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Biophysics 1 > Biophysics exam > Flashcards

Biophysics exam Flashcards

1
Q

1: Results of a measurement

A

the number of the given magnitude
the unit
the estimated error

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2
Q

1: Errors

A

systematic error: fault in equipment = accuracy

Random error: lack in precision = precise

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3
Q

1: accuracy and precision

A

accuracy: how close to the real value the experiment is (low systematic error)
precision: how close the values are to each other (low random error)

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4
Q

1: SI-system, fundamental quantities

A 
Lenght (l), units= meter (m)
luminous intensity (lo) = candela (cd)
electric current (l) = ampere (A)
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5
Q

2: Macro and micro transport

A

macro: large molecules + large distances = carried in tubes and vessels
micro: small amounts, short distances = diffusion

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6
Q

2: Archimedes principle

A

and object in a fluid experiences an upward movement (buoyant force)
buoyant force = sum of forces due to fluid pressure

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7
Q

2: Flow of ideal fluid

A

Ideal fluid is incompressible and without friction

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8
Q

2: macro and micro transport measurement

A 
Pressure (P) = F/A 
(F= force, A=unit area)
Density (p) = m/V 
(m=mass, V= volume)
Newtons secound law: F= m*a 
(m=mass, a= accelleration)
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9
Q

2: Flow rate

A

the volume of a fluid flowing past a point in a tube per unit of time
streamline flow: line of stream, does not mix or swirl =predictable
flow tube: the wall of the tube is made of streamlines no flow in / out of tube, flow rate (Q) is the same at all points of the tube

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10
Q

2: Bernoullis equation

A

velocity depends on pressure and hight

NB: whem flow increases, pressure will drcrease
P+pgy+1/2pv^2=constant

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11
Q

2: Fluid at rest

A

Fluid at rest at the bottom of a container will bear the weight of the fluid above, bc the fuid has no speed (v)

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12
Q

2: Manometer (measure of pressure)

A

Fluid in a U-shaped tube, one end attached to a sealed container. diff. in hights= calculate pressure

Pb=Patm+pgh

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13
Q

Bl. pr. measurement by cannulation

A

Like a manometer, artery workes as sealed container, diff. in hights = pressure

Pblood= Patm+pgh-psgh’

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14
Q

2: Role of gravity in circulation

A

when standing = pressure diff. in diff. parts of body
when lying= equal
brain needs the flow rate to be constant

Pf= Ph+pghh=Pb+psghb ( see drawing ppt)

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15
Q

2: dynamic consequences

A

velocity high -> low pressure
velocity constant, area smaller -> high pressure

A1V1=A2V2

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16
Q

3: Flow of viscous fluids (n)

A

thick, sticky consistency w/ internal friction

depends on fluid temp. high temp= less viscosity

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17
Q

3: newtons flow

A

you move upper plate at constant speed, the force needed to move.
see equation

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18
Q

3: Laminar fow

A

often laminar when the velosity is low, when all layers move in almost the same speed.

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19
Q

3: Parabolic velocity profile

A

the velocity is higher in the middle, then decreases towards the walls where it is 0

see eq.

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20
Q

3: Poiseuilles law

A

high viscosity leades to low flow rate
flow rate is proportional to the pressure
flow rate is proportional to R4, and extremely dependent o the radius of the tube

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21
Q

3: Power of maintaining a flow

A

Needs continous work, power must be equal to the power taken by the friction bw the wall and the fluid

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22
Q

4: turbulent flow

A

above a critical pressure the laminar flow becomes turbulent and unpredictable
more work is required to maintain flow rate

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23
Q

4: Reynolds number

A

is used to clculate if the flow is laminar or turbulent.
bigger than 3000 = turbulent
less than 2000 = laminar
bw 2000-3000= unstable

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24
Q

4: Measurement of bl. pr. by sphyngomanometer

A

block brachial artery. Use stetoscope, let more and more air ot of the band around the arm, the pressure will decrease more and more and you can hear the turbulent flow as a tapping sound.
increase pr. until you reach systolic pr, then let out air until you reach diastolic pr.

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25
Q

4: Viscous drag froce

A

forces that tries to retard an object in a flow
layer next to the object is at rest
object moves, friction bw the two closest layers
Fd= v*n
(v=velocity, n= viscosity)

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26
Q

4: terminal viscosity

A

knowing velocity, size and density of the liquid we an calculate the viscosity using strokes law

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27
Q

4: Hesslers viscometer

A

if an object is moving to it’s terminal veloity, it’s speed is constant due to the restraining force of exerted by the fluid/air

vwater/vblood= nwater/nblood

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28
Q

4: Hopplers viscometer

A

sphere of known size and density is allowed to decend through the liquid of a vertical glass tube
when it reaches it’s terminal velocity which can be measured by the time it uses to pass 2 markers on the tube

