Tag: the muscular system and digestive system in human beings

• Muscle is a  bundle of fibrous tissue in a body that has the ability to contract, producing movement in or maintaining the position of parts of the body.
• The total number of muscles in the human body comes in the range of 640-850.
• Latissimus dorsal muscle is a shoulder muscle.
• The latissimus dorsi muscle is responsible for extension, adduction, the transverse extension(horizontal abduction), flexion from an extended position, and (medial) internal rotation of the shoulder joint.
• So, the correct answer is 'Shoulder joint'.

The human body is comprised of about 639 muscles in total. Muscles are found within the muscular system, which is the body's own network of tissues and fibers responsible for both outward and inward movements of the body.

Unstriated muscles consists of muscle fibres which are long flattened and uninucleate because these muscles are smooth muscle fibres. They are present in the form of thin sheets and spindle shaped fibres wth only one nucleus in them.

It helps in adduction, extension and medial rotation of the shoulder as in swimming, rowing, climbing, pulling folding the arm behind back and scratching the opposite scapula. It also helps in violent expiratory efforts as coughing, sneezing, etc.

Arrector pili muscles are small muscles attached to hair follicles in the skin. They are smooth muscles and are controlled by the autonomic nervous system, making them involuntary.

Cardiac muscle is immune to fatigue because it has more mitochondria than skeletal muscles. It contains up to 35% mitochondria whereas skeletal muscles contain only 1-2%. Mitochondria is necessary for ATP production that provides energy to the cells. Hence even if the heart pumps for a lifetime it resists fatigue due to presence of cardiac muscles. Thus the correct answer is option B.

When the triceps muscle contracts, the biceps muscle relaxes and the arm straightens. As triceps muscles are not as powerful as the biceps it does not have to exert great force to straighten the arm. Thus. the biceps exerts force to straighten the arms and lifting a heavy object.
Therefore, the correct answer is option B.

• Each muscle fibre(muscle cell) is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm(cytoplasm of muscle fibre). 
• Sarcoplasm is a water solution containing ATP and phosphagens, as well as the enzymes and intermediate and product molecules involved in many metabolic reactions. The most abundant metal in the sarcoplasm is potassium.
• Hence The cytoplasm of muscle fibre is known as sarcoplasm.
• So, the correct answer is 'Sarcoplasm'.