Biofizika - Učno gradivo za študijski program Zdravstvena nega

Zbirka kartic s temeljnimi fizikalnimi in biofizikalnimi pojmi, definicijami ter formulami iz učnega gradiva Biofizika za študente zdravstvene nege.

Displacement (Premik)

The distance and direction a body moves along a straight path; its SI unit is the meter ($\text{m}$).

Velocity (Hitrost)

The rate of displacement over travel time ($v = \frac{s}{t}$); its SI unit is meters per second ($\text{m/s}$ or $\text{m}\,\text{s}^{-1}$).

Acceleration (Pospešek)

The change in velocity per unit time ($a = \frac{\Delta v}{\Delta t}$); a vector quantity measured in the SI unit $\text{m/s}^2$ or $\text{m}\,\text{s}^{-2}$.

Weight (Teža)

The vertically downward gravitational force exerted on an object by Earth ($F = mg$); its SI unit is the newton ($\text{N}$).

Newton's First Law (Prvi Newtonov zakon)

A principle stating that a body remains at rest or maintains a constant velocity if the vector sum of all forces acting upon it equals zero ($\sum F = 0$).

Newton's Second Law (Drugi Newtonov zakon)

A law describing systems where the net external force is non-zero, resulting in acceleration proportional to that net force ($F = ma$).

Newton's Third Law (Tretji Newtonov zakon)

The law of action and reaction stating that if body A exerts a force on body B, body B simultaneously exerts an equal and oppositely directed force on body A ($F_{21} = -F_{12}$).

Torque (Navor sile)

A vector quantity measuring rotational force relative to a pivot point, calculated as the product of the force and the perpendicular lever arm ($M = F \times r$).

Law of Conservation of Energy (Zakon o ohranitvi energije)

The physical law stating that energy cannot be created from nothing or destroyed, but can only transform from one form to another.

Latent Heat (Utajena toplota)

The thermal energy required for a substance to undergo a phase transition between liquid and gas or solid and liquid without altering its temperature.

Thermal Conduction (Kondukcija)

The spontaneous transfer of internal thermal energy via direct microscopic physical contact between bodies without bulk mass movement.

Thermal Convection (Konvekcija)

The transfer of thermal energy via the macroscopic circulatory movement of fluids or gases caused by temperature-dependent density differences.

Thermal Radiation (Toplotno sevanje)

The transfer of energy through the emission and absorption of electromagnetic waves, such as infrared radiation, emitted by any matter with a non-zero temperature.

Ionizing Radiation (Ionizirajoče sevanje)

High-energy particles or rays possessing sufficient energy to dislodge electrons from the outer shells of atoms and molecules, which can cause biological mutations or cell death.

Alpha Radiation (Alfa sevanje)

A stream of helium-4 ($^4_2\text{He}$) nuclei with low penetrating power that can be stopped by skin or a sheet of paper, but poses severe biological damage if inhaled or ingested.

Beta Radiation (Beta sevanje)

Particulate radiation composed of high-energy electrons released during the nuclear decay of neutrons ($n \rightarrow p + e^-$); stopped by a few millimeters of aluminum.

Gamma Radiation (Gama sevanje)

Highly penetrating, high-energy electromagnetic photons emitted during nuclear decay that require thick layers of lead, concrete, or water to be absorbed.

Absorbed Dose (Absorbirana doza)

The measure of ionizing radiation energy absorbed per unit mass of matter, expressed in the SI unit gray ($1\,\text{Gy} = 1\,\text{J/kg}$).

Effective Dose (Efektivna doza)

A measure of potential biological harm caused by radiation, quantified in sieverts ($\text{Sv}$); the annual permissible dose from artificial sources is $1\,\text{mSv/year}$.

Becquerel (Bq)

The SI unit of radioactive activity representing the rate of decay as one nuclear disintegration per second ($1\,\text{Bq} = 1\,\text{decay/s}$).

Half-life (Razpolovni čas)

The specific time interval ($t_0$) required for half of the unstable radioactive nuclei in a given sample to decay spontaneously.

