Topic 38 - The regulation of respiration

Question 1

Words to include in nerval control

Answer 1

The respiratory center

• Medulla oblongata
• Pons
• Receptors
  
  • Sense gas tension of blood
• Pneumotaxic center
  
  • Inhibits inspiration
• Apneustic center
  
  • Stimulates inspiration senter
• Primary inspiration center (DRG)
  
  • Inhibits center of expiration
  • Generates continous spontaneous inspiration
• Secondary expiration center (VRG)
  
  • Inhibits inpiration center
• Nucleus of n. phrenicus
  
  • Gets stimulus from DGG

Severance experiment

• Cut above pons
  
  • No effect
• Cut in middle of pons
  
  • Deep inspiration
  • Inspiration-inhibiting center in upper pons
    
    • Pneumotaxic
• Cut on border of pons and medulla
  
  • Deep and shallow breathing
  • Apneustic center
• Cut on medulla above exit opint of n. phreinicus
  
  • Respiratory cycle stops
  • Autonomous respiratory group
  • DRG (dorsal respiratory group)
    
    • Inspiration
  • VRG (ventral respiratory group)
    
    • Expiration
• Cut below exit point of n. phrenicus
  
  • No change in respiration
• Hering-Breuer reflex
  
  • N. vagus cut
  • Deep inspiration
  • Sudden expiration

Afferent nervous factor

• Nervous afferentation
  
  • Mechanoreceptors (most important)
• Hering-Breuer reflex
  
  • Stretch receptors in lung
    
    • Stimulate expiratory cells of VRG
    • Inhibits inspiratory cell groups of DRG
      
      • Via n. vagus
  • Nucleus of n. phrenicus
    
    • Stops expiration
• Afferent signals
  
  • Emotion
  • Hyperventilation caused by movement of limbs
  • Pain
    
    • Somtic
    • Visceral
  • Sleep
  • Baroreceptor effect

Afferent nervous factors

• Forced expiration
  
  • Inspiratory muscles are inhibited actively
  • Expiratory muscles are stimulated

Chemical regulation

• Central regulation
  
  • Sensitive to:
    
    • pCO₂ in blood
    • Cerebrospinal fluid
    • pH
  • Bottom of 4^th ventricle
    
    • Receptor location
  • DRG activity stimulation
    
    • CO₂ drop
    • pH drop
  • Apneustic
    
    • Sensitive to pCO₂
• Peripheral reception
  
  • Receptors
    
    • Glomerus caroticum (carotid body)
    • Glomerus aorticum (arotic body)
  • Sensitive to pO₂
  • Central chemoreception is reduced
    
    • Secondary protective mechanism (pO₂)
      
      • Hyperventilation

Question 2

Words to include in type of breathing

Answer 2

• Normal respiration
  
  • Uniform deepness of inspiration and expiration
• Dyspnea
  
  • Random breathin
• Apnea
  
  • Absence of breathing
• Biot’s rhythm
  
  • Encephalitis
  • Meningitis
  • Breathing cycle is interrupted by apnea
• Asphyxia
  
  • Suffication
• Cheynes-stokes’s breathing
  
  • Long apnea
  • Increasing inspiration expiration cycles
• Kussmaul breathing
  
  • Deeper and longer inspiration and expiration
  • Uremia
  • Diabetic coma

Question 3

Words to include in defensive respiratory reflexes

Answer 3

• Sneezingin
  
  • Irritation of upper respiratory tract
  • Extensive inspiration followed by explosion-like expiration
• Coughing
  
  • Tracheo-bronchial irritation
  • Chemoreceptors
    
    • Smaller and larger bronchial segements
• Nociceptive apnea
  
  • ​Prevents inhalation of harmful gases
  • Apnea
• Diving reflex
  
  • ​Defensive apnea
• Combined swallowing reflex
  
  • ​Food touches pharyngeal wall → reflex-pause in breathing
  • Prevents choking

Question 4

Topics to include in the essay

Answer 4

1. Nerval control
   
   • The respiratory center
   • Severance experiment
   • Afferent nervous factors
   • Efferent nervous factors
   • Chemical regulation
2. Types of breathing
3. Defensive respiratory reflexes

Question 5

Nerval control

The respiratory center

Answer 5

• Nuclear arrys responsible for the different aspects of respiration are located in medulla oblongata and the pons
  
  • These arease can act like receptors: they can sense the gas tension of blood
• Pneumotaxic center
  
  • Inhibits inspiration
• Apneustic center
  
  • Stimulates the inspiration center
• Primary inspiration center (DRG)
  
