Biophysics exam Flashcards
1: Results of a measurement
the number of the given magnitude
the unit
the estimated error
1: Errors
systematic error: fault in equipment = accuracy
Random error: lack in precision = precise
1: accuracy and precision
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)
1: SI-system, fundamental quantities
Lenght (l), units= meter (m) luminous intensity (lo) = candela (cd) electric current (l) = ampere (A)
2: Macro and micro transport
macro: large molecules + large distances = carried in tubes and vessels
micro: small amounts, short distances = diffusion
2: Archimedes principle
and object in a fluid experiences an upward movement (buoyant force)
buoyant force = sum of forces due to fluid pressure
2: Flow of ideal fluid
Ideal fluid is incompressible and without friction
2: macro and micro transport measurement
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)
2: Flow rate
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
2: Bernoullis equation
velocity depends on pressure and hight
NB: whem flow increases, pressure will drcrease
P+pgy+1/2pv^2=constant
2: Fluid at rest
Fluid at rest at the bottom of a container will bear the weight of the fluid above, bc the fuid has no speed (v)
2: Manometer (measure of pressure)
Fluid in a U-shaped tube, one end attached to a sealed container. diff. in hights= calculate pressure
Pb=Patm+pgh
Bl. pr. measurement by cannulation
Like a manometer, artery workes as sealed container, diff. in hights = pressure
Pblood= Patm+pgh-psgh’
2: Role of gravity in circulation
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)
2: dynamic consequences
velocity high -> low pressure
velocity constant, area smaller -> high pressure
A1V1=A2V2
3: Flow of viscous fluids (n)
thick, sticky consistency w/ internal friction
depends on fluid temp. high temp= less viscosity
3: newtons flow
you move upper plate at constant speed, the force needed to move.
see equation
3: Laminar fow
often laminar when the velosity is low, when all layers move in almost the same speed.
3: Parabolic velocity profile
the velocity is higher in the middle, then decreases towards the walls where it is 0
see eq.
3: Poiseuilles law
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
3: Power of maintaining a flow
Needs continous work, power must be equal to the power taken by the friction bw the wall and the fluid
4: turbulent flow
above a critical pressure the laminar flow becomes turbulent and unpredictable
more work is required to maintain flow rate
4: Reynolds number
is used to clculate if the flow is laminar or turbulent.
bigger than 3000 = turbulent
less than 2000 = laminar
bw 2000-3000= unstable
4: Measurement of bl. pr. by sphyngomanometer
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.
4: Viscous drag froce
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)
4: terminal viscosity
knowing velocity, size and density of the liquid we an calculate the viscosity using strokes law
4: Hesslers viscometer
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
4: Hopplers viscometer
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
5: Transmural pressure
the pressure exerted against the wall of the blood vessels
5: the law of laplace
tension in the walls are related to the radius of the tube and the pressure inside the tube
5: indicator diagram
describes the corresponding changes in volume and pressure in a system
5: flow in elastic tubes
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
5: newtonian fluids and pseudoplatic fluids
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!
6: Diffusion
a spontaneous process where molecules migrate / flow from high concentration to low concentration.
6: Ficks first law
describes the transport rate of a substance by diffusion
6: diffusion properties
high temp. -> increased diffusion rate
bigger size molecules -> lower diff. rate
increased viscosity -> lower diff. rate
6: Ficks secound law
Describes the diffusion change over time
6: time course simple diff.
the longer time -> lower diff.
6: Gas exchange
diff. of o2 through 1 nm mem. takes 250 ns. Blood is connected to the mem. for 0,3 sec.
7: Osmosis
Diffusion of water through a semipermeable mem. from higheter conc. of water to lower conc. of water
7: Van’t hofff’s law
dilute sol., ex. sugar molecules act like ideal gases. ideal gas law can be applied
7: isotonic sol.
equal conc. no flow of water.
ex. NaCl (0.15M or 0,9%)
7: Hypotonic sol.
Inner sol. has lower water content, water flows in.
ex. red blood cell. will rupture = hemolysis
7: Hypertonic sol.
outer sol. has lower water cont., water flows out.
ex. red blood cell. will shrink = plasmolysis
7: measurement of osmotic pressure
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)
8: Str. of the cell mem.
lipid bilayer. hydrophobic and hydrophillic ends. tran. ions and molecules in/out of cell
8: Passive diff.
Does not require energy. Mem. contains small pores, where some particles are allowed to pass.
