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FRCA Guide Qs 2003 > Physiology 2003 > Flashcards

Physiology 2003 Flashcards

1
Q

What does the resting potential of a nerve fibre depend on?

A

The electronegative charge in the interior of the nerve

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2
Q

What happens to the RMP of a nerve fibre when extracellular potassium increases?

A

The RMP will become more positive

(ratio of extracellular to intracellular potassium will fall, hence it’s Nernst potential will become less negative with respect to the inside of the cell)

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3
Q

Do local anaesthetics alter RMP?

A

No, they impair passage of ions and reduce membrane excitability

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4
Q

What does acetylcholine do to RMP?

A

It does not affect the RMP of nerve fibres

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5
Q

What converts AMP to ADP?

A

Adenylate cyclase

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6
Q

What does phosphorylase do?

A

Enzyme responsible for breakdown of glycogen.

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7
Q

Is cAMP secreted by the adrenal medulla to breakdown glycogen?

A

No. Glucagon and adrenaline activate the enzyme phosphorylase via cAMP - this breaks down glycogen.

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8
Q

Where is cAMP found?

A

All cells

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9
Q

What will increase oxygen content of blood at a given partial pressure of oxygen?

A

An increased haematocrit usually denotes an increased Hb - which indicates an increased ability to bind oxygen.

Factors that increase metabolic demand (raised temp, low pH - also caused by a high PaCO2) and/or a relative shortage of O2 will assist in offloading O2 from Hb, usually in peripheral tissues.

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10
Q

How does pregnancy affect insulin requirement?

A

Increases it

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11
Q

What is closing capacity?

A

The lung volume at which airways begin to close, reflecting earlier closure of the smaller, dependent lung units.

It increases with age, is unaffected by body position and decreases with FRC at the onset of anaesthesia.

Measured with single breath tracer technique. CC is the point where there is an increase in tracer.

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12
Q

What does calculation of intrapulmonary shunt require?

A

Shunt fraction = (pulmonary end capillary O2 content - arterial O2 content) / (pulmonary end capillary O2 content - mixed venous O2 content)

O2 content of a given blood volume comprises both O2 bound to Hb and that dissolved in plasma. This requires partial pressure of O2, oxygen saturation and the Hb concentration to be known.

Since pulmonary end capillary O2 tension cannot be measured directly it can be estimated from alveolar O2 tension.

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13
Q

What does the pressure in the SVC reflect?

A
  • blood volume
  • right ventricular contractility

SVC varies with circulating blood volume and right atrial pressure, which in turn will reflect right ventricular pressure. RV pressure will depend on efficiency of ejection, determined by right ventricular contractility.

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14
Q

What does intrapleural pressure change with?

A

It’s negative at FRC, more so at the apices (-10cmH20) than the bases (-2.5cm) in the upright position due to gravity acting on the lung.

The intrapleural space is negative pressure and is empty with no gas.

Balloon placed in the lower 1/3 of oesophagus can reflect intrapleural pressure at that level.

During forced expiration the contraction of the chest wall causes a rise in intrapleural rpressure to positive values.

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15
Q

Distribution of ventilation in the lung of an upright subject is related to what?

A
  • regional airway diameters
  • regional differences in compliance
  • gravitational forces on the lung
  • intrathoracic pressure

NOT inspired O2 concentration.

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16
Q

How does exercise affect FRC?

A

Increases FRC due to sustained tone in the inspiratory muscles which raises FRC and decreases airways resistance.

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17
Q

How is convection decreased?

A

If air next to the body is warm

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18
Q

What type of heat loss would aluminium foil blankets reduce?

A

Radiation

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19
Q

How is sweating affected if relative humidity increases?

A

The cooling effect of sweating is decreased

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20
Q

Is molecular CO2 freely diffusible?

A

Yes, it diffuses passively down it’s concentration gradient.

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21
Q

Is carbonic anhydrase essential for CO2 transport?

A

It would result in a marked increase in alveolar/capillary PCO2 gradient, but it’s not essential in CO2 transport.

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22
Q

Does the transport of bicarbonate into and out of erythrocytes require energy?

A

No, it is not active transport as it is not against a concentration gradient and no energy is consumed

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23
Q

How is carbamino-Hb formed?

