Tissues Test - 50

Correct Option: D
Explanation:

• Smooth muscles or Visceral muscles are located in the inner walls of hollow visceral organs of the body like the alimentary canal, reproductive tract, etc. 
• Each spindle-shaped smooth muscle fibre contains a single, central nucleus. 
• They do not exhibit any striation and are smooth in appearance. Hence, they are called smooth muscles (non-striated muscles).
• Their activities are not under the voluntary control of the nervous system and are therefore known as involuntary muscles. 

Myosin filament is a polymerised protein. Many monomeric proteins, called meromyosin constitute one thick filament. Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The HMM component, i.e., the head and short arm projects outwards at regular distance and angle from each other from the surface of a polymerised myosin filament and are known as the cross arm. The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin. Actin is another contractile protein but it lacks ATPase activity.

Tissues vary considerably in their sensitivity to hypoxia (oxygen deficiency).  Smooth muscle can survive for several days without oxygen. Skeletal muscle can tolerate about 60-90 minutes of hypoxia. The brain and heart will not survive more than a few minutes without oxygen.

• Multi-unit smooth cells can be found in the in the trachea, the large elastic arteries, the iris of the eye, in the lungs, erectile tissues of hair follicles ( Arrector pili of the dermis) and the vas deferens in the male genital tract.
• The response of the whole muscle depends on upon the number of motor units active, the frequency of discharge in the fibers and the relative amount of excitatory and inhibitory input. 
• Multi-unit smooth muscle activity can be initiated by hormones, but it is not much affected by rapidly stretching the muscle.
• Hence the correct option is D.

Correct Answer: A

Skeletal muscles are closely associated with the skeletal components of the body like limbs. They have alternate light and dark bands and hence, are called striated muscles. As their activities are under the voluntary control of the nervous system, they are also known as voluntary muscles. They are primarily involved in locomotory actions and changes of body postures. They are seen in the legs but are absent in the lungs, trachea, and gall bladder. Smooth muscles are found in internal organs.

The gluteus maximus (also known as glutus maximus or, collectively with the gluteus medius and minimus, the glutes) is the largest and most superficial of the three gluteal muscles. It makes up a large portion of the shape and appearance of the hips. It permits a variety of motion and allows us to sit upright.

Like all other mammals, camel also have 7 cervical vertebre. The only exceptions in mammals are the manatee and the 2-toed sloth, which have 6 cervical vertebrae and the 3-toed sloth having 9 cervical vertebrae.

A Nissl body is also known as Nissl or tigroid substance. It is a large granular body found in neurons. These granules are formed of rough endoplasmic reticulum (RER) with rosettes of free ribosomes and are the sites of protein synthesis.