Wireless sensor networks are appealing to researchers due to their wide range of application. This paper proposes EA2MAC (Energy-efficient Adaptive and Asynchronous Medium Access Protocol), an adaptive and low-latency MAC protocol designed for wireless sensor networks. EA2MAC improves the pattern and timeslot schedule, which make nodes save energy by the proper sleep mechanism according to the nodes' own traffic. And the grid quorum-based mechanism solves the asynchrony in the multi-hop wireless sensor network. This paper develops a better pattern and schedule generation schemes with less state transformation frequency. The analytical and experimental results show that EA2MAC obtains more energy savings and reduces the latency.