BBB - Overview of the Nervous System Lesson

Learning Target:

• Describe the nervous system and its subdivisions and functions.

Courtesy of the AP psychology course and exam description, effective fall 2024. (n.d.). Links to an external site.

Nervous System

The nervous system is a complex and organized communication network that responds to internal and external stimuli. Information is received, interpreted, and responded to through the nervous system. It is made up of the brain, spinal cord, nerves, and sense organs, and is divided into two parts. However, for behavior to occur the two must function as one.

Central Nervous System

The central nervous system is made up of the brain and spinal cord and is responsible for our thoughts, feelings, and actions. Acting as a command center, the brain commands and the spinal cord is responsible for ingoing and outgoing messages. The spinal cord utilizes two neural tracks to communicate messages from the body to the brain and the brain to the body. Sensory messages traveling to the brain are called ascending and those traveling from the brain are called descending. This system is so critical that it is entirely encased in bone. Every thought, feeling, and action is processed through it.

The spinal cord also produces reflexes. Reflexes are simple automatic behaviors that occur without any brain involvement. In a spinal reflex, sensory neurons send information to the spinal cord, and interneurons relay the information to motor neurons, who then signal the reflex. The brain receives the information last. Reflexes are our body's way of minimizing injury. By skipping the brain our reaction times to injury or pain is much faster and prevents further damage.

Peripheral Nervous System

The peripheral nervous system comprises the sensory and motor nerves connecting the CNS to the body. It plays a key role in communication throughout the body. Like the nervous system, the peripheral nervous system has two divisions: somatic and autonomic. 

The somatic nervous system controls skeletal muscles voluntarily. For example, when you raise your hand to ask a question in class, the somatic nervous system conveys this intention to your brain, initiating your arm movement.

In contrast, the autonomic nervous system controls the function of glands and internal organ muscles. Its functions include glandular secretion, heart rate, and digestion. The autonomic nervous system is further divided into two subdivisions with distinct functions. The sympathetic nervous system activates and expends energy, while the parasympathetic nervous system conserves energy and induces calm.

 

The sympathetic and parasympathetic systems work to control most of the same organs but in the opposite way. The sympathetic nervous system is your body's emergency system and activates your "fight or flight responses." Threats and emergencies are met head-on, or you flee the situation. Bodily responses when the sympathetic nervous system is activated include accelerated breathing, faster heart rate, digestion slows down, pupil dilatation, and perspiration. 

The parasympathetic nervous system calms you down after an emergency. All your bodily functions return to normal. Heart rate and breathing settle, pupils constrict, and digestion resumes. It is important to note that they work together to keep the body balanced.

Complete the Divisions in the Nervous System activity below.

 

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