythm generated?
it is not well understood, but most popular belief is:
reciprocal inhibition of interconnected neuronal networks in the medulla. VRG sets the pace and alternate active inspiration and passive expiration
during deep breathing, more muscles are contracted
What are the 6 factors that influence breathing rate and depth?
- Chemical factors
- Arterial pH
- Higher brain centers
- Pulmonary irritant reflex
- Hering-Breur reflex
What are the two types of chemoreceptors and where are they located?
central chemosensors: located in the brain stem
peripheral chemosensors: located in the aortic and carotid bodies
Explain the influence of PCO2 on breathing.
It is the MAIN force that controls respiration and is carefully regulated at 40 +- 3 mm Hg
- CO2 is converted to carbonic acid which dissociates releasing H+ and dropping pH
- H+ stimulates the central chemoreceptors and the peripheral (Central are much more sensitive to CO2 drops than peripheral). Chemoreceptors synapse with DRG resulting in an increase of rate and depth of breathing (HYPERVENTILATION)
The reverse effect will happen if blood CO2 is too low.
Also, when PCO2 is too low (HYPOCAPNIA) the vessels in the brain constrict resulting in cerebral ischemia
What is apnia?
periods of cessation of breathing. Happens when CO2 levels are very low
What is hypocapnia
when CO2 levels decline below the norm
Explain what happens to respiration when PO2 drops
the peripheral chemoreceptors are primarily O2 centers. When excited they cause increased ventilation
substantial drops in arterial PO2 to <60 mm Hg must occur to stimulate a response
this is because there is a massive reserve of O2 in blood
Describe the influence of arterial pH on respiratory rate.
decreased pH may reflect:
CO2 retention
Accumulation of lactic acid
Excess ketone bodies in patients with diabetes mellitus
Respiratory rate will attempt to raise pH by increasing respiratory rate and depth.
What is chronic pulmonary disease?
it is chronically high arterial PCO2
chemosensors adjust and become insensitive to PCO2 and PO2 level regulates respiration
Explain the influence of higher brain centers on respiration.
hypothalamic controls act through the limbic system to modify rate and depth in respiration under intense emotions
Cortical controls are our voluntary control system. They allow us to override the control centers to hold our breath, but after a time the automatic centers will take over when the chemical levels become too low
What is the pulmonary irritant reflex?
reflexes in response to the receptors in the respiratory being stimulated by irritants.
in bronchioles - constriction
in trachea and bronchi - cough
in nasal cavity - sneeze
Receptor is stimulated -> send impulse via vagus nerve -> medulla and pons -> reflex innitiated
What is the Hering -Breuer reflex (inflation reflex?
it is a protective response.
stretch receptors in the pleurae and airways are stimulated by lung inflation
inhibitory signals sent to medulla via vagus nerve end and allow ventilation to occur
what is hyperpnea?
the abrupt increase in ventilation as exercise starts
rate drops off to a more steady state plateau
Explain what happens to respiration during exercise
Experience a spike called hyperpnea then sees a decline to a steady state
PCO2, PO2, and pH remain fairly constant
3 neural factors cause increase in ventilation as exercise begins:
- Anticipation
- Motor cortex activates respiratory centers in skeletal muscles
- Preparation for action
as exercise ends these stimuli stop, ventilation declines as oxygen debt is repaid
Explain oxygen debt in terms of exercise.
it represents the increased amount of oxygen consumption after exercise that is needed to replenish food stores :
converting lactic acid back to pyruvic
replenishing ATP creatine stores
etc
It is not due to the inefficiency of the lungs, but has to do with inadequate CO or tissues not being able to absorb O2 fast enough
What is acute mountain sickness (AMS)?
quickly ascending to a height above 8000 ft
causes headaches, shortness of breath, and in extreme cases lethal pulmonary and cerebral edema
How does the body adjust to AMS
chemoreceptors become more responsive to PCO2 when PO2 declines
substantial decline in PO2 directly stimulates peripheral chemoreceptors
result: minute ventilation increases and stabilizes in a few days 2-3 L/min higher than at sea level
Compensates long-term by stimulating the kidneys to release EPO to increase RBC
What is chronic obstructive pulmonary disease (COPD) and its 2 types
irreversible decrease in the ability to force air out of the lungs.
common features:
more than 80% of patients are smokers
Dyspnea - difficult/labored breathing
Coughing and frequent pulmonary infections
Respiratory failure -> hyperventilation -> respiratory acidosis
treated with: bronchodilators, corticosteroid inhalers
obstructive emphysema
chronic bronchitis
What is obstructive emphysema.
a type of COPD
permanent enlargement of the alveoli and destruction of alveolar walls results in:
- loss of elasticity
- hyperinflation of the lungs
- damage to pulmonary capillaries in alveoli causes right ventricle to overwork to compensate
- breathing takes 15-20% of total body energy as opposed to 5%
often referred to as “pink puffers” because they drop weight with the effort but maintain normal levels of gases
What is chronic bronchitis?
a COPD
irritants lead to excessive mucus production and inflammation and fibrosis of the mucosa. Results in:
- obstructed airways and impaired ventilation
- frequent infections because of pools of mucus
- bronchial edema
called blue bloaters because they become cyatonic
What is asthma?
Begins with an immune response to an allergen. The airway becomes permanently inflamed.
The inflamed area becomes hypersensitive to irritants and the bronchospasm effect is multiplied greatly reducing airflow
TREATED WITH: Bronchiodilators
What is tuberculosis?
infectious disease caused by Mycobacterium tuberculosis.
SYMPTOMS: fever, night sweats, weight loss, racking cough, spitting up blood
TREATMENT: 12 month course of antibiotics.
Seeing a great rise in resistant strains. Necessary to take entire course. Some cities will detain ppl to ensure they do
Explain Lung cancer.
It is the leading cause of cancer deaths in BC
estimated 2500 ppl would die in 2011 in bc
SMOKING is the main risk factor
three most common types:
SQUAMUS CELL CARCINOMA (20-40% of cases) in bronchial epithelium
ADENOCARCINOMA (40% of cases) originates in peripheral lung areas
SMALL CELL CACINOMA (20% of cases) contains lymphocyte-like cells that originate in the primary bronchi and metastasize
TREATMENT: complete removal of lung if not metastasized, chemo and radiation therapy, antibodies that target tumor growth factors, cancer vaccines that stimulate immune system to fight the cancer, gene therapy to replace defective genes
Explain cystic fibrosis.
most common lethal genetic disease among Caucasians
gene codes for faulty chloride channel protein, less chloride is secreted from cells and less water follows.
mucus becomes thick and sticky and clogs the respiratory passages
infection with pseudomonas aeruginosa causes a pos feedback loop where more and more mucus is produced
bacteria and inflammatory chemicals damage tissue and immune system cannot reach site and begins attacking the lungs
results in excessive damage to the lungs
explain how respiratory rate changes throughout life?
at birth respiratory centers are activated
newborns 40-80 breaths/min
5 years of age 25 breaths/min
adult 12-18 breaths/min
in old age see an increase because of decreased efficiency
