Nervous System

The Nervous System controls and interprets all the activities that happen within the body. It enables us to move, think, laugh, feel pain, or enjoy the taste of food.

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It makes the body respond quickly to changes in the environment by accomplishing the four basic functions, namely:

• gathers information both from the outside world and from inside the body;

• sends information to muscles, glands, and organs so they can respond correctly;

• transmits information to the processing areas in the brain and spinal cord and

• processes information to determine the best response.

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• Neurons are cells with the special ability to carry signals or impulses. Thoughts, emotions, learning, and many-body functions are carried by nerve impulses in the neurons. A nerve impulse is a combination of an electrical charge and a chemical reaction. It is not a flow of electricity but an electrochemical signal that is moving along a neuron.

• Imagine that you have a board with a row of switches. Quickly click each switch in the row on and off. This will give you an idea of how a nerve impulse travels along a neuron.

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• A nerve impulse cannot jump from one neuron to another. When a nerve impulse comes to the end of an axon, it produces and releases the chemical called a neurotransmitter. The chemical crosses the space between neurons called a synapse and stimulates the nerve impulse to start in the next dendrite.

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• A feedback mechanism is a process that uses the condition of one component to regulate the function of the other.

• It is done to either increase or dampen the change in the system.

• For example, when blood pressure suddenly increases or reduces, it starts a series of responses that aim to bring the blood pressure to regular levels.

• Another example is when thyroxin secretion is more; it prevents the secretion of thyroid-stimulating hormone from the pituitary gland so that thyroxin is not produced from the thyroid gland.

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• Positive feedback is when the end products of action cause more of that action to occur in a feedback loop. This amplifies the original action. For example, milk is secreted by a mother's mammary gland.

• As the baby suckles on the mother's mammary gland, nerve messages from the nipple cause the pituitary gland to secrete prolactin. Prolactin, in turn, stimulates the mammary glands to produce milk, so the baby suckles more. This causes more prolactin to be secreted and more milk to be produced.

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• Positive feedback is contrasted with negative feedback, which is when the end results of action inhibit that action from continuing to occur.

• For example - the secretion of insulin by the pancreas. Insulin is a hormone that plays a key role in the regulation of blood glucose levels. It is produced by the beta cells in the pancreas and acts to lower blood sugar levels. When the body does not have enough insulin, it cannot transform excess glucose in the blood into glycogen. As a result, the blood sugar level is high, and it can cause a condition known as diabetes. So, the secretion of insulin must be balanced for the body to have just the right amount of sugar in the blood.

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• Homeostasis is the state reached when each part of the body functions in equilibrium with other parts. This is attained through the regulation of the bodily functions of the endocrine and nervous systems. What does this mean? When something changes inside or around an organism, it must be able to get itself back to a "healthy normal."

• Shivering when cold, making more red blood cells when oxygen levels drop, and releasing bicarbonate when you eat something acidic are just some of these bodily reactions.