NEET BIOLOGY

Detailed explanation-1: -Smooth muscle, found in the walls of the hollow internal organs such as blood vessels, the gastrointestinal tract, bladder, and uterus, is under control of the autonomic nervous system. Smooth muscle cannot be controlled consciously and thus acts involuntarily.

Detailed explanation-2: -Involuntary muscles of the heart, respiratory and digestive systems work automatically. These operations are triggered by nerves and the nerves are stimulated by complex chemical fluids (such as acetylcholine and norepinephrine) that surround them and other living cells.

Detailed explanation-3: -The 3 types of muscle tissue are cardiac, smooth, and skeletal. Cardiac muscle cells are located in the walls of the heart, appear striped (striated), and are under involuntary control.

Detailed explanation-4: -The smooth muscle responsible for movements of the digestive tract is arranged in two layers, an inner circular layer and an outer longitudinal layer. The myenteric plexus is between the two muscle layers. Above the diaphragm, the outermost layer of the digestive tract is a connective tissue called adventitia.

Detailed explanation-5: -The muscles in the upper portion of the esophagus are under voluntary control. The remaining portion consists of smooth muscle like the rest of the digestive tract and is not under voluntary control. To keep food from coming back up from the stomach, the esophagus has two circular bands of involuntary muscle.