![]() ![]() For example, the size of our pupils is adjusted automatically to allow the correct amount of light into our eyes for optimum vision, our sweat glands are turned on when we get too hot and our salivary glands produce saliva when we eat food (or even think about it!). Together, they coordinate a multitude of adjustments required for our changing personal needs as we move through our environment. These systems act on the body in opposite ways. The autonomic nervous system is made up of two parts: the sympathetic and the parasympathetic. One of its main roles is to regulate glands and organs without any effort from our conscious minds. ![]() The autonomic nervous system is part of the peripheral nervous system. It is made up of two main parts: the autonomic and the somatic nervous systems. Nerves connect the brain and spinal cord to the peripheral nervous system, which is what nerve tissue outside of the central nervous system is called. Nerves branch off from the spinal cord into the arms, legs and torso. It is protected by the bones of the spine (vertebrae). The spinal cord is connected to the brain and runs the length of the body. The brain oversees the workings of the body, while its higher functions give us consciousness and personality. This soft, jelly-like organ has countless billions of neural cross-connections. The brain is the powerhouse of the body, even though it only makes up 2 per cent of the body’s weight. They are wrapped in a thin lining called meninges and bathed with cerebrospinal fluid (CSF). The brain and the spinal cord make up the central nervous system. Unlike other cells in the body, neurones aren’t easily replaced if they die or are damaged by infection or injury. Messages jump the synapse from one neurone to the next, using special chemicals called neurotransmitters. The space between the bump and the dendrite is called a synapse. Each bump sits near to a dendrite from another neurone. The axon feathers out and has a number of bumps on it. In many cases, the axon is coated by a specialised membrane called a myelin sheath. All neurones have finger-like projections called dendrites and a long fibre called an axon. Neurones are shaped differently depending on where they are in the body and what role they play. The basic building block of the nervous system is a nerve cell, or neurone. The nervous system uses both electrical and chemical means to send and receive messages. It also reacts to changes both outside and inside the body. The nervous system helps all the parts of the body to communicate with each other.
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