FC: The Nervous System
1: By Rachel Morgan
2: The Neuron The nervous system is made of nerves, the spinal cord, and the brain. These nerves are wired like a telephone system. There is a central switchboard, controlling all messages and where they go, and then there is the wires going from the switchboard to the rest of the body. These wires are the nerves. Each nerve is composed of nerve cells called neurons. The neuron is composed of a nucleus, enclosed in the cell body. Coming out from the cell body is the dendrites, which carry messages to the cell body, and the axon, which carries the message to the end plates, and then the message crosses a space in between the two neurons called a synapse. then the next neurons carry the message along to where it is supposed to go.
4: Sensory Neurons There are three different types of neurons. The first one is the sensory neuron. These neurons carry messages from the sense organs such as the ears, eyes, nose, and tongue, to the brain and spinal cord.
7: The Association Neuron Association neurons carry messages from a sensory neuron to a motor neuron. These are normally found in the brain and spinal cord.
9: The Motor Neuron The motor neuron carries messages from the brain and spinal cord. They then go to a muscle or a gland causing movement or a secretion.
11: The Reflex A reflex is an involuntary muscle movement that serves to protect the body. What happens is a sensory neuron from the skin carries a message to the spinal cord, then through an association neuron to a motor neuron and finally to a muscle or gland causing movement or a secretion. This round trip is called a reflex arc. Reflexes are protective mechanisms. Some examples are blinking. sneezing, and coughing.
12: The Central Nervous System The central nervous system is the "central switchboard" of the nervous system. It is composed of the brain and spinal cord, which are vital to survival. If you injured certain parts of the brain then you could not be able to speak, think, or feel. If you severe the spinal cord, you would be paralyzed below the point of injury. The brain and spinal cord are enclosed in hard bones. The surface is protected further by tissue and fluid.
15: The Cerebrum The cerebrum forms the top part of the brain. It is composed of both white and gray matter. It is divided up into two halves, called hemispheres. The surface, or cortex, of the cerebrum is folded into ridges called convolutions. Each area of the cerebral cortex has its own specific job to do. One area controls muscles. Another controls touch. Some others are speech, sight, hearing, taste, and smell.
16: The Cerebellum The cerebellum is below and behind the cerebrum. It is also composed of both white and gray matter, is divided into hemispheres, and is folded. The cerebellum's main function is to control coordination. If you were to injure this, you're muscle movements would become jerky and unpredictable.
17: The Medulla Oblongata The medulla is connected to the spinal cord. The white matter is on the outside, and it serves as a pathway for messages from other parts of the brain. The gray matter serves as a switchboard for motor messages going out to a gland. It also controls vital functions such as breathing and digestion.
18: The Spinal Cord Te spinal cord is a cord of nerves running down the vertebral column. Branching out from the spinal cord are thirty one pairs of nerves that reach out to all parts of the body.
20: The Peripheral Nervous System The peripheral nervous system connects the centrasl nervous system to all other parts of the body. It consists of forty-three pairs of nerves. Twelve of these are called cranial nerves. They connect directly to your brain and involve the senses. The other thirty-one are called spinal nerves. They connect the spinal cord to the external parts of the body. Some of these nerves fall into a category called the autonomic nervous system. That means that you don't need to think about doing it. There are two divisions to this system. Sympathetic, and parasympathetic. Parasympathetic tends to slow down and restrict activity, and sympathetic tends to speed the activities up.