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Physiology Flashcards

1
Q

CSF flow

A 
Lateral ventricle —>
Interventricular foramen of Munro —>
3rd ventricle —> 
Aqueduct of Sylvius —>
4th ventricle —>
Medial and lateral Foramina of Magendie and Luschka —>
Subarachnoid space
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2
Q

Air embolism

A

Gold standard for detection is TOE

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3
Q

Blood flow during exercise

A

Blood supply to skeletal muscle increases from 1-4ml/100g/min at rest to 50-100ml/100g/min at exercise
Main mechanism is local autoregulation - hypoxia, hypercarbia, NO, K ions, adenosine and lactate
Overrides the sympathetic-driven vasoconstriction

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4
Q

Anterior pituitary hormones

A

Are glycoproteins which share a common ALPHA subunit and have unique BETA subunits

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5
Q

Shunt in pregnancy

A

15% in lateral position

14% in supine position

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6
Q

Starling forces in the lung

A

Interstitial oncotic pressure = 17mmHg
Capillary hydrostatic pressure = 13mmHg (arteriolar end), 6mmHg (venous
end)
Interstitial hydrostatic pressure = 0 to slightly negative
Capillary oncotic pressure = 25mmHg

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7
Q

Intracellular ions

A 
Potassium 150mmol/L
Phosphate 100mmol/L
Magnesium 20mmol/L
Sodium 15mmol/L
Chloride 10mmol/L
Calcium 100nnmol/L
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8
Q

ASA grades

A 
I = healthy, non-smoking, minimal/no alcohol consumption 
II = mild, well-controlled systemic disease without symptoms. Includes: pregnancy, BMI 30-40, smoker, social alcohol consumption, well-controlled lung disease, HTN or DM
III = moderate to severe systemic disease with substantive functional limitations. Includes BMI >40, COPD, poorly controlled HTN/DM, alcohol dependence, pacemaker, reduced EF, hepatitis 
IV = severe systemic disease that is a constant threat to life e.g. CVA/TIA/MI in past 3mths, stents, IHD, severely reduced EF, sepsis etc
V = moribund patient not expected to survive without operation 
VI = brain-dead organ donor
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9
Q

IV fluids

A 
3% NaCl - 513mmol/L Na
5% NaCl - 856mmol/L Na 
0.9% NaCl - 154mmol/L Na 
Hartmanns- 131mmol/L Na
0.45% NaCl + 5% Glucose - 77mol/L
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10
Q

TBW in neonates

A

Approx 75% of total body weight

Higher circulating volume per unit mass and lower percentage body fat than older children

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11
Q

Solubility of CO2 in blood

A

Solubility factor = 0.03mmol/L/mmHg or 0.225mmol/L/kPa at 37’C
20x more soluble than O2
0.5ml/kPa in 100mls of blood = 3mls per 100mls in venous blood (PCO2 6.1kPa) and 2.5mls per 100mls arterial blood (PCO2 5.3kPa)
Henry’s Law: number of particles in solution is proportional to the partial pressure at the liquid surface
Content is higher in deoxygenated blood than oxygenated blood at a given PCO2 because reduced Hb is a better buffer of H ions as it is less acidic (Haldane Effect)

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12
Q

Changes in pregnancy

A

Total blood volume increases
Plasma volume increases proportionately more than red cell volume so Hb decreases
Hct and packed cell volume decrease
Increased production of T3 and T4 and TBG so plasma conc of free thyroid hormones remains constant

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13
Q

Changes with hypothermia

A 
Decreased insulin production so hyperglycaemia can occur 
Decreased P50 of Hb 
Increased myocardial irritability 
Decreased coagulation 
Decreased metabolic rate
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14
Q

Calcium

A

Normal plasma conc = 2.5mmol/L
At higher pH, plasma proteins become ionised and bind more Ca so free ionised Ca conc decreases
Extracellular, unbound Ca influences PTH secretion

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15
Q

Iron

A

Is bound to transferrin in its ferric form (Fe3+)
2 molecules carried per transferrin molecule
Daily loss in a man is 0.5-1mg mainly in the faeces
Iron deficiency —> hypochromic microcytic anaemia

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16
Q

Pseudocholinesterase

A 
Found in:
Plasma 
Placenta 
Kidney
Brain 
Pancreas

Synthesised in the liver

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17
Q

Rate dissociation of water

A

Is 10^-14 = [H+] x [OH-]

So [H+] is 10^-7 mol/L

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18
Q

Blood supply to different organs

A

Brain: 50ml/100g/min

Carotid bodies: 2000ml/100g/min

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19
Q

Meissner’s corpuscles

A

Rapidly adapting cutaneous mechanoreceptors which respond to light touch

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20
Q

Uric acid

A

Is filtered by the glomerulus

Reabsorbed and secreted by PCT

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21
Q

Surgical 3rd nerve palsy

A

Causes pupillary dilatation due to compression of parasympathetic supply to pupil

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22
Q

CSF composition

A

Protein conc 0.5% of plasma protein conc
Lower pH due to reduced protein buffering
Higher chloride conc to maintain electro neutrality

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23
Q

Closing capacity

A

Does not change with position

But FRC increases on standing so CC less likely to encroach on FRC

24
Q

ODC

A

Shifted to the right in anaemia to facilitate offloading of O2
Cannot he used to determine oxygen carrying capacity

