Class 11 Biology - TAMILNADU
Body Fluids and Circulation
The chapter Body Fluids and Circulation in Class 11 Biology under Tamil Nadu Samacheer Kalvi syllabus explores the transport mechanisms in human beings. It details the composition of blood and lymph, blood groups, coagulation, and the structure and working of the human heart, including the cardiac cycle and ECG. Students also learn about regulation of cardiac activity and common cardiovascular disorders like hypertension and coronary artery disease. This chapter is vital for board exams as it features frequently in both objective and long-answer questions, carrying significant weightage in the annual examinations and medical entrance tests.
Start Learning FreeKey Concepts
Composition of Blood
Blood consists of a fluid matrix called plasma (55%) and formed elements (45%) including erythrocytes, leucocytes, and thrombocytes.
Blood Grouping
Human blood is categorized into ABO groups based on the presence or absence of surface antigens on red blood cells, alongside the Rh factor.
Human Heart Structure
The human heart is a mesodermally derived muscular organ with four chambers—two upper atria and two lower ventricles—separated by muscular walls and valves.
Cardiac Cycle
The sequential events in the heart which cyclically repeat from the beginning of one heartbeat to the next, consisting of systole and diastole.
Double Circulation
The blood flows twice through the heart in one complete cycle—systemic circulation and pulmonary circulation—ensuring strict separation of oxygenated and deoxygenated blood.
Electrocardiograph (ECG)
A graphical representation of the electrical activity of the heart during a cardiac cycle, showing distinct P, QRS, and T waves.
Important Formulas
Board Exam Info
In the Tamil Nadu Samacheer Kalvi Class 11 Biology board examinations, this chapter typically carries around 6 to 8 marks. Questions usually include 1-mark objective questions, 2 or 3-mark short answers on heart disorders or blood groups, and 5-mark detailed questions describing the cardiac cycle, double circulation, or the internal structure of the human heart.
Frequently Asked Questions
What is the difference between open and closed circulatory systems?
In an open circulatory system, blood flows through open spaces or sinuses (found in arthropods), whereas in a closed system, blood is confined to blood vessels (found in vertebrates like humans).
Why is the SA node called the pacemaker of the heart?
The Sino-atrial node (SA node) is responsible for initiating and maintaining the rhythmic contractile activity of the heart by generating action potentials spontaneously.
What causes Erythroblastosis foetalis?
It is a hemolytic disease of the newborn caused by Rh incompatibility when an Rh-negative mother carries an Rh-positive foetus.
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