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29
Q

5: Transmural pressure

A

the pressure exerted against the wall of the blood vessels

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30
Q

5: the law of laplace

A

tension in the walls are related to the radius of the tube and the pressure inside the tube

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31
Q

5: indicator diagram

A

describes the corresponding changes in volume and pressure in a system

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32
Q

5: flow in elastic tubes

A

increase pressure -> increase radius -> increase flow rate

elastic wall steals some kinetic energy of the blood into the elastic energy of the expansion and contraction of the wall.
more fluid can flow through an elastic tube than a rigid one

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33
Q

5: newtonian fluids and pseudoplatic fluids

A 
newtonians = air + urine
pseudoplastic= have a change in viscosity when accelerating depending on the str. of the molecules, but later the viscosity becomes constant. Ketchup effect!
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34
Q

6: Diffusion

A

a spontaneous process where molecules migrate / flow from high concentration to low concentration.

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35
Q

6: Ficks first law

A

describes the transport rate of a substance by diffusion

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36
Q

6: diffusion properties

A

high temp. -> increased diffusion rate
bigger size molecules -> lower diff. rate
increased viscosity -> lower diff. rate

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37
Q

6: Ficks secound law

A

Describes the diffusion change over time

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38
Q

6: time course simple diff.

A

the longer time -> lower diff.

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39
Q

6: Gas exchange

A

diff. of o2 through 1 nm mem. takes 250 ns. Blood is connected to the mem. for 0,3 sec.

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40
Q

7: Osmosis

A

Diffusion of water through a semipermeable mem. from higheter conc. of water to lower conc. of water

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41
Q

7: Van’t hofff’s law

A

dilute sol., ex. sugar molecules act like ideal gases. ideal gas law can be applied

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42
Q

7: isotonic sol.

A

equal conc. no flow of water.

ex. NaCl (0.15M or 0,9%)

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43
Q

7: Hypotonic sol.

A

Inner sol. has lower water content, water flows in.

ex. red blood cell. will rupture = hemolysis

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44
Q

7: Hypertonic sol.

A

outer sol. has lower water cont., water flows out.

ex. red blood cell. will shrink = plasmolysis

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45
Q

7: measurement of osmotic pressure

A

direct: measurement of hight diff. in a cylinder
indirect: can be calculated by measuring conc. which can be measure by change in freezing point (decrease) or boiling point (increase)

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46
Q

8: Str. of the cell mem.

A

lipid bilayer. hydrophobic and hydrophillic ends. tran. ions and molecules in/out of cell

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47
Q

8: Passive diff.

A

Does not require energy. Mem. contains small pores, where some particles are allowed to pass.

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48
Q

8: Mem. permeability

A

Semipermeable = selectively for diff. mol.
larger diffusion constant = faster diff.
thickness of mem. pays role in speed
use can dertermine permeability using ficks law

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49
Q

8: correlation bw mem. permeability and lipid solubility

A

correlation
porportional to eachother
greater sol in lipids -> passes more quickly

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50
Q

8: prpoerties of facilitated diffsion

A

faster
saturating
spesific
can be inhibited

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51
Q

8: active transport

A

needs energy atp->adp
ex. sodium potassium pump
against conc. gradient

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52
Q

9: Sedimentation

A

depends on the radius of the sphere
used to differentiate substances (very slowly), but in a centrifuge = faster
in abcense of viscous drag force= the fall of the object in independent of their size
in presence of viscous drag froce= fall is not independent of size bc velocity depends on density and size

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53
Q

9: Centrifugation

A

rotation of an object gives an outgoing force, a centripetal acceleration
bigger particl moves faster than a small one-> higher svedbergs value
denser particle moves faster than a less dense one
denser sol. -> particle moves slower
bigger fractional coefficient -> moves slower

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54
Q

9: ultracentrifuges

A

extremly high angular velocity
analytical= determine conc. distibution at any time of the experiment (contains motor, rotor, armoured chamber and photographic system)
preparative= require fractination of the contents of the centrifuge cell and measurement of the conc. of each fraction to determine a concrete destribution

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55
Q

9: det. of mol. mass by sedimentation-diffusion

A

sedimentation experiment is preformed
sed. coefisient is measured
final calc. of mol. weight we use the experemental value of diffusion constant d

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56
Q

9: det. of mol. mass by edimentation equilibrium

A

low speed centrifugation where the sedimentation is in equilibrium with the counter acting diffusion
direct det. of molecular mass

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57
Q

9: density gradient centrifugation

A

separate particles w/ diff. density
a medium that changes the densiry is usned during centrifugation followed by a boltzman destribution.
medium can be heavy metal salts
during the centri. diff. partiles will group up due to diff. in density in the sol. heavy particles will be further away from the centre

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58
Q

10: consept of light ray

A

light is represented by geometric lines
crossing light rays does not influence eachother- independent
don’t need any medium to propagate
path of light ray is reversable

