Type Ia Afferents
Type Ia afferents transmit signals from the muscle spindle to the central nervous system.
During a dynamic stretch, the muscle spindle detects changes in muscle length and transmits these signals via type Ia afferents1.
Tonic activity during Steady-state length is a static response which is transmitted through both type Ia and type II afferents1.
The signals transmitted through type Ia afferents are important in the physiology of muscle tone1
- Type Ia afferents synapse on the agonist or homonymous muscle as well as heteronymous synergists2.
When the Type Ia afferents synapse on on the motor efferents, the Type Ia afferents use divergence to make widespread connections to all the homonymous motor efferents, amplifying the motor signal2. A muscle’s excitatory to response to its own afferent signalling, is known as autogenic excitation2.
The type Ia afferents also have excitatory synapses on up to 60% of the motor efferents of the heteronymous synergists2.
The type Ia afferents also synapse on inhibitory interneurons in the spinal cord that inhibit the motor efferents of the antagonist muscles resulting in autogenic inhibition2.