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Physiology of Organisms > Practicals > Flashcards

Practicals Flashcards

1
Q

What is low/high pass filtering?

A

Low pass: low frequency components allowed to pass
High pass: high frequency components allowed to pass through

Filtering generally removes noice from data

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2
Q

What is aliasing

A

When the sample rate is too low to accuractly capture changes in the sample

Ideally sampling rate should be twice the frequency of the original signal

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3
Q

What is the resolution of the powerlab?

A

The number of ‘steps’ in between the minimum and maximum voltage. Basically how clean the data will look.

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4
Q

Define systolic and diastolic pressure

A

Peak pressure reached during the cardiac cycle (after ventricular contraction)

Diastolic is the the lowest measurement for arterial blood pressure.

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5
Q

What side of the artifical cell do we change the concentration of KCl in?

A

The reference side

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6
Q

How is potential difference across an artifical membrnae reported from the power lab?

A

Test side relative to reference
+20mV means the test side is 20mV more positive than the reference

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7
Q

Nernst equation

A

Eion = 58/z log(10) ([ref]/[test])

Eion = equilibrum potential at 20 degrees in mV

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8
Q

Relate voltage charge and capacitance

A

V = Q/C (= IR)

  • the larger the capacitance, the more charge that can be stored at a given voltage
  • capacitance of a capacitor can be increased by having a larger surface area or the plates being close together
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9
Q

Some capacitance things to remember

A

Current only flows through the capacitor when it is charging

Voltage increases at a capacitor while it is charging till it reaches a maximum (Q/C)

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10
Q

Time constant definition

A

Resistance*Capacitance.
Time taken for voltage to reach 63% original value after capacitor is attached.

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11
Q

Equation for voltage across a charging capacitor?

A

V(t) = Vt(1-e^(-t/T))

T = time constant

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12
Q

What does the finger pulse transducer measure?

A

Change in force not a measure of the actual force applied

Can convert change in force to force by intergrating with respect to time.

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13
Q

What is the dicrotic notch?

A

As the heart relaxes, aortic pressure exceeds that in left ventricle and the backflow of blood as the aortic valve closes creates a small notch.

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14
Q

What graph should we plot for values for voltage against reference concentration?

A

Semi log plot
y-axis: voltage
x-axis: log([K+]ref)

To give a straight line

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15
Q

Why might measured membrane potentials be different to those predicted by the nernst equation?

A

Membrane is partially permeable to chloride as well as to potassium.

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16
Q

Why do membranes have such a high capacitance?

A

Because the phospholipid bilayer is thin and very close together

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17
Q

Some key features of the earthworm and their location

A

Prostomium at the anterior end

Clitellum on dorsal side: glandular structure that produces coocoon for eggs to be deposited into

Gonopore: male openings on the body surface

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18
Q

What makes up the ventral nerve cord of earthworms?

A

1000 neurones
Median giant fibre (myleinated - unusal in inverebrates) and two lateral giant fibres

Each giant fibre behaves as though it were a singal axon

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19
Q

Role of median and lateral fibres

A

Median: action potentials from anterior to posterior

Lateral: action potentials from posterior to anterior

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20
Q

Role of stimulating electrodess

A

Produce an electrical current that depolarises the nerve fibres
Specifically the cathode (as it reduces the potential difference between the inside and outside of the axon)

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21
Q

Role of the earth electrode

A

Reduce noice and the stimulating artifact

Stimulus artefact: due to teh stimulating current traveling directly to the recording electrodes rather than through stimulating the nerve fibres

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22
Q

Calculation for nerve conduction velocity

A

Difference method
(D2 - D1) / (LP2 - LP1)

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23
Q

Define latency period

A

Delay between point of stimulation and the action potential reaching the first recording electrode.

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24
Q

What may change the ampnitude of the action potential measured in the worm median giant fibre?

A

The distance between the recording electrodes and the actual nerve fibre

Furthur distance = more resistance = smaller recorded action potential.

Overall, the electrical resistance of the tissue will make a difference

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25
Q

Which earthworm fibres are stimulated at low stimulating voltages?

A

The median giant fibres are stimulated at low volatges

Lateral fibres respond at higher voltages due to recruitment (and they have a longer latency)
- possibly due to fewer sodium ion channels

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26
Q

Which of the earthworm fibres has a lower conduction velocity?

A

The lateral giant fibres (not myleinated)

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27
Q

Why does latency period increase with freezing the fibres?

A

Affects kinetic properties of channel opeing mechanism (slow the rate that they open)

Sodium channels also inactivate more slowly and potassium channels open more slowly, effecting repolarisation

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28
Q

How can we determine the scaling coefficent?

A

Plot a log log graph
The gradient of the graph is equal to the scaling coefficent

Use a statistical test to determine is scaling coefficent differs significantly from what was predicted

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29
Q

How to calculate volume O2 consumed by shrimp in the time frame? (a measure of metabolic rate)

A

VO2 = (V x C (PO - P1) x 60) / t

V = volume of water that the shrimp was in
C = concentration O2 at 100% saturation at experimental temperature
P0 = reading 1
P1 = reading 2
t = time in minutes between readings

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30
Q

Assumptions made when using oxygen concentration to measure metabolic rate?

