The human nervous system contains three main types of nerves, categorized by their function:
1. Sensory Nerves
Sensory nerves, also known as afferent nerves, transmit signals from the body's periphery (e.g., skin, muscles, organs) to the central nervous system (CNS), which includes the brain and spinal cord. These signals provide information about touch, temperature, pain, pressure, and other sensations. Think of them as the body's reporting system.
- Example: Touching a hot stove sends a signal via sensory nerves to your brain, alerting you to the danger.
2. Motor Nerves
Motor nerves, or efferent nerves, carry signals from the CNS to muscles and glands, triggering actions. These nerves control voluntary movements like walking and talking, as well as involuntary actions like digestion and heart rate. They are the body's command system.
- Example: Deciding to lift your arm involves your brain sending signals down motor nerves to the appropriate muscles, causing them to contract.
3. Autonomic Nerves
Autonomic nerves control involuntary bodily functions, such as heart rate, breathing, digestion, and temperature regulation. These nerves operate largely unconsciously, maintaining homeostasis within the body. They are further subdivided into the sympathetic and parasympathetic nervous systems, which often have opposing effects.
- Example: Your heart rate increases during exercise due to signals from the sympathetic autonomic nervous system; your heart rate slows down after exercise due to the parasympathetic autonomic nervous system.
While some sources mention other classifications of neurons (like interneurons within the CNS), the three types described above represent the primary functional categories of nerves within the peripheral nervous system, which is the focus of many discussions about nerve types.
