Why does a mouse twitch when it moves? - briefly
Mice produce quick, involuntary muscle contractions to adjust balance and negotiate irregular surfaces, driven by sensory input from whiskers and the vestibular system. These twitches enhance stability during rapid locomotion.
Why does a mouse twitch when it moves? - in detail
A mouse’s rapid, involuntary muscle contractions during locomotion arise from the integration of several physiological mechanisms.
The primary driver is the spinal central pattern generator (CPG), a network of interneurons that produces rhythmic motor output without direct cortical input. The CPG coordinates flexor and extensor muscles, but its output is modulated by sensory feedback, causing brief, high‑frequency adjustments that appear as twitches.
Proprioceptive receptors—muscle spindles and Golgi tendon organs—detect changes in muscle length and tension. When a limb encounters an unexpected obstacle or slip, these sensors trigger a reflex loop that momentarily activates antagonist muscles, producing a corrective jerk.
A secondary contributor is the vestibular system. Head movements generate vestibular signals that fine‑tune limb positioning. Sudden accelerations or decelerations induce vestibulo‑spinal reflexes, which can manifest as short, sharp contractions.
Neuromuscular junction transmission also plays a role. Small motor units fire at high rates to maintain fine motor control. Variability in synaptic release probability leads to occasional extra spikes, visible as micro‑twitches.
In summary, the observed twitches result from:
- CPG‑driven rhythmic output
- Proprioceptive‑mediated reflex corrections
- Vestibulo‑spinal adjustments
- High‑frequency firing of motor units
These components operate simultaneously, ensuring the animal can navigate complex environments while maintaining balance and agility.