Student Exploration Senses

Student Exploration: Senses  Read the Explorelearning Enrollment Handout in the Introduction materials folder to learn how you can access Gizmos.  Make sure you use a name your instructor can recognize when you log in and don’t forget to do the 5 question quiz at the end of the Gizmo. They are part of your mark. Vocabulary: auditory cortex, auditory nerve, cerebrum, cone, gustatory cortex, hair cells, hypothalamus, involuntary, nerve impulse, neural pathway, neuron, olfactory cortex, olfactory bulb, optic nerve, rod, sensory neuron, somatosensory cortex, somatosensory nerves, spinal cord, stimulus, thalamus, visual cortex Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. What are different types of information that your body can detect from the outside world? Different types of information that our body can detect are the six senses which are sight, hearing, smell, taste, touch and extrasensory Perception. 2. What organs does your body use to collect the information described in the last question? The organs that our body uses to collect the information are eyes, ears, nose, tongue and skin. Gizmo Warm-up Stimuli are changes inside or outside the body that cause a response. In the Senses Gizmo™, you will explore how different sense organs detect stimuli from the environment and send messages about that stimulus to the brain. On the NEURAL PATHWAYS tab, drag the apple slice into the white Stimulus box. Drag the eye into the Sense organ box. Click Play ). 1. What do you observe? Light receptors at the back of the eye are activated by incoming light 2. How do you know that the eye senses the apple? We know this as we can see that the nerve cells transmit light signals to the brain. 3. The neural pathway represents the nerves that connect the sense organ to the brain. What happens along the neural pathway when the eye sees the apple? The visual cortex in the brain processes the signals to create the perception of vision. Activity A: Senses and the brain Get the Gizmo ready:  On the NEURAL PATHWAYS tab, click Reset ). Introduction: The brain is organized into different regions that have different functions. Most sensory information is processed in the cerebrum, the “wrinkly” area that forms the outer part of the brain. The nerves that connect a sense organ to the part of the brain responsible for that sense is called the neural pathway. Question: What happens when stimuli are detected by sense organs? 1. Observe: Drag the apple into the Stimulus box and the tongue into the Sense organ box. Click Play. A. What does the tongue detect? The taste B. What happens along the neural pathway when the tongue detects the stimulus? Taste receptor cells in the taste buds of the tongue react to molecules in food, activating nerve cells. Nerve cells transmit taste signals to the brain. The gustatory complex in the brain processes the signals to create perception of taste. The glowing dot represents the transmission of a nerve impulse along the nerves that make up the neural pathway. A nerve impulse is an electrical signal that travels from one nerve cell to another. C. Which part of the brain processes this signal? Gustatory cortex 2. Compare: Click Reset. Select the speaker for the stimulus and the ear. Click Play. A. What part of the brain detects the signal from the ear? Auditory cortex B. What are similarities between this pathway and the pathway in question 1? Both the nerve cells transmit sound signals to the brain. C. Test other stimuli that produce sound. Are all of these stimuli processed in the same part of the brain? Yes, they are all processed in the auditory cortex of the brain. 3. Explore: Test different combinations of stimuli and sense organs. Are there any cases where the signal is processed by more than one brain region? Are there any cases where the signal is not processed in the brain at all? Explain. When we touch the pin with our fingers touch receptors in the skin react to stimuli including pressure, temperature and pain. Activated nerve cells transmit touch signals through the spinal cord and back to muscle cells, triggering muscles to move away from the source of pain. This whole process takes place in the spinal cord the signal does not reach the brain at all. Activity A (continued from previous page) 4. Label: Click Reset. Drag the apple to the white “Stimulus” box. Below is a diagram of the brain with arrows to different brain regions. Test each sense organ. Label each part of the brain with its name and the sense organ from which it receives a signal. Gustatory Cortex Somatosensory Cortex Auditory Cortex Olfactory Cortex Visual Cortex 5. Compare: Select the pin for the stimulus and the hand for the sense organ. Click Play to watch how the signal is handled by the spinal cord. Click Next, and then Play, to