Tag: skeleton and joints

Stapedius is a muscle on the wall of the tympanic cavity of the middle ear. It is the smallest skeletal muscle in the human body. It acts reflexively in response to loud sounds by reducing excessive vibrations that may injure the internal ear. Thus the correct answer is option B.

• The exoskeleton of animals within the phylum Arthropoda mainly consists of a coating called the cuticle.
•  On the exterior surface of the cuticle is a thin, waxy layer called the epicuticle. 
• The epicuticle is formed of three layers; the inner layer is the cuticulin, which is made from lipoproteins. Hence, Epicuticle in exoskeleton is made up of Lipoprotein
So, the correct answer is 'Lipoprotein'.

• The human skeleton is the internal framework of the body.
•  It is composed of around 270 bones at birth this total decreases to around 206 bones by adulthood after some bones get fused together. 
• The skeleton serves six major functions: support, movement, protection, production of blood cells, storage of minerals and endocrine regulation. Hence, Excretion is not a biological function of the skeleton.

• Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa.
•  Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed.
• The remnants of the old, empty exoskeleton are called exuviae. 
• In arthropods, such as insects, arachnids and crustaceans, Moulting is the shedding of the exoskeleton (which is often called its shell), typically to let the organism grow. Hence, Shedding of the exoskeleton to replace it due to growth in the body is called ecdysis and moulting. 

• Locomotion occurs when a body changes its position from one place to another. 
• Walking, running, climbing are the forms of locomotion. 
• But some movements of our body parts like tongue, jaws does not result in any locomotion. 
• Thus it can be said that all locomotions are movements but all movements are not locomotion. Hence, the correct statement. All locomotion is movement but all movements are not locomotion. 

• The Muscles work by contraction and relaxation this represents that muscles can pull bones, but they can't push them back to the original position.
• For this reason, muscles are often arranged in pairs that pull bones in opposite directions.
• Hence muscles attached to the bones move the body by pull movement only.
• So, the correct answer is 'Pull movement only'.

• Your brain sends messages through your spinal cord and the peripheral nervous system to: control the movement of your arms and legs. control the automatic functions of your body, such as the operations of your heart, your organs and your glands. Hence, All movement of the human body is coordinated and controlled by the Nervous system.

• High extracellular K+  leads to depolarization and ensuing inactivation of voltage-gated Na+ channels and loss of excitability in isolated muscles, exercise-induced loss of K+ is likely to reduce muscle excitability and thereby contribute to muscle fatigue. Hence, Muscular and nervous excitability is lowered by K.

• Locomotion is when the movement of a part of the body leads to change in the position and location of the organism. 
•  In multicellular animals, these movements include walking, running, jumping, crawling, climbing, swimming, flying, galloping, slithering, and so on. Hence, the Movement of the whole animal from one place to another place is called Locomotion. 
So, the correct answer is 'Locomotion'.

•  Upon muscle contraction, the A-bands do not change their length, whereas the I-bands and the H-zone shorten.
•  This causes the Z lines to come closer together. The protein [tropomyosin] covers the myosin binding sites of the actin molecules in the muscle cell. Hence, A-Band remains constant  is true of muscle contraction
 So, the correct answer is 'A-Band remains constant'.