Respiration 5: Control of Respiratory System
Central CO2/pH chemoreceptors A. What is the Medulla sensitive to? -give 3 related points
-In brain there are no oxygen sensors, just pH and CO2 receptors 1. Medulla wants pH to be 7.4 2. Blood has lots of buffers in it but CSF doesn't hav emuch buffering A. pH in CSF 1. CSF is poorly buffered 2. **H+ passes poorly thru BBB but CO2 passes easily*** -when u hyperventilate, in brain u feel whoozy =not enough CO2 in brain and pH has gone up (not acidic enough) so brain stops doing good thinking stuff 3. ***Blood pH transmitted via CO2 to CSF***** B. Adapt to elevated CO2 levels (reduced pH) by transfer of HCO3- or Cl- into CSF (really slow) C. If pH gets too low aka brain gets too acidic, Stimulation of this system in the brain tells u to breath (increase ventilation, "breathe off CO2") -CSF and blood vessel in diagram -CO2 goes easily into brain right there and protons don't
Table of Contents 1. Control of rate & rhythm of breathing -Controllers, sensors, effectors 2. Autonomic control -Respiratory rate, bronchial tone 3. O2 sensors -Carotid & aortic bodies 4. CO2 sensors -Carotid & aortic bodies, medulla (brainstem) -CO2 dominates respiratory drive, not O2 5. Fun stuff not for the test -Diving physics, amazing adaptations
-eyes dilate -> CN3 -Where do CN come from? brain stem -Brain stem is responsible for automatic responses -> including breathing *will go over today in fairly minimal details and won't be held for the details
KNOw
1. All basic rhythm of breathing comes from brain stem 2. Rhythm from brain stem can be overridden by conscious brain. cortex 3. Things from the limbic system (like fear & panic) can also cause you to breath differently 4. Know the 4 different flavors of whacky breathing 5. A little bit about the chemoreceptors in peripheral & central area
Alpaca chasing you
1. Bronchodilation due to sympathetic NS 2. Pons, medulla & limbic system tell him to run 3. Phrenic n. tells diaphragm to move to get more oxygen in 4. heart beats faster =more cardiac output so Q matches increasd V (from opening bronchioles)
4 Abnormal breathing patterns -know for clinics (not red though) **learn these the difference between each 20:30 especially Cheyne stokes vs apeustic breathing & the agonal breath
1. Cheyne Stokes respiration -alternating episodes of apnea (no breathing) then {crescendo aka get bigger and bigger} hyperpnea (too big breath) -usually due to damage to respiratory centers in a 2. Apneustic breathiketon due to interruption of pneumotaxic center {no breathing then agonal last dying breath} 3. Biot's breathing -normal breathing interrupted by sudden apnea (stop) -due to damage {C-fibers} in brain centers 4. Kussmaul's breathing -not a brain problem -hyperventilation with hypocapnea caused by acidosis (diabetic) -body breathes really fast to get rid of CO2 if there is other acid in the body -kid peeing in the middle of the night and is diabetic Other notes: tachypnea=too fast breathing
Respiratory Effectors (4)
1. Diaphragm -Innervated by **phrenic nerve** i. Contains motor, sensory, & sympathetic nerve fibers ii. Provides only motor supply to diaphragm 2. Intercostal muscles 3. Abdominal muscles 4. Accessory muscles
Other Ventilation Control Mechanisms (6) -don't memorize this Slide 19
1. Lung Inflation 2. Irritant receptors in the lung -cause coughing & bronchoconstriction 3. J-receptors -senses interstital fluid changes (pulmonary edema) 4. Temperature -stimultes peripheral sensors 5. Exercise -Increase sensitivity of chemoreceptors, probably thru catecholamines 6. Speech -Inhale before speaking
Describe the triangle of 3 aspects involved (in regulating respiration?)