UV-A Radiation

Ultraviolet radiation with the longest wavelengths ($320\text{--}400\,\text{nm}$) and lowest energy; it is not absorbed by ozone, passes through the atmosphere, and induces skin aging.

UV-B Radiation

Mid-wavelength ultraviolet radiation ($280\text{--}320\,\text{nm}$) largely absorbed by the stratospheric ozone layer; it is the most hazardous UV type reaching Earth's surface, causing sunburns and skin cancer.

UV-C Radiation

Shortest-wavelength ultraviolet radiation with the highest energy; capable of cleaving $O_2$ molecules, but almost entirely absorbed by the atmosphere before reaching Earth's surface.

Coulomb's Law (Coulombov zakon)

The physical law stating that the electrostatic force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them ($F = k \frac{q_1 q_2}{r^2}$).

Electric Voltage (Električna napetost)

The potential difference between two distinct points in an electric field ($U = \frac{\text{Energy}}{\text{Charge}}$), measured in volts ($\text{V}$).

Ohm's Law (Ohmov zakon)

The law stating that the electric current passing through a conductor at constant temperature is directly proportional to the voltage applied across its terminals ($U = R \cdot I$).

Series Circuit (Zaporedna vezava)

A circuit configuration where identical electric current passes sequentially through all elements ($I = I_1 = I_2$) while the total voltage is partitioned ($U = U_1 + U_2$); a break in any component interrupts the entire loop.

Parallel Circuit (Vzporedna vezava)

A circuit configuration where components share the exact same voltage ($U = U_1 = U_2$) while total electric current splits into separate branches ($I = I_1 + I_2$).

Ferromagnetism (Feromagnetizem)

The physical property of materials containing microscopic magnetic domains that align under an external magnetic field to strongly attract or become permanent magnets.

Cell Membrane (Celična membrana)

A selective biological barrier consisting of a phospholipid bilayer with polar heads and non-polar tails, interspersed with proteins, cholesterol, and carbohydrates.

Diffusion (Difuzija)

The spontaneous passive movement of particles down a concentration or chemical potential gradient from a region of higher concentration to a region of lower concentration.

Osmosis (Osmoza)

The passive transport of solvent molecules (water) across a semipermeable membrane toward an area of higher solute concentration, driven by osmotic pressure.

Na+/K+-ATPase (Na+/K+-črpalka)

A primary active transport enzyme that consumes $1\,\text{mol}$ of ATP to pump $3\,\text{Na}^+$ ions out of the cell while transporting $2\,\text{K}^+$ ions into the cell.

Ca2+-ATPase

A primary active transporter that pumps calcium ions out of the cell against their gradient, maintaining an extracellular concentration $1000\times$ higher than inside the cell.

Endocytosis (Endocitoza)

An energy-dependent cellular transport process by which large molecules (e.g., proteins, lipids) or fluids are internalized into the cell enclosed within membrane vesicles.

Exocytosis (Eksocitoza)

An energy-dependent process by which cells package metabolic waste, proteins, hormones, or neurotransmitters into secretory vesicles that fuse with the plasma membrane to release contents externally.

Resting Membrane Potential (Mirovni membranski potencial)

The static electrical voltage difference across a resting cell membrane, negative on the inside relative to the outside (e.g., $-70\,\text{mV}$ in neurons, $-90\,\text{mV}$ in cardiac cells).

Nernst Equation (Nernstova enačba)

An equation used to calculate the equilibrium electrical potential ($\Delta E_N$) established across a membrane for an individual ion species based on its concentration ratio ($\Delta E_N = \frac{RT}{z_i F} \ln\left(\frac{C_z}{C_n}\right)$).

Depolarization (Depolarizacija)

A decrease in electrical membrane potential where the interior of the cell becomes less negative and shifts toward $0\,\text{mV}$ or into positive values, primarily triggered by $\text{Na}^+$ influx.

Hyperpolarization (Hiperpolarizacija)

An increase in membrane potential polarity where the cell interior becomes more negative than its resting membrane potential, primarily caused by prolonged $\text{K}^+$ efflux.

Refractory Period (Refraktarna doba)

The recovery period following an action potential during which the cell membrane cannot generate another action potential (or requires a stronger stimulus) due to inactivation of $\text{Na}^+$ channels.