A

By Co2 linkage with the N-terminal or side chains of amino groups (NH2) of blood proteins

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24
Q

What is Henry’s law of solubility?

A

The higher the temperature, the less gas dissolved in solution, therefore solubility of CO2 will decrease with temperature

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25
Q

Why are the heat conservation mechanisms of the newborn less effective than adult?

A
  • have poor vasomotor control
  • cannot shiver
  • have little subcut fat
  • have higher surface area to weight ratios
  • have immature hypothalamus
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26
Q

In the uteroplacental unit in pregnancy, how is fetal oxygenation determined?

A

It is impaired if the maternal OxyHb curve shifts to the LEFT as in maternal repiratory alkalosis, or if there is a shift in the fetal Hb curve RIGHT as in fetal acidosis.

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27
Q

What is the normal uterine blood flow at term?

A

>700 ml/min

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28
Q

What maintains placental blood flow?

A

NOt autoregulated, an adequate maternal blood pressure must be delivered to the uterus to maintain the uteroplacental circulation.

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29
Q

Is fetal oxygen extraction dependent on fetal demands?

A

No, the umbilical artery carries relatively deoxygenated blood from the fetus to placenta for oxygenation.

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30
Q

What will happen when a healthy adult breathes through a wide bore 300mm tube?

A
  • the ventilatory response is directly proportional to the increase in PaCO2
  • the response is mediated by both the peripheral and central chemoreceptors
  • tube increases anatomical Vd and leads to rebreathing
  • mixed venous PCO2 is >end tidal CO2
  • hyperventilation will not increased PaO2
  • ventilatory response won’t be limited by increased resistance (wide bore tube)
  • response is mediated by both peripheral and central chemoreceptors (peripheral accounts for <20% of response)
31
Q

What is surfactant made of?

A

62% phospholipidm dipalmitoylphosphaditylcholine (DPPC) and is secreted by type 2 pneumocytes.

DPPC molecules are hydrophobic at one end and hydrophilic at the other. The intermolecular repulsive forces oppose the normal attracting forces between the surface molecules that are responsible for surface tension.

32
Q

How is surfactant affected at low lung volumes?

A

It will reduce the surface tension even more because the molecules of DPPC are then crowded, close together and repulse each other more.

33
Q

What happens to the alveolar partial pressure of carbon dioxide during normal breathing?

A
  • it is equal to end-capillary pCO2 at rest
  • relationship between PCO2 and alveolar ventilation is hyperbolic, not linear
  • during inspiration inspired gas dilutes alveolar gas and alveolar CO2 falls by about 0.4 kPa
  • CO2 output varies with cardiac output
  • alveolar CO2 may not be calculated solely from CO transfer factor
34
Q

Which of the following will increase GI intraluminal pressure?

  • enflurane
  • morphine
  • suxamethonium
  • neostigmine
  • adrenaline
A
  • morphine
  • suxamethonium
  • neostigmine (increases ACh and hence promotes muscarinic effects)
35
Q

The mixed venous return from the following organs is likely to have an O2 content less than mixed venous blood?

  • heart
  • brain
  • kidney
  • liver
  • resting skeletal muscle
A
  • heart
  • brain (these two extract > 5ml/dl )
  • liver (65% of it’s blood supply is venous blood from the gut via the hepatic portal vein)
36
Q

What is the usual mixed venous oxygen content of blood compared to arterial blood?

A

Mixed venous = 15ml/dl

Arterial = 20ml/dl

37
Q

What will the adrenal cortex produce aldosterone in response to?

  • ingestion of sodium chloride
  • increased blood volume
  • increased potassium intake
  • angiotension II
  • surgery
A

FFTTT

38
Q

What will happen if you breathe oxygen 100% at 3 atmospheres for long periods?

A
  • convulsions
  • damage to alveolar membranes
  • an alveolar partial pressure of more than 240kPa
  • O2 carrying capacity will only increase by 6ml/100ml of blood as it is only the dissolved oxygen which can increase in proportion to inspired partial pressure - Hb is nearly 100% saturated in normal conditions
39
Q

In the cardiac cycle the:

  • phase of isometric contraction begins when the aortic valve opens
  • end-diastolic pressure is the same in both ventricles
  • duration of PR interval is linearly related to the HR
  • duration of diastole is reduced when the HR is increased
  • ventricular systole extends from the Q wave to the S wave of the ECG
A

FFFTF

  • PR interval inversely related to HR
  • ventricular systole starts near the end of the R wave and ends just after the T wave
40
Q

What muscles are active in forced expiration?