1. Sensors (Chemoreceptors, lung & other receptors) -receive info such as oxygen, CO2, stretch -send input to Central controller to breathe more or less 2. Central controller (pons, medulla, other parts of brain) -sends output to effectors {cortex=more complex part of brain-in charge of thinking -cerebellum is for balance -brain stem-heart beat, CN to eye, breathing=if damage big part of brain, no more deep thinking, but breathe still} -has nerves that go to effectors 3. Effectors (respiratory muscles) -mainly diaphragm but intercostal muscles too
Give more details on O2 sensor -don't memorize all of this, just be aware A. What cells have O2 sensors? Give steps
A. Glomus cells =oxygen sensor cells -if low oxygen sensed, opens channel & hyperpolarizes cell -if no oxygen 1. K-channel with O2 sensor 2. O2 opens channel & hyperpolarizes cell 3. Drop in O2 causes reduction in K current into cell & cell depolarizes 4. Resulting Ca2+ influx triggers release of dopamine (exocytosis of dopamine containing vesicles) 5. Dopamine binds dopamine receptor of sensory neuron -> action potentials intiated in sensory nerve How does channel close: 1. Oxygen sensor detects no oxygen-> KO2 channel closes
Rate Control Mechanisms A. How does pacemakers work? B. Rhythm is a function of what? 1. How does breath affect rate? 2. What do stretch receptors do? C. Describe breathing while awake D. Describe breathing while sleeping
A. Mechanism is not known [equivalent of SA node for breathing is unknown} B. Previous breath So, if you take a Deeper the breath, you'll breathe a little slower afterwards -stretch receptors sense inspiration C. Breathing is continuous while awake -Inspiratory impulses dominate {as long as brain reminds u to breathe in, bc expiration is passive} -Expiratory stimulation is constant D. Sleep -Breathing is episodic -Central drive {brain stem rhythm generating part} reduced so most of breathing is based on peripheral chemoreceptors stimulating based on O2 & CO2 levels {aka hye need more O2}
Innervation of Respiratory System
A. Parasympathetic innervation comes off medulla & pons: associated with constriction -Vagus nerve B. Sympathetic Innervation comes off cervical vertebrae: dilation -Sympathetic paravertebral ganglion aka sympathetic chain C. Motor Innervation -Phrenic nerve & intercostal nerves (recall only inspiration is active while expriation is passive aka relax and goes back to FRC) -phrenic nerve comes off at C5, so now this for life. & this is the breathing nerve. So if you break your neck at C6, C7, then you can't walk but can breath But if you break your neck at C2, then you can't breathe and can't walk=need to be on a ventilator
A. Describe function of Pneumotaxic center B. Describe function of Apneustic center
A. Pneumotaxic center -Coordinates speed of inhalation & exhalation -Sends inhibitory impulses to inspiratory area -Involved in fine tuning of respiration rate B. Apneustic center -Coordinates speed of inhalation & exhalation -Sends stimulatory impulses to inspiratory area -> activates & prolongs inhalate (long deep breaths)
A. What is the goal of respiration? B. Ventilation should match _____ C. What 3 aspects are involved in ventilation matching perfusion? D, E, F: Describe each aspect
A. maintain sufficient ventilation with minimal energy B. Perfusion C. Central processor, Sensors, Feedback D. Central processor -controls how deep & rate of breath =breath without thinking 1. Pattern generator of breathing depth/amplitude 2. Rhythm generator for breathing rate {10 or 20x a min for ex} E. Sensors 1. Chemoreceptors -Central & peripheral {oxygen & carbon dioxide} 2. Stretch receptors in lungs, bronchi, & bronchioles {if you take a really deep breath, u can feel the uncomfortable stretch & want to breathe out} F. Feedback 1. Nerves from diaphragm, lungs tell brain stuff
_______ control of bronchioles A. Bronchiolar smooth muscle has many ____ receptors -stimulated by which system? -what leads to bronchodilation & bronchoconstriction? B. Why?