8: Mem. permeability
Semipermeable = selectively for diff. mol.
larger diffusion constant = faster diff.
thickness of mem. pays role in speed
use can dertermine permeability using ficks law
8: correlation bw mem. permeability and lipid solubility
correlation
porportional to eachother
greater sol in lipids -> passes more quickly
8: prpoerties of facilitated diffsion
faster
saturating
spesific
can be inhibited
8: active transport
needs energy atp->adp
ex. sodium potassium pump
against conc. gradient
9: Sedimentation
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
9: Centrifugation
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
9: ultracentrifuges
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
9: det. of mol. mass by sedimentation-diffusion
sedimentation experiment is preformed
sed. coefisient is measured
final calc. of mol. weight we use the experemental value of diffusion constant d
9: det. of mol. mass by edimentation equilibrium
low speed centrifugation where the sedimentation is in equilibrium with the counter acting diffusion
direct det. of molecular mass
9: density gradient centrifugation
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
10: consept of light ray
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
10: reflection and refraction
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
10: snell’s law
ratio of the series of angles of incidence and refraction is a constant that depends on the wavelenght
10: total reflection
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
10: light pipes
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
10: light path in parallel slab
angle will not change when the ray leaves the slab
ray will be shifted laterally depending on the thickness of the slab
10: refraction in a prism
snells law
wall of prism has an angle, light will be bent according to snells law
10: dispersion of light
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
11: Optical image formation
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
11: real and virtual images
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
11: objects
most of them = real, rays comes from location of object
viritual objects occur in multicomponent system with two lenses or mirrors
11: plane mirror
simplest image forming device
rule of reflection is followed- image distance
11: thin spherical lenses
small thickness compared to radius
converging/convex lenses= bends rays towards axis
diverging/concave lenses= bends rays away from axis
11: focal point of lens
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
12: Image formation by lenses
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
12: Ray tracking method
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
12: thin lens formula
calc. the image dist.
12: power of a lens
p=1/f
f=focal lenght, unit: diopter 1/m
12: Combination of thin lenses
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
12: Lens aberrations
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
12: thick lenses
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
12: ray tracking (thick lenses)
use the cardinal points, light path inside lens can be ignored
13: Biconvex lens
not homogenous, successive fibrous layers having varying refractive index
13: human eye
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
13: light path inside eye
most bending happens at cornea, bc of small curvature and large change of refractive index from air to water
13: function of lens
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
13: far and near points
far point : infinity
near point 205 mm
13: visual acuity
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
13: color perception
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
13: optical defects
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
13: Simple magnifier
converging lens. place object just inside focal point of lens, object is brought closer to the eye and the angle of vision is increased
13: str. of image formation
two lenses, objective and ocular
ocular mignifies the image prod. by the objective and focuses it to the retina of the eye
13: optical tube length
distance bw focal point and the two lenses
14: the wave nature of light
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)
14: sinusoidal waves
waves w/ sinus or cosine (equal) function. They repeate themselves move / swing back and forth at a regular speed
14: electromagnetic spectrum
x-rays, gamma rays, uv= <400nm
visible light 400-700nm
infrared, microwaves, radiowaves >700nm
14: superposition
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
14: interference of light
when waves are i phase = strenghten each other
out of phase= weaken each other out
14: Huygens-fresnel fronts
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
14: concept of light fronts
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
15: Diffraction of light
single source of interference
bending of light going through a narrow slit
15: Coherent waves
For visible interference the phase difference should be constant for a long time = coherent waves
lasers
15: Light diffraction by circular aperture
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
15: diffraction disc
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
15: resolving power of optical devices
two distinct image points are needed
the corresponding distance of two points is the resolution limit of the instrument
15: raylight criterion
criterion for the minimum resoluble detail. the distance bw those two points is the resolution unit of the instrument
15: Abbes criteria
at least two diff. orders of a beam should enter into the objective to see any detail. the two orders are usually non-diffracted
15: numerical aperture of microscope
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
15: immersion microscope
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
15: UV microscope
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
16: wave property of matter
matter has wave property like light
16: De Broglie waveleght of a particle
The electrical potential energy of an electron having an electric charge should be equal to its final kinetic energy
16: principle of electron accererated by an electric potential diff.
electrons are accelerated by the electrical potential difference (U)
the electron= acts in vaccume the same way as light, but has smaller wavelenght
16: Transmission electron microscope (TEM)
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
16: Scanning electron microscope (SEM)
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
17: the photoelectric effect
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
17: photon concept and photoelectric concept of Einstein
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
17: photoelectron multiplier
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
18: Interaction of light w/ matter
Light can be prod. by changing the state of valence electrones
18: Light emission
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)
18: Rayleigh, Raman and Campton scattering
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
18: Absorption
If freq. of incoming photon is just enough to raise the energy state to a higher level it will be totally abs.
18: Photoluminescense
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
18: Lambert law
if light intensity I0 passes through a sub. of thickness d, the intensity of the transmitted light obeys lambert law
18: lambert-beer law
if sub. is in solution
19: Properties of lasers
L-ight A-mplification S-timulated E-mission R-radiation
19: stim. emission
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
19: Porperties of laser light
monochromatism (one wavelenght)
coherence
direct
well focusable
19: types of lasers
Lasers w/ wavelenghts or tunable lasers
continoused or pulsed
in medicine we use it to destroy tissue, cornea surgery and coagulate tissue
20: prod. of x-rays
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
20: effects of x-rays
ionization luminescense photographic effect chemical effect biological effects x-ray much higher penetration power than light --> can easily go through body
20: Bremsstrahlung
Breaking radiation
prod. by e colliding w/ atoms and subsequently beig stopped by the atomic force (of nucleus)
20: characteristic x-rays
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
20: attenuation of x-rays in matter
x-ray intensity decrease in a similar fashion to that of light (when it propagates through a medium)
20: five processes that takes place during attenuation
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)
20: attenuation coefficient
sum of contribution of the five processes of attenuation
21: Passive electric properties of living sub.
low current = behaves like commoon passive elements in ordinary electric circuits
high current= mat lead to damages, shock or death
21: Resistance and capacity of cells and tissues
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
21: harmful effects of electric current
Freq. bw 30-300 hz are especially harmful.
