The nervous system is first subdivided into two large branches: the peripheral and central nervous systems. The central nervous system is composed of the brain and the spine and the peripheral is slightly more complicated. It can be subdivided into the autonomic (controlling internal organs and glands) and the somatic (skeletal). The enteric nervous system does not play a part in this overall nervous system. Instead, it is responsible for gastrointestinal processes. 

The sympathetic nervous system is responsible for initiating the fight or flight response. Conversely, the parasympathetic nervous system is responsible for ending the response. The parasympathetic nervous system will oppose the effects via conserving energy, lowering blood pressure and heart rate, and lowering your blood sugar. 

The somatic nervous system makes it possible for an organism to sense and move in its environment. This system is primarily comprised sensory receptors—found in eyes, ears, nose, tongue, and skin—and motor nerves that relay information from the central nervous system. The nerves in the somatic nervous system are usually under conscious control. Unconscious control such as cardiac muscle movement is regulated by the autonomic nervous system. Nerves that transmit messages from the central nervous system to glands, cardiac muscle, and smooth muscle are part of the autonomic nervous system. 

Wernicke's area is the language area that is responsible for comprehending spoken word as well as formulating written and spoken language. A person with damage to this area could develop speech that is incomprehensible. This particular speech disorder is known as Wernicke's aphasia. 

The sympathetic nervous system mobilizes the body during emergencies. These responses include the dilation of pupils, inhibition of salivary glands, relaxation of bronchi, acceleration of heartbeat, inhibition of digestive activity, the release of glucose from the liver, relaxation of the bladder, and inhibition of sexual arousal.

After an emergency the parasympathetic nervous system depresses the heightened bodily responses to normal levels. These responses include the constriction of pupils, stimulation of salivary glands, constriction of bronchi, slowing of heartbeat, stimulated digestive activity, stimulated gall bladder activity, contraction of the bladder, and the stimulation of sexual arousal. 

The somatosensory cortex is the site that registers touch, pressure, temperature, and pain in the cerebral cortex. This area is also responsible for awareness associated with bodily movement and position.

There are two cerebral hemispheres in the human brain. Each cerebral hemisphere is divided into four lobes. These four lobes include the following: frontal lobe, parietal lobe, occipital lobe and temporal lobe. 

The frontal lobes contain the motor cortex, Broca's area, and frontal association areas. The right motor cortex is responsible for movement on the left side of the body and the left motor cortex is responsible for movement on the right side of the body. 

Broca's area is the area in the frontal lobe that directs the muscle movement patterns responsible for producing speech sounds. When a person suffers from Broca's aphasia they often know what they want to say but physically can not say it.