SEMMELWEIS UNIVERSITY, MEDICAL BIOPHYSICS - FINAL
EXAM ACTUAL 2026 QUESTIONS AND 100% DETAILED
ANSWERS
The donnan-equilibrium.
Refers to theequilibrium state in which there is anuneven
distributionof ions across a membrane, and the particles are
not able to diffuse because of impermeability of the
membrane. In cells this equilibrium is realized by the sodium
potassium pump, which actively controls this uneven
distribution.
Properties of the action potential.
1. Unaltered ion concentration: only the permeability is
changing (ghk equation is valid)
2. Refractory period (dead time) 2 types:
- absolute: voltage gated of na are inactive
- relative: action potential can occur but it requires much
higher threshold stimuli to (prevent the backpropagation)
3. Special ap: cardiac ap the duration is much longer (200-400
ms) thanks to additional channels, ca(2+) channels.
4. (''all or none''- stimuli have to exceed a threshold level to
trigger action potential.
5. Controlled by the opening and closing of voltage driven
channels
6. Action potential is very fast 1.5ms)
pg. 1
,Propagation of the action potential, refractory period and its
role.
The propagation has a special exponential decay because of its
rc circuit nature.
Refractory period is a time in which the cell is not able to
respond to the stimulus by generating an action potential. It is
characterised by an absolute refractory period and a relative
refractory period (where a stimulus of much higher magnitude
would be required to generate an action potential).
Electric signals measured on the body surface, for diagnostic
purposes.
Based on dipole moment : d=q*l
Ekg:
A. A graph of the voltage vs. Time of the electrical activity of
the heart b. Measured using electrodes placed on the skin
Eeg: records the electrical activity of the brain
Emg: records the electrical activity of skeletal muscles by
placing electrodes on diff. Places on the skin
Electrochemical potential.
There are two components; charge difference/ potential across
the membrane and chemical difference/ potential.
pg. 2
,Ion currents during action potential.
Steps:
1. Stimulus above threshold
2. Voltage-gated channels of na(+) open = na+influx
3. Voltage-gated channels of k(+) open = k+ outflux
4. Voltage-gated channels of na(+) inactive (partial)
5. Voltage-gated channels of na(+) close
6. Voltage-gated channels of k(+) close
T is approx. 1-5 ms (muscle and neuron)
U is approx. 100 mv
Sound as a wave.
Sound is a mechanical wave - a "pressure wave" which are
sinusoidal oscillations.
It is a longitudinal wave in liquid and in gases, which means
that the oscillation is parallel to the direction of propagation.
In solids the waves can be either longitudinal or transverse.
Acoustic impedance, reflection, of sound, reflectivity.
Acoustic impedance:quantity that shows to what extent the
medium resists when particles are brought into motion,
practical equation:
Z = rho * c
pg. 3
, (product of the density and the speed of sound in the specific
medium)
(z also can be measured by the ratio of the square root of
density and compressibility)
Reflection: at the boundary of 2 media part of the intensity of
the sound reflect into the opposite direction and not penetrate
the body the extent of this phenomenon is measured by the
reflectivity equation.
*ultrasound diagnostic methods are based on that
phenomenon.
Reflectivity: measured by the ratio of the reflected intensity
according
To this formula: r = jr/j0 = (z1-z2/z1+z2)^2
When r=1 → max reflection, when r=0 → no reflection
Imaging modes in sonography .
One dimensional a image (amplitude modulation): single
transducer, time/distance corresponding to amplitude
changes.
One dimensional b image (brightness modulation): single
transducer where the amplitude is represented a brightness
pixels on grayscale.
Two-dimensional b-image (2-d brightness modulations): an
array of transducers, manipulated so that the wave direction
can be controlled (allows back and forth scanning without
needing to move the transducer).
pg. 4
EXAM ACTUAL 2026 QUESTIONS AND 100% DETAILED
ANSWERS
The donnan-equilibrium.
Refers to theequilibrium state in which there is anuneven
distributionof ions across a membrane, and the particles are
not able to diffuse because of impermeability of the
membrane. In cells this equilibrium is realized by the sodium
potassium pump, which actively controls this uneven
distribution.
Properties of the action potential.
1. Unaltered ion concentration: only the permeability is
changing (ghk equation is valid)
2. Refractory period (dead time) 2 types:
- absolute: voltage gated of na are inactive
- relative: action potential can occur but it requires much
higher threshold stimuli to (prevent the backpropagation)
3. Special ap: cardiac ap the duration is much longer (200-400
ms) thanks to additional channels, ca(2+) channels.
4. (''all or none''- stimuli have to exceed a threshold level to
trigger action potential.
5. Controlled by the opening and closing of voltage driven
channels
6. Action potential is very fast 1.5ms)
pg. 1
,Propagation of the action potential, refractory period and its
role.
The propagation has a special exponential decay because of its
rc circuit nature.
Refractory period is a time in which the cell is not able to
respond to the stimulus by generating an action potential. It is
characterised by an absolute refractory period and a relative
refractory period (where a stimulus of much higher magnitude
would be required to generate an action potential).
Electric signals measured on the body surface, for diagnostic
purposes.
Based on dipole moment : d=q*l
Ekg:
A. A graph of the voltage vs. Time of the electrical activity of
the heart b. Measured using electrodes placed on the skin
Eeg: records the electrical activity of the brain
Emg: records the electrical activity of skeletal muscles by
placing electrodes on diff. Places on the skin
Electrochemical potential.
There are two components; charge difference/ potential across
the membrane and chemical difference/ potential.
pg. 2
,Ion currents during action potential.
Steps:
1. Stimulus above threshold
2. Voltage-gated channels of na(+) open = na+influx
3. Voltage-gated channels of k(+) open = k+ outflux
4. Voltage-gated channels of na(+) inactive (partial)
5. Voltage-gated channels of na(+) close
6. Voltage-gated channels of k(+) close
T is approx. 1-5 ms (muscle and neuron)
U is approx. 100 mv
Sound as a wave.
Sound is a mechanical wave - a "pressure wave" which are
sinusoidal oscillations.
It is a longitudinal wave in liquid and in gases, which means
that the oscillation is parallel to the direction of propagation.
In solids the waves can be either longitudinal or transverse.
Acoustic impedance, reflection, of sound, reflectivity.
Acoustic impedance:quantity that shows to what extent the
medium resists when particles are brought into motion,
practical equation:
Z = rho * c
pg. 3
, (product of the density and the speed of sound in the specific
medium)
(z also can be measured by the ratio of the square root of
density and compressibility)
Reflection: at the boundary of 2 media part of the intensity of
the sound reflect into the opposite direction and not penetrate
the body the extent of this phenomenon is measured by the
reflectivity equation.
*ultrasound diagnostic methods are based on that
phenomenon.
Reflectivity: measured by the ratio of the reflected intensity
according
To this formula: r = jr/j0 = (z1-z2/z1+z2)^2
When r=1 → max reflection, when r=0 → no reflection
Imaging modes in sonography .
One dimensional a image (amplitude modulation): single
transducer, time/distance corresponding to amplitude
changes.
One dimensional b image (brightness modulation): single
transducer where the amplitude is represented a brightness
pixels on grayscale.
Two-dimensional b-image (2-d brightness modulations): an
array of transducers, manipulated so that the wave direction
can be controlled (allows back and forth scanning without
needing to move the transducer).
pg. 4
