Tonus

Tonus refers to the continuous and passive partial contraction of muscles or the muscle's intrinsic state of readiness to respond to stimuli. It is a fundamental aspect of muscle physiology that ensures muscles are slightly contracted at rest, maintaining posture and enabling quick responses to movement demands.

In human physiology, muscle tone is regulated by the nervous system, particularly by the reflex activity of muscle spindles and the central nervous system. It plays a critical role in stabilizing joints, supporting body posture, and facilitating coordinated movements. The level of muscle tone varies depending on factors such as fatigue, emotional state, and neurological health.

Abnormal muscle tonus can manifest as either hypertonia or hypotonia. Hypertonia involves increased muscle tension, which can lead to stiffness and restricted movement. It is commonly observed in conditions like spasticity associated with stroke, multiple sclerosis, or cerebral palsy. Conversely, hypotonia, characterized by decreased muscle tension, results in floppiness or weakness, often seen in conditions such as muscular dystrophy or neurological developmental disorders.

Assessment of muscle tone is a standard part of neurological examinations and is crucial in diagnosing various neuromuscular conditions. Treatment approaches may include physical therapy, medications, or interventions targeting the nervous system to restore or improve muscle function.

Overall, tonus is an essential component of motor control and musculoskeletal stability, influencing both everyday movements and overall posture. Its proper regulation is vital for maintaining efficient, adaptable, and balanced muscular function.