Nodes of Ranvier (Ranvierovi zažemi)

Unmyelinated, approximately $1\,\mu\text{m}$ segments of bare axonal membrane situated between Schwann cells that facilitate rapid, saltatory conduction of action potentials.

Voltage-Gated Ion Channels (Napetostno odvisni ionski kanalčki)

Transmembrane protein pores (such as voltage-gated $\text{Na}^+$, $\text{K}^+$, or $\text{Ca}^{2+}$ channels) whose conformational opening and closing is triggered by shifts in transmembrane voltage.

Ligand-Gated Ion Channels (Od liganda odvisni ionski kanalčki)

Transmembrane ion channels (e.g., nicotinic acetylcholine, NMDA, or GABA receptors) that alter their open/closed state in response to the specific binding of a chemical messenger (ligand).

Transverse Wave (Transverzalno valovanje)

A wave in which the oscillatory displacement of particles or fields occurs perpendicular to the direction of wave propagation (e.g., light waves).

Longitudinal Wave (Longitudinalno valovanje)

A wave in which particle vibrations occur parallel to the direction of wave travel, creating alternating areas of compression and rarefaction (e.g., sound waves).

Organ of Corti (Cortijev organ)

The acoustic receptor structure located on the basilar membrane in the middle scale of the cochlea, composed of sensory hair cells that transduce mechanical fluid vibrations into nerve impulses.

Otoliths (Otoliti)

Microscopic inorganic calcium carbonate crystals embedded within the gelatinous otolithic membrane of the macular vestibular organs that shift under gravity to detect head tilt.

Convex Lens (Konveksna ali zbiralna leča)

A converging optical lens that focuses refracted light rays to a focal point; clinically utilized to correct hyperopia (farsightedness), where images focus behind the retina.

Concave Lens (Konkavna ali razpršilna leča)

A diverging optical lens that spreads light rays outward; clinically utilized to correct myopia (nearsightedness), where light rays focus in front of the retina.

Class 1 Lever (Vzvod prvega tipa)

A two-armed anatomical lever where the fulcrum/pivot point lies between the applied muscular effort and the load (e.g., the head and neck balancing at the atlanto-occipital joint).

Class 2 Lever (Vzvod drugega tipa)

A single-armed lever where the load is located between the fulcrum and the effort force, making the effort arm longer than the load arm (e.g., lifting the body onto the toes).

Class 3 Lever (Vzvod tretjega tipa)

The most common anatomical lever system, where the effort force is positioned closer to the fulcrum than the load, maximizing velocity at the expense of requiring large muscular forces (e.g., the biceps flexing the elbow).

Electronic Baropodometry (Elektronska baropodometrija)

A non-invasive diagnostic method using an active multi-sensor platform to evaluate plantar pressure distribution, posture, stability, and foot dynamics during stance and gait.

X-ray Tube (Rentgenska cev)

An evacuated tube where electrons emitted by a heated cathode are accelerated toward a heavy metal anode (e.g., tungsten or molybdenum), with $1\%$ of electron kinetic energy converted to X-ray photons and $99\%$ to heat.

Computed Tomography (Računalniška tomografija - CT)

A diagnostic imaging technique that reconstructs thin cross-sectional slices ($1\text{--}10\,\text{mm}$) of internal anatomy using computer-processed multi-angle X-ray transmissions.

Positron Emission Tomography (PET)

A molecular imaging technique that detects metabolic processes via injected positron-emitting radionuclides (such as Fluorine-18); electron-positron annihilation yields two $511\,\text{keV}$ gamma photons emitted at $180^\circ$.

Nuclear Magnetic Resonance (Jedrska magnetna resonanca - MRI)

A non-ionizing medical imaging method based on placing tissue into a strong magnetic field (e.g., $1\,\text{T}$) and exciting hydrogen nuclei with radiofrequency pulses to detect tissue-specific relaxation times.

Electrocardiogram (Elektrokardiogram - EKG)

A diagnostic recording tracing the cyclic variations in electrical potential differences across the body surface generated by cardiac cell depolarization and repolarization.

