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Q12:
Define a cardiac cycle and the cardiac output.
Solution :
1. Definition of the Cardiac Cycle
The cardiac cycle is defined as the complete sequence of coordinated electrical, mechanical, and pressure-related events that occur in the heart from the beginning of one heartbeat to the beginning of the next. In a healthy adult human heart beating at an average rate of $72$ beats per minute, the cycle duration is approximately $0.8$ seconds.
The process is divided into two primary phases based on the state of the cardiac musculature [Per Physiological Standard Nomenclature]:
- Atrial Systole: The contraction of the atria, forcing the remaining blood into the ventricles (lasting $\approx 0.1$ seconds).
- Ventricular Systole: The contraction of the ventricles, ejecting blood into the pulmonary artery and the aorta (lasting $\approx 0.3$ seconds).
- Joint Diastole: The state of relaxation where all four chambers are in a relaxed state, allowing for passive filling (lasting $\approx 0.4$ seconds).
2. Definition of Cardiac Output
Cardiac Output ($CO$) is defined as the total volume of blood pumped by each ventricle into the systemic or pulmonary circulation per minute. It is a critical indicator of cardiovascular performance and systemic perfusion.
The mathematical derivation is expressed as:
$CO = SV \times HR$
Where:
- $SV$ (Stroke Volume): The volume of blood pumped out by each ventricle during a single cardiac cycle. An average value is $\approx 70\text{ mL}$.
- $HR$ (Heart Rate): The number of cardiac cycles occurring per minute. An average value is $\approx 72\text{ beats/min}$.
3. Mathematical Calculation & Analysis
Using the standard physiological constants:
$SV = 70\text{ mL/beat}$
$HR = 72\text{ beats/min}$
$CO = 70\text{ mL/beat} \times 72\text{ beats/min} = 5040\text{ mL/min}$
Conversion to Liters: $CO \approx 5.04\text{ L/min}$ [By the standard unit conversion $1000\text{ mL} = 1\text{ L}$].
4. Visual Representation of Cardiac Cycle Phases
Final Solution: The Cardiac Cycle is the sequential electrical and mechanical event of one heartbeat, typically lasting 0.8 seconds. Cardiac Output is the volume of blood pumped by the ventricles per minute, calculated as the product of Stroke Volume and Heart Rate, averaging approximately 5 liters per minute in a healthy adult.
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?
- Q13: Explain heart sounds.
- Q14: Draw a standard ECG and explain the different segments in it.
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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