Tag: muscle contraction

1. sarcoplasmic reticulum is a specialized type of smooth ER that regulates the calcium ion concentration in the cytoplasm of striated muscle cells. 
   
3. sarcoplasmic reticulum  is a membrane-bound structure found within muscle is also known as endoplasmic reticulum of muscle. so option A is correct answer .

• The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils.
  
• In the centre of each ‘I’ band, there is an elastic fibre called ‘Z’ line which bisects it. The thin filaments are firmly attached to the ‘Z’ line. 
• The portion of the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and is called sarcomere.
• Hence Sarcomere is the unit of contraction.
  

• 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.
  
• So,the correct answer is '640-850'

Movement is performed by muscular tissues. Every bone moves with the help of 2 muscles required to move it. 

•  Syncytial or syncytium is a multinucleated cell that can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus), which can result from multiple nuclear divisions without accompanying cytokinesis. 
• Syncytial is also referring to cells interconnected by the specialized membrane with gap junctions, as seen in the heart muscle cells and certain smooth muscle cells, which are synchronized electrically in an action potential. Hence, Condition of having a number of nuclei in a muscle fibre is syncytial.

Answer is option C i.e. "Sacroplasmic reticulum"
Neurotransmitter acetylcholine generates an action potential in the sarcolemma causing the release of calcium ions into the sarcoplasm from the sarcoplasmic reticulum.
When Ca++ level increases it leads to the binding of calcium with a sub-unit of troponin on actin(thin) filaments and thereby activating the movement.

Myoglobin is the iron and oxygen-binding protein that is found in the muscle tissue of the vertebrates and in almost all mammals. This contains heme, the pigment responsible for the red color of meat.

Sarcomere is the structural and functional unit of a myofibril and consists of thick myosin filaments and thin actin filaments. If the allele for actin filament continues to synthesize linear chains of the protein, sarcomere structure would be same as normal. Thus, the correct answer is option C.

• Muscle contraction thus results from an interaction between the actin and myosin filaments that generates their movement relative to one another. 
• The molecular basis for this interaction is the binding of myosin to actin filaments, allowing myosin to function as a motor that drives filament sliding. Hence, The binding of troponin to calcium in muscle cells exposes the binding site of Myosin.