Lecture 17: Physiological responses of the Cardiovascular system/ respiration

Question 1

Is it true that ventilation and breathing are different aspects of external respiration?

Answer 1

Yes

Question 2

What is external respiration?

Answer 2

The exchange of oxygen and carbon dioxide between an organism and external environment

Question 3

What is breathing?

Answer 3

The contraction/ relaxation of respiratory muscles to move air in and out of the lungs

Question 4

What is ventilation?

Answer 4

Gas exchange

Question 5

Ventilation…

Answer 5

• Change in partial pressure of Carbon dioxide/ oxygen.
• Gas exchange

Question 6

Breathing..

Answer 6

• Involves respiratory muscles
• Lung inflation

Question 7

What are the 3 aspects to the central control of breathing?

Answer 7

• Voluntary/ behavioural
• Reflex/automatic
• Emotional

Question 8

What key things does breathing involve that ventilation doesn’t?

Answer 8

The respiratory muscles

Question 9

What does Reflexive/automatic control of breathing generate?

Answer 9

Generates respiratory rhythm

Question 10

What is inspiritory rhythm generated by?

Answer 10

Inspiratory rhythm is generated
by the preBötzinger Complex

Question 11

What is expiratory rhythm generatd by?

Answer 11

Expiratory rhythm is generated by
the parafacial respiratory group

Question 12

Where is Reflex/automatic control of breathing coordinated?

Answer 12

in the ventral respiratory column (brainstem/medulla oblongata)

Question 13

Where does the voluntary control of breathing originate?

Answer 13

Voluntary control of breathing
originates in the motor cortex

Question 15

Voluntary control cannot be maintained when stimuli, such as PCO2 or H+, become too intense - the breaking point.

Answer 15

Voluntary control cannot be maintained when stimuli, such as PCO2 or H+, become too intense - the breaking point.

Question 15

Is it true that voluntary control of breathing is remarkable?

Answer 15

Yes

Question 16

What can emotional control of breathing override?

Answer 16

Voluntary control cannot be maintained when stimuli, such as PCO2 or H+, become too intense - the breaking point.

Question 17

Does voluntary control of breathing occur in locked-in syndrome?

Answer 17

No

Question 18

What does emotional control of breathing arise through?

Answer 18

Emotional control of breathing arises through corticospinal projections. (not the pons)

Question 19

What is voluntary/ behavioural breathing coordinated by?

Answer 19

Emotional control of breathing overrides breathing at the final point of output

Question 20

Breathing is patterned via feedback mechanisms: chemoreceptors, protective reflexes, pulmonary stretch receptors.

Answer 20

Breathing is patterned via feedback mechanisms: chemoreceptors, protective reflexes, pulmonary stretch receptors.

Question 21

What is the major chemical factor regulating minute breathing?

Answer 21

Arterial CO2 is the major chemical factor regulating minute breathing

Question 22

What is a potent regulator of breathing?

Answer 22

Hypercapnia is a potent regulator of breathing

Question 23

Hypercapnia is a potent regulator of breathing…

Answer 23

• Even small increases in inhaled CO2 will stimulate breathing
• 10% rise in CO2 gives rise to a 100% increase in breathing
• A 20% rise in CO2 more than trebles breathing

Question 24

Is it true that Hypoxia modulates breathing to a lesser degree than hypercapnia?

Answer 24

Yes

Question 25

Arterial PO2 has to fall to about half normal before breathing is stimulated:

Answer 25

35% drop in O2 gives rise to a 20% increase in breathing A 55% drop in O2 is required for breathing to double

Question 26

What detects alterations in blood gases, like oxygen?

Answer 26

Peripheral Chemoreceptors

Question 27

Where are carotid bodies situated?

Answer 27

situated close to bifurcation of common carotid arteries in the neck

Question 28

Where are aortic bodies situated?

Answer 28

situated close to aortic arch

Question 29

What sort of changes do peripheral chemoreceptors respond to ?