  • diaphragm
  • external oblique
  • internal oblique
  • rectus abdominus
  • scalenus anterior
A

FTTTF

41
Q

FRC:

  • decreases on standing upright
  • increases in COPD
  • is increased in obese subjects
  • if less than closing capacity leads to regional hypoventilation
  • is measured by helium dilution
A

FTFTT

42
Q

Parathyroid hormone:

  • increases plasma calcium concentration
  • secretion is regulated by the plasma concentration of ionised calcium
  • enhances resorption of calcium from bone
  • is a mucopolysaccharide
  • increases the urinary output of phosphate
A

TTTFT

  • PTF is a polypeptide with 84 amino acid residues

PTH is secreted in response to low plasma calcium levels

  • it mobilises calcium from bone, increases urinary phosphate excretion and bioactivates Vit D
  • it also enhances conversion of 25-hydroxycholecalciferol to 1, 25 in the kidney and increases reabsorption of calcium in the DCT
43
Q

In red cells, iron in Hb is retained in the reduced ferrous form by:

  • EPO
  • reduced glutathione
  • hexokinase
  • NADH methaemoglobin reductase
  • pyruvate kinase
A

FTFTF

44
Q

Axons:

  • are classified by conduction velocity
  • connecting sympathetic ganglia to the cord are unmyelinated
  • arising from the alpha motor neurones have large diameters
  • can conduct impulses in either direction
  • are absolutely refractory during the period of increased potassium conductance
A

TFTTF

45
Q

The following are true or follow Starling’s Law of the Heart:

  • increased end diastolic volume increases stroke volume
  • increased ventricular fibre length increases the force of contraction of ventricular muscle
  • increased atrial fibre length increases the force of contraction of atrial muscle
  • the duration of systole is decreased when the stroke volume increases
  • the law operates less efficiently in the denervated or partially denervated heart
A

TTTFF

46
Q

Left atrial pressure is:

  • directly related to pulmonary artery diastolic pressure
  • higher than pulmonary artery mean pressure
  • normally greater than 15mmHg
  • lower than left ventricular end diastolic pressure
  • directly related to central venous pressure
A

TFFFF

47
Q

Calculation of SVR requires measurement of:

  • coronary blood flow
  • stroke volume
  • MAP
  • cardiac output
  • rate of peripheral arteriolar flow
A

SVR = (MAP - CVP)/CO x 80

FFTTF

48
Q

A sudden, powerful passive stretch of a group of muscles will:

  • activate golgi tendon organs
  • directly stimulate fusimotor endings in the muscle spindles
  • dissociate the motor unit
  • inhibit the dynamic response of muscle spindle secondary (flower spray) endings
  • cause clonus
A

TFFFT

Golgi tendon organs register tension in muscles. They have a rapidly adapting dynamic response.

The secondary endings do not have a dynamic response.

The fusimotor endings are of the gamma efferents onto the intrafusal muscle fibres, whose tension regulates the sensitivity of the spindle. Cannot be affected directly by stretch.

49
Q

Prolonged passive hyperventilation results in:

  • diminuation in CSF lactic acid content
  • displacement to the left of the O2Hb curve
  • increased urinary pH
  • increased mixed venous PCO2
  • cutaneous vasodilatation
A

FTTFF

50
Q

A diver breathing air at 30m underwater:

  • is exposed to a pressure of 4 atmospheres absolute
  • becomes unconsious from nitrogen narcosis
  • has a 3 fold increase in O2 content of blood
  • expends more energy on work of breathing than at the surface for a given ventilation
  • runs the risk of developing gas bubbles in the CNS while at this depth
A

TFFTF

  • the gas mix is 4 times denser at this depth, the inertia of the demand valve is increased and must be overcome and pulmonary pooling of blood occurs
51
Q

Alveolar:

  • dead space exceeds tidal volume at rest
  • ventilation decreases as tidal volume increases
  • partial pressure of water vapour exceeds that of CO2
  • partial pressure of O2 falls with an increase in physiological dead space
  • oxygen uptake exceeds alveolar CO2 output
A

FFTFT

52
Q

Voluntary (skeletal) muscle:

  • contracts because the A bands shorten
  • contracts from release of calcium from SR
  • contracts isometrically when a load is lifted
  • develops max tension at it’s resting length
  • can acquire energy for contraction from anaerobic metabolism
A

FTFTT

  • A bands are myosin filaments, between which the actin filaments slide
  • isometric means contraction without muscle shortening
53
Q

Glucose:

  • concentration in normal fasting human blood is 4-7 mmol/l
  • is produced by enzymatic breakdown of glycogen in skeletal muscle
  • is converted to glucose- 1-phosphate by action of hexokinase
  • has the same concentration in plasma and glomerular filtrate
  • is converted to glycogen in the liver
A

TTFTT

-hexokinase converts it to glucose-6-phosphate

54
Q

CSF:

  • is secreted by arachnoid villi
  • has a lower osmotic pressure than plasma
  • absorption depends on the action of the Pacinian corpuscles
  • production is independent of CSF pressure
  • secretion is about 500ml per day
A

FFFTT

55
Q

Hepatic blood flow

  • decreases during halothane anaesthesia
  • is primarily venous
  • decreases during IPPV
  • is unaffected by spinal anaesthesia in the absence of hypotension
  • preferentially perfuses the centrilobular vessels
A

TTTTF

56
Q

The following are true of sinus arrhythmia:

  • there is a varying of the PR interval
  • there is a varying RR interval
  • it is most marked during breath holding
  • it is more marked at age 70 than 20
  • it is more marked during exercise than rest
A

FTFFF

57
Q

In aerobic metabolism

  • substrate utilisation requires the presence of molecular O2
  • lactate enters the krebs cycle directly
  • oxidative phosphorylation of ADP to ATP occurs only in the mitochondria
  • the hexose-monophosphate shunt is an alternate pathway of glycolysis
  • acetyl coA may mediate the conversion of lipids to glucose
A

TFTTF

58
Q

Calcium:

  • is necessary for absorption of vit D in gut
  • is necessary for blood coagulation
  • is absorbed through the stomach
  • is necessary for release of ACh from motor nerve endings
  • is taken up by actin during skeletal muscle contraction
A

FTFTF

  • VIt D increases calcium absorption in intestinal tract
  • except for the first 2 steps in the intrinsic pathway, calcium ions are required for promotion of all reactions
  • the brush border of the SI (not present in stomach) contains calcium binding protein which transports calcium into the cell cytoplasm
  • troponin C reversibly binds calcium ions
59
Q

Bilirubin

  • is derived from Hb breakdown
  • in the unconjugated form is carried in plasma bound to albumin
  • in the unconjugated form is excreted in the urine
  • blood levels of the conjugated form are increased in haemolytic anaemia
  • has a steroidal molecular structure
A

TTFFF

  • conjugated bilirubin binds to albumin much more weakly than unconjugated, and can therefore be filtered at glomeruli
  • haemolytic anaemia results in overproduction of unconjugated bilirubin
60
Q

Glucose:

  • can be synthesised in the brain
  • when metabolised aerobically yields one molecule of carbon dioxide per molecule of oxygen used
  • stimulates the secretion of glucagon by the pancreas
  • can be synthesised from lactate in the liver
  • has a higher concentration in cerebrospinal fluid than plasma
A

FFFTF

61
Q

Characteristic findings in a pregnant woman at 36 weeks would include:

  • a PaO2 greater than in non-pregnant state
  • an increase in FRC
  • decreased O2 consumption
  • a BE of + 10 mmol/l
  • a PaCO2 of 6kPa
A

TFFFF

62
Q

Compared with intracellular fluid, the interstitial fluid contains a greater concentration of:

  • sodium ions
  • magnesium
  • protein
  • hydrogen ions
  • bicarbonate ions
A

TFFFT

63
Q

The following release ACh:

  • preganglionic fibres of the sympathetic nervous system
  • all postganglionic fibres of the sympathetic nervous system
  • preganglionic of parasymp
  • postganglionic of parasymp
  • motor fibres to skeletal muscle
A

