Final answer:
The reduction of alpha wave production, replaced by theta waves, defines the transition into stage 1 NREM sleep. This stage is marked by a relaxed state with decreases in both muscle tension and body temperature, making it easy to wake a person. As sleep deepens, stage 2 introduces sleep spindles and K-complexes amidst the theta waves.
Step-by-step explanation:
Understanding Sleep Stages and Brain Waves
During the transition from wakefulness to sleep, known as the first stage of NREM sleep or stage 1 sleep, an individual's brain wave patterns shift from alpha waves to theta waves. Alpha waves, which occur at a frequency of 8-12 Hz, are indicative of a relaxed, yet awake state. As a person falls deeper into stage 1 sleep, there is an increase in theta wave activity, having even lower frequencies (4-7 Hz) than the alpha waves. These stages are accompanied by a decrease in both overall muscle tension and core body temperature, indicating the body's transition into a restful state.
It's during this stage of sleep where the body begins to relax, the heartbeat and respiration rates slow down, and it becomes relatively easy to wake the individual. The brain's electrical activity during this period can be observed using an EEG, illustrating the decline in frequency and increase in amplitude of brain waves.
Moving into stage 2 sleep, the body enters a deeper state of relaxation. Theta waves continue to be present but are interspersed with sleep spindles and K-complexes, which are associated with learning and memory. These stages lay the foundation for the deeper stages of sleep that follow, where the brain wave patterns change even more dramatically.