25
Kety-Schmidt technique
Measures CBF using difference between arterial and venous conc of a tracer eg N2O
26
Aldosterone
Causes water and Na retention in equal amounts so does not change urine osmolality
27
Changes during exercise
CO increase 5-10x Skeletal muscle blood flow increase 20-30x due to precapillary sphincter relaxation by local auto regulation Partial pressure gradient for O2 into mitochondria increases x2 O2 offloading from Hb increase 2-3x
28
SVR
= k (MAP - CVP) / CO
29
Cardiac AP
Takes 0.2s to travel through atria Conduction is slowest at the AVN Travels between atria via Bachmann’s bundle
30
Circulatory changes at birth
1st breath generates negative pressure of 50cmH2O PVR falls by >80% so increased PA pressure and increased blood flow to LA DA closes due to increased O2 levels and low PG within 24hrs PFO fuses within 48hrs due to reversal in atrial pressures SVR and MAP increase Blood flow in IVC falls (due to loss of placenta blood supply) Hypoxia, hypercarbia, acidosis and hypothermia will increase pulmonary vascular resistance and cause a right to left shunt or persistent foetal circulation
31
Atrial stretch receptors
Type A discharge during systole | Type B discharge during diastole
32
Increase in atrial pressure
Can increase HR via Bainbridge reflex can decrease HR via baroreceptor reflex Increase/decrease depends on initial HR (will decrease if high, increase if low)
33
Atrial contraction
Right atrium contracts before left atrium
34
Ventricular contraction
LV contracts before RV
35
Afterload
= the tension developed in the ventricular wall during systole Anrep effect increases SV when afterload is high by increasing LVEDV Likely to be low in heart failure due to low intraventricular pressure Higher in a hypertrophied ventricle because of increased radius (La Place’s Law: P = 2T/r)
36
Electrolyte abnormalities and cardiac function
Hypokalaemia makes the membrane potential more negative so it is less excitable but has more automaticity and increases QT interval Hyperkalaemia makes the membrane potential less negative so it is closer to TP Hypercalcaemia makes the TP less negative, decreases conduction velocity and shortens refractory period Hypermagnesaemia increases PR interval
37
2,3-DPG
Binds to beta chains of Hb Formed in RBCs from a byproduct of glycolysis Thyroid hormones, GH and androgens increase levels
38
Aortic valve opening
Occurs when ventricular pressure > aortic pressure, 80mmHg
39
Left ventricle
Is 3x thicker than RV | Has papillary muscles on the MV but not aortic valve
40
Veins and venules
Capacitance vessels Hold 2/3 of the circulating volume Venules have a diameter of 0.01-0.2mm Veins have diameter of 0.2-5mm Easily distensible walls so very compliant between 0 and 10mmHg blood entering venules has pressure of 12-20mmHg Blood entering veins has pressure of 10mmHg
41
Bohr Equation
VD/VT = PaCO2 - PECO2/PaCO2
42
Lung metabolises
``` Bradykinin Noradrenaline Serotonin PGE2 and F2a Leukotrienes ATI —> ATII ```
43
Blood flow to different organs
Coronary blood flow = 5% CO, 250ml/min Renal blood flow = 25% CO, 1.2L/min, 500ml/min/100g Cerebral blood flow = 15% CO, 700ml/min, 50ml/min/100g (majority to grey matter) Hepatic blood flow = 25% CO (75% from HPV, 25% from hepatic artery)
44
Muscle spindles
Sense muscle length so respond to stretching/contraction of muscles When they are stretched, they fire via type Ia or II fibres to efferent gamma-motor neurones These can be altered by descending pathways in the spinal tract Involved in polysynaptic withdrawal reflex
45
Swallowing
Involuntary process Triggered by bolus of food moving into back of the mouth and sensed by swallowing receptors The most sensitive are the tonsillar pillars Soft palate is pulled up Larynx is pulled up and anterior by the neck muscles Epiglottis covers the opening of the larynx Palatopharyngeal folds are pulled medially to prevent larger food pieces from passing Upper oesophageal sphincter relaxes Whole process takes 1-2seconds
46
Cholecystokinin
Peptide hormone Produced in the duodenal mucosa by enteroendocrine cells Production triggered by fats and proteins Slows GI transit time to increase digestion of fats Causes release of digestive enzymes from pancreas and bile from gallbladder Reduces gastric acid secretion Increases satiety
47
Drugs excreted unchanged in the urine
``` Aminoglycosides Cephalosporins Ephedrine Digoxin Lithium Milrinone/mannitol Neostigmine Oxytetracycline Pencilling ```
48
Lipid metabolism
90% ingested lipids are triglycerides 10-30% are broken down in the stomach, the rest in duodenum and upper jejunum Bile salts are solubilising agents for fats and aid absorption
49
Cerebral metabolic rate
Increases by 8% for every 1’C increase in temperature
50
Lactate
Produced from pyruvate in anaerobic metabolism So 2 molecules produced from 1 glucose Lactate level rises sharply at 50-80% of VO2 max - in untrained people, lactate level rises sooner 80% is converted back to glucose in the liver via the Cori cycle Filtered by the kidneys and reabsorbed to a Tmax of 75mg/min
51
Glucagon
Stimulated by: cortisol, infection, theophylline, PDE inhibitors Inhibited by: alpha stimulation, insulin, glucose, ketones, phenytoin and somatostatin
52
Ranitidine
Increases pH and decreases volume of gastric secretions IV dose is 50mg Not an enzyme inhibitor (unlike cimetidine)
53
Barbiturates
Alkalosis increases duration of action because tautomerisation from keto to enol form occurs at higher pH and makes the drug more lipid soluble Excreted more readily when the urine is alkalinised
54
Thiopental
``` 2mins post IV dose - in vessel-rich tissues 4mins - in muscle 7mins - in fatty tissue Slowly recirculates (half life 8.4hrs) Can cause demyelination in porphyria ```
55
Heavy bupivicaine
0.5% bupivicaine + 8% dextrose

Primary FRCA (3 decks)

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