Answer 29

- Decreased PO2 (hypoxia) - Increased PCO2 (hypercapnia) - Increased [H+] (acidosis) - 80% of O2 detection, and 20% of CO2 detection

Question 30

What detects altercations in blood gases, like carbon dioxide?

Answer 30

Central Chemoreceptors

Question 31

Where are central chemoreceptors located?

Answer 31

- Mainly located in medulla oblongata - But can be in other brain structures

Question 32

Central Chemoreceptors..

Answer 32

- Respond to changes in cerebrospinal fluid - Stimulated by increased PCO2 or associated changes in [H+]/pH - 70% of CO2 detection, and 30% of O2 detection

Question 33

What does blood gas regulation involve?

Answer 33

Blood gas regulation involves many medullary nuclei

Question 34

What does blood gas regulation require?

Answer 34

Blood gas regulation requires peripheral integration and integration from higher brain areas

Question 35

Must blood gases and blood pressures be regulated together?

Answer 35

Yes

Question 36

What monitors lung inflation?

Answer 36

Slowly adapting pulmonary stretch receptors monitor lung inflation

Question 37

Slowly adapting pulmonary stretch receptors monitor lung inflation...

Answer 37

- In smooth muscles of bronchi and trachea. - Stimulated by stretch of lungs - Signal lung volume to brain - Inhibit inspiration and lengthen expiration Hering-Breuer inflation reflex - Regulating respiratory rhythm e.g. exercise and sleep in neonates.

Question 38

What monitors irritants?

Answer 38

- Rapidly adapting pulmonary stretch receptors monitor irritants

Question 39

Rapidly adapting pulmonary stretch receptors monitor irritants

Answer 39

- In epithelial cells in larnyx, trachea and airways. - Respond to mechanical stress: large inflation/deflation - Respond to chemical environment of lung: noxious gases, dust, cold, histamine. - Constrict airway & promote rapid shallow breathing - Promote cough in trachea and larynx - Promote sighing due to gradual collapse of lungs (actelectasis). ~ 5 minutes -

Question 40

Where is the control circuit for sighing located?

Answer 40

The control circuit for sighing is located in the RTN and preBötC

Question 41

Why do lungs require compliance?

Answer 41

So that they can inflate and deflate

Question 42

Lungs require compliance so that they may inflate and deflate

Answer 42

- Change in lung volume produced by changes in transpulmonary pressure (Ptp) - Compliance: ability to expand lungs at any given change in (Ptp) -

Question 43

What are the 2 major determinants of lung compliance?

Answer 43

1. “Stretchability” of tissues 2. Surface tension within alveoli

Question 44

What is surface tension within the alveoli lowered by?

Answer 44

Surface tension within alveoli is lowered by pulmonary surfactant

Question 45

Surface tension within alveoli is lowered by pulmonary surfactant...

Answer 45

The surface of alveoli is moist Surface tension at air-water interface resists stretching Pulmonary surfactant lowers surface tension and increases compliance

Question 46

When is pulmonary surfactant released from type II alveolar cells?

Answer 46

during sighing

Question 47

Pulmonary Surfactant is released from type II alveolar cells during sighing

Answer 47

A mixture of phospholipids and protein Makes lungs easier to expand Secreted by type II alveolar cells Sighing increases secretion (by stretching the type II cells) Production in foetal lung in late gestation Deficiency in premature babies causes respiratory distress syndrome of the newborn

Question 48

Why are coughs and sneezes protective reflexes?

Answer 48

Because they are responses that protect the respiratory system from irritants.

Question 49

Cough reflex:

Answer 49

Due to receptors in epithelial cells of upper airway Air speed of 960 km·h-1

Question 50

Sneeze reflex:

Answer 50

Due to receptors in epithelial cells of nose or pharynx. Air speed of 160 km·h-1

Question 51

To summarise, this lecture has considered:

Answer 51

Respiratory control Reflexive Volitional Emotional Respiratory reflex Chemoreception Stretch receptors Protective