Write the difference between(c) Pectoral girdle and pelvic girdl

Describe the important steps in muscle contraction.


The important steps muscle contraction:

1. Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron and reach the neuromuscular junction. As a result, neurotransmitter (Acetyl choline) which generates an action potential in the sarcolemma.

2. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.


3. Increase in Calcium level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.

4. The actin filaments are pulled. As a result, the H-zone reduces. It is at this stage that the contraction of the muscle occurs.

5. After muscle contraction, the myosin head pulls the actin filament and releases ADP along with inorganic phosphate. ATP molecules bind and detach myosin and the cross bridges are broken and decreases the calcium ions contraction. As a result, masking the actin filaments and leading to muscle relaxation.

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Write the difference between
(c) Pectoral girdle and pelvic girdle.


Pectoral girdle

Pelvic girdle

1. It is present in shoulder.        

1. It is present in hip.

2. Helps in the articulation of the lower limbs.             

2. Helps in the articulation of the lower limbs.

3. It is formed of clavicle and a scapula.

3. It is formed of two coxal bones. Each coxal bone is a fusion of three bones ie ileum, ischium and pubis.

4. It has glenoid cavity.

4. It has acetabulum cavity. 

5. Pubic symphysis is absent.

5. Pubic symphysis is present between two pelvic girdles.

 
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Write differences between
(b) Red and White muscle 

Red muscle 

White muscle 

1. Myoglobin content is high 1. Myoglobin content is very less.
2. Appear red in colour. 2. Appear white in colour. 
3. Have aerobic respiration and utilise large amount of oxygen.  4. Carry out anaerobic process and produce energy.
4. Amount of sarcoplasmic reticulum is low. Amount of sarcoplasmic reticulum is high.
5. More number of mitochondria. 5. very few number of mitochondria. 
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What are the different types of movement exhibited by the cells of human body ?

Types of movements in cells of human body : The different types of movements exhibited by the cells of human body :

1. Amoeboid movement : Some specialised cells in our body like macrophages and leucocytes in blood exhibit amoeboid movement. ln this type the movement is done by the formation of pseudopodia by the streaming of protoplasm (as in Amoeba). Cytoskeletal elements like microfilamens are also involved in amoeboid movement.

2. Ciliary movement : Ciliary movement occurs in most of our internal tubular organs which are lined by ciliated epithelium. The coordinated movements of cilia in the trachea help in removing dust particles and some of the foreign substances inhaled along with the atmospheric air. Passage of ova through the female reproductive tract is also facilitated by the ciliary movement.

3. Muscular movement : Movement of our limbs, jaws, tongue etc. require muscular movement. The contractile property of muscles are effectively used for locomotion and other movements by human beings and majority of multicellular organisms. Locomotion requires a perfect coordinated activity of muscular, skeletal and neural.

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Define sliding filament theory of muscle contraction.

The sliding filament theory explains the mechanism of muscle contraction. A proposed mechanism of muscle contraction in which the actin and myosin filaments of striated muscle slide over each other to shorten the length of the muscle fibres (see sarcomere). Myosin-binding sites on the actin filaments are exposed when calcium ions bind to troponin molecules in these filaments. This allows bridges to form between actin and myosin, which requires ATP as an energy source. Hydrolysis of ATP in the heads of the myosin molecules causes the heads to change shape and bind to the actin filaments. The release of ADP from the myosin heads causes a further change in shape and generates mechanical energy that causes the actin and myosin filaments to slide over one another

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