Chapter 9- ventilation- Rosen Flashcards
Respiratory acidosis
Retention of CO2 decreases pH. Ex: COPD CO2 retention
Respiratory alkalosis
low CO2= high pH. Ex: hyperventilating before Dr. Walkers test.
A _______ indicates a stronger acid
larger K’
Important physiological bufferes
Hb in RBC
Phosphate, HCO3-
Buffer capacity of CO2 if pKa is 6.1—is it effective?
yes, even though physiological pH is 7.4
When acid added to body…..
HCO3- ===>H2CO3 (which then dissociates to H20 and CO2)
CO2 is
eliminated by respiration,
COPD
Elasticity of the lung is lost. Incomplete exhalation so CO2 is retained.
low pH on O2 dissociation curve?
Right shift (decreased affinity)
Hyperventilation
CO2 blown off= higher pH= respiratory alkalosis
Primary factor in respiratory control
CO2. Low CO2= slower respiration. Respiration may stop ==> hypoxia
Voluntary control system
Neurons in cerebral cortex send impulses to respiratory motor neurons via corticospinal tracts. Controls: speech, voluntary breath holding, fear and pain.
Autonomic control system. Where are lower motor neuron cell bodies?
neurons in pons and medulla generate rhythmic patterned excitatory output to inspiratory/expiratory muscles. Lower motor neuron cell bodies in phrenic motor nucleus from C3-C5
Transection of brainstem below medulla will:
stop breathing completely. Do this if someone is trying to rape you…
Transection of brainstem above medulla will:
“not affect breathing greatly”
Medullary neurons that control breathing constitute
central pattern generator (CPG)
A CPG is
a group of neurons capable of rhythmic patterned output in the absence of outside influence or sensor feedback.
Cutting sensory neurons in the vagus nerve does what to CPG neurons?
NOTHING. does not block patterned breathing.
What is the primary stimulus for inspiration?
Dorsal respiratory group
DRG (dorsal respiratory group, not dorsal root ganglion) inputs (x5)
gets input from 1) central and 2) peripheral chemoreceptors, 3) pulmonary stretch receptors, 4)somatic pain receptors, and 5)mechanoreceptors.
During inspiration, phrenic nerve activity—–
increases in terms of rate and number of units discharging (recruitment)
What increases tidal volume? What causes the thing that causes the increase in tidal volume?
Increase in number of motor units from increased phrenic nerve activity.
termination of inspiration by?
natural CPG rhythm modulated by sensory feedback
Expiration is
primarily passive, but there is always tonic expiratory output that can increased for forced expiration
Ventral respiratory group
Both inspiratory (accessory) and expiratory neurons.
Accessory inspiratory muscles
input from ventral respiratory group
Transection above pons is:
without effect on breathing—I guess this means there is not an effect.
Transection at inferior pons
causes sustained gasping breathing
What causes sustained gasping breahting
Superior pons pneumotaxic center usually regulates inspiratory neurons in the apneustic center. If that regulation stops (if apneustic center goes unregulated) then apneustic center goes nuts and you have long inspirations and gasping.
You cut the vagus nerve, and now are stimulating the proximal stump..?
inspiration can be stopped. Basically shows experimentally that the vagus n (which normally carries efferents from lung stretch receptors) is inhibitory
Inhibition of inspiration from vagus?
activated stretch receptors in lungs send efferent impulses VIA vagus to inhibit inspiration
Conclusion: Medulla is capable of _______ but___________
this is in bold and italics, guessing it’s important?
Medulla is capable of SUSTAINED PATTERNED BREATHING but the patter can be FINE TUNED BY NEURONS IN THE PONS AND FEEDBACK VIA VAGUS.
Chemical control of ventilation- Central
CO2 and H+ concentrations of CSF on central chemoreceptors
Chemical control of ventilation- Principal control
Principal control is via arterial CO2 acting at central chemoreceptors (idk how it’s arterial…i thought it was CSF?)
CO2 production is directly related to _____ and ____.
rate of oxidative metabolism and pH via bicarb system
chemical control of ventilation- peripheral
via pH, CO2 and O2 on carotid body and aortic body receptors. MOSTLY O2!!!
Location of carotid and aortic bodies. Size?
2-3mm diameter (idk why anyone would ask this…but its W LA campus..)
Carotid bodies at bifurcation of common carotid
Aortic bodies near aortic arch
Aortic body/carotid bodies contain:
islands of 2 cell types (I and II) surrounded by sinusoidal capillaries
Type I cells in carotid/aortic bodies
Type I= glomus cells. Make synapses with nerve endings.
Aortic/carotid body afferents via?
Aortic bodies to medulla via Vagus nerve
Carotid bodies to medulla via glossopharyngeal
Fibers carrying afferents from aortic bodies/carotid bodies
Diameter and conduction speed
CN IX, X
2-5 micrometers in diameter
Speed: 7-12m/s
when pH decreases, what happens to peripheral receptors?
Neurons from carotid and aortic bodies INCREASE discharge when pH decreases===> increased ventilation rate AND increased tidal volume
_____ receive among the highest blood flow in the body, per gram weight. 40x’s great than brain.
carotid bodies
Carotid bodies account for ____ of ventilatory drive
20%
carotid bodies account for _____ of ventilatory response to high CO2
30%
How do we know that the influence of aortic bodies in response to high CO2 is minimal?
Ablation of just carotid bodies = -30% response to high CO2
Ablation of carotid bodies AND aortic bodies= pretty much same result.
What can enhance the response to lowered O2?
high CO2= hypercapnea
Acidosis
Maximal receptor activity at carotid/aortic bodies is to:
very low O2 values. So the high CO2 and acidosis “enhance” the response, but are not the major contributors to the response.