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59
Q

10: reflection and refraction

A

reflect: throw back without absorbing it
on smooth surface the incident ray and the reflected ray has the same angle
refraction: make ray change dir when it enters an angle. angle of reflected ray depneds on the medium
index of refraction: measurement of how the medium reflects the light. index of refraction depends on the wavelenght

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60
Q

10: snell’s law

A

ratio of the series of angles of incidence and refraction is a constant that depends on the wavelenght

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61
Q

10: total reflection

A

none of the incident rays enters the second medium
angle of reflection = 90 degrees
incident angle = critical angle
no energy loss
appears when the angle of refraction is bigger than the angle of incidens

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62
Q

10: light pipes

A

total reflection is used in fiber optics
ray can travel great lenghts bounching off the wall of the pipe medium without loosing strenght/engery
smaller radius of pipe = better light transport

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63
Q

10: light path in parallel slab

A

angle will not change when the ray leaves the slab

ray will be shifted laterally depending on the thickness of the slab

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64
Q

10: refraction in a prism

A

snells law

wall of prism has an angle, light will be bent according to snells law

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65
Q

10: dispersion of light

A

index of refraction depends on the wavelenght of the refracted light
more refracted light= higher index og refraction
suitable to prod. monochromatic light.
white light will leave the prism in diff. colors

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66
Q

11: Optical image formation

A

If diverging light rays from a point called object, or the continuations of these rays are crossing eachother after series of reflection / refraction, the crossing point is called the image of the object

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67
Q

11: real and virtual images

A

viritual : the image is not where it is supposed to be
ex. mirror, the image appears to be behind the mirror, only the continuation ofthe light ays cross each other
real: an image where the object is where it seems to be. waves are coming from the loation of the object
object is real if the rays actually pass through the image point

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68
Q

11: objects

A

most of them = real, rays comes from location of object

viritual objects occur in multicomponent system with two lenses or mirrors

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69
Q

11: plane mirror

A

simplest image forming device

rule of reflection is followed- image distance

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70
Q

11: thin spherical lenses

A

small thickness compared to radius
converging/convex lenses= bends rays towards axis
diverging/concave lenses= bends rays away from axis

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71
Q

11: focal point of lens

A

focal point of converging lens= in front of it (pos. value)
focal point of diverging lens= behind it (neg. value)

focal point= the point where the rays meet after passing through the convex lens.
shorter focal lenght= stronger lens

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72
Q

12: Image formation by lenses

A

Light rays from very distant points hit paralell with the axis of the lens and form an image at the focal point
rays from other ponits froms images whose locations can be found graphically or lgebraically if the focal lenght of the lens is known

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73
Q

12: Ray tracking method

A

1: rays going parallel to the axis of the lens and then hit the focal point
2: rays going through the center of the lens does not change dir. (like a thin slab)
3: rays goig through the focal point on the image side and emerge from the lens parallel to the axis

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74
Q

12: thin lens formula

A

calc. the image dist.

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75
Q

12: power of a lens

A

p=1/f

f=focal lenght, unit: diopter 1/m

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76
Q

12: Combination of thin lenses

A

the image of the first lens workes as the object for the next lens
if lenses are in close contact we can add up their power
1/f=1/f1+1/f2 ect. or P=p1+p2

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77
Q

12: Lens aberrations

A

Spherical aberrations= diff. focal points of rays
Chromatic aberrations= diff. wavelenght, diff. refraction
Astigmatism= lens does not focus the circular light bea to a point, but prod. two images at diff. distances

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78
Q

12: thick lenses

A

two refraction points
to make an image = you have to devide the lens into two principal planes (each side of the axis) where the ray bends
has 6 cardinal points = 2x focal points, 2x principal planes , 2x nodal points

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79
Q

12: ray tracking (thick lenses)

A

use the cardinal points, light path inside lens can be ignored

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80
Q

13: Biconvex lens

A

not homogenous, successive fibrous layers having varying refractive index

81
Q

13: human eye

A

field of view: 180 degrees
resolution: close to the limit determined by wave lenght
refractive index of lens: 1,38 in periphery and 1,42 in the centre
blind spot where optical nerve leaves
light reseptors: rods and cones
rods, gray shades, light and movement
cones, color vision
macula delsa/yellow spot: best vision, lots of cones

82
Q

13: light path inside eye

A

most bending happens at cornea, bc of small curvature and large change of refractive index from air to water

83
Q

13: function of lens

A

provides fine adjustments needed to fokus on objects at a diff. distane. this ability of the lens to adjust it’s focal lenght is called accommondation

84
Q

13: far and near points

A

far point : infinity

near point 205 mm

85
Q

13: visual acuity

A

the finest detail that can be seen w/ the naked eye depends on distance bw cones
there most be at least one unexited cone bw two exited cones

86
Q

13: color perception

A

minimum intensity to create a nerve signal depends on the wavelenght. visible light 400-700nm
dark, higher sensitivity than in daylight, rods are always active
adaption time dark: 30 min
three diff. types of cones, red, green, blue with diff. sensitivity peak:
red= 575
green=535
blue=445

