Physiology Flashcards
Partial pressure of oxygen (Pa O2) in normal arterial blood
100 mm Hg
Partial pressure of oxygen in mitochondrion
4-22 mmHg
Delivery of O2 (DO2)
DO2=CaO2*Q
CaO2 arterial blood content
Q- blood flow (cardiac output)
Arterial blood content (Ca O2)
CaO2=1,34HbSaO2+0.003*PaO2
causes of hypoxemia
1) alveolar hypoventilation
2) diffusion impairment
3) ventilation -perfusion mismatch
4) right -to-left shunt
Cardiovascular system and magnesium
1)Direct depressant effect on myocardial and vascular smooth muscle.
2) Inhibits the release of catecholamines from the adrenal medulla, peripheral adrenergic terminals and directly blocks catecholamine receptors.
3) As a result, cardiac output and vascular tone are reduced resulting in hypotension and decreased pulmonary vascular resistance.
4) Anti-arrhythmic: slows the rate of impulse formation at the SA node and prolongs SA conduction, the PR interval and the AV node refractory period
Nervous system and magnesium
1) Reduces the release of acetylcholine at the neuromuscular junction by antagonising calcium ions at the presynaptic junction.
2) Causes reduced excitability of nerves
3) Anticonvulsant.
4) Reverses cerebral vasospasm
Musculusaletal system and magnesium
1) Involved in terminating contraction, initiating relaxation in skeletal muscles
2) In combination with the effects above excessive plasma concentrations can cause muscle weakness
Respyratory system and magnesium
1) Magnesium is an effective bronchodilator but does not affect respiratory drive.
2) Respiratory failure may occur as a result of excessive muscle weakness
Geniito_urinary system and magnesium
1) Powerful tocolytic, decreasing uterine tone and contractility
2) Mild diuretic properties.
Heamatalogical system and magnesium
Platelet activity is reduced resulting in prolonged bleeding time.
Global CBF
45-55 ml/100 g/min
Cortical CBF
75-80 ml/100g/min
