Respiratory Physiology Lecture 7 Part 29: Neural Control of Breathing

Question 1

Where is the rythm of breathing established?

Answer 1

Rhythm of breathing is established in the CNS which is constantly running to control INS and EXP

Question 2

Where is breathing initiated?

Answer 2

in the medulla by specialized neurons

Question 3

What three important areas in the brainstem control breathing?

Answer 3

• Pontine respiratory group
• Dorsal respiratory group
• Ventral respiratory group

Question 4

What modifies breathing?

Answer 4

Modified by higher structures of the CNS & inputs from central and peripheral chemoreceptors & mechanoreceptors in the lung and chest wall

Question 5

What factors infleunce respiratory rythm?

Answer 5

• Higher centers of the brain (Speech, emotions, voluntary control of breathing, and action potentials in motor pathways)
• Medullary (Chemosensitive area) chemoreceptors ↓pH, ↑CO2
• Carotid and aortic body Chemoreceptors ↓pH, ↑CO , ↓O
• Hering-Breuer reflex (Stretch receptors in lungs)
• Proprioceptors in muscles and joints
• Receptors for touch, temperature, and pain stimuli

Question 6

Where does neural control of breathing happen?

Answer 6

occurs at the level of the brainstem

Question 7

What must be established for contraction of the respiratory muscles?

Answer 7

Neuronal networks must establish the automatic rhythm for contraction of the respiratory muscles

Question 8

automatic rhythm

Answer 8

Breathing is an automatic and rhythmic act produced by networks of neurons in the hindbrain (the pons and medulla). The neural networks direct muscles that form the walls of the thorax and abdomen and produce pressure gradients that move air into and out of the lungs.

Question 9

What are the groups of respiraotry neurons located in the brain?

Answer 9

Pontine respiratory group, dorsal respiratory group, ventral respiratory group

Question 10

Which group of respiratory neurons are most important?

Answer 10

Ventral respiratory group is the most important because both INS and EXP generators are located in this area

Question 11

What are the INS and EXP generators?

Answer 11

• INS → PreBötzinger complex (PreBötC)
• EXP → Parafacial respiratory group (pFRG)

Question 12

PreBötC

Answer 12

PreBötzinger complex

Question 13

PreBötzinger complex (PreBötC)

Answer 13

• Group of neurons in the ventral respiratory group
• Generates excitatory inspiratory rhythmic activity that excites INS muscle (via polysynaptic pathway)
• Allow for rhythmic contraction from 6 months gestation till your last breath
• Continuously active (fire AP every time you take a breath)

Question 14

pFRG

Answer 14

Parafacial respiratory group

Question 15

Parafacial respiratory group (pFRG)

Answer 15

• Group of neurons in the ventral respiratory group
• Important for generating rhythmic excitatory active expiratory rhythmic activity that excites expiratory muscles (via polysynaptic pathway)
  
  • Important for active contraction of abdominal muscles

Question 16

Why must the rhythm of breathing change?

Answer 16

Neuronal networks must adjust this rhythm to accommodate changes in:

– Metabolic demands (As reflected by changes in blood PO2, PCO2, and pH)

– Varying mechanical conditions (eg. Changing posture)

– Non-ventilatory behaviors (eg. Speaking, sniffing, eating)

– Pulmonary and non-pulmonary diseases

Question 17

Where does trhe rhymth of breathing happen?

Answer 17

Generated in the Ventral Respiratory Group (VRG) in medulla

Question 18

What drives the breathing activity?

Answer 18

PreBötC and pFRG neurons drive activity in premotor neurons, which excite motor neurons that activate rhythmically respiratory muscles

Question 19

What influences rhythmic activity?

Answer 19

Rhythmic activity is influenced by sensory and neuromodulatory (NTs) inputs originating from different regions within and outside CNS

Question 20

What neuromodulatory inputs influence rhymthmic breathing?

Answer 20

Raphe → 5-HT peptides CO2

Locus coerulus → NE peptides

Dorsolateral pons → Glutamate

Hypothalamus → Orexin

Question 21

Where is there cross talk with neural control of breathing?

Answer 21

Cross talk between the suprapotine structures and the respiratory control

Volitional

Phonation, Breath holding, Hyperventilation

Emotional

Laughing, Sighing, Crying

Question 22

Neuro-respiratory pathway for inspiration

Answer 22

• preBötC → INS premotoneuron (ROSTRALVRG) → phrenic & thoracic motorneurons (In cervical & thoracic spinal cord) → DIAPHRAGM & EXT. INTERCOSTAL muscles
• preBötC → INS premotoneuron (ROSTRAL VRG & parahypoglossal region, pXII) → cranial motoneurons (In medulla) → TONGUE & UPPER AIRWAY MUSCLE

Question 23

Neuro-respiratory pathway for expiration

Answer 23

Active expiration

pFRG → EXP premotoneurons (Caudal VRG) → thoracic & lumbar motoneurons (In spinal cord) → INT. INTERCOSTAL & ABDOMINAL MUSCLES