Question

Muscles are characterized by (a) Excitability and contractility (b) Extensibility (c) Elasticity (d) All of these

Short answer

The correct answer is (d) All of these. Muscles exhibit all these characteristics: excitability, contractility, extensibility, and elasticity.

Step-by-step solution

Identification

Identify the characteristics of muscles which are: Excitability, Contractility, Extensibility, and Elasticity.

Explanation

Excitability is the ability to respond to stimuli. Contractility is the ability to shorten and exert a pull or tension. Extensibility pertains to the ability to be stretched without being torn. Elasticity, on the other hand, is the ability to return to the muscles' original length when relaxation occurs after contraction or extension.

Selection

Upon identifying these characteristics and explaining each one, it is noticeable that all these characteristics - Excitability, Contractility, Extensibility, and Elasticity - are inherent in muscles.

Key concepts

Excitability in Muscles

Excitability is the ability of muscle tissue to respond to a stimulus by generating an electrical change called an action potential. This is a crucial characteristic as it allows muscles to react to various signals, such as those from the nervous system. In everyday activities, this translates to your muscles jumping into action when you decide to sprint to catch a bus or quickly pull your hand away from a hot surface.

Neurotransmitters released from nerve cells or changes in your external environment like temperature or even a tap on the muscle can trigger this response. This electrical change then spreads across the muscle cell's membrane, leading to muscle contraction. As you can imagine, without excitability, muscles wouldn't be able to perform any action in response to stimuli, rendering them useless for movement and responses to the environment.

Muscle Contractility

Muscle contractility refers to the ability of muscles to shorten and generate force. When a muscle cell receives an excitatory signal, the proteins within the muscle fibers interact to produce contraction. This interaction pulls the muscle ends closer, therefore shortening the muscle. Whether lifting weights, climbing stairs, or even blinking, contractility is at work.

Contractility is not just about strength; it's about control and precision as well. It allows the heart to pump blood throughout the body and enables the fine motor skills needed for writing or playing a musical instrument. This characteristic is vital for all movement and is a unique feature that sets muscles apart from other types of tissues.

Muscle Extensibility

Extensibility is the characteristic that allows muscle tissue to stretch or extend. When you reach for an object or perform a yoga pose, you're relying on your muscles' extensibility. It's what gives you the range of motion necessary for various activities without causing injury to the muscle.

It's important to note that while extensibility allows stretching beyond the normal resting length, it has its limits. Overstretching can lead to muscle damage. However, regular stretching exercises can improve muscle extensibility over time, enhancing flexibility and performance in physical activities. Understanding and respecting the balance between stretching for improvement and overextending is a key part in maintaining healthy muscle function.

Muscle Elasticity

Lastly, muscle elasticity is the capability of a muscle to return to its original resting length after it has been stretched or contracted. Imagine a rubber band snapping back after being stretched; similarly, muscles have the property to recoil post-stretching or contracting. This is thanks to the elastic properties of the muscle tissues and proteins.

Without elasticity, muscles would remain in a state of contraction or extension, leading to potential strain or injury. It's this unique characteristic that enables athletes to perform repeated movements with efficiency and precision. In day-to-day life, elasticity allows muscles to maintain stability and posture, contributing to overall mobility and preventing joint and muscle discomfort.