The thalamus is part of the humanoid brain. It consists of two general parts. The sensory thalamus receives impulses from sensory nerves – nerves stimulated by changes in the organism's environment. The sensory thalamus combines and switches this information, sending it to the proper regions of the cerebral cortex. The motor thalamus is connected to axons of the pyramidal cells that originate in the motor cortex (chiefly those of the precentral gyrus). It switches the signals from the cortex to the basal ganglia, and thence to the spinal cord and ultimately the muscles. Because the thalamus receives so many signals, it is believed to be one of the architecturally oldest parts of the humanoid brain.