  • Inhibits the center of expiration and generates continuous spontaneous inspiration
• Secondary expiration center (VRG)
  
  • Inhibits the center of inspiration
• Nucleus of phrenic nerve
  
  • Gets stimulus from the DRG

Question 6

Nerval control

How to study the division of respiration-control in the brain

Answer 6

​Severance experiment

• With or without intact n. vagus

1. Cut above the pons
   
   • No effect
   • CNS above pons has no direct effect on respiration, plus n. vagus stimulates the expiration
2. Cut in the middle of pos
   
   • Deep inspirations
   • There is an inspiration-inhibiting center (called pneumotaxic) in the upper Pons
3. Cut on the border of pons and medulla
   
   • Deeper and shallower breathing
   • Above the cut there is an apneustic center responsible for normal rhythm of respiration
4. Cut on the medulla above the exit point of n. phrenicus
   
   • The respiratory cycle stops
   • Autonomous respiratory group
   • DRG (dorsal respiratory group): responsible for inspiration
   • VRG (ventral respiratory group): responsible for expiration
5. Cut below the exit point of n. phrenicus
   
   • No change in respiration

• Cutting n. vagus: ​
  
  • Hering-Breuer reflex: Deep inspiration and then sudden expiration

Question 7

Nerval control

Afferent nervous factor

Answer 7

• Inspiration and expiration stimulates mechanoreceptors (most important nervous afferentation)​
• Hering-Breurer refle:
  
  • ​The stretch receptors in the lung:
    
    • Stimulate the expiratory cells of the VRG via n. vagus
    • Inhibit the inspiratory cell group (DRG) via n. vagus
  • Result: Nucleusofn. phrenicus stops expiration
• Other reflexes:
  
  • CNS, emotion changes
  • Limb - muscle work - hyperventilation
  • ​Somatic pain sensing reflexes
  • Visceral pain sensing reflexes
  • Sleep effects
  • Baroreceptor effects

Question 8

Nerval control

Efferent nervous factors

Answer 8

• During forced expiration:
  
  • Inspriatory muscles are inhibited actively
  • Expiratory musclesarestimulated

Normally expiration is a passive process

Question 9

Nerval control

Chemical regulation

Answer 9

1. Central regulation​
   
   • Sensitive to pCO₂ in:
     
     • Blood
     • Cerebrospinal fluid
     • pH
   • Receptors are located at the bottom of 4^th ventricle
   • Too much CO₂: ​pH drop, stimulating DRG activity indirectly
   • Apneustic area is specifically sensitive to pCO₂
2. Peripheral regulation
   
   • ​Receptors in:
     
     • Glomus caroticum (carotid body)
     • Glomus aorticum (aortic body)
   • Mostly sensitive to pO₂
   • Important when central chemoreception is reduced → secondary protective mechanism activated (pO₂ reception) → hyperventilation

Question 10

Give the differen types of breathing

Answer 10

1. Normal respiration
   
   • Steady alternation of inspiration and expiration of uniform deepness
   • Anything deviating from that is abnormal
2. Dyspnea
   
   • Random breathing
3. Apnea
   
   • Absence of breathing
4. Biot’s rhythm
   
   • Observes primarily in the case of encephalitis or meningitis
   • Breathing cycles are interrupted by a longer apnea
5. Asphyxia
   
   • Too long pause leads to suffocation
6. Cheynes-Stokes’s breathing
   
   • Long apnea which ends with increasing inspiration expiration cycles
7. Kussmaul’s breathing
   
   • Deeper and longer inspiration and expiration
   • Observed in:
     
     • Uremia
     • Diabetic coma

Question 11

Give the defensive respiratory reflexes

Answer 11

1. Sneezing
   
   • Due to mechanical or chemical irritation of upper respiratory tract
   • Mechanism: extensive inspiration followed by an explosion-like expiration
   • Clears the upper respiratory tract
2. Coughing
   
   • Due to tracheo-bronchial irritation
   • Chemoreceptors are in the bronchial segments
   • Mechanism: similar to sneezing (though less intensive)
3. Nociceptice apnea
   
   • Preventing the body from inhaling harmful gases or fumes
   • Mechanism: sudden break in breathing (apnea)
4. Diving reflex
   
   • Irritating the skin of the head with water (diving) results in defensive apnea
   • Breathing motions are generally inhibited under the water
   • Protection against inspiration of water into the lungs
   • Humans and young animals
5. Combined swallowing reflex
   
   • When the food touches the pharyngeal wall, reflex-pause in breathing happens
   • Prevents choking