CBSE Questions for Class 11 Medical Biology Locomotion And Movement Quiz 2 - MCQExams.com

• Active sites for myosin are present on actin which are masked by troponin in resting state. When  Ca++ level increases it leads to the binding of calcium with a subunit of troponin on actin(thin) filaments and thereby remove the masking of active sites for myosin.
  
• Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge. 
• This pulls the attached actin filaments towards the centre of ‘A’ band.
  
•  The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction.
• When EDTA  injected into muscles combines with Ca ++ and prevents the binding of calcium with troponin and slows down contraction.
• So, the correct answer is 'Slows down contraction'. 
  

• The myofibril is composed of two types of filaments. They are thick filament(Myosin) and Thin filament(Actin).
  
• Increase in Ca++ level leads to the binding of calcium with a subunit of troponin i.e troponin-C on actin filaments and thereby remove the masking of active sites for myosin. Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
  
• Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins constitute one thick filament. Each meromyosin has the globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.
  
• Hence actin binding sites are located over meromyosin'.
• So, the correct answer is 'Meromyosin'.

• The detrusor muscle is a layer of the urinary bladder wall made of smooth muscle fibres arranged in a spiral, longitudinal, and circular bundles. 
• The detrusor muscle remains relaxed to allow the bladder to store urine, and contracts during urination to release urine. Hence, The muscles of the urinary bladder can be categorized as Smooth muscle.

• The muscle contraction cycle is triggered by calcium ions binding to the protein complex troponin, exposing the active-binding sites on the actin. 
• ATP can then attach to myosin, which allows the cross-bridge cycle to start again; further muscle contraction can occur. 
• Cardiac myosin activators stimulate myosin ATPase, thereby increasing force generation. Hence, Calcium ions bring about muscle contraction
• through Activation of myosin ATP-ase.

• Metabolic arthritis is also known as gout is a form of arthritis in which uric acid appears in excessive quantities in the blood and is deposited in the joints and other tissues. 
• During an acute attack, there is swelling, inflammation, and extreme pain in a joint.

• Troponin is a group of globular proteins found in skeletal and heart muscle fibers that regulate muscle contraction. 
• Actin and myosin are contractile proteins of striated muscles.
• A tendon is a fibrous connective tissue that attaches muscle to bone.
  
• Smooth muscles are involuntary muscles.
  
• Red muscles are red because of the presence of dense capillaries that are rich in myoglobin and mitochondria.

• Cartilaginous joints are found between the ribs and sternum where the rib articulates with the sternum via costal cartilage. 
• This joint is connected by cartilage. 

Correct Option: C

Explanation:

• Cardiac muscle (also known as heart muscle or myocardium) is one of three kinds of vertebrate muscles, with skeletal and smooth muscles being the other two.
• It is a striated and involuntary muscle that makes up the primary tissue of the heart's walls.

Hence, the option, striated and involuntary correctly describes the heart muscles