5 Respiration under unusual conditions Flashcards
Describe O2 and CO2 changes during normal exercise
- Increase in O2 consumption - promotes
respiratory metabolism - Hence increases CO2 production
- Exercise intensity can vary
Describe O2 and CO2 changes during mild and moderate exercise
- Arterial pO2 and pCO2 remain normal despite
increases ventilation - pO2 at 13.3kPa and pCO2 at 5.3kPa
Describe the phases of ventilation during exercise
- Just before ventilation: neural-anticipatory mechanisms which will initiate an increase in ventilation (pO2 and pCO2 are normal)
- With moderate exercise: normal pO2 and pCO2, with an increase in ventilation, and will eventually plateau
- With strenuous exercise: much faster + deeper breathing as unable to meet O2 demand
> anaerobic respiration begins - build-up of lactic acid
Describe the events that occur in respiration at the start of exercise
- Neural mechanism anticipating the extra demand through detection by proprioceptors
- Sensory receptors involved with movement, position, and respiration
- Sends a message to respiratory muscles to increase ventilation
Describe the events that occur in respiration during moderate exercise
- pO2 and pCO2 remain relatively normal
- Hyperventilation occurs, where breathing is faster
- Increase in CO2 release from cells, resulting in an increase in ventilation:
o Leads to increase in [H+], detected by central
chemoreceptors found on the medulla, which
sends a signal to respiratory muscles
o To clear excess CO2 - But this increased ventilation will plateau once the excess CO2 is cleared
Describe the events that occur in respiration during strenuous exercise
- Unable to meet oxygen demands, even with hyperventilation
- Anaerobic respiration starts
- Increase in body temperature + metabolic production of acid leads to further increases in ventilation
- Breathing is faster (increase in respiratory rate) and deeper (increase in tidal volume – more O2 taken in with each breath)
- Aim is to maintain arterial pCO2 (within range)
- Massive increase in ventilation (5-6l/min to 120l/min)
Describe some cardiovascular adaptations to exercise
When we exercise, the heart beats harder and faster
We get peripheral vasoconstriction:
- Skeletal muscles will contract and compress blood vessels
- This moves blood to organs like the heart and lungs (from peripheral vessels)
- This increases cardiac output
So, cardiac output and blood flow to active muscles increases during exercise
Describe adaptations in respiration to high altitude
At high altitude, there is a significant drop in barometric partial pressure
- it affects pO2 (at Mt. Everest - 5.8kPa)
So, one can be susceptible to hypoxia at a high altitude
Define hypoxia
Hypoxia -
- Inadequate delivery of oxygen to body tissues
Describe changes in respiration to acute exposures of hypoxia (from high altitude)
Acute hypoxia is detected by peripheral chemoreceptors, which try to increase breathing:
- As ventilation increases, arterial pCO2 falls, and CSF becomes alkaline
- So, this means if we need more O2, we breathe more, but then pCO2 falls, altering the acid/base balance, increasing pH
The system is trapped: - Breathe more = more O2, less CO2 > BUT (die from alkalosis) - Don't breathe less = less O2, more CO2 > BUT (die from hypoxia)
Describe changes in respiration to chronic exposures of hypoxia (from high altitude)
Mild hypoxia (activates peripheral chemoreceptors) - less pO2, increased ventilation, so less pCO2
- Less pCO2 - increases CSF pH (alkaline), this increases [HCO3-]
- Choroid plexus cells export HCO3- from CSF in order to correct pH
- Hypoxic drive is re-instated, and ventilation increases further
Oxygen carrying capability of blood is increased with adaptations like:
- Increased 2,3-diphosphoglycerate (2,3DPG)
- Polycythaemia - the body will also produce more red blood cells at high altitude
Cardiac output is increased + directed to vital organs
Systemic acid/base imbalance is corrected (increased urination - more HCO3- excreted)
THERE IS A LIMIT - ONLY EFFECTIVE UP TO 5,500m
Explain what occurs in the next few hours following chronic exposures to hypoxia at a high altitude
HOURS: breathing is controlled around lower pCO2, with increased ventilation from the hypoxic drive
- All around an environment that has become more alkaline
Explain what occurs in the days following chronic exposures to hypoxia at a high altitude
DAYS: alkalinity of the blood is corrected by excretion of HCO3- in urine
- To compensate + correct the acid/base imbalance (so, increased rate of urination)
Describe what happens in the body during descent following chronic exposure to hypoxia at high
On the descent, one can suffer left upper quadrant (abdomen) pain due to enlargement of the spleen (splenomegaly), as it breaks down excess RBC’s (no needed)
List some cures of chronic hypoxia (from high altitude)
Only cures are:
- Acclimatisation
- or Descent
