Ch 8Respiration and Circulation — Class 12 Biology, concept-first.

Every living organism needs a continuous supply of energy to carry out its everyday life processes. That energy starts out stored inside the body as potential energy, locked away in the chemical bonds…

Respiratory exchange is a simple physical process. For efficient gaseous exchange the respiratory surface should have the following features:

In humans, the respiratory system has two parts: an upper part (external nares, nasal cavities, internal nares, nasopharynx, nose, throat and associated structures) and a lower part (larynx, trachea,…

Respiration is a biological process involving the exchange of gases between the atmosphere and the lungs, and it results in the formation of ATP. It includes the following processes:

Breathing is not something we have to think about — it runs automatically under dual control, nervous and chemical, and is only loosely under voluntary override.

Not every breath follows the ordinary quiet rhythm of inspiration and expiration described above. Some respiratory movements are modified versions of normal breathing, used either to clear irritants a…

Because the respiratory tract is in constant contact with the outside environment, it is vulnerable to infection, irritation and long-term damage from inhaled particles, and a number of common disorde…

Every living organism, whether made of a single cell or many, has to constantly exchange material with its surroundings and move material between different parts of its own body — taking in what it ne…

In higher animals the circulation is carried out by special fluids - blood and lymph.

The human circulatory system is composed of the blood vascular and the lymphatic system.

Erythrocytes, or red blood corpuscles, are the single most abundant cell type in the human body. They are small, circular, biconcave discs, and in humans they lack a nucleus once mature (unusually, ca…

Leucocytes, or white blood corpuscles, are the blood's mobile defence force. Unlike RBCs, they are colourless, nucleated, larger, and capable of amoeboid movement, which lets them squeeze out through…

Thrombocytes, or platelets, are not whole cells but small cell fragments, broken off from large bone-marrow cells called megakaryocytes; they are oval, lack a nucleus, and are much smaller than either…

The heart is the circulatory system's central pump — a reddish-brown, hollow, muscular organ roughly the size of a closed fist, weighing about 300 g in males and 250 g in females.

Cardiac Cycle : The heart's pumping action comes from the rhythmic contraction and relaxation of cardiac muscle.

Blood travels through three distinct kinds of vessel — arteries, veins and capillaries — each structurally suited to a different job.

Blood pressure is the pressure exerted by circulating blood against the walls of blood vessels, most often measured in the arteries using an instrument called a sphygmomanometer.

An electrocardiogram (ECG) is a graphical recording — printed out or shown on screen — of the small electrical changes detectable at the body's surface as they spread through the walls of the heart du…

The lymphatic system is made up of lymph (the fluid itself), lymphatic vessels, and a set of associated organs and tissues.

Q.1 of the textbook exercise (p180): fifteen multiple-choice questions.

Q.2 of the textbook exercise (p180): one matching question.

Q.3 of the textbook exercise (p180): four very-short-answer questions.

Q.4 of the textbook exercise (p181): nine short-answer questions.

Q.5 of the textbook exercise (p181): five 'give scientific reason' questions.

Q.6 of the textbook exercise (p181): five 'distinguish between' questions.

Q.7 of the textbook exercise (p181): ten long-answer questions.

The textbook's end-of-chapter Project (p181): five field/lab tasks. A guided approach is given for each.

Sample papers and previous-year board questions for this subject.