Tag: human muscular system

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'.

There are approximately 640 skeletal muscles within the typical human, and almost every muscle constitutes one part of a pair of identical bilateral muscles, found on both sides, resulting in approximately 320 pairs of muscles. Nevertheless, the exact number is difficult to define because different sources group muscles differently. 

• The smooth muscle fibres(muscle cell) are tapered at both ends (fusiform) and do not show striations.
  
• Smooth muscles are involuntary muscles because their functioning cannot be directly controlled.
  
• The wall of internal organs such as the blood vessels, stomach, intestine and iris contains this type of muscle tissue.
  
• Hence Iris-Involuntary, smooth muscle.
• So, the correct answer is 'Iris-Involuntary, smooth muscle'.

• The stroma and the anterior border layer of the iris are derived from the neural crest, and behind the stroma of the iris, the sphincter pupillae and dilator pupillae muscles, as well as the iris epithelium, develop from optic cup neuroectoderm. Hence, Muscles of iris and ciliary body are not smooth muscles of mesodermal origin.
• Pericytes are multi-functional cells that wrap around the endothelial cells that line the capillaries and venules throughout the body. Pericytes are specialized mural cells located at the abluminal surface of capillary blood vessels, embedded within the basement membrane. Hence,  Quiescent mononucleate myogenic cells of skeletal muscles are not called pericytes.

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. Muscle fibers are incorporated with an oxygen-carrying protein called myoglobin. Myoglobin receives oxygen from the red blood cells and transports it to the mitochondria of muscle cells, where the oxygen is used in cellular respiration to produce energy. Hence myoglobin is incorporated into muscle fibers. So, the correct answer is 'Myoglobin'.