Physiology Laws

·         Fick's first law of diffusion: The flux by simple passive diffusion is directly proportional to the concentration of dissolved molecules.

Rate of Diffusion: (A/T) x D x (P1-P2)

·         Einstein's relation states that for average molecules in biological media, the mean displacement squared, (dx)², is equal to 2 multiplied by D and by the time (t) elapsed, since the molecules started to diffuse.

·         The Donnan effect of plasma is the extra osmotic pressure of protein solutions caused by uneven distribution of small, permeable cations and anions.

·         The flow of each ion across the plasma membrane tends to bring the resting membrane potential toward the equilibrium potential for that ion. The more conductive the membrane to a particular ion, the greater will be the ability of that ion to bring the membrane potential toward its equilibrium potential. This is described by the chord conductance equation.

·         Waller’s law of neuronal degeneration: When a motor axon has been severed, the rough endoplasmic reticulum accumulates proteins required for repair of the axon. The axon and the myelin sheath distal to the injury die and are phagocytized. The neuroglial Schwann cells remain alive, proliferate and form long rows along the pathway previously occupied by the dead axon. The severed axon regenerate along this pathway.

·         Dale’s law: A single neuron liberates only one neurotransmitter at all its synapses. Although the law is frequently valid, there are several exceptions, where two or more co-transmitters are released at all the synapses of a single neuron.

·         Sherrington’s integration law. The integrative action of the nervous system unifies separate organs to form an individual personality.

·         Stevens proposed the power law to account for the non-linearity of most physiological mechanisms. The interpreted stimulus strength (ISS) is equal to a constant (k) multiplied by the actual stimulus strength (SS) raised to the power n.

·         Cannons law: The peristalsis in the small intestine is polarised, so it always proceeds in the oral-aboral direction.

·         Poiseuille´s law: The volume rate (Vdot) is equal to the driving pressure (DP) divided by the resistance:  V°  = DP/Resistance

·         The law of Laplace. For a thin-walled organ with two main radii, the relationship between transmural pressure (DP) and tension (T) is determined by the radii: DP = T /(r1 + r2).

For Surface Tension: P @ 1/r (in alveoli, MEMO: why double bubble disappears)

·         Einthoven’s law states that any two of the three bipolar standard limb leads determine the third one with mathematical precision.

·         Bernoulli’s law states that the driving energy equals the sum of the kinetic energy, the constant positional energy and the laterally directed energy (ie, the lateral pressure directed towards the walls). The maximum expiratory airflow is effort-independent according to Bernoulli’s law. Thus, during expiration the lateral pressure is lowest where the cross sectional area is smallest (the trachea), and the last part of the trachea collapses.

·         Haldane’s law: Any saturation dive to less than 10 m does not cause decompression sickness and allows ascent without decompression stops.

·         The inert gas narcosis increases in intensity with depth according to Martini’s law: Each 10 m of diving depth changes the behaviour as much as one drink. Therefore, the limit for compressed air diving should be 50 m.

·         Van´t Hoof´s rule: The rate of energy conversion in chemical reactions increases in proportion to the rise in temperature.

·         Boyle’s Law: P is inverse to Volume.