87
Q

13: optical defects

A 
emmetropia= normal sight, image on retina
myopia= short/near sight, image in front of retina. corrected w/ negative lens(diverging lens)
hypermetropia= far sighted, image behind retina, corrected with positive lens (converging lens)
presbyopia= old sight, lens hardens
astigmation= uneven curvature of cornea
88
Q

13: Simple magnifier

A

converging lens. place object just inside focal point of lens, object is brought closer to the eye and the angle of vision is increased

89
Q

13: str. of image formation

A

two lenses, objective and ocular

ocular mignifies the image prod. by the objective and focuses it to the retina of the eye

90
Q

13: optical tube length

A

distance bw focal point and the two lenses

91
Q

14: the wave nature of light

A

light is a transverse electromagnetic wave characterized by frequency, period, wavelenght and amplitude
(f=number of waves per second, t= time bw two waves, w= distance bw two peaks, a= maximum amplitude)

92
Q

14: sinusoidal waves

A

waves w/ sinus or cosine (equal) function. They repeate themselves move / swing back and forth at a regular speed

93
Q

14: electromagnetic spectrum

A

x-rays, gamma rays, uv= <400nm
visible light 400-700nm
infrared, microwaves, radiowaves >700nm

94
Q

14: superposition

A

linear behavoir
the net response at a given place and time caused by two or more stim. is the sum of the responses which would have been caused by each stim. induvidually

95
Q

14: interference of light

A

when waves are i phase = strenghten each other

out of phase= weaken each other out

96
Q

14: Huygens-fresnel fronts

A

each point of an advancing wave front is the centre of a fresh disturbance and source of new waves. the advancing waves as a whole may be regarded as a sum of all the secondary waves rising from its point

97
Q

14: concept of light fronts

A

wave fronts are surfaces on which at every point are in phase
they trave outward from the source with the speed of the wave
ray is the line goig prependicular to the wave front that indicates the direction of the wave

98
Q

15: Diffraction of light

A

single source of interference

bending of light going through a narrow slit

99
Q

15: Coherent waves

A

For visible interference the phase difference should be constant for a long time = coherent waves
lasers

100
Q

15: Light diffraction by circular aperture

A

gives diffraction pattern w/bright round centre, and the dark circle around it.
prod. by interference of the wavelets or orienting from diff. points in the aperture

101
Q

15: diffraction disc

A

airy pattern are descriptions of the best focsed spot of light that a perfect lens w/ a circular aperture can make
smaller wavelenght/larger the diameter= more concentrated image

102
Q

15: resolving power of optical devices

A

two distinct image points are needed

the corresponding distance of two points is the resolution limit of the instrument

103
Q

15: raylight criterion

A

criterion for the minimum resoluble detail. the distance bw those two points is the resolution unit of the instrument

104
Q

15: Abbes criteria

A

at least two diff. orders of a beam should enter into the objective to see any detail. the two orders are usually non-diffracted

105
Q

15: numerical aperture of microscope

A

object is illuminated from below
light is transmittet directly from diff parts of the section
image is a result of interference og these transmitted light waves

106
Q

15: immersion microscope

A

when you put oil bw the object and the lens (oil has high index of refraction) the numerical aperture is increased and resolution power increases

107
Q

15: UV microscope

A

shorter wavelength, resolution power is increased
gives good contrast of cellular comp.
downsides: expensive equipment
special photo/video techniques must be used bc uv light hurts eyes and can’t be seen with the naked eye

108
Q

16: wave property of matter

A

matter has wave property like light

109
Q

16: De Broglie waveleght of a particle

A

The electrical potential energy of an electron having an electric charge should be equal to its final kinetic energy

110
Q

16: principle of electron accererated by an electric potential diff.

A

electrons are accelerated by the electrical potential difference (U)
the electron= acts in vaccume the same way as light, but has smaller wavelenght

111
Q

16: Transmission electron microscope (TEM)

A

Requires very thin samples
Very good resolution, but not 3D bc of thickness of sample
stained with heavy metal salts
magnigication can be changed by changning the current of the magnetic lenses
magnetic lenses= converging
sends electron beam through specimen

112
Q

16: Scanning electron microscope (SEM)

A

Workes like TEM
electrones bounce of the surface of the sample, can be increased w/ thin heavy metal film
the electron detector catches the electrons, gives 3D image
bigger samples
lower magnification than TEM
Spatial resolution up to 20nm

113
Q

17: the photoelectric effect

A

The release of electrones from a clean metal surface when electromagnetic radiation (ex. light) of proper frequency hits/shines on it

if there is a retarding voltage after a while you will reach the cut off frequency where no eletrones longer bounch off the metal plate

114
Q

17: photon concept and photoelectric concept of Einstein

A

light consists of light particles =photons of energy
these photons collide with individual electrones of the metal plate (ex.) and knock them out by giving them their entire energy