P Wave (P val)

The initial deflection wave on an ECG tracing representing the electrical depolarization of both cardiac atria initiated by the sinoatrial (SA) node.

QRS Complex (QRS sestav)

The prominent sharp series of deflections on an ECG tracing corresponding to the rapid electrical depolarization of the cardiac ventricles.

T Wave (T val)

The deflection on an ECG tracing that represents the repolarization phase of the cardiac ventricles returning to their resting state.

Premik

Razdalja, za katero se telo premakne v določeni smeri. Enota SI je meter ($\text{m}$).

Pospešek

Sprememba hitrosti na časovno enoto z enoto SI $\text{m/s}^2$ ali $\text{ms}^{-2}$. Gre za vektor, ki ga označimo s predznakom $+$, če se hitrost poveča, oziroma $-$, če se hitrost zmanjša.

Teža

Gravitacijska sila, s katero Zemlja privlači vsako telo navpično navzdol. Enota SI je newton ($\text{N}$).

Prvi Newtonov zakon

Zakon gibanja, po katerem telo miruje ali se giblje s konstantno hitrostjo natanko takrat, ko je vsota vseh sil na telo enaka nič ($F_1 + F_2 + F_3 + \dots + F_n = 0$).

Tretji Newtonov zakon

Zakon akcije in reakcije, ki pravi, da če telo A deluje na telo B z določeno silo, potem tudi telo B deluje na telo A z enako veliko, a nasprotno usmerjeno silo ($F_{21} = -F_{12}$).

Navor sile ($M$)

Vektor, pravokoten na ravnino, ki jo določata sila in osišče; enak je produktu sile in ročice ($M = F \cdot r'$), pri čemer je ročica pravokotna razdalja od osi do premice delovanja sile.

Utajena (latentna) toplota

Količina toplote, ki je potrebna, da kapljevina preide v plin ali da trdna snov preide v tekočino pri stalni temperaturi.

Kondukcija

Prevajanje toplotne energije z neposrednim dotikom delcev snovi brez makroskopskega mešanja same snovi.

Konvekcija

Prenos toplote s kroženjem oziroma tokovnim gibanjem delcev v tekočinah (kapljevinah ali plinih).

Alfa ($\alpha$) delec

Visokoionizirajoč delec z majhno prodornostjo, ki ga sestavlja atomsko jedro helija-4 ($^4_2\text{He}$) z dvema protonoma in dvema nevtronoma.

Beta ($\beta$) sevanje

Tok hitrih elektronov z visoko energijo, ki nastanejo ob razpadu nevtronov v nestabilnem atomskem jedru ($n \rightarrow p + e^-$).

Gama ($\gamma$) sevanje

Visokoenergijsko elektromagnetno valovanje brez mase ali naboja, sestavljeno iz fotonov z izredno visoko prodorno močjo, ki spremlja razpade $\alpha$ in $\beta$.

Gray (Gy)

Enota SI za absorbirano dozo ionizirajočega sevanja v telesu, določena kot en joule prejete energije na kilogram snovi ($1\,\text{Gy} = 1\,\text{J/kg}$).

Sievert (Sv)

Enota za merjenje ekvivalentne oziroma efektivne doze sevanja, ki izraža potencialno biološko škodo ionizirajočega sevanja na človeško tkivo.

Bequerel (Bq)

Enota za merjenje aktivnosti radioaktivnega vira, ki pomeni natanko en radioaktivni razpad atomskega jedra v časovnem intervalu ene sekunde.

Razpolovni čas ($t_0$)

Čas, v katerem se število prvotnih radioaktivnih jeder v vzorcu zaradi spontanih razpadov zmanjša na točno polovico.

Coulombov zakon

Zakon, ki pravi, da je električna sila med dvema točkastima nabojema premo sorazmerna produktu obeh nabojev in obratno sorazmerna s kvadratom razdalje med njima ($F = k \frac{q_1 q_2}{r^2}$).

Ohmov zakon

Fizikalni zakon, ki določa, da je pri stalni temperaturi električni tok skozi prevodnik premo sorazmeren električni napetosti med njegovima priključkoma ($U = R \cdot I$).