A

Constant amount of energy produced for each litre of oxygen
(will actually differ depending on food consumed)

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31
Q

How would tibia length of a locus expect to scale with body mass?

A

length is proportional to mass^(1/3)

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32
Q

How is force expected to scale with body mass?

A

Force is proportional to cross sectional area of muscle
Area is proportional to mass^(2/3)

Therefore expect force to be proportional to mass^(2/3)

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33
Q

How is acceleration expected to scale with body mass?

A

Accleration = force/mass

accleration proportional to mass^(-1/3)

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34
Q

How does take off velocity scale with body size?

A

velocity = root(2 x acceleration x distance)

= m^0 = constant

Take of velocity expected to be independent of body mass

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35
Q

Why might the prediction that take off velocity is independent of mass not be met?

A

Drag disproportionally affects smaller animals

Also possible that small and large locusts are not isometric

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36
Q

How to estimate mean arterial blood pressure

A

diastolic + 1/3(pulse pressure)

Pulse pressure = systolic - diastolic

37
Q

Where and how is human blood pressure usually measured?

A

Brachial artery using a sphygmomanometer

Pressure applied to artery to cut off blood flow. Gradually decrease pressure and when it becomes equal to systolic pressure, blood will start to flow again (korotkoff sound begins)

Pressure is lowered and sounds become louder until diastolic pressure is reached and the sounds stop as blood can flow as normal.

38
Q

What may affect blood pressure readings?

A

Auscultatory gap: disappearence of sounds between systolic and diastolic pressures

Width of the cuff relative to the arm

Too narrow: pressure seems higher than actual (because artery is compressed at a higher pressure)
Too wide: pressure seems lower

Recommended that cuff is 40% the circumference of the midpoint of the arm

39
Q

How to estimate diastolic and systolic blood pressure?

A

Estimate systolic by palpitation first (raise pressure until no radial pulse)

Then take pressure of cuff to 30mmHg above estimated and slowly deflated. Hold stethescope over bracial artery and determine when korokoff sounds appear and disappear

40
Q

What to the ECG components represent?

A

P wave: atrial depolarisation
PR: delay at AV node
QRS: ventricular depolarisation
T wave: ventricular depolarisation

41
Q

What does the PR interval represent?

A

Time from start of atrial depolarisation to ventricular depolarisation (delay at the AVN)

42
Q

What effect does standing up rapidly have on blood pressure and why?

A

Venous pooling may occur in the lower limbs, which means that venous return is impaired and so cardiac output falls (and so blood pressure falls)

This drop in pressure is recognised by receptors in the carotid sinus, which initate a baroreflex

43
Q

What is electrical systole in an ECG?

A

Period of time between the QRS beginning and end of the T wave

44
Q

What is electrical diastole

A

Any remaining time in teh ECG cycle outside of sytole (which is start of QRS to end of T)

45
Q

Converting partial pressure of gases when water pressure is involved?

A

Partial pressure of gas = (A - 47) * (%gas (dry)/100)

Useful because the gas anazlyser measures dry percentages

46
Q

Equation for calculating exercise efficentcy from work rate and energy expendature?

A

100 x work rate / total energy expenditure

47
Q

Absorbance definition (in terms of light entering and leaving the sample)

A

A = log(light before sample/light leaving sample)

48
Q

Function of subsidory cells in stomata

A

Buffer changes in tugor pressure of guard cells
Commelina communiais and Zea mays both have sunsidory cells

49
Q

What is standard error of the mean used for?

A

Indicates confidence in the position of the population mean relative to sample mean

50
Q

Why does systolic pressure increase with exercise but diastolic pressure does not?

A

Stroke volume rises with exercise so more blood is forced into the aorta per peat = increase in systolic pressure

Metabolic vasodilatation reduces TPR means the arterial pressure drops more rapidly following systole, which offsets the difference

51
Q

Equation for alveolar ventilation rate? Relationship between ventilation rate and CO2 partial pressure

A

Va (l/min) = rate CO2 production/partial pressure CO2

Inversley proportional relationship (so greater ventilation rate lowers pCO2)

52
Q

Where are peripheral chemoreceptors?

A

Carotid and aortic bodies

53
Q

How to estimated alveolar partial pressures of carbon dioxide and oxygen?

A

Use end-expiratory sample (assume to be in equilbrum with the blood around the alveoli)

54
Q

What is standard conditions (for STPD)

A

760mmHg

293K

55
Q

How does pulse oximeter work?

A

Measures colour of blood to determine haemoglobin O2 saturation

56
Q

Equation for max pulse rate

A

208 - (0.7 x age)

57
Q

What would we expect to happen to ventilation rate as work rate increases

A

Increase linearlly with work rate

Might see disproportionally large increase at high work rates as acidosis takes place when anaerobic exercise is occuring

58
Q

Effect of exercise on %spO2? (and pCO2 / pO2)

A

No change - blood gas partial pressures do not change significantly becuase they are not controlled only through negative feedback

A rise in pCO2 and a fall in pO2 are not observed during normal exercise. Due to feed forward mechanisms ventilation rate increases as soon as exercise begins and not in response to changes in blood gas partial pressures.

