Though there are over 10,000 specific types of neurons, the three general classifications are sensory neurons, motor neurons and interneurons. Sensory neurons send signals from outside the body into the central nervous system, motor neurons transmit signals to activate muscles and glands, and interneurons act as connectors between neurons.Continue Reading
The sensory neurons inform the central nervous system of outside stimuli through the senses of touch, sight, hearing, taste and smell. By causing muscles to contract and relax, motor neurons enable such involuntary muscle functions as the beating of the heart and the passage of food through the intestines, as well as voluntary skeletal muscle function. Interneurons form the connections that enable communication between the sensory neurons and the motor neurons and also perform many other complex signaling functions within the nervous system.
The brain is not always involved in signal transmission between neurons. In a monosynaptic reflex pathway, such as a knee-jerk reflex, sensory neurons pass messages directly to motor neurons, which stimulate the leg muscles to react automatically. As tasks increase in complexity, the pathways become more convoluted, and the brain comes into play. To process all this information, scientists estimate that the human brain contains roughly 200 billion neurons.Learn more about Nerves
During the reflex arc, sensory neurons carry signals from receptors to interneurons in the spinal cord, which send signals to activate muscles via motor neurons without first signalling the brain. This sequence provides much quicker responses to certain stimuli and is totally involuntary.Full Answer >
The brain is made up largely of neurons, or nerve cells, blood vessels and glial cells. Glial cells create a supporting structure for the brain. The brain is about 60 percent fat.Full Answer >
According to Dartmouth, the cerebral cortex is the outer layer of the brain and is responsible for numerous functions including sensation, language, creativity, motor processes, memory, abstraction, emotion, attention and judgement. The cerebral cortex is generally associated with the higher-level functions of the brain, and in animals with large brains, it is wrinkled as to provide more surface area for grey matter to flourish.Full Answer >
The myelin sheath is formed as individual cells extend their plasma membranes around the axons of neurons in a spiral fashion. In the central nervous system, these are called oligodendroglial cells, while in the peripheral nervous system, they are called Schwann cells.Full Answer >