Final answer:
In the myotatic reflex, group Ia afferents form excitatory connections with alpha motor neurons, leading to the contraction of the homonymous and synergistic muscles for leg extension.
Step-by-step explanation:
The connections formed between group Ia afferents and the alpha motor neurons that project back to the homonymous muscle and synergistic muscles that promote extension of the leg in the myotatic reflex are excitatory connections. In this reflex, muscle spindles are activated due to a stretch, which sends a signal through Ia afferent fibers into the spinal cord and synapses directly onto the ventral horn motor neurons, causing muscle contraction. The involvement of alpha motor neurons and the exclusive excitatory nature of the neuromuscular junction ensures that muscle fibers contract in response to the nerve impulses, thereby facilitating the reflex response crucial for stability and motor control.