Wireless Sensor Networks (WSN) are recently attracting significant research and commercial interest. Since data dissemination is different from traditional Ad Hoc sensor networks, WSN results in a new challenge. Basically, the challenges are the outcome of limited energy, communication, and processing capacity of wireless sensor nodes. Those challenges can be mitigated by the effective use of the medium access layer of wireless sensors network. Basically, there are three types of medium access control (contention-based, contention-free, and hybrid) in wireless sensors networks. The contention-based MAC layer scheduling technique consumes sensor nodes' energy due to idle listening and overhearing. Sensor medium access control is one of the contention-based protocols that have a strong reputation. The fixed duty cycle and fixed contention window size pose a challenge in Sensor medium access control (SMAC). As the network traffic increase fixed contention window of SMAC deteriorate throughput of the network and data transmission delay. The fixed duty cycle of SMAC reduces energy efficiency as a sensor node energy deplete due to using the same idle listening period for high remaining energy node and low remaining energy node. In this article, enhancement is made to SMAC protocol by introducing network load and remaining energy of nodes to adjust contention window as well as duty-cycle dynamically. Performance evaluation was performed on Network Simulator-2 (NS2).