Body Systems L21 Notes Flashcards
What are the two types of breathing control?
Subconscious
Conscious
Give an example of when subconscious breathing occurs
- Subconscious
» Until something goes wrong
-> Dyspnea Eg. High altitude
Give an example of when conscious breathing occurs
- Conscious
|»_space; Scuba diving, partners -> Snorers.
What are the tasks of breathing control?
- Establish automatic rhythm
- Adjust rhythm -> Accommodate
- > Metabolic
- > Mechanical
- > Episodic Non-Ventilatory Behaviours
Give examples of -> Metabolic -> Mechanical -> Episodic Non-Ventilatory Behaviours changes which need to be accommodated by breathing control
Metabolic >> Arterial Blood gases & pH Mechanical >> Postural changes Episodic Non-ventilatory Behaviours >> Speaking, sniffing, eating etc.
Describe the normal rates of O2 absorption as a result of breathing control
- Rates:
O2:
»_space; Rate -> absorption matched to delivery
Describe the normal rates of CO2 absorption as a result of breathing control
CO2:
|»_space; Rate -> generation matched to removal.
Describe the two conditions involved in maintenance of balance in regards to breathing control
- Maintenance -> Balance:
Local:
» Changes -> Blood flow & oxygen delivery
Central:
» Changes -> Depth & rate of respiration
What are local factors involved in maintenance of balance of breathing control?
Local:
|»_space; Changes -> Blood flow & oxygen delivery
What are central factors involved in maintenance of balance of breathing control?
Central:
|»_space; Changes -> Depth & rate of respiration
What are the two complexities regarding the control of breathing?
- Complexities:
No single pacemaker generating basic breathing rhythm
No single muscle devoted -> pumping of air
What three locations are involved in local control of gas transport?
Active tissue
Lung perfusion
Alveolar ventilation
Describe local control of gas transport in active tissue
- P(O2) & P(CO2) -> Active Tissue
- Incr. P(CO2)
Vasodilation
»_space;Incr. Blood Flow
i) Decr. P(O2)
»_space; Incr. Delivery -> O2
ii) Incr. Removal -> CO2
Describe local control of gas transport in lung perfusion
- Lung Perfusion:
- Decr. P(O2)
Vasoconstriction
»_space; Decr. Blood Flow
Directs blood -> Areas of higher P(O2)
Describe local control of gas transport in alveolar ventilation
- Alveolar Ventilation:
- Incr. P(O2)
Bronchodilation
»_space; Incr. Air Flow
Directs airflow -> Areas of higher P(CO2)
»_space; Improves efficiency -> Gas transport
What are the aims of the central control of ventilation?
Aims -> Maintenance of arterial P(CO2) & P(O2)
Describe the process of central control of ventilation
• Central Control -> Ventilation: Aims -> Maintenance of arterial P(CO2) & P(O2) 1. -> Detection >> Change -> arterial P(CO2) & P(O2) Central & Peripheral Chemoreceptors Mechanoreceptors 2. Send impulses / signals -> Central Controller Respiratory Centres >> Pons >> Medulla 3. Send impulses / signals -> Effectors >> Muscles of Ventilation Initiate change
Name the major types of receptors involved in control of breathing
Central Chemoreceptors
Peripheral Chemoreceptors
Mechanoreceptors
Describe the effects of the central chemoreceptors
1. Central chemoreceptors >> Medulla Change -> pH Hypercapnia No effect of hypoxia
Where are the central chemoreceptors located?
- Central Chemoreceptors:
Location:
Just beneath ventral surface of medulla
»_space; Close -> Entry of VIII & XI cranial nerves
What are the central chemoreceptors stimulated by?
Stimulated
Acidic pH / High P(CO2) -> within CSF
Describe the response of the central chemoreceptors to incr. P(CO2)
Incr. P(CO2)
Decr. pH
» Incr. ventilation
> Decr, P(CO2)
Describe the response of the central chemoreceptors to CO2 passing the blood-brain barrier
CO2 crosses blood-brain barrier
» Lipid soluble
Decr. pH -> CSF
( CSF weakly buffered )
Describe the response of the central chemoreceptors to decr. O2
Decr. O2
|»_space; No effect -> Central chemoreceptors
Describe the effects of the peripheral chemoreceptors
2. Peripheral chemoreceptors >> Aortic & carotid body Hypoxia Hypercapnia Change -> pH
Where are the peripheral chemoreceptors located?
