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Q14:
Draw a standard ECG and explain the different segments in it.
Solution :
Given Variables & Initial Setup
An Electrocardiograph (ECG) is a graphical representation of the electrical activity of the heart during a single cardiac cycle. The standard ECG is recorded using a machine called an Electrocardiograph, utilizing three electrical leads (two at the wrists and one at the left ankle) to monitor heart function. The waveform is categorized into specific waves (P, Q, R, S, T) that correspond to specific phases of cardiac depolarization and repolarization.
Visual Representation of a Standard ECG
Step 1: Analysis of the P-Wave
The P-wave represents the electrical excitation (or depolarization) of the atria. This electrical impulse leads to the contraction of both atria [Per the physiological principle of atrial systole].
Step 2: Analysis of the QRS Complex
The QRS complex represents the depolarization of the ventricles. This signals the initiation of ventricular contraction. The contraction starts shortly after the Q-wave and marks the beginning of the ventricular systole [Per the mechanism of excitation-contraction coupling].
Step 3: Analysis of the T-Wave
The T-wave represents the return of the ventricles from an excited state to a normal state (repolarization). The end of the T-wave marks the end of systole.
Comparative Summary of ECG Segments
| Feature | Physiological Event |
|---|---|
| P-wave | Atrial Depolarization |
| QRS Complex | Ventricular Depolarization |
| T-wave | Ventricular Repolarization |
| P-R Interval | Atrioventricular conduction time |
Clinical Significance
By counting the number of QRS complexes that occur in a given time period, one can determine the heart rate of an individual. Since the ECG represents a standard cardiac cycle, deviations in the shape, duration, or timing of these waves are used in clinical diagnostics to detect myocardial infarction, arrhythmias, or electrolyte imbalances [Per clinical cardiology standards].
Final Solution: The standard ECG consists of the P-wave (atrial depolarization), the QRS complex (ventricular depolarization), and the T-wave (ventricular repolarization), collectively mapping the electrical sequence of a functional heartbeat.
More Questions from Class 11 Biology Body Fluids and Circulation EXERCISES
- Q1: Name the components of the formed elements in the blood and mention one major function of each of them.
- Q2: What is the importance of plasma proteins?
- Q3: Match Column I with Column II : Column I Column II (a) Eosinophils (i) Coagulation (b) RBC (ii) Universal Recipient (c) AB Group (iii) Resist Infections (d) Platelets (iv) Contraction of Heart (e) Systole (v) Gas transport
- Q4: Why do we consider blood as a connective tissue?
- Q5: What is the difference between lymph and blood?
- Q6: What is meant by double circulation? What is its significance?
- Q7(a): Write the differences between : (a) Blood and Lymph
- Q7(b): Write the differences between : (b) Open and Closed system of circulation
- Q7(c): Write the differences between : (c) Systole and Diastole
- Q7(d): Write the differences between : (d) P-wave and T-wave
- Q8: Describe the evolutionary change in the pattern of heart among the vertebrates.
- Q9: Why do we call our heart myogenic?
- Q10: Sino-atrial node is called the pacemaker of our heart. Why?
- Q11: What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart?
- Q12: Define a cardiac cycle and the cardiac output.
- Q13: Explain heart sounds.
CBSE Solutions for Class 11 Biology Body Fluids and Circulation
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Excretory Products and Elimination
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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