Response to Being Stranded Flashcards
What is the short term response to blood lose?
Baroreceptor reflex
What is the medium term response to blood loss?
Anti-diuretic hormone, aldosterone and angiotensin 2 (promotes secretion of the previous two) are all involved in retaining water to increase blood volume
What is the long term response to blood loss?
Erythropoetin stimulates bone marrow to produce red blood cells
What is the problem with being at a higher altitude in terms of PO2?
The atmopsheric pressure of air is lower so therefore the partial pressure of oxygen in the arterial blood is lower
Why would the respiratory rate increase at high altitude?
Activation of the peripheral chemoreceptors by hypoxic drive (oxygen receptors rather than carbon dioxide receptors are activated)
Apart from in long term response to blood loss when else is erythropoetin secreted?
Due to chronic hypoxia at high altitude
What happens to haemoglobin at high altitude?
Since PO2 is decreased the % of hb saturated with oxygen decreases as it is being released
What causes the release of oxygen from Hb?
Increased secretion of 2-3 bisphosphoglycerate
What secretes BPG?
Red blood cells produced it as a by product in metabolism
At a given PO2 what % oxygen release do high levels of BPG cause?
10%
What causes the increase in BPG levels in red blood cells at altitude?
Thyroid and growth hormones
Why would an increase is BPG be beneficial at high altitude?
Increase O2 delivery to the tissues
What is the long term response to injuries i.e. fractures
Secretion of cortisol
What is cortisol?
A glucocorticoid that promotes glucose production, mutes the immune system and increases reponse to catecholamines and angotension II
What are the initial responses to cold conditions?
Peripheral vasoconstriction to prevent blood cooling and shivering to make muscles generate heat
What eventually happens after a long time of cold exposure?
Vasodilation when constriction is reduced
What are the consequences of lack of protein due to starvation?
Breakdown of protein from the liver and skeletal muscles (spares the heart and brain)
What are the consequences of lack of carbohydrates due to starvation
Gluconeogensis (converts protein to glucose) caused by glucagon
What happens once carbohydrate stores have been depleted?
Fats are broken down into fatty acids and ketone bodies (starvation ketosis)
What does lowered plasma glucose cause in times of starvation?
Glucagon secretion to promote glucose breakdown from protein and promotes fat breakdown
Why is fat breakdown beneficial?
Produces keto acids to be used by the brain
Why cant you drink salt water?
because it is so concentrated when you drink it it increases the osmolarity of the blood and draws blood out of the cells which shrinks them and cause mlafunction
Why cant you drink large amounts of water?
Dilutes plasma electrolytes and water entering cells are the extracelluar water conc is higher than the intraceullar which results in cell swelling and in the brain leads to swelling and death
Why are marathon runners particulary at risk when it comes to drinking too much water?
Cause they are already losing their plasma electrolytes through their sweat
What is the problem with breathing air higher than normal atmospheric pressure?
Henrys law states more gas will be dissolved if the pressure is higher - if this is rapid bubbles can form in solution (decompression)
What is the consequence of decompression bubbles?
Joint pain and if the CNS is affected cause lead to paralysis and death
What type of people have the most problem with decompression sickness?
Divers when they are ascending back to the surface
How would divers avoid decompression sickness?
Rising back up slowly with breaks and then going into a hyperbaric chamber
What depth of water is twice atmospheric pressure?
10m deep
What is another problem apart from decompression involved in breathing air under high pressure?
N2 Narcosis
What is N2 Narcosis?
Nitrogen is an inert gas but at high pressures have anaesthetic effects
How do deep sea divers get around n2 narcosis?
They use helium which is inert even at high pressure
