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
Muscles for inspiration
1) normal inspiration: diaphragm+external intercostal
2) forced inspiration:
Sternocleidomastoid+ serratus anterior+scalene muscles
Muscles for expiration
1) normal: passive -elastic recoil
2) forced expiration: internal intercostal+abdominal muscles+triangularis sterni
Tidal volume
Alveolar ventilation+dead space
Alveolar ventilation
5 l/min
Anatomic dead space
100-150 ml
Alveolar O2 tension
Inspired O2 tension- alveolar CO2 tension/expiratory exchange range
Pulmonary vascular resistance
1) (mean pulmonary pressure - left atrial pressure)/ cardiac output
2) 0.25-1.6 mmHg*min/L
The major stimulus for HYPOXIC PULMONARY VASOCONSTRICTION
low alveolar oxygen tension (PAO2)
Fick’s low
Vx=DADelta P/Delta X
Vx volume of gadgets transfer from membrane
D- coefficient
A -square
Delta P- partial pressure difference of gas across the membrane and
Delta X is the membrane thickness
Vascular resistance
(Mean arterial pressure-venous pressure )/ cardiac output
Norma of pulmonary vascular resistance
< 1.5 wood unit( WU)
PVR> 2WU-indicated of pulmonary vascular disease
Norma of middle pulmonary artery pressure
10-20 mmHg
Effects of GA on V/Q relationship
1) muscle relaxation => lost tonic activity => decrease FRC 10-30%=> Closing capacity >FRC =>atelectasis => areas perfused, not ventilated
2)GA=> low CO and pulmonary hypertension =>reduced perusing in non dependent region
Dorsal respiratory group of respiratory center
1) close to the nucleus tractus solitarius
2) mainly inspiratory neurons
3) responsible for timing of the respiratory cycle
Ventral respiratory group of respiratory center
1) caudal group:
1. Inspiratory +expiratory neurons
2. Controlling the force of contraction of the contralateral Inspiratory muscles
2) rostal group nucleus ambiguous
1. Controlling airway dilatation, function of the larynx, pharynx, tongue
3) pre-Botzinger complex
1. Central pattern generation
Neurotransmitters for central pattern generation
1) expiratory: glutamate (NMDA+nNDMa)
2) inhibitory: glycine +GABA
Alveoli
300 mln in adults lungs, 0,3 mm in diameter at FRC, the wall of alveoli 0,5 mcm
Ventilation/perfusion ratio (V/Q)
0.8
The Paintal juxtapulmonary capillary receptor (J receptor)
1) type of sensory receptor in the alveolar, specifically within the pulmonary capillaries and interstitial tissues.
2) sensitive to changes in increases in interstitial fluid volume, pulmonary capillary pressure, and the presence of certain chemical stimuli.
3) stimulated-can induce rapid shallow breathing, apnea, or a combination of both, depending on the intensity and nature of the stimulus.
Chemical+irritant receptors in the nasopharyngeal, larynx, trachea
1) stimul: smoke, gastric acid
2) reflex: coughing, laryngeal closure, apnea, bronchoconstriction
Pulmonary stretch receptors
1) slowly adapting stretch receptors:
1. In bronchial smooth muscle
2. Stimul: lung inflation
3. Volume sensor
2) rapidly adapting stretch receptors
1. Superficial mucosal layer
2. Stimul: change TV, RR, lung compliance
3. Inhibition of inspiration in response to lung distention+ reduce RR by increasing expiratory time
Residual volume
20 ml/kg
Expiratory reserve volume
15 ml/kg
Inspiratory reserve volume
45 mlkg
Dead space ventilation with facemask
+32-42% of physiological dead space
P transpulmonary
P airway-P pleuraly
Compliance of respiratory system
Delta V/Delta P
Compliance normal level
0.2-0.30 l/cmH2O