watch how the signal is handled by the brain. A. How are the two pathways different? In the first pathway activated nerve cells transmit touch signals through the spinal cord and back to muscle cells, triggering muscles to move away from the source of pain. In the second pathway activated nerve cells transmit touch signals through the spinal cord to the brain. B. Which path would occur faster, and why is this advantageous? Path number 1 would occur fast as the signals transmitted through the spinal cord and back to muscle cells triggers muscle to move away from the source this whole process is involuntary. When a signal is processed by the spinal cord, it is called a reflex. These responses are involuntary, which means they occur without thought. 6. Observe: Select the ice cube and the hand. Click Play and observe. A. Which part of the brain processes hot and cold? Hypothalamus B. Click Next and Play again. What happens when the signal travels back to the hand? The hypothalamus sends signals back through the spinal cord to the muscles, which contract to produce a shivering motion Activity B: Vision and hearing Get the Gizmo ready:  Select the SENSE ORGANS tab.  With Eye selected, click the left circle to enlarge. Question: How do the eye and ear detect stimuli? Lens Retina 1. Observe: Select Show labels. On the image to the right, label the lens and retina. Watch the yellow light waves enter the eye. On the image to the right, draw two lines to represent light waves. What do you notice when light passes the lens? Light waves enter the eye and are focused by lens as shown. As a result, the image is flipped when projected on the retina. The focusing of light by the lens results in an upside-down image on the retina. 2. Observe: Select the central circle. The squiggly lines represent light waves of different colors. As on the first tab, the glowing yellow dots represent nerve impulses. A. What do you see? Light waves travel to the back of the eye and activate rod and cone cells of the retina. The rod and cone cells activate inter neurons, which activate the ganglion cells of the optic nerve. B. Turn on Show labels. The retina contains two types of sensory neurons, rods and cones. Label these on the diagram. Turn off Show labels and view the animation carefully. Rod Cones 1 3 2 Which cells detect colors? Cones C. On the diagram, label one path that a signal can follow in order from 1 to 3. 3. Describe: Select the right circle. Signals from the eye travel to the brain via the optic nerve. A. Turn on Show labels. Describe the path of the signal (yellow dot) through the brain. Signals are sent from the optic nerve to the thalamus and then the visual cortex Most sensory signals are routed through a region of the brain called the thalamus. B. Read the description above the circles. What happens when the signal reaches the visual cortex? When the signal reaches the visual cortex the brain interprets the signal into what we perceive as vision. Activity B (continued from previous page) 4. Label: Select Ear. Click on the left circle to watch what happens when sound waves enter the ear. Turn on Show labels. A. Notice there are three main parts to the ear. The outer ear consists of the pinna and ear canal. The middle ear includes everything between the eardrum and cochlea. The inner ear consists of the cochlea and semicircular canals. On the diagram below, label the anvil, cochlea, ear canal, ear drum, hammer, pinna and stirrup. Pinna Cochlea Stirrup hammer Ear canal Anvil Ear drum B. Describe what sound wav parts of the middle ear. Some waves vibrate the eardrum, which vibrate the hammer. The hammer vibrates the anvil. The anvil vibrates the stirrup, and the stirrup pushes on the cochlea. 5. Observe: Select the central circle. This is a cellular view of the inside of the cochlea. A. What happens to the hair cells when the basilar membrane vibrates? When the cochlea is vibrated by the stirrup, the basilar membrane moves up and down dragging the hair cells against the tectorial membrane. B. Where does the signal go after leaving the hair cells? The activated hair cells send signals through the auditory nerve to the brain 6. Observe: Select the right circle. Nerve impulses exit the ear via the auditory nerve and travel to the brain. A. Describe the path of the signal (yellow dot) through the brain. Signals are sent from the auditory nerve to the brain stem, through the thalamus, and then to the auditory cortex of the brain. B. Read the description above the circles. What happens when the signal reaches the auditory cortex? the arrival of the message may first of all trigger a reflex and cause us to jump or turn our head. Thereafter, the processing might also unfold in the auditory cortex, where the sound is consciously perceived. Other brain areas can allow the perception to become conscious as well and hence recognize the sound by relating it to those that have been memorized in the past. This assessment is followed-up by an appropriate voluntary response. Activity C: Touch, smell, and taste Get the Gizmo ready:  On the SENSE ORGANS tab, select Skin. Question: How do the skin, nose, and tongue detect stimuli? 