3 - Respiration Flashcards
What are the three major components of the respiratory center?
- dorsal respiratory group (dorsal medulla, inspiration)
- Ventral respiratory group (ventrolateral medulla, exp)
- Pneumotaxic center (superior pons, rate and depth of breathing)
What does the dorsal respiratory group control?
inspiration and respiratory rhythm
Most of the neurons in the dorsal respiratory group are located in the _______
Nucleus of the tractus solitarius (NTS)
What is the NTS?
Nucleus tractus solitarius
Main component of the dorsal resp group
sensory termination of both the vagal and glossopharyngeal nn
Where is the basic rhythm of respiration generated?
the dorsal respiratory group
even when it’s completely severed from afferent and efferent nerves, it will still emit inspiratory action potentials!
Instead of sending bursts of inspiratory action potentials, the dorsal group signal is an inspiratory _______
ramp
steadily increases and then ceases abruptly
results in inspiration rather than gasping
How does the inspiratory ramp signal change with heavy respiration?
Increases the rate of increased signalling (increases the steepness of the ramp)
How is the inspiratory ramp modified to acheive a change in respiration?
the limiting point at which the ramp suddenly ceases is lengthened or shortened.
The earlier the ramp ceases, the shorter the duration of inspiration and therefore expiration, and therefore the more breaths that take place per minute
What is the function of the pneumotaxic center?
limits duration of inspiration and increases respiratory rate
When the pneumotaxic signal is strong, respiration is _____
increased
What is the function of the ventral respiratory group?
Overdrive mechanism when high levels of pulmonary ventilation are required
When there are an excess of signals to the dorsal ventral group, they “spill over” into the ventral respiratory group
How does the ventral respiratory group contribute to resting rate and rhythm?
It doesn’t. It’s completely inactive during normal quiet respiration
What is the Hering-Breuer Inflation Reflex?
Stretch receptors in the muscular walls of the bronchi and bronchioles send messages through the vagus when they’re overstretched
The signal causes a completely switching off of the dorsal group, preventing further inspiration
Mostly prevents against extreme overinflation, not triggered during normal inspiration
What is the effect of oxygen levels on the respiratory centers of the brain?
Pretty much no effect on the respiratory centers of the brain
acts almost entirely on peripheral chemoreceptors in the carotid and aorta, which transmits nervous signals to the respiratory center
How do CO2 and H interact with the respiratory center?
Indirectly
Changes in CO2 and H trigger the chemosensitive area (near the pneumotaxic center)
the chemosensitive area then excites other portions of the respiratory center
What is the primary stimulus for excitation of the chemosensitive area?
Hydrogen, not CO2
If CO2 does not readily cross the blood brain barrier, how is it the primary stimulus of the chemosensitive area?
In blood, CO2 is dissociated into carbonic acid, then bicarb and H, which is what the chemosensitive area responds to
Even though CO2 isn’t technically reaching the brain, an increase in the level of CO2 will trigger the chemosensitive area indirectly because of its buffered state
A change in blood [CO2] has a potent _______ effect but a weak _____ effect
acute
chronic
Subsides after a couple of days
Do chemoreceptors respond to arterial or venous O2 levels?
Arterial
They have a massive arterial supply with almost no O2 extraction, leading to accurate interpretation of PaO2
During hypoxia, which neurotransmitter is released by the carotid body glomus cells to trigger the respiratory center?
ATP!
Since CO2, O2, and pH levels remain constant throughout exercise, what stimulates the increased respiratory rate seen during strenuous exercise?
When motor impulses leave the brain to stimulate the exercising muscles, they transmit collateral impulses to the respiratory center
When a person begins to exercise, how quickly does respiration increase?
Almost immediately, before there are any chemical changes in the blood
In fact, PCO2 decreases below normal initially in anticipation of the increase in serum CO2
What are J receptors?
stimulated when the pulmonary capillaries become engorged or pulmonary edema occurs
May be responsible for the sensation of dyspnea
How does acute brain edema impact respiratory function?
depresses the respiratory center
What causes Cheyne-Stokes breathing?
CO2 and O2 flux causing over-reactions in the respiratory center
Why doesn’t Cheyne Stokes breathing occur in everyone?
