3.6

Question 1

I. The muscles of respiration and the breathing movements
1. What are the 2 types of muscles of respiration?

Answer 1

Muscles of inspiration and expiration

Question 2

I. The muscles of respiration and the breathing movements
2. What are the characteristics of muscles of inspiration?

Answer 2

• Diaphragm contracts and chest wall expands → more negative intrapleural pressure → lungs expand passively
  => Innervated by phrenic nerve
• External intercostal muscles may also be used for vigorous inspiration

Question 3

I. The muscles of respiration and the breathing movements
3. What are the characteristics of muscles of expiration?

Answer 3

• Normally a passive process, accomplished simply by relaxation of the muscles of inspiration
• Abdominal muscles (compress abdominal cavity) and internal intercostal muscles (pull the ribs down and
  inward) may contribute during exercise or asthma (↑airway resistance)
  => Innervated by int. intercostal nerve

Question 4

II. Respiratory centers
1. Where are the respiratory centers?

Answer 4

• control of respiration comes from the respiratory centers
• located in the medulla and pons

Question 5

II. Respiratory centers
2. What are the 3 groups of respiratory centers?

Answer 5

1. Dorsal respiratory group (DRG)
2. Ventral respiratory group (VRG)
3. Pontine respiratory group (PRG)

Question 6

II. Respiratory centers
2A. What is the role of Dorsal respiratory group (DRG)?

Answer 6

inspiratory output

Question 7

II. Respiratory centers
2B. What is the feature of Ventral respiratory group (VRG)?

Answer 7

• area of nucleus ambiguous and retro-ambiguous
• In the rostral part:
  +) Bötzinger complex
  +) Pre-bötzinger complex

Question 8

II. Respiratory centers
2C. What is the location of Pontine respiratory group(PRG)?

Answer 8

In the pons

Question 9

II. Respiratory centers
3. What are the 4 things that control breathing?

Answer 9

respiratory control centers, central chemoreceptors, peripheral chemoreceptors and mechanoreceptors.

Question 10

II. Respiratory centers
4. The brainstem controls the frequency of normal, involuntary breathing via 3 centers in the brain stem.
-> What are they?

Answer 10

1. Medullary center
2. Apneustic center – (apneustic = abnormal breathing)
3. Pneumotaxic center (upper pons)

Question 11

II. Respiratory centers
5A. What are the location and center types of Medullary center

Answer 11

Medullary center is located in the reticular formation and is divided into the inspiratory and expiratory center

Question 12

II. Respiratory centers
5B. What is the role of inspiratory center of Medullary center

Answer 12

Inspiratory center or pre-Bötzinger complex controls the basic rhythm of the breathing.
-> It sends repetitive APs motor output via the phrenic nerve

Question 13

II. Respiratory centers
5C. What is the role of expiratory center of Medullary center

Answer 13

expiratory center controls the expiration, but because expiration is a mostly passive process, these neurons are inactive during quiet breathing and mostly only active with exercise

Question 14

II. Respiratory centers
6. What are the characteristics of Apneustic center?

Answer 14

Apneustic center – (apneustic = abnormal breathing)
- Produces a breathing pattern of prolonged inspiratory gasps followed by brief expiratory movement
- sends signals to the dorsal respiratory center in the medulla to delay the ‘switch off’ signal of the inspiratory ramp provided by the pneumotaxic center of pons
- It controls the intensity of breathing

Question 15

II. Respiratory centers
7. What are the characteristics of Pneumotaxic center (upper pons)?

Answer 15

• This center turns off inspiration, limiting the burst of APs coming from the Bötzinger area via the phrenic nerve
• It limits the size of the tidal volume and regulates the respiratory rate, but is not totally necessary because normal breathing persists without this center

Question 16

II. Respiratory centers
8. Can cerebral cortex override the brain stem control centers?

Answer 16

The cerebral cortex can temporarily override the brain stem control centers and this is because people can choose to hyperventilate or hold their breath until their body is negatively affected
- In some cases, the person goes unconscious and the regular breathing pattern is regained

Question 17

II. Respiratory centers
9. Explain this graph

Answer 17

A: inspiratory center, gets input from chemoreceptors and apneustic center, sends APs to the respiratory muscles (diaphragm)
B: vagal stretch receptors in lung cause increase in breathing rate by sending activating signals to the apneustic center = even more inspiration
C: pneumotaxic center inhibits breathing via the apneustic center to ensure proper frequency

Question 18

III. Non-chemical control of respiration
1. What are the types of non-chemical control of respiration?

Answer 18

1. Cortical effect
2. Mechanoreceptor and other receptors (all sensory input via vagal n!)
3. Limbic system/hypothalamus

Question 19

III. Non-chemical control of respiration
2. How can cortical effect control respiration?

Answer 19

.Cortical effects: directly affect respiration
- cortical effect is a pathway which goes from the cortex to the spinal cord -> bypasses medullary respiratory centers)
- if we do not breath for a long time, the activity of the medullary centers takes over
 inspiration, even if we do not want to
 effects of medullary centers override the cortical effects
- Cortical effects are very important during exercise:
 when we exercise, our cortex not only gives input to working muscles to contract, but also provides input to the respiratory centers to increase respiration
 that is why CO2-production and alveolar ventilation change in parallel (PACO2 remain constant)

Question 20

III. Non-chemical control of respiration
3A. What are the type of receptors participate in the control of respiration?

Answer 20

1. Stretch receptors
2. Irritant receptors
3. Juxtacapillary receptors

Question 21

III. Non-chemical control of respiration
3B. Characteristics of stretch receptors in respiration control

Answer 21

• Located in bronchial smooth muscle.
• When stimulated by stretching of lungs and airways, mechanoreceptors initiate Hering-Breuer reflex to ↓ breathing rate (inhibit inspiration).

Question 22

III. Non-chemical control of respiration
3C. Characteristics of Irritant receptors in respiration control

Answer 22

• Located in epithelial cells and they detect Chemical substances (smoke, dust, powder inhaled, histamine)
• As result, bronchoconstriction and increase in breathing rate (hypernea), coughing.

Question 23

III. Non-chemical control of respiration
3D. Characteristics of Juxtacapillary receptors in respiration control

Answer 23

1. Located in alveolar wall near pulmonary capillary.
2. They are activated by Over-stretching of lung, fluid (pulmonary edema), which results in an increased breathing rate.
3. The reflex response that is produced is apnea, followed by bradycardia, hypotension and bronchoconstriction.

Question 24

III. Non-chemical control of respiration
4. How can Limbic system/hypothalamus participate in respiration control?

Answer 24

send info to respiratory center, and allow pain and emotions to affect breathing.