1,a*QRS Complex in ECG Waveform (2 Marks):* 4.
*Selective Permeability of Membranes:* Cell
The *QRS complex* represents the *depolarization of membranes allow only specific ions to pass, contributing
the ventricles, which leads to **ventricular to voltage differences and signal generation.
contraction*. It is the largest wave in the ECG and
indicates the electrical activity as the impulse spreads
through the ventricles.
1,b.*Use of Microelectrode (2 Marks):*
Microelectrodes are used to *record electrical activity
from individual cells, especially **neurons and muscle
cells. They are commonly used in **neurophysiology* to
study *action potentials* and in *research* to measure
intracellular potentials.
1,c*Refractory Period (2 Marks):*
The *refractory period* is the time during which a
*nerve or muscle cell is unable to respond to a second
stimulus* after an action potential. It ensures *one-way
transmission* of impulses and includes:
- *Absolute refractory period:* No new action potential
can be initiated.
- *Relative refractory period:* A stronger-than-normal
stimulus is needed to initiate another action potential.
1d,*Thermistor (2 Marks):*
A *thermistor* is a type of *temperature-sensitive
resistor* whose resistance *changes significantly with
temperature. It is commonly used for **temperature
measurement, control, and compensation* in electronic
circuits.
1e,*Types of Thermocouples (2 Marks):*
Thermocouples are classified based on the metals used.
Common types include:
1. *Type J (Iron–Constantan):* Suitable for lower
temperature ranges, up to 750°C.
2. *Type K (Chromel–Alumel):* Most common, used up
to 1260°C.
3. *Type T (Copper–Constantan):* Accurate at low
temperatures, used in cryogenics.
4. *Type R/S (Platinum–Rhodium):* Used for high-
temperature applications, up to 1600°C.
Each type differs in temperature range, accuracy, and
application suitability.
1f,*CMRR (Common Mode Rejection Ratio) – 2 Marks:*
CMRR is the *ability of a differential amplifier* to reject
*common-mode signals* (signals that are present on
both inputs). It is defined as the ratio of differential gain
to common-mode gain.
A *high CMRR* means better noise rejection, especially
in biomedical signal acquisition.
2,a,*Types of Pre-amplifiers in Medical Instruments:*
1. *Instrumentation Amplifier:*
Commonly used due to its high input impedance and
excellent common-mode rejection. Ideal for amplifying
low-level physiological signals like ECG and EEG.
2. *Chopper Amplifier:*
Used to amplify very low-frequency or DC signals with
minimal noise and drift. Suitable for bio-potential
measurements.
3. *Capacitive-coupled Amplifier:*
Uses capacitors to block DC components and amplify
AC signals. Effective for reducing baseline drift in signal
processing.
4. *Transformer-coupled Amplifier:*
Employs transformers for signal isolation and
amplification, mainly in older or specific applications
requiring isolation.
3,b,Sure! Here's a column-wise comparison suitable for
a 4-mark answer:
| *Sensor* | *Transducer*
|
|--------------------------------------|----------------------------------
-------|
| A sensor detects physical changes in the environment
(e.g., temperature, pressure). | A transducer converts
one form of energy into another. |
| It only senses/measures a physical quantity. | It both
senses and converts the physical quantity into a
readable signal. |
| Example: Thermometer (measures temperature). |
Example: Thermocouple (converts heat into voltage). |
| Output is generally not usable without a transducer. |
Output is usually an electrical signal suitable for
processing. |
4,a,Here’s a concise 4-mark answer:
*Generation of Physiological Potentials in the Human
Body:*Physiological potentials are electrical signals
produced by the movement of ions across cell
membranes, mainly in nerve and muscle cells. These
potentials are generated due to:
1. *Resting Membrane Potential:* Cells maintain a
voltage difference across their membrane using ion
pumps (like the sodium-potassium pump), creating a
negative charge inside the cell.
2. *Action Potential:* When stimulated, ion channels
open, allowing Na⁺ to enter the cell and K⁺ to exit,
causing depolarization and then repolarization. This
rapid change creates an action potential.
3. *Ion Concentration Gradients:* Differences in ion
concentrations (Na⁺, K⁺, Ca²⁺, Cl⁻) across the membrane
drive the generation of potentials.
