Question

During the excitation phase of the skeletal muscle cell contraction, the following occurs:

1) the muscle fiber develops tension and shortens

2) the muscle fiber relaxes and returns to its original length

3) nerve action potentials lead to muscle action potentials

A growing long bone in a child has only two types of cartilage at the epiphysis. These two areas are

1) elastic cartilage and epiphyseal plate

2) epiphyseal plate and epiphyseal line

3) primary and secondary ossification centers

4) articular cartilage and epiphyseal plate

During the building up and breaking down of a bone during childhood _______________:

1)osteoclast activity will increase and osteoblast activity will decrease

2)osteoblast activity will increase and osteoclast activity will decrease

3) both osteoblast and osteoclast activity will increase

Answer 1

A. During the excitation phase of the skeletal muscle cell contraction

Ans: 3

• 1. The muscle fiber develops tension and shortens - This occurs during the contraction phase.
• 2 The muscle fiber relaxes and returns to its original length-This occurs during the relaxation phase.
• 3 Nerve action potentials lead to muscle action potentials-- This occurs during the excitation phase of the skeletal muscle cell contraction.

B. A growing long bone in a child has only two types of cartilage at the epiphysis. These are,

Ans:4. Articular cartilage and epiphyseal plate:

In the developing bone, the cartilage in the epiphyses continues to grow and increases in length. After the completion of secondary ossification, the hyaline cartilage is totally replaced by bone. Hyaline cartilage remains over the surface of the epiphysis as the articular cartilage and remains between the epiphysis and diaphysis as the epiphyseal plate

• Elastic cartilage is more pliable and in addition to collagen contains elastic fibres also. The areas where elastic cartilage is seen in the human body are the auditory tube of the middle ear, the external ear, and the epiglottis.
• Primary and secondary ossification centres are two types of ossification centres. A primary ossification centre is the first area of a bone to start ossifying and usually appears during prenatal development. The secondary centres appear in the epiphyses in long bones.

C.During the building up and breaking down of a bone during childhood

Ans: 3. Both osteoblast and osteoclast activity will increase

During childhood building up and breaking down of a bone occurs by a process called modelling, which allows for the formation of new bone at one site and the removal of old bone from another site within the same bone. This needs both osteoblast and osteoclast activity.

• Osteoclast activity will increase and osteoblast activity will decrease-Bone remodelling will be affected and bone get diseased
• Osteoblast activity will increase and osteoclast activity will decrease-Bone remodelling will be affected and bone get diseased