Types of Muscle Tone and Their Biological Importance
Muscles are one of the most important supporting structures of our body. We can sit, move, stand, talk or do any physical activity for the flexibility of our muscles. Under normal circumstances, friction or resistance acts on the muscular tissues. Hence, it acts against the tissues getting extended. This tension detected in the muscles is known as muscle tone. This property of the body helps to undergo different movements and modify its speed.
Therefore, to check the condition of the muscles, this factor is examined. The physician usually asks the patient to relax completely. Then he goes on to expand or move each joint through its full range. It acts as a muscle tone assessment.
Types of Muscle Tone Abnormalities
In a body, muscle tone might alter due to several problems. The muscle tone refers to the degree of resistance offered by the muscles. This degree of resistance can be usual, hypotonic, or hypertonic. When diagnosed with a hypotonic situation, the muscle tone is lower or less than what it should be under normal circumstances. A muscle tone assessment helps to identify this situation.
Hypertonic suggests that the muscle tone is high or more than the regular. Due to the condition of hypotonia, a person might have to put more effort. To be able to undergo a single movement becomes a task. Hypertonia, on the other hand, might result in the stiffness of the muscles.
Low Muscle Tone
Usually, people have different types of muscle tones. A low muscle tone suggests that the muscle has become floppy. This condition is also known as hypotonia and results in difficulty in any muscle movement. Due to this state, it might be difficult for a person to maintain their posture. A person with hypotonia might require much more effort for any ordinary movement. In children, low muscle tone can cause difficulty in growth.
Low muscle tone often gets detected in babies at birth. However, this condition might also develop in the later stages of life. Nervous disorders or weakness in the bones might lead to hypotonia. A muscle tone abnormality might sometimes have no diagnosed reason. Such a condition is called idiopathy.
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How to Check Muscle Tone?
Low Muscle Tone
According to muscle tone physiology, the muscle tone of an individual remains low during sleep. Some people experience difficulty in maintaining their posture. The body posture might be poor or strain the person. It leads him to put extra effort into his movement. Children, when lifted, might have limp arms or legs. Activities like sitting, crawling, or walking may be very slow. In such cases, a muscle assessment should be done to check the condition that causes these problems in the body.
High Muscle Tone
In the case of hypertonia, the muscle tone becomes so high, that makes it is very difficult to regulate any movement. To understand what muscle tone is, we also need to know that muscles send the brain signals which allow them to contract or expand. Certain regions of the brain or spinal cord control these signals. If these get injured or damaged, hypertonia can occur. Hypertonia reduces the flexibility of the joints. Headstrokes, brain tumours, and other toxins can result in high muscle tone.
Several symptoms emphasize the fact that a person is suffering from hypertonia. The functionality and movement of the joints decrease due to increased muscle tone. When this condition affects the legs, the person might trip and fall as he will not be able to maintain balance. Among the types of muscle tone, spasticity is the condition that results in increased muscle spasms. The affected muscles become very tender and can often cause pain.
Balance is not a learned phenomenon. As a child grows up, he or she automatically balances her body. This can be either to sit in a stable posture, crawl or even to stand or walk. However, in the case of those kids who suffer from hypotonia, balance develops very slowly. The joint muscles are soft and hence there remains the risk of dislocation of the neck, jaw, or hip muscles. Children with hypotonia usually face difficulty in eating as their muscles are too weak to stably control the processes of eating, chewing, or swallowing. Often the child takes in very shallow breaths and can speak out words clearly with difficulty.
FAQs on Understanding Muscle Tone in Biology
1. What is muscle tone in the context of human physiology?
In physiology, muscle tone, also known as tonus, refers to the continuous and passive state of partial contraction present in skeletal muscles even when they are at rest. It is the muscle's inherent resistance to passive stretching. This is not a voluntary contraction but an unconscious, low-level nerve impulse that keeps muscles firm and ready for action. It is essential for maintaining posture and balance.
2. What is the physiological mechanism that maintains muscle tone?
Muscle tone is primarily maintained by the nervous system through a mechanism called the stretch reflex. Here’s how it works:
- Specialised sensory receptors within the muscle called muscle spindles detect the length and stretch of the muscle.
- When a muscle is stretched, these spindles send signals to the spinal cord.
- The spinal cord, in response, sends signals back to the muscle via alpha motor neurons, causing a slight contraction to resist the stretch.
3. What is the importance of having normal muscle tone?
Normal muscle tone is crucial for several bodily functions:
- Posture and Stability: It provides the necessary tension in neck, back, and leg muscles to keep the body upright against gravity without conscious effort.
- Readiness for Action: It keeps muscles primed, allowing for faster and smoother voluntary movements when needed.
- Heat Generation: The constant low-level metabolic activity in muscles contributes to maintaining the body's core temperature.
- Shock Absorption: It helps to absorb shock and protect joints during movement.
4. How is physiological 'muscle tone' different from 'muscle toning' achieved through exercise?
This is a common point of confusion. Physiological muscle tone is an involuntary, unconscious neural function related to the muscle's resting tension. In contrast, 'muscle toning' from exercise is a fitness term referring to the process of reducing body fat and increasing muscle definition, making the muscles appear more firm and visible. While exercise can improve the efficiency of motor units, it does not change the fundamental neurological basis of resting muscle tone.
5. What are hypertonia and hypotonia?
Hypertonia and hypotonia are two types of abnormal muscle tone, usually resulting from neurological conditions:
- Hypertonia: This refers to an abnormally high muscle tone, where muscles are stiff and resistant to movement. It can manifest as spasticity (velocity-dependent resistance) or rigidity.
- Hypotonia: This refers to an abnormally low muscle tone, where muscles are floppy and offer little resistance to passive movement. It is often described as 'floppiness' in infants.
6. Can you give an example of muscle tone in a daily activity?
A simple example is holding your head up while sitting and reading this. You are not consciously flexing your neck muscles, but they have enough innate tension or tone to prevent your head from slumping forward or sideways. This continuous, low-level contraction is a perfect demonstration of muscle tone maintaining your posture automatically.
7. How does muscle tone differ from a voluntary muscle contraction?
The key difference lies in consciousness and mechanism. A voluntary muscle contraction, like lifting a book, is a conscious, high-energy process involving the recruitment of many motor units to generate significant force. In contrast, muscle tone is an unconscious, low-energy state involving the asynchronous firing of a small number of motor units just to maintain firmness and posture. It does not produce active movement but provides a stable base for it.