Feromagnetna snov

Snov z magnetnimi domenami, ki močno privlači železne in jeklene predmete ter jo je mogoče trajno ali začasno namagnetiti.

Difuzija

Spontan prehod snovi iz področja z višjo koncentracijo v področje z nižjo koncentracijo vzdolž koncentracijskega gradienta.

Osmoza

Prehajanje molekul topila (vode) skozi polprepustno membrano iz področja z nižjo koncentracijo topljenca v področje z višjo koncentracijo topljenca.

$$\text{Na}^+/\text{K}^+\text{-ATPaza}$$

Primarni aktivni transportni protein v celični membrani, ki z energijo hidrolize ene molekule $\text{ATP}$ istočasno prenese tri ione $\text{Na}^+$ iz celice in dva iona $\text{K}^+$ v celico.

Endocitoza

Oblika celičnega transporta, pri kateri celica s pomočjo uvihavanja membrane in tvorbe mešičkov (veziklov) ob porabi energije vnese večje molekule ali tekočino.

Mirovni membranski potencial (MMP)

Razlika v električni napetosti med notranjo in zunanjo stranjo membrane neaktivne vzdražne celice (pri živčni celici znaša $-70\,\text{mV}$, pri srčni mišični celici $-90\,\text{mV}$).

Depolarizacija

Sprememba membranskega potenciala, pri kateri se negativna napetost v notranjosti celice zmanjša in premakne proti $0\,\text{mV}$ ali v pozitivno območje.

Hiperpolarizacija

Povečanje membranske napetosti, pri katerem postane notranjost celične membrane še bolj negativna glede na izhodiščni mirovni potencial.

Akcijski potencial

Kratkotrajen, hiter preobrat električnega potenciala na membrani vzdražne celice, ki nastane ob doseženem pragu po načelu »vse ali nič«.

Refraktarna doba

Časovno obdobje po sprožitvi akcijskega potenciala, ko se zaradi inaktiviranosti natrijevih kanalčkov nov akcijski potencial začasno ne more sprožiti ali pa zahteva znatno močnejši dražljaj.

Nernstov potencial

Električna napetost čez celično membrano, ki nastane ob doseženem elektrokemičnem ravnotežju posameznega iona, pri čemer se njegov neto pretok popolnoma ustavi.

Ranvierovi zažemi

Kratki, približno mikrometer dolgi nemielinizirani odseki membrane na živčnem vlaknu med sosednjimi Schwannovimi celicami, ki omogočajo skokovito prevajanje akcijskega potenciala.

Cortijev organ

Čutilni receptorski organ sluha, nameščen na bazilarni membrani v notranjem ušesu, ki premik dlačnih čutnic pretvarja v električne živčne impulse.

Otoliti

Drobni anorganski kristali v otolitski membrani ravnotežnega organa, ki se premikajo pod vplivom gravitacijske sile in vzdražijo receptorske dlačne celice.

Kratkovidnost (miopija)

Motnja vida, pri kateri se svetlobni žarki zaradi predolgega očesnega zrkla ali prevelike lomnosti zberejo pred mrežnico; korigira se z razpršilno (konkavno) lečo.

Daljnovidnost (hipermetropija)

Motnja vida, pri kateri se svetlobni žarki zberejo za mrežnico zaradi premajhne lomnosti ali prekratkega očesnega zrkla; popravlja se z zbiralno (konveksno) lečo.

Biomehanika

Veda o zakonitostih mehanike v biologiji, ki preučuje mirovanje človeškega telesa v ravnovesju (statika) ter gibanje teles pod vplivom notranjih in zunanjih sil (dinamika).

Vzvod prvega tipa

Dvokraki vzvod, pri katerem se oporna točka nahaja med delovanjem mišične sile in bremenom (primer v telesu je gibanje glave v zatilnem sklepu).

Vzvod drugega tipa

Enokraki vzvod, pri katerem je breme med oporno točko in delovanjem sile, pri čemer je ročica mišične sile daljša od ročice sile bremena (primer je dvig na prste na stopalu).