Final answer:
The brain controls speech, feelings, body movement, and thoughts. It is responsible for cognitive functions like reasoning and language, and also regulates voluntary and involuntary activities through both the central and peripheral nervous systems.
Step-by-step explanation:
The organ that controls your speech, feelings, body movement, and thoughts is the brain. As the most complex organ of the human body, the brain is the control center of the nervous system. The brain is responsible for cognitive processes like reasoning, imagination, memory, and crucially language. It also orchestrates sensory interpretation and voluntary physical activities, such as writing or playing an instrument. The brain is divided into major parts, including the cerebrum, cerebellum, and brain stem. The cerebrum is the brain's largest part and is in charge of intellectual functions like memory and language. The cerebellum aids in movement coordination, and the brain stem handles involuntary actions such as breathing and heart rate. Collectively, these components form the central nervous system (CNS), which, along with the peripheral nervous system (PNS), regulates all human activity.
Muscle movement is controlled by the brain via several systems. The motor system, which involves the motor cortex and other areas, facilitates voluntary muscle movements while the somatic nervous system carries messages that control these movements actively.