Normally actions and reactions to the chemoreceptors are highly damped because there are large amounts of O2 and CO2 dissolved in the blood, so fluctuations are slight
When does Cheyne Stokes breathing occur?
- Severe cardiac failure (delayed delivery and removal of blood from the alveoli leads to large swings in the level of CO2 and O2 at the level of the chemoreceptors)
- Damage to the respiratory center (causes an increased negative feedback gain). brain damage turns off respiratory drive for a few seconds, then an extra-instense increase in CO2 turns it back on with a vengeance
Two types of constrictive lung disease
fibrotic (TB, silicosis)
disease that constrict the rib cage (kyphosis, scoliosis, fibrotic pleurisy)
In airway obstruction disease, which is more difficult: expiration or inspiration?
Why?
Expiration
The airway is already predisposed to close, and when you add the positive pressure in the chest that causes expiration, it puts even more pressure on the structures to close off
Conversely, when the rib cage expands it pulls the airway open, making it relatively easy to get air in
What is the FEV1?
Forced expiratory volume during the first second. The percentage of the FVC that is expired in the first second (FEV1) is indicative of obstruction.
In normal lungs, 80% of air is expelled in the first second
In airway obstructions, it takes a long time for the same amount of air to escape.
Pulmonary emphysema is the result of chronic _________
obstruction of the smaller airways
caused by chronic infection and ciliary damage which leads to excess mucus and inflammatory edema
How does emphysema impact individual alveoli?
Entraps air inside them
causes destruction of as much as 50-80% of the alveolar walls
Why do emphysema patients have increased CO2 levels?
loss of alveolar walls decreases the diffusing capacity of the lung
Why do emphysema patients have abnormal V/Q ratios?
some parts of the lung are better ventilated than others
Can get a very high V/Q (phsyiologic shunt) in some areas, and an extremely low V/Q (phsyiologic dead space) in others
Why is emphysema associated with pHTN?
Loss of the alveolar walls also causes loss of capillaries, so there’s the same amount of blood traveling through fewer capillaries
causes pHTN and eventual Cor Pulmonale
What is pneumonia?
Any inflammatory condition of the lungs that fills alveoli with fluid and blood cells
What is the number one cause of pneumonia?
Pneumococci bacteria
What does it mean when areas of the lung become “consolidated”?
They’re filled with fluid and cellular debris
What kind of V/Q ratio will you see in a patient with pneumonia?
Decreased
What are the two causes of atelectasis?
Airway Obstruction
Lack of surfactant
What is the usual cause of asthma?
Contractile hypersensitivity to particles in the air
In most young people, asthmas is caused by ________
In most old people, it’s caused by _______
Allergic hypersensitivity (usually plant pollen)
nonallergenic irritants (smog, cigarette smoke)
In patients with allergic asthma, the antibodies are attached to:
mast cells in the lung instertitium
When pollen reacts with a mast cell in the lung insterstitium, what substances are released?
Histamine
Slow-reacting substance of anaphylaxis
Eosinophili chemotactic factor
bradykinin
When an allergic reaction occurs in an asthmatic patient, what is the result in the lungs?
Localized edema and thick secretions
Bronchiolar smooth muscle spasms
Overall: increase airway resistance
What lung metrics will decrease during an asthma attack?
Which ones will increase?
Maximum expiratory rate, timed expiratory volume
functional residual capacity, residual volume
The tubercle bacilli causes what reaction in the tissue of the lungs?
invasion the tissue by macrophages
“walling off” of the lesion by fibrous tissue to from the so-called tubercle
Eventually causes thickening of the respiratory membrane
What happens to tissues during cyanide poisoning?
Cytochrome oxidase is blocked and the tissue cannot utilize oxygen
What happens in beriberi?
several steps in O2 utilization are compromised because of vitamin B deficiency
Cyanosis occurs with the arterial blood contains:
more than 5g/dL of deoxygenated hemoglobin
Who is more likely to get cyanotic: a patient with anemia, or a patient with polycythemia
Polycythemia
Mild to moderate hypercapnea cause increased respiratory rate. At what point does it cause respiratory depression?
120-150 mmHg
causes a vicious cycle
What is dyspnea
mental anguish associated the inability to ventilate enough to satisfy the demand for air