115
Q

17: photoelectron multiplier

A

energy of a photon is converted into a measureable current. light hits a cathode. bounches off an electron. this e hits another cathode, bounches off 2 e. and so on. in the end they are collected ad measured by a collector

116
Q

18: Interaction of light w/ matter

A

Light can be prod. by changing the state of valence electrones

117
Q

18: Light emission

A

When an electron goes from an exited state to ground state energy is released.
photons can be emitted in two ways:
spontanously (light)
stimulated (laser)

118
Q

18: Rayleigh, Raman and Campton scattering

A

Light consists of photons, when it travels through a medium (which contains atoms) the photons cn disturb the atoms i the medium for a short period of time

Rayleigh scattering= photon stim. atom –> exited state–> when it returns to ground state –> releases a photon w/ same frequency as the incident one

Raman scattering= photon emitted by the atom has higher or liwer energy than the incident photon

Compton scattering= the photon collides with a free electron and transfer energy to it

119
Q

18: Absorption

A

If freq. of incoming photon is just enough to raise the energy state to a higher level it will be totally abs.

120
Q

18: Photoluminescense

A

The process when exitation by emission of light of proper freq. and the de-exitation process is going on w/the emission of light
two ways:

Fuorescense: electrone goes from exited to ground state dir.

phsporescense: electrones goes from exited to ground stat via an intermidiate energy level

121
Q

18: Lambert law

A

if light intensity I0 passes through a sub. of thickness d, the intensity of the transmitted light obeys lambert law

122
Q

18: lambert-beer law

A

if sub. is in solution

123
Q

19: Properties of lasers

A 
L-ight
A-mplification
S-timulated
E-mission
R-radiation
124
Q

19: stim. emission

A

an electron, exited by a photon (havning the correct energy), may drop to a lower energy level resulting in the creation of another photon

the induced stim. emission can only be a dominant process if more atoms are in the upper state than lower state. this is called inversed population and it is rare. we need to add energy to keep this state

125
Q

19: Porperties of laser light

A

monochromatism (one wavelenght)
coherence
direct
well focusable

126
Q

19: types of lasers

A

Lasers w/ wavelenghts or tunable lasers
continoused or pulsed
in medicine we use it to destroy tissue, cornea surgery and coagulate tissue

127
Q

20: prod. of x-rays

A

x-rays are prod. whenever elecrones are stopped after striking a target with high enough velocity.
prod. of x-rays in medical practice
evacuated sealed glass tubes are used

smaller focus=more contrast (diagnosis)
extended focus (therapy)
the anoe must not overheat, cool or rotate to prevent overheating
128
Q

20: effects of x-rays

A 
ionization 
luminescense 
photographic effect
chemical effect
biological effects 
x-ray much higher penetration power than light --> can easily go through body
129
Q

20: Bremsstrahlung

A

Breaking radiation

prod. by e colliding w/ atoms and subsequently beig stopped by the atomic force (of nucleus)

130
Q

20: characteristic x-rays

A

energic e ionize the inner atomic shells og the atoms of the anode, During re-arrangement process x-rays are emitted
x-ray energy depends on the material of the anode
exitation of outer electrones gives light
energy of the inner e depends on the charge of the nuclus

131
Q

20: attenuation of x-rays in matter

A

x-ray intensity decrease in a similar fashion to that of light (when it propagates through a medium)

132
Q

20: five processes that takes place during attenuation

A

1= photo effect: ray hits inner shell–> ionize atom
energy of x-ray photon is completly transferred to the atoms of the material
2= compton scattering: ray hits an electron and splits into two rays w/ reduced energy
3=pair production: extremly high photon energy can create a postrion and an electron
x-ray goes close to nucleus, photon dissapears (abs.)
4=coherent scattering (negliable)
5=nuclear reactions (negliable)

133
Q

20: attenuation coefficient

A

sum of contribution of the five processes of attenuation

134
Q

21: Passive electric properties of living sub.

A

low current = behaves like commoon passive elements in ordinary electric circuits

high current= mat lead to damages, shock or death

135
Q

21: Resistance and capacity of cells and tissues

A

the resistance (R) of the cell mem. is higher than that of inra/extra cellular fluids
it’s a bad conductor
the rsistance of the cell suspension is higher thn that of the suspensor fluid, you can’t count cells by leading them through an magnetic field

136
Q

21: harmful effects of electric current

A

Freq. bw 30-300 hz are especially harmful.