Autonomic control Sympathetic vs PS -Bronchioles dilate/open as much as possible =reduces pulmonary resistance =recall tubes determine resistance & stretchiness of parenchyma determines compliance A. Beta-2 receptors -ANS 1. Catecholamines (sympathetic) leads to bronchodilation 2. Parasympathetic stimulation causes bronchoconstriction B. So more air can pass into airways (less resistance)
Responses to CO2 & O2 are coupled
Imagine u have alveolar PO2, see really hypoxemic to normal vs ventilation (no breathing at all vs puffing like a train) -if u change amt of PACO2, then this rate changes -> if breathing off plenty of CO2 aka it hasn't gone up, respiration rate doesn't start changing until oxygen levels drop below 60 then u start panting i guess. -if alveolar PCO2 48 (little hypercapnic), now small drops in oxygen make u pant more this is not a key point but kind of interesting 43
Rhythm controllers in brainstem -Name the 4 Rhythm Controllers & what forms each ****DON"T MEMORIZE, just stuff in red: Brainstem, also know pons & medulla refer to brainstem
These are just different places in brain stem 1. Inspiratory center -reticular formation, medulla oblongata 2. Expiratory center -reticular formation, medulla oblongata 3. Pneumotaxic center -various nuclei of pons 4. Apneustic center -nucleus of pons
What are some things that affect how u breathe?
Things that feed into central pattern generator (3 paths) -CO2 amt-> chemoreceptors in CSF and brain stem -O2 & pH-> carotid & aortic chemoreceptors talk thru CN9 & 10 to central pattern gen (pons & medulla) then u see respiratory groups (don't memorize ventral vs dorsal) -she went thru each level. -like if u hold ur breath, ur brain tells u to breath
Peripheral Chemosensors A.Where are peripheral chemosensors located? -What are these sensitive to? B. What nerves do these chemosensors send info back on? C. Peripheral chemosensors adapt to what? -For example:
A. Carotid & aortic bodies=chemoreceptors that sense see 1. -aortic chemoreceptors r little dots on aortic arch 1-Sensitive to PO2, PCO2, & pH -CO2 sensitivity may originate in pH aka very related, may be same thing, they arne't sure -**All** O2 sensing is here at aortic arch -at carotid body, there are chemoreceptors & baroreceptors. -> so if ur a guy, if too much blood passing carotid, baroreceptor stretches and detects this and sends a signal back to heart that pressure is too high so when guys are shaving, if really sensitive baroreceptors, can faint from touching these blood pressure receptors B. Afferent: CN9 & CN10 respectively, back to respiratory center in medulla -these CNs take the messages from these specialized cells back to respiratory center in brain stem and say theres too much or too little oxygen or CO2 C. Adapt to CO2 levels 1. With chronic lung disease, you eventually acclimate to high CO2 -recall PaCO2 should be ~40 mmHg -so if chronic lung disease and pCO2 is 60, he should be hyperventilating to breathe off CO2 but eventually brain stops responding to CO2 and says its the new norm
Ondine's Curse A. What syndrome relates to this? B. How common is this? C. How fatal is this? & How? -don't need to know this stuff (just cocktail party info)
A. Congenital central hypoventilation syndrome (CCHS) -occasionally babys r born without the rhythm system that reminds them to breathe B. Very rare-200 cases worldwide C. Fatal -failure of autonomic breathing control -"forget" to breathe while sleeping
Other regions of brain can affect respiration
A. Cortex -can exercise voluntary control -"take a deep breath. Hold it. & Breathe out" -can override brainstem if it wants to B. Limbic system (panic system) & Hypothalamus -Emotional states -Panic attack
***What is the dominant control factor?*** A. Is it O2? Why or why not? B. Why do sherpas on Mt Everest smoke?
CO2 ****so important bc CO2 levels can change really quickly bc so soluble A. PO2 must dorp to 60 mmHg (= normal PaO2 if at 10,000 ft mt) before it triggers change =need to get really hypoxemic before body tells u to breathe more B. PsubB is 349 mmHg -What creates this sherpa's respiratory drive? (at 21,000 feet on Mt) -PaO2 is probably 40 right ish -when he smokes, he is inhaling CO2, which bumps up his respiratory drive so centers in his medulla make him breathe a little bit more & feel more comfortable up there