TFTTT

64
Q

Renal clearance:

  • is expressed in units of mass per unit time
  • of glucose will double if the plasma glucose increases from 5 to 10 millimoles per litre
  • of an actively reabsorbed substance must exceed that of inulin
  • of PAH exceeds that of creatinine
  • of urea exceeds that of inulin
A

FFFTF

  • expressed in volume from which a substance is removed in unit time (ml/min)
  • clearance of glucose is zero below renal threshold
  • inulin freely filtered but not reabsorbed or secreted
  • PAH both filtered and secreted
  • creatinine can be reabsorbed
  • urea is both filtered and reabsorbed
65
Q

Fetal blood concentration of lignocaine following maternal administration would be higher than expected:

  • if administered during uterine contractions
  • in the presence of umbilical cord compression
  • in the presence of maternal acidosis
  • in the presence of fetal acidosis
  • in the presence of increased maternal metabolism
A

FFFTF

  • uterine contractions reduce blood flow to fetus, and so does umbilical cord compression
  • raised maternal metabolism would lead to increased lidocaine breakdown so not an increase for the fetus
66
Q

Left ventricular stroke volume increases when:

  • SVR increases
  • activity in the cardiac sympathetic nerves increases
  • stimulation of cholinergic receptors in the heart increases
  • right ventricular stroke volume increases
  • subject is tilted into head up
A

FTTTF

67
Q

Blood flow through skeletal muscle:

  • in the resting subject amounts to more than half the cardiac output
  • is increased by epinephrine
  • can stop during isometric contraction
  • is increased by noradrenaline
  • increases during rhythmic exercise of the muscles involved
A

FTTFT

  • blood flow at rest is 20% of CO (1200ml/min)
  • adrenaline stimulates sympathetic activity which enhances skeletal muscle blood flow
  • when a muscle develops 70% of max tension the blood flow completely stops
68
Q

The arterial pulse pressure wave

  • is normally transmitted as far as the venules
  • travels faster than the flow of blood
  • amplitude increases with exercise
  • commonly has a larger amplitude in the peripheral than in central arteries
  • central amplitude increases with advanced age
A

FTTTT

  • foot has highest amplitude
  • in old people arterial walls are stiffer so central amplitude increases
69
Q

In a resting nerve fibre:

  • the membrane potential can be estimated from the transmembrane difference in sodium concentration
  • transmembrane potential is 30 mV
  • transmembrane chloride influx is passive
  • intracellular and extracellular calcium concentrations are similar
  • sodium pump is active
A

FFTFT

  • minus 70mV intracellularly
  • transmembrane flux of Cl is passive due to concentration (inward) and electrical (outward) gradients
  • intracellular calcium is 1/10th of ECF level
70
Q

Adrenaline:

  • is formed by the methylation of noradrenaline
  • directly dilates the coronary arterioles
  • mobilises liver glycogen
  • decreases CO due to reflex bradycardia
  • has no action on FFA metabolism
A
  • TTTFF
71
Q

Closure of the FO after birth is facilitated by

  • onset of spontaneous ventilation
  • reversal of fetal pressure gradients between right and left atria
  • a decrease in TBV immediately after birth
  • hypoxaemia which continues after delivery
  • an increase in systemic arterial pressure after delivery
A

TTFFT

72
Q

Physiological dead space is:

  • increased by haemorrhage
  • measured by helium dilution
  • increased after pulmonary embolism
  • increases are frequent cause of hypoxia
  • increased by breath holding
A

TFTFF

  • dead space is measured using the Bohr equation
  • breath holding reduces it due to better mixing
73
Q

Reabsorption of sodium in the nephron:

  • is greated in the descending than the ascending LoH
  • is accompanied by net reabsorption of chloride
  • is accompanied by net reabsorption of H+ ions
  • requires expenditure of energy
  • occurs mainly in exchange for potassium ions
A

FTFTF

  • >75% of Na reabsorption is coupled to Cl- uptake
  • Na can be exchanged for H+
  • only a small amount of Na+ is exchanged for K+ (<1%)

FRCA Guide Qs 2003 (3 decks)

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