137
Q

21: dangerous intensities

A

10 mA = muscle contr.
80 mA= heart arrythmia
100 mA= reversible stop of heart

138
Q

21: active electric properties of living matter

A

active cells are exitable cells
necessary for living organism to adapt
higher organisms there are spesialized cells (nerve, muscle )

139
Q

21: resting mem. potential

A

Electric potential in resting cell
measured bw intra and extra cellular regions usually less than 100 mV
Intracellular part = neg pot.
Extracellular part = zero

potential diff. caused by the non-uniform destribution of ions on the two sides of the mem. –> mem. potential caused by diffusion and ion pumps

140
Q

21: Diffusion potentials

A

some inons diffuse faster than others –> builds up diff. in charge, not permanent but can last for hours in eukaryots

141
Q

21: Donnan potential

A

when the mem. is impermeable to one kind of ions. leads to stable potential,

142
Q

22: electrochemical potential

A

thermodynamic measure that combines the concepts of energy stored in the form of chemical potential and electrostaticks. it is the sum of electrical and chemical potentials

143
Q

22: nernst equation

A

used to calculate cell potential under non-standard conditions

144
Q

22: calculated and measured resting potentials

A

The calculated values are simplified
the cell is not a closed system
the immobile ions are assumed to be perfectly immobile and the mem. is assumed to put no obstacles for the mobile ions
does not count for the ineraction bw membrane and ion
model considers only one type of mobile ions at the same time

145
Q

22: sodium/potassium pumps

A

pumps na+ out and k+ in
k more mobile, deffuse quicker out of cell, pos. charge on the outside cl- wants out and reduces the + charge
since tot. system is electrically neutral there is an equal slight exess of ions on the inside = potential difference
ratio: 3na-2k

146
Q

23: changing R.P

A

Usually electrical stim. is applied in experiments
weak stim.=smaller than threshold= no response
above threshold = action potential is created

147
Q

23: poroagation, non-myelinated axon

A

all or nothing principle. stim. makes na gate open, changes the potential
gradually returns to resting potential due to outflow of k

148
Q

23: propagation along myelinated axon

A

action potentials are “created” at the nodes of ranvier

faster propagation velocity proportional ith the thickness of the myelin sheat

149
Q

24: measuremtn of mem. potential

A

mem. pot. = diff. in ion conc bw inside and the outside of cell

to metholds to measure : electric or optical

150
Q

24: electric measurements of mem. pot.

A

if the cell is thick enough to insert a measuring electrode, potential can be measured dir.
most cases too thin
midroelectrodes- thin capillary of AgCl

electrode is a thin glass capillary filled with proper electolyte sol.

diff. techniques .
voltage clamp tech.= measuring device is continously monitoring the mem. pot. and very precise
fixing current of proper magnitude and size is introduced to the cell

patch-clamp tech.= measure opening / closing of induvidual channels separatly

optical=
use spectroscopy
spesific stains, two gr.
dyes that change their spectroscopic properties in an electrified strenght change
dyes having neg. or pos. charge destributed on both sides of the mem.
if mem. pot changes, dye will due the same

151
Q

25: body surface bio pot.

A

weak electric signals can be detected at the body surface

EMG, electromyogram
ECG, electrocardiogram
EEG, electroencephalogram
eyes= electroretinogram

ECG: measurement of electric potentials resulting from the function of the heart on the sur. of the body
rythmical action of heart is controlled by an electrical sig. initiated by spontaneous stim. of special muscle cells located in the right atrium SA node)

heart cycle= pulmonary circuit= right ventricle, pulmonary arteries, lung capillary bed, pulmonary veins, left atrium, left ventr.
systematic circuit= aorta, body, right ventr.

152
Q

25: Einthoven triangle

A

measures voltage bw pairs of electrodes
most common loc.
right arm, left arm, left leg

153
Q

25: Wilson type arrangement

A

unipolar lead

one electrode placed at active point , the other of the point at costant potntial

154
Q

25: EEG

A

electrodes places on scalp, 4-16
measure electrical activity of neurons, weak complex signals are obtained.

classification: 
according to freequency=
0,3-3,5 hz, delta, rare/deep sleep
4,7 hz, theta, when ill 
8-13 hz, alpha, when resting 
above 13 hz, beta, when working
155
Q

26: Cathode ray-oscilloscope

A

Can desplay and record action potentials
an electron bea is accelerated from the heater through the anode it lights up on the screen upon impact
cathoderays travel in straight line

156
Q

26: high freequency electricity diathermy

A

a medical and surgical technique involving the prod. of heat in a part of the body by high freequency electric currents, not exited effects to stim. circulation, relieve pain, destroy unhealthy tissue or cause bleeding vessels to clot

157
Q

26: Capasistance method

A

tissue placed bw two capacitors with an oscillating electric field makeing the ios in the tissue move
when they collide w the tissue mol. kinetic energy is released as heat
energy loss is called joule heating, warming of the skin and fat tissues, bc they have the highet electric field

158
Q

26: inductance method

A

30 MHz
tissue is place within or near the inductor that prod. alternating magnetic feild in the tissue.
method preferred for musce heating

159
Q

26: microwave diathery

A

2450 MHz
tissue abs. electromagnetic waves, prod. of heat
energy deposited more effectively in tissues with hight water content

