Neural Control Ventilation (M2) Flashcards
1
Q
LO’s
A
- Describe the location and names of centres in the brain stem controlling ventilation
- Describe how brain stem centres interact to control activity of the respiratory muscles
- Describe how respiratory centre activity is modulated by chemical and neurogenic input
- Describe the integration of neural and chemical control systems
- Describe the importance of reflexes that protect and/or clear the airways
2
Q
Describe output to respiratory muscles
A
- The respiratory groups/centres receive chemical input (messages from chemoreceptors to increase the ventilation rate) and neurogenic input.
- Output happens to the external and internal intercostal muscles and the diaphragm, making them expand/contract
- The phrenic nerve (from cervical vertebrae C3, C4, C5) makes the diaphragm contract.
- The nerves from the thoracic vertebrae T5 and T6 make the external intercostals contract.
- The nerves from the T11 and T12 make the internal intercostals expand.
3
Q
Where are the respiratory groups/centres?
A
- At the top of the brainstem is the PONS (pontine respiratory group). This doesn’t initiate breathing, but regulates it.
- Underneath the PONS, in the medulla oblongata is the Ventral Respiratory Group (to the sides of the medulla.) In the middle of the medulla is the Dorsal Respiratory Group.
4
Q
What does the pontine (PONS) region do?
A
- Influence pattern ventilation
- “Phase switching”
- JUST LEARN: I CAN’T FIND WHAT THIS MEANS*
5
Q
Why is nerves output to internal/external intercostals and the diaphragm ramp like, ratehr than on/off?
A
- Ramp like, slow build up, to reflect how we slowly inspire.
- If it was on/off, then we would inspire all at once, forcefully, so couldn’t speak.
6
Q
What does the Ventral Respiratory Group (VRG) do?
A
- Contains Inspiratory & Expiratory neurons
- Amplitude (depth)
- Rhythm generation (pre-Bӧtzinger complex)
JUST LEARN
7
Q
What does the Dorsal Respiratory Group (DRG) do?
A
- Inspiratory (I) neurons
- Integrate sensory information (solitary tract)
8
Q
How does the VRG generate rhythym in exhaling and inhaling?
A
- Two theories
- Pacemaker theory: When inspiratory neurones stimulated, expiratory neurones are silenced, so an output to inspire only is sent. And vica versa.
- However pacemaker theory doesn’t explain how we can also consciously change our breathing.
9
Q
How is respiratory centre activity modulated by neurogenic input/ reflexes?
A
- We have conscious control over breathing = cortical factors.
- We have reflexes from lung receptors:
- Irritant receptors
- C-fibre receptors
- Hering-Breuer inflation reflex (Stretch receptors)
- J-receptor reflexes
- Baroreceptor reflex: low arterial BP causes increased ventilation.
- Reflexes from muscles/ joints: increase ventilation.
- Reflexes from the periphery: (pain and heat cause increased ventilation).
-
Protective reflexes:
- Laryngeal (protect lungs)
- Cough (protect lower airways)
- Sneeze (protect upper airways)
-
Co-ordination with other functions:
- Speech (prolong expiration)
- Defaecation (expiration against a closed glottis = increased abdominal pressure)
- Sigh, Hiccup, Yawn
10
Q
What is the J-receptor reflex in the lungs?
A
- Juxtapulmonary capillary receptor
- Simulated by pulmonary capillary hypertension and oedema in the alveolar walls
- Causes impulses to shoot up vagus nerve, causing the pattern of breathing seen in left heart failure = rapid, shallow breathing.
11
Q
Describe the Hering-Breuer inflation reflex (stretch receptor in the lungs)
A
- Prevents overinflation of the lungs
- Info transmitted to pneumotaxic centre- upper pons
- “Phase switching” by inhibiting apneustic centre- lower pons
- Stimulates expiration
12
Q
Why are neural and chemical reflexes important?
A
- Chemical reflexes are of primary importance in adjusting ventilation to body’s metabolic needs
- Neural reflexes are of secondary importance and tend to modify the pattern of ventilation rather than regulate the overall level of ventilation
