Lecture 18 Flashcards
what is hypoxia and hypercapnia (how does it tend to occur)?
insufficient oxygen to supply metabolic needs is hypoxia.
too much carbon dioxide in the blood ( leading to pH problems) is hypercapnia, this typically occurs due to hypoventilation leading to accumulation of carbon dioxide. This shifts the bicarbonate equation towards the acid production. as ventilation is the most important factor in removing CO2.
Hyperventilation can also lead to pH problems in the opposite direction.
What is respiratory acidosis and alkalosis? How can these be dealt with?
Respiratory acidosis is too high body pH due to not breathing out enough carbon dioxide, respiratory alkalosis is too low body pH due to breathing out too much carbon dioxide. The kidneys (via excreting more H+ and synthesising more HCO3-, this can take 18-24 hours though) and lungs can both work together to compensate for pH abnormalities (lungs for metabolic problems, kidneys for respiratory problems)
Why is control of breathing done?
Control of breathing is done to maintain normal levels of oxygen and carbon dioxide for metabolic and biochemical stability, the oxygen uptake and carbon dioxide production can be quite variable, this means tight ventilation control must occur to keep levels constant.
What are the main elements of breathing control?
Central control occurs in the brainstem (setting pattern/rhythm of breathing, coordinates sensors and effectors to maintain respiratory homeostasis), sensors in the central (in the brainstem)/ peripheral system gather information in the form of chemical (e.g oxygen concentration) and physical (e.g lung stretch) information and send this information to the respiratory centre (brainstem (pons, medulla and some other parts of the brain)) in the form of neural and chemical inputs and then effectors (respiratory muscles) adjust the ventilation.
What part of the brain allows us to consciously control breathing?
The cortex can override/modify the brainstem’s rhythm.
What does the medullary respiratory centre do? What are other areas of the brain involved in respiration?
The medullary respiratory centre generates the rhythm, the dorsal area is for inspiration, the ventral area is mainly for expiration, other involved parts are the apneustic centre and pneumotaxic centre.
What are the two chemical respiratory receptors, where are they found and what do they act on?
The two chemical receptors are peripheral chemo receptors (found in carotid and aortic bodies, they respond to decreased arterial oxygen pressure, they have a limited small response to carbon dioxide change and they are rapidly responding, they are less important than the central ones) and central chemo receptors (located in the medualla, sensitive to carbon dioxide , not oxygen levels, this is due to the changes in pH of the brain extracellular fluid caused by carbon dioxides diffusion out of the cerebral capillaries).
What is the main chemical which determines breath rate? What is it normally maintained at? What can change this?
arterial carbon dioxide levels, normally maintained within around 40 mmHg. This limits breath holding as increased levels become too high, the response changes based on varying factors (e.g sleep, increasing age, genetic factors, training and drugs).
What is the ventilatory control to oxygen?
We also respond to low oxygen levels via only the peripheral chemoreceptors, during normal conditions this doesn’t occur, only realistically below 60mmHg, this response will be increased when combined with being hypercapnic, hypoxic control becomes important at high altitude and in long term can be caused by lung diseases.
What are the non chemical controls of breathing? Where are they located?
non chemical controls of breathing include receptors located in the airways and lungs and is connected to respiratory centers via the vagus nerve, lung receptors are stretch receptors (based on lung distension) or irritant receptors (e.g smoke, dust, cold air). There are also other receptors in the nose/upper airway, the joints and muscles, arterial barorecepors and pain and temperature can also have an effect.
What parts of respiratory control does exercise affect?
Exercise has an effect on all parts of the respiratory system (physical receptors, chemo receptors and motor cortex).