160
Q

26: hight frequency electric surgery

A

using the probe to rapidly boil cell fluids –> cell explodes
used for cutting tissue
for oagulation tissue is heated slowly and the fluid evaporates without destroying the cell walls. tissue shrinks and helps in the coagulating process

161
Q

27: Radioactivity

A

unstable atomic nucleus spontaneously loosed energy by emitting ionizing particles and radiation
parent nucleotide = emmits radiation and becomes daughter nucleotide

162
Q

27: Alpha, beta and gamma radiation

A

alpha= pos. charged particles has low penetrating power can be stopped by thin sheets of Al
beta=electrones neg. charged. have higher speed anf therefore greater penetrating power
gamma= neutral electromagnetic radiation (like light or x-ray) has short wavelenght, highest penetrating power

163
Q

27: composition of the atom

A 
atom= nucleus, electrones
nucleus= neutrons + protones 
a nucleus is spesified by:
atomic no. (no of protons)
mass no. (protons + neutrons)
164
Q

27: isotopes

A

has same no of protons, diff. no. of neutrons

same chem. properties

165
Q

27: size and binding of energy in nuclei

A

volume is dir. propotional to mass no.

when energy of nucleus is measured it is always less than the value obtained from calculated with the individual energy of the particles
the missing energy is ssumed to be there to be the binding energy of the nucleus

we can use einstein formula to calc. the energy of the nucleus

166
Q

27: properties of nuclear forces

A

very strong
short range
does not depent on el. charge
very reproductible at short inter nucleon diatances

167
Q

27: ways to gain nuclear energy

A

if heavy nucleus splits = fisson, into to intermediate size nuclei, the binding energy increases

if to light nucli such as 2h or 3h combine, this fusion releases several MeV energy

168
Q

27: fusion

A

fusion of two light nuclei

form a heavier nucleus releasing a large amount of energy in the process + radiation

169
Q

27: fission

A

nucleus splits into smaller parts releasing enrgy + radiation
induced fission: large nucleus splits into two parts on the effect of a neutron called induced fission

170
Q

28: properties of radioactivity

A

SI unit :Bequerel
radioactive decay is a random process characterized by half life
natural radioactivity: caused by instability of nuclei
artificial: the result of unstable isotopes prod. by nuclear reactions

171
Q

28: half life

A

time required for half of the nucleus to be present to decay
biological half life= Is the time it takes for eg a drug to loose half its pharmalogic activity
effective half life = halving of the radioactive material in a living organism

172
Q

28: Radio carbon dating

A

14c always present in the environment and ingested by all living organisms
when organism dies c14 intake stops and begins to decay
determine age and death
14c/12c ratio decreases quantity og 14c left indicates time of death

173
Q

28: nuclear reaction

A

prod. of 14c good ex of nuclear reaction

large projectile, heavy target –> heavy product + light product
two nuclei or nuclear particles collide and prodproduct diff. than the initial particles. releases a lot of energy
a nucleus is changed by the ineraction with other nulear particles

174
Q

28: chain reactios

A

a neutron will devide a large atom and give rise to energy and more neutrons which in their turn will bombard other atoms
controlled in nuclear reactors and power plants
sudden: nuclear weapons

175
Q

28: Transmisssion og nuclear radiation through matter

A

leaves a trail of ionized atoms along it’s path which can disrupt a living cell
in air, four major categories
heavy charged particles= short range, straight tail
eletrones and positrons= 100 times greater than those of alpha particle electrones are slowing down along a randomly changing path
photons= energy of photons are transferred to electrones- electrones cause inonization - longer range -highly penetration (photoelectric effect, campton scattering, pair production)
neutrons= prod. ionization dir. - very long range. can penetrate deep into target atoms bc of their lack of charge !

176
Q

29: radiatio units

A

four types of radiation measurements :

source activity= rate of decrease oin the number of radioactive nuclei present in the material
unit: bequrele 1 disintegration/second

radiation exposure= the amount of radiation that reaches the material
unit: rontgen

abs. dose: the amount of radiation abs. in the material from the beam

dose equivalent dose: describes radiation risk after radiation

effective dose: sum of dose equivalents of diffrent organs

177
Q

29: biological effects of ionizing radiations

A

damages living cells (ionization)
the str. of essential mol. can change and wont be ale to function noramlly - cold leave to death

major injury semms to be reproductive mechanisms

178
Q

30: Stochastic effects

A

only the probability of the occurance of the effect and not its severity, is regarded as a func. of dose without threshold. the principal stochastic effects are considered to be heritable carcinogenic

179
Q

30: deterministic effects (non-stochastic)

A

those types of damages that result from collective injury of substainal number of cells in an affected tissue.
cataract of lens

180
Q

30: prinsipal radiation protection

A

justification: should provide more benefit than harm
optimization= As Low As Reasonably Achivalbe (ALARA)
dose limits: limits should not be exeeded (avrage industrial risks)