21: dangerous intensities
10 mA = muscle contr.
80 mA= heart arrythmia
100 mA= reversible stop of heart
21: active electric properties of living matter
active cells are exitable cells
necessary for living organism to adapt
higher organisms there are spesialized cells (nerve, muscle )
21: resting mem. potential
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
21: Diffusion potentials
some inons diffuse faster than others –> builds up diff. in charge, not permanent but can last for hours in eukaryots
21: Donnan potential
when the mem. is impermeable to one kind of ions. leads to stable potential,
22: electrochemical potential
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
22: nernst equation
used to calculate cell potential under non-standard conditions
22: calculated and measured resting potentials
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
22: sodium/potassium pumps
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
23: changing R.P
Usually electrical stim. is applied in experiments
weak stim.=smaller than threshold= no response
above threshold = action potential is created
23: poroagation, non-myelinated axon
all or nothing principle. stim. makes na gate open, changes the potential
gradually returns to resting potential due to outflow of k
23: propagation along myelinated axon
action potentials are “created” at the nodes of ranvier
faster propagation velocity proportional ith the thickness of the myelin sheat
24: measuremtn of mem. potential
mem. pot. = diff. in ion conc bw inside and the outside of cell
to metholds to measure : electric or optical
24: electric measurements of mem. pot.
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
25: body surface bio pot.
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.
25: Einthoven triangle
measures voltage bw pairs of electrodes
most common loc.
right arm, left arm, left leg
25: Wilson type arrangement
unipolar lead
one electrode placed at active point , the other of the point at costant potntial
25: EEG
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
26: Cathode ray-oscilloscope
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
26: high freequency electricity diathermy
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
26: Capasistance method
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
26: inductance method
30 MHz
tissue is place within or near the inductor that prod. alternating magnetic feild in the tissue.
method preferred for musce heating
26: microwave diathery
2450 MHz
tissue abs. electromagnetic waves, prod. of heat
energy deposited more effectively in tissues with hight water content
26: hight frequency electric surgery
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
27: Radioactivity
unstable atomic nucleus spontaneously loosed energy by emitting ionizing particles and radiation
parent nucleotide = emmits radiation and becomes daughter nucleotide
27: Alpha, beta and gamma radiation
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
27: composition of the atom
atom= nucleus, electrones nucleus= neutrons + protones a nucleus is spesified by: atomic no. (no of protons) mass no. (protons + neutrons)
27: isotopes
has same no of protons, diff. no. of neutrons
same chem. properties
27: size and binding of energy in nuclei
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
27: properties of nuclear forces
very strong
short range
does not depent on el. charge
very reproductible at short inter nucleon diatances
27: ways to gain nuclear energy
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
27: fusion
fusion of two light nuclei
form a heavier nucleus releasing a large amount of energy in the process + radiation
27: fission
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
28: properties of radioactivity
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
28: half life
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
28: Radio carbon dating
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
28: nuclear reaction
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
28: chain reactios
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
28: Transmisssion og nuclear radiation through matter
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 !
29: radiatio units
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
29: biological effects of ionizing radiations
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
30: Stochastic effects
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
30: deterministic effects (non-stochastic)
those types of damages that result from collective injury of substainal number of cells in an affected tissue.
cataract of lens
30: prinsipal radiation protection
justification: should provide more benefit than harm
optimization= As Low As Reasonably Achivalbe (ALARA)
dose limits: limits should not be exeeded (avrage industrial risks)
30: gas filled radiation detectors
ionization chamber
proportional counter: counts particles of ionizing radiation and measures their energy
geiger counter (GM tube )
30: scintillation detector
instrument used to dected and measure ionizating radiation
31: radioactive tracker method
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
31: preferences in the selection of radioisotopes
its a requrement that the organism is exposed to the smallest dose possible
it is advantageous to use isotopes of short half life
31: In vitro methods
used to determine the amounts of diff. hormones
ex. antigens (virology)
31: in vivo methods
diagnosis of thyroid gland, measure the uptake of iodine
administered orally NaI sol.
measured with a scintillation counter
32: ultrasound
mechanical waves propagating in medium. cannot propagate in vaccume
sound above 20000 Hz
32: ultrasound effects
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
32: Diagnostic use of ultrasound
used for diagnostic, surgical and theraputical purposes
32: echo measurement
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
32: echoencephalography
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)
33: conventional linear and axial tomography
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
33: ct
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
33: Image formation using radio isotopes
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
33: rectilinear scanner
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
33: thermography
prod. images by scanning over surface
infrared/heat
based on thermal radiation
scanning thermographic camera measures IR- converts to an electrical signal
34: Positron emission tomography
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
34: NMR
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
