Body Systems L18 Notes Flashcards by Jade Benita McLaughlin

Define pulmonary ventilation

• Pulmonary Ventilation:

- Physical movement of air into & out of the respiratory tract

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What are the functions of pulmonary ventilation

Function:
 Ensure continuous oxygen supply
 Prevent accumulation of CO2

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What two principals govern pulmonary ventilation?

 Boyle’s Law:

 Air flows from area -> high pressure to low pressure.

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Outline Boyle’s Law

 Boyle’s Law:
 The pressure of a given quantity of gas is inversely proportional to it’s volume.
 Decr. Vol -> Incr. pressure
 Incr. Vol -> Decr. pressure

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Outline the principal  Air flows from area -> high pressure to low pressure.

 Air flows from area -> high pressure to low pressure.
 Incr. volume -> decr. pressure
&raquo_space; Air moves in
 Decr. volume -> incr. pressure
&raquo_space; Air expelled

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Describe the movement of air during different conditions in pulmonary ventilation

• Ventilation:
- Atmospheric pressure > Intrapulmonary / Intraalveolar pressure
 Air enters lungs
- Intrapulmonary / intraalveolar pressure > atmospheric pressure
 Air expelled from lungs
- Change -> volume = change -> pressure

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What is the normal value for atmospheric pressure?

Atmospheric pressure = 760mmHg

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What factors influence incr. thoracic volume?

Incr. Vertical diameter
Incr. Anterior Posterior diameter
Incr. transverse diameter

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Describe the influence of incr. vertical diameter on incr. thoracic volume

Incr. Vertical diameter
 Contraction of diaphragm incr. vertical diameter
Responsible for 75% incr. thoracic capacity

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Describe the influence of - Incr. Anterior Posterior diameter on incr. thoracic volume

Incr. Anterior Posterior diameter
 Elevation of ribs incr. Anterior Posterior diameter
-> (Joint with Transverse Diameter)
Responsible for 25% thoracic capacity.
 Elevation of ribs -> external end -> makes them more horizontal & pushes sternum forward (pump handle movement)
Incr. AP diameter

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Describe the influence of Incr. transverse diameter on incr. thoracic volume

Incr. transverse diameter
 Elevation of ribs incr. transverse diameter
-> (Joint with Transverse Diameter)
Responsible for 25% thoracic capacity.
 Many of the ribs
 Lowest near their middle
 Rise at each end
Eg. Bucket handle
 Rise of middle of rib -> movement away from midline of body
Transversally widens chest (Left -> Right)

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Describe the role of the pleura in ventilation

• Role of Pleura in Ventilation:
- Surface tension created by film of serous fluid between Parietal & Visceral pleura
Prevents pulling apart
- Incr. volume of thorax causes incr. volume of lungs.

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Describe the intrapleural pressure

Inrapleural pressure:
 Pressure within pleural cavity
 Always lower than atmospheric & intrapulmonary pressures
 Created -> Elastic recoil of lungs

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Describe the influence of pneumothorax on ventilation

Pneumothorax:
 Accumulation -> Air / gas in pleural cavity
 Disease / injury -> Eg. Puncture Wound
 Loss of negative intapleural pressure (approx. 760mmHg)
 Lung collapse

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What kind of process is inspiration? Is it the same at both rest & when forced?

Active -> Both at rest & when forced

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Describe inspiration at rest

At rest:
 Diaphragm (75%)
 External intercostal muscles (25%)
 Contracted diaphragm flattens
-> Vertical diameter of thorax increased.
 External intercostals elevate ribs -> incr. Anterior Posterior & Transverse
diameters.

Describe inspiration when it is forced

-	Forced:
	Pectoralis major 
	Pectoralis minor
	Scalenes
	Serratus anterior
	Sternocleidomastoid
 Assist -> rib elevation 
    -> Incr. speed &amp; amount of movement

What kind of process is expiration? Is it the same at both rest & when forced?

Passive at rest

Active when forced

Describe expiration at rest

-	At rest:
	Passive process
	Diaphragm 
	External intercostals
 Relaxation of diaphragm &amp; external intercostal muscles

Describe expiration when it is forced

-	Forced:
	Active process
	Internal intercostals
	Abdominal muscles
-> Rectus abdominis 
-> External oblique 
-> Internal oblique
-> Transversus abdominis
 Internal &amp; innermost intercostals depress ribs 
    -> Reduce size of thoracic cavity
 Abdominal muscles compress abdomen &amp; force diaphragm upwards

List the abdominal muscles involved in forced expiration

 Abdominal muscles

> Rectus abdominis
> External oblique
> Internal oblique
> Transversus abdominis

Describe neural control of ventilation

• Neural Control of Ventilation:
- Chemoreceptors detect changes in PO2, PCO2 & pH
-> Send impulses / signals
 Vagus (CN X) & Glossopharyngeal (CN IX) nerves
(Afferent pathway)
- Impulses transported -> Vagus (CN X) & Glossopharyngeal (CN IX) nerves
 Respiratory Centres of Brain Stem
- Respiratory Centres of Brain stem
-> Send impulses / signals
 Phrenic, intercostal & other nerves
(Efferent pathway)
- Impulses transported -> Phrenic, intercostal & other nerves
 Muscles in ventilation

Describe the central chemoreceptors

• Central Chemoreceptors:

Located -> Medulla oblongata of brainstem
Respond to changes in PCO2 & pH

Describe the peripheral chemoreceptors

•	Peripheral Chemoreceptors:
-	Detect changes -> PO2, PCO2 &amp; pH
-	Aortic Bodies
 Located -> Aortic Arch
 Innervated -> Vagus (CN X)
-	Carotid Body
 Located -> Common Carotid Artery
 Innervated -> Glossopharyngeal (CN IX)

Where are the aortic bodies of the peripheral nerve located & what are they innervated by?

- Aortic Bodies  Located -> Aortic Arch  Innervated -> Vagus (CN X)

Where are the carotid body of the peripheral nerve located & what are they innervated by?

- Carotid Body  Located -> Common Carotid Artery  Innervated -> Glossopharyngeal (CN IX)

Describe the respiratory centres of the brain

• Respiratory Centres: - Group of neurons -> Brain stem - Send impulses to muscles of ventilation - Medullary Rhythmicity Area  Dorsal Respiratory Group (DRG)  Sets rhythm, stimulates muscles of quiet inspiration  Ventral Respiratory Group (VRG)  Involved in forced inspiration & expiration - Pneumotaxic area (Pons)  Influences DRG by regulating duration of inspiration.

Name the two areas of the respiratory centres

- Medullary Rhythmicity Area | - Pneumotaxic area (Pons)

What is the function of the medullary rhythmicity area of the respiratory centre

- Medullary Rhythmicity Area  Dorsal Respiratory Group (DRG)  Sets rhythm, stimulates muscles of quiet inspiration  Ventral Respiratory Group (VRG)  Involved in forced inspiration & expiration

What is the function of the Pneumotaxic area (Pons)of the respiratory centre

- Pneumotaxic area (Pons) |  Influences DRG by regulating duration of inspiration.

Describe the Hering-Breuer Reflex

``` • Hering-Breuer Reflex: - Prevents over-inflation of lungs - Stretch receptors  Visceral pleura  Bronchioles  Alveoli - Impulses sent via vagus nerve  Pneumotaxic centre - Duration of inspiration shortened. ```

Outline the pathway involved in neural control of ventilation

Chemoreceptors -> Vagus (CN X) & Glossopharyngeal (CN IX) nerves -> respiratory centres of brain -> Phrenic, intercostal & other nerves -> Muscles in ventilation