Describe the internal structure of human heart. Or Which organ is acts as the command and control system of all body activities in humans? Discuss about their location and protective covering.

Internally, the chambers of heart, i.e. two auricles (atria) and ventricles are separated by different septa and valves.
Auricles (Atria)
These are the upper two thin-walled and smaller chambers. They serve to receive the blood, therefore are called receiving chambers (right atrium and left atrium). Both the right and the left atria are separated by a thin, muscular wall, known as interatrial septum.
(i) Right Atrium This right chamber deals with only impure (deoxygenated) blood. It receives impure blood from various parts of the body, through two major veins, i.e. superior and inferior vena cava.
It also receives blood from the walls of the heart itself (through a coronary sinus).
(ii) Left Atrium This chamber is meant to deal with only pure (oxygenated) blood. It receives blood (pure) from lungs through two pulmonary veins (i.e. one from the each lung).
Ventricles These are lower two chambers of the heart, that pumps the blood away from the heart. These functions as pumping chambers. Both the right and the left ventricles are separated by the interventricular septum.
The atrium and the ventricle of the same side are also separated by another septum, a thick fibrous tissue called Atrio-Ventricular septum (i.e. AV septum).

(i) Right Ventricle It receives impure blood from right atrium and pumps blood into pulmonary artery, which further takes this blood to lungs for purification.
(ii) Left Ventricle It receives pure (oxygenated) blood from left atrium and pumps its pure blood to aorta (largest artery in the pathway), which in turn takes this blood to whole body and organs.
Or The brain is the central information processing organ of our body and acts as the 'command and control system' of all body activities.
It controls the following activities
(i) The voluntary movements and balance of the body.
(ii) Functioning of vital involuntary organs, e.g. lungs, heart, kidneys, etc.
(iii) Thermoregulation, hunger and thirst.
(iv) Circardian (24 hrs) rhythms of our body.
(v) Activities of several endocrine glands and human behaviour.
(vi) It is also the site for processing of vision, hearing, speech, memory, intelligence, emotions and thoughts.
Location The brain is the anterior most part of the central neural system, which is located in the cranium (cranial cavity) of the skull.
Protective Coverings of the Brain It is covered by three membranes or meninges (cranial meninges) present in the cranial region of the skull. These membranes are as follows
(i) The outermost membrane, the duramater is the tough fibrous membrane adhering close to the inner side of the skull.
(ii) The middle membrane, is very thin layer called arachnoid membrane (arachnoid mater).
(iii) The innermost membrane, the piamater is thin, very delicate, which is in contact with the brain tissue.