Nervous+System

**Nervous System Section 1 – Giovanna and Girlany **

__Functions__: - to receive information from the external and internal environment - to interpret the information - to maintain homeostasis

**Stimulus**: any change in the environment that can make an organism react in some way. **Response**: what the body does in the response to a stimulus. **Neuron**: carries information through the nervous system. **Sensory neuron**: receives information about environment. **Interneuron**: connects both motor and sensory neurons. **Motor neuron**: sends the message to the effector (muscle or gland) causing a response

**Reflex Path:** receptor à sensory neuron à interneuron à motor neuron à effector Examples of reflex: when the doctor hits your knee with that little hammer and you move your leg unconsciously; when the pupil changes size depending on how much light you have available in the environment...

__** Section 3: The Senses; The Eye and Ear **__

The eye is a complex organ that allows you to sense light and see images which will be interpurted by the brain(cerebrum). In the eye, there is an opening caled the pupil which light enters the eye through. In bright light, the pupil will become smaller. In dim light, the pupil will become larger to allow more light into the eye. Behind the pupil is the lens. It is a flexible stucture used to magnify and focus light.

__** Parts of the eye: **__ **Cornea**- clear tissue that covers the front of the eye. **Pupil**- the opening through which light enters the eye. **Iris-** a circular structure that surrounds the pupil and regulates the amount of light by controling the size of the pupil. **Lens**- a flexible stucture that focuses light. **Retina**- the layer of receptor celss that lines the back of the eye. **Optic Nerve-** the nerve which acts as a passage from the eye to the brain. **Vitreous Humor-** the muscle inside the eye. **Vitreous Aqueous-** produces tears (tearducts). **Sclera**- is a tough tissue covering all of the eye except the cornea. (this is the white of the eye.

**nearsightedness**- can see nearby objects clearly but has trouble seeing objects far away.(result of the eye being too long) **farsightedness**- can see distant objects clearly but not close by objects. (result of eye being to short)
 * __ Problems of the eye: __**



__**The Ear:**__ Your ears are the sense organs that respond to the stimulus of sound. The ears conver the sound to nerve impules that your brain interprets. The ear senses sound that is produced by vibrations but the ear is used for more than just hearing. It is used for balance! The ear contains liquid in the Cochlea which is used for balance. When you spin around and suddenly stop you are dizzy because the liquid in the ear is still moving.


 * Outer ear:** sounds enters through the outer ear and reaches the eardrum.The outer ear includes the ear canal.
 * Middle ear**: vibrations pass from the hammer tothe anvil and stirrup. Includes eardrum, hammer (maleus), stirrup, and anvil.
 * Inner ear:** vibrations in the cochlea cause nerve cells to transmit signals to the brain. Includes semicurcular canals, cochlea, and auditory nerve.

**Section 4: Mary and Courtney** **The effects of Drugs on the Central Nervous System:**


 * // A Drug //is a substance that changes a person's body/behavior.
 * // Tolerance //is when you need more and more of the drug you are taking to have the same effect on the body as the first time you used it.
 * // Addiction // is when the body is physically dependant on a drug.
 * // Withdrawl // is a period of adjustment that occurs when a person stops using a drug you rely on by using less and less of it over time.
 * // Abuse // is when you over use a drug.
 * A // depressant // is a kind of drug that slows down your heart rate and you // Central Nervous System //, for example: marijuana, alcohol, and tranquilizers.
 * A // stimlulant // is the opposite of a depressant. It speeds up your heart rate and you Nervous System. Some examples of stimulants are caffeine which is found in coffee, nicotine that is used in cigarettes, and cocaine which of course is an illgeal drug.
 * // Inhailants // are sniffed by the person to create mood-altering effects on the body. For example nail polish remover, glue, gasoline, etc...
 * // Hallucinogens // like LSD make you hallucinate.
 * // Anabolic Steroids //increase your muscle mass and allow you to improve in physical activities. However, they have horrible side effects on your body. Also the use of anabolic steroids in a competion is illegal. Before any professional competion or event, a doctor must test a sample of your blood to check if you are using steroids.