Location:
Outside Brain
Name the components of the peripheral chemoreceptors
Carotid body
Aortic bodies
Describe the location of the carotid body of the peripheral chemoreceptors
Bifurcation of carotid arteries
Describe the location of the aortic bodies of the peripheral chemoreceptors
Above & Below aortic arch
How is the carotid body of the peripheral chemoreceptors innervated?
> > Innervated -> Carotid Sinus Nerve -> Glossopharyngeal
How is the aortic bodies of the peripheral chemoreceptors innervated?
> > Innervated -> Vagus
What are the peripheral chemoreceptors stimulated by?
Stimulated:
» Decr. P(O2)
Incr. P(CO2)
Decr. pH -> Arterial Blood
Why are the peripheral chemoreceptors vital to the response of decr. P(O2)?
Vital -> Response to Decr. P(O2)
|»_space; No effect -> Central Chemoreceptors
Describe the characteristics of the Mechanoreceptors controlled in breathing
Mechanoreceptors >> Lung receptors ->> Respond -> Stretch >> Characterised -> Response to lung inflation >> Innervated -> Fibres of Vagus Nerve
Name the types of mechanoreceptors involved in control of breathing
Rapidly growing receptors
Slowly adapting receptors
C-fibres receptors
Describe the slowly-adapting mechanoreceptors involved in control of breathing
- Slowly adapting
» Hering Breuer Reflex
Bronchopulmonary Stretch receptors
»_space; Visceral Pleura, Bronchioles & Alveoli
Over-inflation -> Incr. Discharge
»_space; Inhibition -> Respiratory Centres
Describe the rapidly-adapting mechanoreceptors involved in control of breathing
- Rapidly adapting
» Cough Reflex
Irritant Receptors
»_space; Airway epithelia -> Close to mucosa
Shape ventilatory pattern & protect airways
Initially fire rapidly
»_space; Decr. within short period
Noxious Gases (Smoke / Dust) / Cold -> Incr. Discharge
»_space; Bronchoconstriction (Coughing reflex)
Describe the c-fibre ending mechanoreceptors involved in control of breathing
3. C-Fibre Endings >> Defence mechanism J receptors Chemical / mechanical stimuli -> Incr. Discharge >> Bronchoconstriction -> Rapid shallow breathing -> Mucus secretion
Describe the J-receptors of the c-fibre endings of mechanoreceptors involved in control of breathing
J receptors
»_space; Alveoli walls -> Close to capillaries
»_space; Conducting airways -> Bronchial mucosa
Give an example of mechanical response fo c-fibre endings in response to left heart failure
E.g Mechanical
»_space; Left heart failure -> Engorgement of pulmonary capillaries
-> Innervate C-fibres
»_space; Rapid shallow breathing
What are the most important factors influencing gas exchange & breathing?
CO2 & H+
Write the equation connecting CO2 , H2CO3 & HCO3-
CO2 + H2O H2CO3 H+ + HCO3-
Describe the response to incr. P(CO2) in terms of the equation connecting CO2 , H2CO3 & HCO3-, Give an example of a situation in which this would occur & the associated P(CO2)
- Incr. P(CO2) Eg. Limited gas exchange -> Emphysema -> Incr. P(CO2) -> ( > 43mmHg ) CO2 + H2O H2CO3 H+ + HCO3- Eqn pushed --> Incr. H+ -> Decr. pH >> (Incr. Acidity) Respiratory Acidosis -> (pH < 7.35)
Describe the response to decr. P(CO2) in terms of the equation connecting CO2 , H2CO3 & HCO3-, Give an example of a situation in which this would occur & the associated P(CO2)
- Decr. P(CO2)
Eg. Hyperventilation
-> Decr. P(CO2) -> ( <37mmHg )
CO2 + H2O H2CO3 H+ + HCO3-
Eqn pushed Incr. pH
»_space; (Incr. Alkalinity)
Respiratory Alkalosis (pH > 7.45)
Describe hyperventilation
[ Excessive ventilation of the lungs, beyond what is required. Rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce.
Little effect on arterial pO2 and almost no effect on oxygen saturation which is nearly 100%
under normal circumstances. Its main effect is to lower pCO2 and produce a respiratory
alkalosis. ]
Describe the affect of incr. P(O2) on breathing & generation of radicals
- Changes -> P(O2) Incr. P(O2) Eg. Breathing -> O2 rich gas mixtures >> Generates free radicals > Coma & Death
Describe the affect of decr. P(O2) on breathing & generation of radicals
Decr. P(O2)
» Arterial P(O2) must drop below 60mmHg before ventilation incr.
» Central chemoreceptors switch off
» Peripheral chemoreceptors incr. breathing rate
What are the factors influencing rate & depth of breathing?
