Human Biology 115 Lecture 17: Senses
Human Biology 115 Lecture 17: Senses Bio 115
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This 3 page Class Notes was uploaded by Jasmine Ngo on Tuesday January 19, 2016. The Class Notes belongs to Bio 115 at Illinois Institute of Technology taught by Dr. Navaratnam in Winter 2016. Since its upload, it has received 65 views. For similar materials see Principles of Biology in Biology at Illinois Institute of Technology.
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Date Created: 01/19/16
Chapter: Senses Sensory Receptors Sensory receptors include pressure, temperature, touch, pain, stretch, chemical stimuli Eye, ear, tongue, nasal cavity are all organs with complex sensory receptors Receptors are constructed from dendrites Examples of receptors include free nerve endings (control pain, heat, cold), Ruffini endings (control pressure), Merkel disks (control touch) The peripheral and central nervous system function in sensory receptors. A stimulus such as a prick of a needle travels to the sensory receptors. The receptor travels to the nerve impulses, which creates an action potential along the sensory fiber that controls pain. The impulse goes to the spinal cord or to the brain depending on the stimulus. Sensory Stimulation and Adaption: Stimulation causes nerve impulses. Nerve impulses as learned in the nervous system chapter is when Sodium channels open, allowing sodium ions in and letting potassium ions out, thus causing depolarization. If it exceeds the threshold, an action potential is produced. Adaption occurs when receptors cease to respond. Pressure receptors can adapt while pressure sensors cannot. Referred pain: When internal pain can be connected with pain on the skin or anywhere outside of the body. This is because neurons from pain receptors travel in the same spinal nerves that carry impulses from the skin. Stretch receptors also known as proprioceptors control posture and movement in joints and tendons by initiating muscle contractions. Smell: Smell receptors detect chemicals in the air and food. Smell is associated with taste and much of what is interpreted as taste is actually smell. Taste: Taste receptors are located in taste buds which are located in small projections called papillae. Taste receptors are also located in the uvula, tonsils, soft and hard palate. Taste receptors that detect bitterness are in back of tongue, sweet is at tip of tongue, salty and sour are at sides of tongue. Few taste receptors are in the middle of the tongue. Humans can taste 5 different sensations: salty, sweet, sour, bitter, and umami Complex sensations can be due to stimulating more than the 5 common sensations at once Vision: The eye contains two fluid filled chambers: Aqueous humor (near the front of eye) and vitreous humor (near back of eye) that are separated by the lens The eye is protected by white connective tissue called sclera Inside the sclera is the choroid layer which contains darkly pigmented cells called choroid. The black pigments of the cells absorb light coming through the pupil, reducing blurred and scattered vision. In order to see: Light first enters the cornea where focusing of light takes place. The iris controls how much light goes into the pupil by relaxing and contracting of the smooth muscle. Light is absorbed and transduced in the retina. The retina houses bipolar cells, ganglion cells and rods and cones. The bipolar cells conduct electrical signals to the ganglion cells which then make interconnections with the rods and cones. This allows for the processing of an image before it reaches the brain. Rods are sensitive to intensity of light while cones are sensitive to color (blue, red, and green) Light Transduction: In rod cells, the disk membranes contain an integral membrane protein called rhodopsin. Consists of protein opsin and a derivative of Vitamin A called retinal. Light is absorbed in a double bond within the retinal molecule causing a cis-trans isomerization. This causes a temporary separation of retinal from opsin which ultimately results in a change in the level of excitation of the cell. When enough opsin is split, impulses are transmitted to the bipolar cells. Color blindness is a lack of pigment in a certain cone. Common in red and green deficiency Accommodation: The act of fine tuning the eye so that it can see far and near objects but not at the same time. Nearsightedness: When the eyeball is too long and rays come to focus in front of the retina. Farsightedness: When eyeball is too short and rays come to focus behind the retina. Astigmatism results from irregularities in the cornea so that not all light rays from all angles focus at the same point on the retina. Hearing: The ear is made up of three sections: The outer, middle, and inner ear. The outer ear consists of the pinna, auditory canal, and eardrum The middle ear contains three small bones: hammer, anvil, and stirrup The inner ear contains the oval window and cochlea. How we hear: Sound goes through the auditory canal to the eardrum, which causes a vibration to occur, hitting the three bones (hammer, anvil, and stirrup). The vibration of the three bones transmit to the oval window. The cochlea contains tiny hair cells that transfers the vibrations into electrical signals that are sent to the brain by the hearing nerve.
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