181
Q

30: gas filled radiation detectors

A

ionization chamber
proportional counter: counts particles of ionizing radiation and measures their energy
geiger counter (GM tube )

182
Q

30: scintillation detector

A

instrument used to dected and measure ionizating radiation

183
Q

31: radioactive tracker method

A

a compound where one or more atoms have been replaced by a radioisotope
it can be used to explore the mechanisms of chemical reactions by tracing the path of the radioisotope from reactants to products
we can label moleules with radio isotopes

184
Q

31: preferences in the selection of radioisotopes

A

its a requrement that the organism is exposed to the smallest dose possible
it is advantageous to use isotopes of short half life

185
Q

31: In vitro methods

A

used to determine the amounts of diff. hormones

ex. antigens (virology)

186
Q

31: in vivo methods

A

diagnosis of thyroid gland, measure the uptake of iodine
administered orally NaI sol.
measured with a scintillation counter

187
Q

32: ultrasound

A

mechanical waves propagating in medium. cannot propagate in vaccume

sound above 20000 Hz

188
Q

32: ultrasound effects

A

Hest effects: some of the vibration energy is transferred into heat. bc of friction bw to adjacent medium
cavitation: in liquids small cavities can be created for a short time
emulgation and dispersing effect: the boundary friction, the effect and cavitation makes it possible to prod. more stable and fine dispersion compared to other methods
chemical effects: in aqueous sol. the water is activated by ionization and exitation
biological effects: bacteria, viruses, fungi, smaller invertebrates and vertebrates may be killed by ultrasound

189
Q

32: Diagnostic use of ultrasound

A

used for diagnostic, surgical and theraputical purposes

190
Q

32: echo measurement

A

ultrasound is sent in shorter pulses at the boundry surface of the sample it is refelcted. a detector is used. distance is proportional to the time of delay of the reflected pulse.

a-scan: oscilloscope displays the emitted pulse and then also the reflective pulse
b-scan: instead of peaks on a screen- dots. by moving the emitter head two dimentional pictures can be obtained

191
Q

32: echoencephalography

A

an a-scan echoencephalogram is takeen to locate the midline bw the hemispheres of the brain. a displaced midline is observed due to a pathological enlargement of one side of the brain (tumor, bleeeing ect)

192
Q

33: conventional linear and axial tomography

A

Linear : most basi from. the x-ray tue is moved from a to b above the patient while the cassette holder moves simoultanously under the patient from a to b. points above/below focal plane = blurred out
these days it is displaces with computer tomography (CT)
axial: an image of a slice across the body is taken by rotating the x-ray tube and film around the patient. usefull when plannning treatment og cancer with radiation since they often show both tumor and normal str. CAT scan

193
Q

33: ct

A

narrow x-ray beam scans linearly across the part of the partiens body and the tansmitted beam is recorded by the detector mooving with the bem on the other side og the patient. data is stored in a computer
process of rotation and scanning is repeated
after scans comp. analyses data
brain scans are still difficult bc most of the abs of the skull. can use contrast agents

194
Q

33: Image formation using radio isotopes

A

counting radioactivity in an organ provides im info but is more useful to know how the radioactivity is distributed in the organ
two devides to prod. images
reticular scanner and the gamma camera
not as fine images as with x-rays but they provide diff info

195
Q

33: rectilinear scanner

A

first mechanical scanner that could measure radiation. a detector moves along a faster pattern over the area of intrest. the detector moves along the pattern over the area of intrest together with a light that alights a film-giving picture. only detects radiation at a few cm, so you have to scan both sides of the patient
good method, but takes a lot of time

196
Q

33: thermography

A

prod. images by scanning over surface
infrared/heat
based on thermal radiation
scanning thermographic camera measures IR- converts to an electrical signal

197
Q

34: Positron emission tomography

A

PET scan
radionucleotides decay through positron emission and are introduced to the body
positrons and electrons are moving slowly.

three factors of importance

1: biological, a lot of positron emitters have a short half life
2: hight probability to detect gamma rays
3: the ring geometry and computer monitored coincidence checking are identically suited to prod. homographs

PET does not depend on comparing abs intensity of rays passing through the object. location labelled substances can easily be obtained by triangulation using a few events only

198
Q

34: NMR

A

NMR imaging - nuclear magnetic resonance
many atom nuclei behave in a magnetic filed as small magnetic dipoles
body is piut into a magnetic filed which causes hydrogen to act as compass needles
well defined ratio of impulses are sent through the body distrotion of the alignment of the hydrogen atoms
when they realign themselfs a small amount of radiation is emitted
radiation can be transitted
in medicine = MRI

no ionizing radiation but magnetic field
tissued with diff. water content can be visualixed well. ex. cancer tissues
brain: grey matter contains more hydrogen, contrast
disadvantage. EXPENSICE AND DANGER OF CAUSING CLAUSTROPHOBIA

Biophysics 1 (1 decks)

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