Question

Which of the following is not a property of skeletal muscle?
A. Excitability
B. Contractility
C. Rhythmicity
D. Tonicity

Answer 1

Hint: Muscles form the contractile tissue, concerned with all kinds of bodily movements, including locomotion. They serve as the biological system for transducing chemical energy to mechanical energy and mechanical work.

Complete Answer:
Muscles have three major functions in the body, namely motion, maintenance of posture and heat production. Motion includes both locomotor bodily movements and localized movements of body parts. Most of these movements involve an integrated functioning of bones and joints and the muscles attached to them; bones and joints provide leverage in movements. Less noticeable localized muscular movements include heart-beat, churning movements of stomach, intestinal peristalsis, contraction of gall bladder to discharge bile, contraction of urinary bladder for voiding etc.

Muscles are endowed with four principal characteristics, which are important in maintaining homeostasis. They are excitability, contractility, extensibility, and elasticity.

1. Excitability: It is the ability of muscles to perceive stimuli and respond to them. Stimuli are changes in the external or internal environment capable of eliciting nerve impulses or action potentials.
2. Contractility: It is the ability of muscles to shorten and thicken when sufficiently stimulated.
3. Extensibility: It is the ability of muscles to stretch or extend. Many muscles are arranged in opposing pairs. So, when one is contracting, the other one relaxes and extends.
4. Elasticity: It is the ability of muscles for extension and recoil. So, muscles can return to their original form and size after contraction or extension.
5. Tonicity or muscle tone is the continuous and passive partial contraction of the muscles, or this is the muscles resistance to passive stretch during resting state.

So, here the correct answer is C) Rhythmicity.

Note: Muscles are also called muscles fibres. They are long, slender, and fibre-like. Their plasma membrane is called sarcolemma of muscle membrane. It encloses the sarcoplasm of muscle cytoplasm. Sarcoplasm contains nucleus, mitochondria, sarcoplasmic reticulum and myofibrils. Each myofibril is formed of numerous short and thin protein filaments called myofilaments. These myofilaments are of two types, thin filaments and thick filaments.