According to Patanjali, this is how our external senses come in close and direct contact with mind and intellect.

Our external senses obtain knowledge about external objects, pass it on to the subtle senses in the brain and they in turn communicate it to the mind. The mind submits this to the intellect which passes its judgment on whether it is right or wrong. It then makes this knowledge available to the conscious body located in the heart in the form of Sanskaras. Our conscious body or consciousness keeps on collecting all these Sanskaras. In this operation, our external senses then have a direct contact with our mind and intellect, but have no access to consciousness. Even in the state of sleep, only our subtle senses have contact with mind and intellect; the external senses remain unaffected and therefore do not show any reaction. As a result the eyes cannot see even if they are open, ears cannot hear, hands do not move, and feet become inactive. Then the consciousness gets busy in self-analysis or attains the niruddha state and lies at rest, with the result that mind and intellect are also at peace. When the senses find that their master is at peace, they stop getting their food from the external world. In this way, the senses get detached from their objects of feeding (the senses of knowledge suspending the activity of collecting information and the service organs not performing their normal functions) and the mind and intellect attain complete rest. This state of mind and body is called Pratyahara.

Patanjali has included Pratyahara in the five external organs of yoga: Yamas, Niyamas, Asanas, Pranayama and Pratyahara. Dharana, Dhyana and Samadhi are its internal organs.

But with the growing accumulation of this external matter in the body, the body is adversely affected and we feel weak and lazy. Yogasanas keep t body free from these impurities and make it healthy. (They also improve the functioning of our intestines so that the stomach ailments like indigestion, gas, constipation, etc. are cured (The regular practice of yogasanas imparts strength to the body, brightness to the face, high spirits to the mind and impetus to the intellect. yogic practices help control the senses, thereby creating favorable situation for Dhyana. Dhyana brings about an excellent state of mind which in turn leads to the highest achievement of human life. All the sorrows then disappear and the problems vanish. The mind rests in peace and experiences bliss.