Control of Breathing

Question 1

State the most powerful respiratory stimulant

Answer 1

Chemical stimuli
- Changes in PCO2
- Changes in H+ concentration.
- Large decreases in PO2

Rising CO2 levels are the most powerful respiratory stimulant

The respiratory centre in the medulla oblongata and pons increases the rate and depth of breathing.

Question 2

Define Hypoxia

Answer 2

absence or depletion of oxygen within cells and tissues

Question 3

Define Hypoxaemia

Answer 3

depletion of oxygen within the blood

Question 4

Define hypercapnia

Answer 4

increase in carbon dioxide level in the blood

Question 5

State which division of the nervous system controls breathing AND where the respiratory centres are located

Answer 5

Controlled by the Autonomic Nervous System
The respiratory centre in the medulla oblongata and pons controls the rate and depth of breathing.

Sympathetic - discharge dilates the bronchioles (bronchodilation) and decreases mucus secretion.

Parasympathetic - discharge constricts the bronchioles (bronchoconstriction) and increases mucus secretion.

Question 6

Discuss changes in rate and depth of inspiration

Answer 6

Inspiration - the muscles contract, increasing thoracic volume and decreasing thoracic pressure

Question 7

Discuss changes in rate and depth of exhalation

Answer 7

Exhalation - the muscles relax, decreasing thoracic volume and increasing thoracic pressure

Question 8

Define Inflation Reflex

Answer 8

The inflation reflex prevents over-inflation of the lungs.

Question 9

Describe conscious control of breathing, and other influences on respiration

Answer 9

Normal breathing is rhythmic and involuntary however can be voluntarily modified by the cerebral cortex which has input into the respiratory centre.

Limbic system stimulation - Anticipation of activity or emotional excitement

Temperature - Rise in temperature during exercise or fever increases respiratory rate

Pain - Prolonged somatic pain increases respiration rate

Blood Pressure - A fall in blood pressure increases the rate of respiration

Medications - Like morphine depress respiratory function.

Question 10

Identify clinical indicators of oxygenation which we may observe/measure

Answer 10

Arterial blood gas sampling
- Measures H+, HCO3- and calculates pH and PCO2 and PO2
- We can then determine the degree of hypoxaemia, hypercapnia and metabolic disturbance that a patient may be experiencing

Pulse oximetry
- Aims to reflect the degree of hypoxaemia by measuring the % oxygen saturation of Hb in capillary blood.

Question 11

Discuss differences and changes in respiratory function across the lifespan

Answer 11

Airways and tissues of the respiratory system become less elastic and more rigid
- The thorax becomes more rigid
- Elasticity of the lungs decreases

The older person is more susceptible to pulmonary disorders like pneumonia and bronchitis.
- Reduced action of Cilla in respiratory tract
- Decreased activity of alveolar macrophages