The<unk>  is the central information-processing organ of the<unk> ody. It innervates the head through cranial nerves, and it communicates with the spinal cord, which innervates the<unk> ody through spinal nerves. Nervous fibers transmitting signals from the<unk>  are called efferent fibers. The fibers transmitting signals to the<unk>  are called afferent fibers (or sensory fibers). Nerves can<unk> e afferent, efferent or mixed (i.e., containing<unk> oth types of fibers).
The<unk>  is the site of reason and intelligence, which include such components as cognition, perception, attention, memory and emotion. The<unk>  is also responsible for control of posture and movements. It makes possible cognitive, motor and other forms of learning. The<unk>  can perform a variety of functions automatically, without the need for conscious awareness, such as coordination of sensory systems (eg. sensory gating and multisensory integration), walking, and homeostatic<unk> ody functions such as<unk> lood pressure, fluid<unk> alance, and<unk> ody temperature.
The Cerebellum controls<unk> alance and movement. Without it, movements would not<unk> e coordinated.
File:Brainlobes.svg
Many functions are controlled<unk> y coordinated activity of the<unk>  and spinal cord. Moreover, some<unk> ehaviors such as simple reflexes and<unk> asic locomotion, can<unk> e executed under spinal cord control alone.
The<unk>  undergoes transitions from wakefulness to sleep (and subtypes of these states). These state transitions are crucially important for proper<unk>  functioning. (For example, it is<unk> elieved that sleep is important for knowledge consolidation, as the neurons appear to organize the day's stimuli during deep sleep<unk> y randomly firing off the most recently used neuron pathways; additionally, without sleep, normal subjects are observed to develop symptoms resembling mental illness, even auditory hallucinations). Every<unk>  state is associated with characteristic<unk>  waves.
Neurons are electrically active<unk>  cells that process information, whereas Glial cells perform supporting function. In addition to<unk> eing electrically active, neurons constantly synthesize neurotransmitters. Neurons modify their properties (guided<unk> y gene expression) under the influence of their input signals. This plasticity underlies learning and adaptation. It is notable that some unused neuron pathways (constructions which have<unk> ecome physically isolated from other cells) may continue to exist long after the memory is absent from consciousness, possibly developing the subconscious.
The study of the<unk>  is known as neuroscience, a field of<unk> iology aimed at understanding the functions of the<unk>  at every level, from the molecular up to the psychological. There is also a<unk> ch of psychology that deals with the anatomy and physiology of the<unk> , known as<unk> iological psychology. This field of study focuses on each individual part of the<unk>  and how it affects<unk> ehavior.
Brain
Heart
Central nervous system
Head 
Bone
Nervous tissue
Skull
Airway