CBSE Questions for Class 11 Medical Biology Structural Organisation In Animals Quiz 5 - MCQExams.com

• 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 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. 

• The dilator muscle of iris is a smooth muscle of the eye. 
• The middle layer of the uterus is formed of smooth muscles. 
• The bronchi and bronchioles also have a layer of smooth muscles which help them to contract and dilate. 

• Tendon is a tough fibrous connective tissue, which connects muscle to bone.
• Blood consists of a fluid or liquid matrix called plasma in which white blood cells, red blood cells and platelets are suspended. Blood flows throughout the body and transports gases, nutrients, digested food, hormones and waste materials to different parts of the body.
• Cartilage has widely spaced cells and interspersed in a matrix made of proteins and sugars. It covers the ends of bones at joints.
• The ligament is a fibrous connective tissue, which connects bone to another bone. 

• Areolar tissue is connective tissue.
• Areolar connective tissue holds organs in place and attaches epithelial tissue to other underlying tissues. It also serves as a reservoir of water and salts for surrounding tissues.
•  Almost all cells obtain their nutrients from and release their wastes into areolar connective tissue.

Skeletal muscle is a striated muscle tissue (alternate light and dark bands are present when observed under a microscope) that supports the skeleton. Skeletal muscles are voluntary muscles and are under the control of our will. For example, we can move our limbs on our will.

Cardiac muscles are not under the control of the conscious will. They are involuntary muscles. Non-striated muscles are also called smooth muscles. These muscles are not under the control of our conscious will.  

Therefore, option B is correct.

• Spinal cord and brain control all activities of our body. Spinal cord possesses nerves, which carry messages between the brain and the body.
•  The brain sends commands for the functioning of different organs of the body via nerves. 
• Therefore, they are made of nervous tissue. Hence, option B is correct.  

Contraction or relaxation of the urinary bladder is not under control of the conscious will. As and when urine is formed, it is stored in the urinary bladder and its muscles are stretched. These muscles are smooth muscles and they are involuntary and unstriated.

Hence the correct option is B.

• Smooth muscle cells are spindle shaped, uninucleate, unbranched and involuntary in nature. 
• The cells are arranged in sheets one above the other.
• Smooth muscle is found in the walls of hollow organs like your intestines and stomach
  

Tendons allow a bone to move. They are fibrous connective tissues that attach muscles to bones. 

Hence, the correct option is B.