Sight and the Eye
Sight is one of the five senses that help us to get information about what is going on in the world around us. We see through our eyes, which are organs that take in light and images and turn them into electrical impulses that our brain can understand.
How do we see?
When we see something, what we are seeing is actually reflected light. Light rays bounce off of objects and into our eyes.
Our Amazing Eyeballs Pupil and Iris: Eyes are amazing and complex organs. In order for us to see, light enters our eyes through the black spot in the middle which is really a hole in the eye called the pupil. The pupil can change sizes with the help of the colored part around it, a muscle called the iris. By opening and closing the pupil, the iris can control the amount of light that enters the eye. If the light is too bright, the pupil will shrink to let in less light and protect the eye. If it's dark, the iris will open the pupil up so more light can get into the eye.
Retina: Once the light is in our eye it passes through fluids and lands on the retina at the back of the eye. The retina turns the light rays into signals that our brain can understand. The retina uses light sensitive cells called rods and cones to see. The rods are extra sensitive to light and help us to see when it's dark. The cones help us to see color. There are three types of cones each helping us to see a different color of light: red, green, and blue.
Focus: In order for the light to be focused on the retina, our eyes have a lens. The brain sends feedback signals to the muscles around the lens to tell it how to focus the light. Just like the way a camera or microscope works, when we adjust the lens we can bring the image into focus. When the lens and muscles can't quite focus the light just right, we end up needing glasses or contacts to help our eyes out.
Off to the Brain: The rods and cones of the retina change light into electrical signals for our brain. The optic nerve takes these signals to the brain. The brain also helps to control the eye to help it focus and to control where you are looking. Both eyes move together with speed and precision to allow us to see with the help of the brain.
Why two eyeballs? With two eyeballs our brain gets two slightly different pictures from different angles. Although we only "see" one image, the brain uses these two images to give us information on how far away something is. This is called depth perception.
Fun facts about the eye
The image at the retina is actually upside down from the actual image.
Our brain figures this out for us and switches it around, or we would get really confused!
The cornea is a clear layer at the front of the eye that helps protect it.
We have a blind spot where the optical nerve connects to the retina.
Tears help keep the eye clean, but scientist don't really understand why we cry when we are sad or upset.
The average person blinks 15 times per minute.
Around eight percent of men are color blind, but less than one percent of women.
Read more at: http://www.ducksters.com/science/sight_and_the_eye.php
QUIZ .. CIRCLE THE CORRECT ANSWER.
1) Our eyes are needed to perceive which of the five senses? Smell Taste Sight Touch Hearing
2) Which of the following parts of the eye is the hole that lets in light? Retina Lens Pupil Focus Iris
3) Which of the following parts of the eye is colored? Retina Lens Pupil Focus Iris
4) The iris can change the ______ of the pupil.
Color Shape Function Size Structure
5) True or False: When it is really dark, the iris will shrink the pupil so your eye can focus and see clearer. TRUE FALSE
6) Where in the eye are rods and cones located? Retina Lens Pupil Focus Iris
7) True or False: Rods help us see in the dark and cones help us see color. TRUE FALSE
8) The retina converts: Rods into Cones Cones into Rods Black and white images into color images Light into electrical signals Images into long-term memories
9) The lens of the eye is similar to the lens of which of the following devices? Telescope Camera Magnifying Glass Microscope All of the Above
10) Having two eyes specifically helps with which of the following?
Farsightedness Nearsightedness Depth Perception Vision Clarity Reaction Tim
HEARING and the ear...
There are three major parts of the ear that help us to hear:
outer ear
inner ear
middle ear
Why two ears? Having two ears helps you to determine the direction of sound. Your brain is smart enough to figure out that if sound hits one ear just before the other and is slightly louder then that's the direction the sound came from. Having an ear on each side of our head also helps us to hear better.
Why do I get dizzy? The brain takes in a number of signals from your body to keep it balanced. One of them is from the fluid in the inner ear. The brain can tell a lot by how the fluid in your ear is moving or tilted. The brain also uses your eyes and sense of touch to tell it about your balance and position. When you spin really fast and then stop, the fluid in your ear is still spinning, but your eyes and body have stopped moving. Your brain gets confused for a bit and you feel dizzy.
TOUCH ...
SKIN
What is it? We all have skin. It covers our entire body and keeps the good stuff in and the bad stuff out. But what exactly is skin? We'll get into the details below, but for starters the skin is an organ. Just like the heart or the brain. It's an important organ that performs many functions to enable us to live.
functions of the skin
The skin is multipurpose, meaning it has a lot of functions. It's our first line of protection against the outside environment, it houses one of our five senses, it absorbs sunlight for vitamin D and heat, and regulates our internal temperature.
Protection - One of the basic functions of the skin is protection. Over the majority of your body the skin is around 2mm thick. In some areas, like your eyelids, it's thinner, while in other areas, like the soles of your feet, it's much thicker. The skin helps to keep bad stuff out of our body, like germs and dirt that can cause infection. It also keeps good stuff in, like fluids such as water and blood.
Sense of Touch - The skin also houses one of our five senses: touch. In our skin are thousands and thousands of sensors or receptor cells. These sensors send information to the brain about things we touch. They can tell the brain if it's hot, cold, rough, smooth, or painful. Different areas of our body have more receptor cells than others. Our hands, feet, and lips all have extra receptors making those areas even more sensitive. There are actually different types of receptor cells for each type of sensation.
Temperature Control - The skin plays a large role in regulating our body's temperature. When we get too hot it sweats to help cool us off. It can also widen the skin's blood vessels to get more blood near the skin where it can cool off. At the same time the skin can narrow the blood vessels to help us warm up. By controlling blood flow and sweat, the skin regulates our body's temperature.
QUIZ
1) True or False: The skin performs many functions to enable us to live, but it is not considered an organ like the heart or the brain.
TRUE FALSE
2) Which of the following is NOT a function of our skin?
2) Which of the following is NOT a function of our skin?
It houses one of our five senses
It absorbs sunlight for heat
It absorbs sunlight for photosynthesis
It absorbs sunlight for vitamins
It protects against the outside environment
3) Which of the following is the primary vitamin produced by our skin while absorbing
3) Which of the following is the primary vitamin produced by our skin while absorbing
sunlight?
Vitamin A Vitamin B Vitamin C Vitamin D Vitamin E
4)Our skin houses which of the five senses? Smell Taste Sight Touch Hearing
SMELL
Smelling and the Nose We use our nose to smell things. At the top of the inside of our nose are millions of tiny little hairs called cilia. These hairs are connected to smell sensors which send signals to our brain about smell via the olfactory nerve. We smell things when they emit small molecules that float in the air and end up in our nose. We can't see these tiny molecules, but they are there. The reason we sniff is to get more of those molecules up into the top of our nose to where they can attach to the special sensors and determine the smell. Smelling helps us in many ways. It first makes our food taste better. We can't really taste that many flavors, but with the help of smell we can "taste" thousands of different things. Also, smell helps to warn us from bad things like rotten food or smoke from fire. TASTE
Tasting and the Tongue We use our tongue to taste things. The tongue uses taste buds or sensor cells to determine the type of food and send taste signals back to our brains.
The tongue can taste four different flavors: bitter, sour, salty, and (maybe best of all) sweet.
It was once thought that each of these tastes came from a different spot on the tongue: sweet from the tip, salty from the sides, sour from the back sides, and bitter from the back. Now scientists say that flavors can be tasted from most any part of the tongue.
WORKSHEETS HERE...file:///E:/2016%20-2017%20tercer%20grado/FiveSenses2.pdf
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