59
Q

How to reduce insesible water loss?

A

Water lost across the skin other than for sweating

Includes respiratory water loss (water loss at respiratory tracts)

60
Q

What is SVP and how does it change with temperature?

A

Saturated water vapour pressure (47 mmHg at 37 degrees)

Decreases with decreasing temperature (because it condenses)

61
Q

Difference between external work rate and total work rate

A

Exernal work rate: that measured by the bike (work done against the resistance of the bike)

Total work rate: bodys metabolic rate
- only 25% of energy produced from total work rate can be converted to useful work rate, the rest must be lost as heat

62
Q

Why is nose breathing good for heat and water loss loss?

A

Nasal passage way cooled as you breath in
As you breath out, warm moist air passes over the cold passageway and some of the water vapour consenses and is reasbsorbed into the blood
Because temperature of exhaled air is lower, loss from water vapour is less

Temporal countercurrent mechanism

63
Q

Work, force and distance equation

A

Work = force (N) x distance (m)

Power = force x velocity (work done per unit time)

64
Q

What is mesentery?

A

Thin web of tissue that surrounts the gut

65
Q

What happens if a smaller current is applied from the power lab (when testing force of muscle contraction)

A

Fewer axons in the ulnar nerve are depolarisaed sufficently to generate action potentials
Fewer motor units stimulated
Smaller muscle contraction

66
Q

What does the Cafar rehab X2 do that is different to previous experiment

A

Stimulates muscles of the hand (abductor muscles) directly (rather than stimulating motor neurones in the ulnar nerve)

Main advantage: can produce stimuli in the pattern we want (eg. high frequency)

67
Q

What is hysteresis?

A

The nature of a physiological event depends on its past history
(eg. contraction ampnitude measured by force transducer are different when stimulation is increasing than when it is decreasing)

Reasons for hysteresis in muscle contraction: muscles were fatigued

68
Q

What is a motor unit

A

Group of muscle fibres all innerverated by the same motor neurone

69
Q

Electromyography?

A

Measures muscle response to nerve stimulation
Represented by an electromyogram

The EMG is not an all or none event becuase it measures a compound action potential

70
Q

Why does force of muscle contraction increased as current produced by Cefar rehab X2 increase?

A

More muscle fibres are recruited with a larger stimulus

71
Q

Why does frequency summation take place?

A

greater contraction ampnitude in the second/third contraction becuase calcium remains in the sarcoplasmic reticulm

As frequency increases, less time for calcium to be pumped back and can get a continous contraction (tetany)

72
Q

How is smooth contraction obtained in vivo?

A

Asyncrousnous stimulation of motor units

In this experiment though, all motor units are stimulated at once.

73
Q

What nerves did we look at in histology

A

Sciatic: motor fibres to leg muscles (larger than ulnar)
Ulnar: motor fibres to forearm muscles
Splanchnic: sympatheic fibres to the gut

74
Q

What is observeable on a nerve tissue slide?

A

Circular structures are myelinated axons

75
Q

Small intestine layers (inside -> out)

A

Muscosa
Submuscosa
Circular smooth muscle (thicker)
Longitudinal smooth muscle (thinner)
Serosa - thin layer of connective tissue

76
Q

More permeable membrane to an ion - closer or furthur from E?

A

Closer to predicited value from nernst equation

77
Q

Why is ampnitude from lateral giant fibres larger?

A

A compound action potential as there are two fibres

78
Q
A
79
Q

What do PR proteins do in plants

A

Accumlate with minutes of plant defence indiction
Regulated by SA
They are useful markers for plant defence induction

80
Q

When is nitrate reductase induced?

A

When nitrate is avalible

Converts nitrate to nitrite (which then goes on to be reduced into ammonium)

81
Q

What are two controls needed for nitrate reductase practical?

A

Negative: no enzyme present
Positive: with enzyme

82
Q

Ideal gas law

A

P1V1/T1 = P2V2/T2

83
Q

Aim of positive/negative control

A

P: Check that the assay works and can produce a response

N: Check for contamination of buffers or chemicals

84
Q

Why does high potassium concentration in the bathing medium decrease guard cell sensitivity to light?

A

At any given membrane potential, a much higher internal concentration of potassium accumlates passivley

85
Q

Equation for turgor pressure

A

Turgor pressure = gas constant x solute concentration (M) x temperature

86
Q

How much space does a mole of gas occupy at SVP?

A

22.4 litres

87
Q

Voltage, current resistance calculation?

A

V = IR

88
Q

When might you use a high pass filter?

A

If we want to examine the high frequency part of the recording
eg. vibrations of the ear in response to a high frequency sound

89
Q
A

Physiology of Organisms (10 decks)

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