JNTU B.Tech IV MEDICAL INSTRUMENTATION Previous Question Paper (October/November - 2020 - R15)

A normal ECG waveform consists of the P wave, QRS complex, and T wave. The P wave represents atrial depolarization. The QRS complex represents ventricular depolarization, where the Q wave is the first negative deflection, R is the first positive deflection, and S is the negative deflection following R. The T wave represents ventricular repolarization. Key intervals include the PR interval (atrial depolarization to ventricular activation) and the ST segment (isoelectric period between ventricular depolarization and repolarization).

The electrical equivalent circuit of an axon models the cell membrane as a passive electrical network. The lipid bilayer acts as a capacitor (Cm) due to its insulating properties, while the ion channels act as variable resistors (Rm) representing membrane conductance. The intracellular and extracellular fluids are represented by longitudinal resistors (Ri and Ro respectively), which account for the axial resistance of the axoplasm and the surrounding medium.

In this model, the membrane potential is maintained by the equilibrium potentials of specific ions (Na+, K+, Cl-), represented as batteries in series with the membrane resistors. The circuit demonstrates how current flows through the membrane (transverse) and along the axon (longitudinal), determining the propagation velocity and attenuation of the action potential along the nerve fiber.