• Factors influencing Rate & Depth -> Breathing: - Variation -> Bodily Demands Eg, Exercise - Altitude -> Acute mountain sickness - Disease - Changing conc. gases -> Arterial Blood >> CO2 >> H+ >> O2 Only a problem when P(O2) -> Alveolar gas & arterial blood below 60mmHg.
At what partial pressure of oxygen do problems start to occur regarding factors affecting rate & depth of breathing?
Only a problem when P(O2) -> Alveolar gas & arterial blood below 60mmHg.
What are the components of the central controller responsible for control of breathing?
Rhythmicity Centre (Medulla) Pneumotaxic & Apneaustic respiratory centre (Pons)
What are the functions of the Rhythmicity Centre (Medulla)?
Controls Automatic Breathing
Sets pace -> respiratory movements
Describe how the rhythmicity centre sets the pace of respiratory movements
Sets pace -> respiratory movements
Interacting neurons -> Fire during diff. stages.
What are the two components of the rhythmicity centre responsible for setting the pace of respiratory movements?
Dorsal Respiratory Group
Ventral Respiratory Group
What centres of respiration does the Dorsal Respiratory Group contain?
Dorsal Respiratory Group (DRG)
-> I Neuron Inspiratory Centre
What centres of respiration does the Ventral Respiratory Group contain?
Ventral Respiratory Group
-> E & I Neuron Expiratory Centre
What is the function of the I Neurons of the I Neuron Respiratory Centre?
-> I Neuron Inspiratory Centre
o I Neurons -> DRG
» Regulate activity -> Phrenic Nerve
» Set rhythm & stimulate muscles -> Quiet respiriation
What is the function of the E Neurons of the E & I Neuron Respiratory Centre?
-> E & I Neuron Expiratory Centre
o E Neurons -> VRG
» Passive process
» Activity inhibits I neurons.
What are the functions of the Pneumotaxic & Apneustic centres (Pons)?
- Pneumotaxic & Apneustic Centres (Pons)
Modify firing patterns -> Medullary Centres.
Adjust output -> Rhythmicity Centres
Regulate respiratory rate & depth of respiration
What is the function of the Apneustic Centre of the Pons?
Apneustic Centre
» Promotes inspiration
–> Stimulates I Neurons
» Incr. intensity -> Inhalation -> Respiratory Cycle
What are the functions of the Pneumotaxic Centre of the Pons?
Pneumotaxic Centre
» Inhibits Apneustic Centre
» Stops inhalation & promotes exhalation
When is the Pneumotaxic & Apneustic centres (Pons) not required?
Not necessary -> Normal respiratory Output.
How do central neurons determine Ventilation rate?
- Central Neurons determine Ventilation Rate (VR) by regulation -> Tidal Volume (TV) & Respiratory Rate (f)
What is the equation for calculation of ventilation rate?
> > VR = TV x f
Describe the role of the central chemoreceptors in control of ventilation rate
- Central Chemoreceptors:
Steep incr. -> Ventilation Rate –
» Incr. P(CO2)
Describe the role of the peripheral chemoreceptors in control of ventilation rate
- Peripheral Chemoreceptors:
Incr. Ventilation Rate -> Incr. Sensitivity
» Decr. P(O2)
Describe the oxygen sensitivity curve
- Oxygen Sensitivity Curve: Little change -> Ventilation Rate >> Until P(O2) < 60mmHg ->> Response -> Peripheral receptors Incr. P(CO2) -> Incr. slope >> Central Chemoreceptors
What locations are responsible for control of breathing by use of neurond?
• Breathing controlled -> neurons >> Pons >> Medulla - Central controller >> Rhythmicity Centre >> Pneumotaxic & apneustic centre
What do the central chemoreceptors detect?
• Central Chemoreceptors
- Detect changes -> CO2
What do the peripheral chemoreceptors detect?
• Peripheral Chemoreceptors
- Detect changes -> O2
Where are the mechanoreceptors located?
• Mechanoreceptors -> Lungs
What affect does incr. CO2 have on ventilation rate & depth?
• Ventilation rate & depth incr. with incr. CO2
What affect does decr. CO2 have on ventilation rate & depth?
• Ventilation rate & depth decr. when CO2 decr.
What are the overall functions of the Central Controller responsible for control of breathing?
Controls Automatic Breathing
Sets pace -> respiratory movements
Modify firing patterns -> Medullary Centres.
Adjust output -> Rhythmicity Centres
Regulate respiratory rate & depth of respiration