Central chemoreceptors -location
ventral surface of medulla near cranial nerves VI-X
Central chemoreceptors contact?
DO NOT CONTACT BLOOD. Bathed in CSF. CSF is close to the choroid plexus (which has a high blood flow) so CO2 equilibrates rapidly.
CSF CO2 is close to?
arterial CO2
BBB is poorly permeable to
H+
BBB is permeable to
CO2. It crosses and is hydrated to H2CO3 and then dissociates to HCO3- and H+.
______ in the medullary CSF enhances _____.
Acidosis enhances tidal volume
What if we increase CO2 without changing pH (CSF in medulla)?
No effect. they did an experiment or something.
THE CENTRAL CHEMORECEPTORS RESPOND DIRECTLY TO _____ BUT INDIRECTLY TO ____.
directly to H+, indirectly to CO2 (experiment thing, remember?)
What happens if high PCO2 persists for hours? Why?
ADAPTATION: ventilatory response wanes. Compensatory HCO3- transport via anion exchange for Cl-.
What is the clinical importance of the adaptation to chronic high CO2? What is the major drive/influence for ventilation.
Patients with COPD will return to normal breathing even though they have high CO2 (it’s high because they can’t exhale and retain CO2).
PO2 drive from periphery becomes major influence on ventilation.
Metabolic acidosis-definition
Accumulation of ketone acids during diabetes mellites
Metabolic acidosis causes ______ to happen?
respiratory stimulation. Hyperventilation to blow off CO2 and increase pH.
Hyperventilation is ___ and causes ____.
respiratory alkalosis==> fall in blood H by blowing off too much CO2
What can cause metabolic alkalosis?
vomiting, nasogastric suctioning, diuretics, corticoid treatment, alkali treatment, sever K+ depletion, Cl- restriction
Metabolic alkalosis causes (ventilation response to it)
depressed ventilation==>rise in arterial CO2 and H+ and eventually restoring pH.
Things that cause metabolic acidosis
hyperchloremic (diarrhea, interstitial renal disease, renal tubular acidosis)
Increased undetermined anion (generalized renal failure, diabetic/alcoholic ketoacidosis, lactic acidosis).
Things that cause respiratory acidosis
Respiratory failure (obstructive lung disease, chest wall disease, hypoventilation), CNS depression, pulmonary edema, pneumothorax, abdominal distension
Things that cause Respiratory alkalosis
hyperventilation, gram (-) sepsis, pulmonary emboli, pneumonia, hepatic failure, high altitude sever anemia
The relationship between alveolar pCO2 and ventilation rate is _____
“nearly linear”
When metabolism increases, PCO2 ______ and ventilation _____ in order to ______.
When metabolism increases, PCO2 increases and ventilation increases in order to lower PCO2
What happens if you inhale elevated CO2 (rebreathing)?
Ventilation increases and alveolar pCO2 will come to equilibrium at a higher value.
What happens if pCO2 of inspired air reaches alveolar pCO2? (what is normal alveolar pCO2?)
Normal alveolar pCO2= 40 mmHg
Elimination is difficult.
When inhaled CO2 levels are > ____, arterial CO2 _______ resulting in ______. Finally, ___ and ___.
When inhaled CO2 levels are >7%, arterial CO2 rises rapidly, resulting in CNS depression (including respiratory center). Finally CO2 narcosis and coma.
PO2 must ______ before ventilation is affected. What happens to ventilation?
must drop below 60mm Hg. When this happens, discharge from peripheral chemoreceptors increases.
CO poisoning binds ___ and makes __.
binds Hb to make carboxyhemoglobin. CO: Hb affinity is 230x’s stronger than O2: Hb affinity. So, if CO binds, the rest of the O2 bound to Hb wont be able to leave for tissues. Shifts curve to the left
Hypoxia caused by high altitude
compensation with erythrocytosis
Increased oxygen demand is
a pathological condition in his notes. Cause by exercise.
Proprioreceptors and stretch receptors-role in respiration?
in muscle, tendons and joints. they can stimulate ventilation in response to physical disturbance (slap and tickle??) and possibly anticipatory exercise
Receptors to irritants (what are irritants?)
Irritants can be chemical or mechanical. Histamine and bradykinin during an allergic reaction
Receptors in the trachea and extrapulmonary bronchi cause coughing
In lungs: cause rapid shallow breathing and bronchoconstrition
A receptor in your lung was activated and caused shallow breathing and bronchoconstriction–what is it?
irritant receptor
stretch receptors in smooth muscle of airway
Exercise or tidal volume >1L excite sensory neurons running in vagus===> inhibition of respiration
Hering Breurer Reflex
Inhibition of respiration via stretch receptors in smooth muscle. Acts on respiratory center in medulla and pneumotaxic center in pons to inhibit inspiration (inhibition of apneustic center indirectly.)
Deflation receptors
stimulate rapid shallow breathing
Ventilatory response during pulmonary congestions/edema?
Deflation receptors contribute to response.
Off switch neurons inhibited by? stimulated by?
inhibited by expiratory neurons
stimulated by pneumotaxic center and vagus nerve carry afferents from airway stretch receptors.
Inspiration is terminated when?
When off-switch neuron inhibition stops (it decreases with time.
CC- girl jumped into the pool
severed spinal cord too high= quadriplegic and unable to breathe on her own
CC-Yelling too much causes?
respiratory alkalosis. Sx: light headed, syncope, tonic seizure. paresthesia in fingers and mouth, thirsty and dry mouth.
