The Nervous System
The nervous system is the network of nerves and other cells that controls and coordinates your body's activities. It uses electrical and chemical means to help all parts of your body communicate with each other, and to react to changes both inside and outside of your body.
Nerves and their Functions
Nerves carry signals from your brain and spinal cord to all the different parts of your body. These include your muscles, glands, organs, and skin. Some neurons control your voluntary actions, while others are involuntary and work without conscious input from your brain.
Sensory Input and Brain Interpretation
Your eyes, ears, tongue, nose, and other nerves send information from the world around you to your brain, so it can tell you what's happening and how to respond. The brain interprets this information to let you move your limbs, feel pain, or temperature change.
Motor and Sensory Neurons
Motor neurons (or motor cells) are the ones that tell your muscles to move. These neurons also detect light, sound, odor, taste, pressure, and heat. Sensory neurons detect these things too, but they also control involuntary processes like breathing, shivering, having a regular heartbeat, and digesting food.
Diverse Structure of Neurons
Neurons come in many shapes and sizes, depending on where they are in your body and what they're programmed to do. Some have dendrites on both ends and a long axon in the middle. They connect to other neurons with synapses, and they make a connection called an action potential, which is a short burst of energy.
Stimulus-Response Coordination
Stimulus-response coordination is the way that the nervous system controls your body and is the basic idea behind how animals learn to move. It's based on the idea that external stimuli that activate sensory neurons create signals that pass along long chains of connections between neurons and nerve fibers, giving rise to activation of motor neurons that cause muscle contractions.
Internal Patterns of Activity
Historically, this has been the dominant view of how the nervous system works. However, more recently scientists have discovered that the nervous system can also function in ways that do not require an external stimulus, using internally generated patterns of activity that give rise to a form of plasticity in the nervous system.
Feature Detection and Visual Processing
A type of neural processing known as feature detection is often the basis for a specific animal's ability to extract biologically relevant information from a collection of simultaneous input signals. This process takes place in the visual system, where a group of primary sensory receptors – each capable of detecting "dots of light" in the surrounding environment – transmits signals to a small number of second-level sensory neurons. Eventually, these signals are processed by higher-level neurons to form an ensemble of "dots" that can be represented in the brain as a representation of objects in the environment and their properties.
Main Subdivisions of the Nervous System
The nervous system has two main subdivisions - the somatic division, which controls voluntary movements, and the autonomic division, which regulates involuntary functions such as your blood pressure or digestion. The somatic division is mainly made up of the spinal cord and the cranial nerves. The autonomic division, on the other hand, is made up of visceral nerves that conduct impulses to control the heart, lungs, smooth muscle in blood vessels, digestive tract, and glands.