1. Observe: Click on the left circle and turn on Show labels. A. Name a few different types of receptors in the skin. Pain, Temp, light touch receptor and strong pressure B. Why do you think light-touch receptors are found at the skin’s surface while strongpressure receptors are found deeper down? Skin detects pressure by using sensory receptors which are structures that are specialized to detect a stimulus. When a stimulus is detected the receptors send impulses to the brain. The brain interprets the impulses as the sensation of touch and then will send messages to the effectors on how to respond. -The outermost sensory part of the body is the hair. Root hair plexuses are receptors with free nerve endings that surround hair follicles and detect hair movement. -Tactile stimuli produce sensations of touch and pressure. -Merkel discs are receptors with free nerve endings that detect surface pressure of light touch. They are located deep in the epidermis. -Meissner's corpuscle are touch receptors in the papillary region of the dermis that detect surface pressure (light touch). -Pacinian Corpuscles are encapsulated nerve receptors that are located deep in the reticular layer of the dermis and detect deep pressure. C. Watch the remaining circles and describe how signals travel from somatosensory nerves to the somatosensory cortex. The signal first comes from the spinal cord which then passes it to the brain cell which transmit it to the thalamus which then passes it to the somatosensory cortex. 2. Observe: Select Nose and enlarge the left circle. Where do the scent particles travel? Olfactory neuron 4 When the scent molecules enter the nose, some are captured in the mucus, membrane on the roof of the nose, where they come in contact with the olfactory bulb. 3 3. Label: Select the center circle to see the pathway from chemoreceptor cells to the olfactory bulb. Observe the neural signals that are produced when scent particles (white dots) hit the top of the nose. On the diagram, label the pathway from 1 to Axon 2 Sensory neuron 4. Observe: Select the right circle. Describe how the signal travels from the olfactory bulb to the olfactory cortex. Dendrite 1 Signals are sent from the olfactory bulb to the cortex in the frontal lobe, it is not routed through the thalamus. Unlike other sensory signals, olfactory signals are not routed through the thalamus. (Activity C continued on next page) 1 Activity C (continued from previous page) Taste bud 5. Describe: Select Tongue. Click on the left circle. What is the function of lingual papillae? Are the small bulbous structures that increase the surface area of the tongue and give the tongue it’s rough texture. Papillae contain taste buds, the nerve endings that detect taste. 2 Sensor y cells 3 6. Label: Select the central circle to zoom in on a ta bud. Observe the neural signals that are produce when taste particles (white dots) hit the taste bud Sensory neuron On the diagram, label the path that a signal can follow in order from 1 to 3. 7. Observe: Select the right circle. Describe how the signal travels from the sensory neurons in the tongue through the brain to the gustatory cortex. Signals are sent from taste nerves to the brain stem then the thalamus and finally to the gustatory cortex of the brain. 8. Compare: Think about the similarities and differences between the five senses. A. How are the sensory receptors for smell and taste similar? Taste and smell are called chemical senses because their receptors are sensitive to molecules in the food we eat and in the air we breath. Taste cells and olfactory cells are classified as chemoreceptors. B. How are the sensory receptors for hearing and touch similar? The sensory receptors for hearing and touch are similar they both use vibration. A lot like hearing sense of touch is traditionally thought of in saptial terms. Receptors in the skin are spread out and when we touch something this grid of receptors transmits information about the surface to the brain. C. In what ways are the sensory receptors for vision different from the others? The receptors in eyes are different because they are stimulated by light. D. Compare the neural pathways of each sense organ to the brain. How are these pathways similar? Different? the neural pathway for vision, hearing, and taste have a similar process where the nerve cells transmit signals to the brain. But for touch the nerve cells transmit signals through the spinal cord and to the brain.