BIOL 109N 1st EditionExam # 3 Study Guide Lectures: 15 - 21Lecture 1 ( Vision ) - Describe wall of eyeball (layers, structures) The outer layer is tough and fibrous Sclera – the white of the eye, protects and shapes the eyes, serves as attachment sitefor muscles Cornea – transparent area at the front of the eye, allows light to enter The middle layer is vascular  Choroid – contains blood vessels that supply eye tissue with nutrients and oxygen Ciliary body – muscular ring formed by the choroid toward the front of the eye, holds lens in place and changes its shape.  Iris – colored portion of the eye, muscular part of the choroid in front of the ciliary body, regulated pupil size. The inner layer is light sensitive tissue layer Retina – lines the eyeball, contains several layer of neurons, location of photoreceptors. Photoreceptors respond to light by generating electrical signalso Rods – dim light o Cornea – bright light and colored visiono Fovea- region of the retina with the greatest concentration of cones, sharp vision - Describe fluid-filled chamber(vitreous and aqueous)Posterior chamber – located in the back of the eye between the lens and eh retina filled with jellylike fluid vitreous humor. It helps keep eyeball from collapsing and holds the thin retina against the wall of the eye. Anterior chamber – located in the front of the eye between cornea and lens filled with aqueous humor. The clear fluid supplies nutrients and oxygen to the cornea and lens and carries metabolic waste away. - How to focus? What structures are used?The ciliary muscles can change the shape of the lens, allowing the image to be focused on the retina. Light rays converge onto retina. The elasticity of the lens allows it to change the shape to change the bending of light – accommodation -> can focus on near and distant objects. - Explain how we visualize an object using eyes Over 70% of all sensory receptors of the body are in the eye! Rods and cones are the two types of photoreceptors. All photoreceptors respond to light with a neural message sent to the brain  Rods allow us to see in dim light, seeing black and white, they are more numerous than cones, contain the pigment rhodopsin, which Is broken down in bright light, resynthesized in dark.  Cones – responsible for color vision, three types – red, blue, green. Produce sharp images. A reduced number or lack of one of the types of cones results in color blindness - Describe common visual impairments (farsightedness/ nearsightedness)  Farsightedness – see distant objects more clearly than nearby objects ( lens too thin)  Nearsightedness- see nearby objects more clearly than distant objects (lens too thick)  With age the lens becomes less elastic -> harder to focus on close objects. A cataract - a lens that has become cloudy, usually due to aging. Lecture 2 (Hearing)- Hearing – sound waves produced by vibrations. In order to hear, the ear collects sound waves-> amplifies them -> converts then to neural messages. - Outer ear (receiver) – consists of the pinna and external auditory canal. Receives the waves. - The eardrum separated the outer ear from the middle ear. The air pressure must be nearly equal on both sides: if not it can be alleviated by the auditory tube – connection with the upper throat. - Middle ear (amplifier) – consists of an air-filled cavity within the temporal bone of the skull and the three auditory bones. Takes sound from the eardrum to the oval window and amplifies it 22 times. - Inner ear- (transmitter) –consists of the fluid-filled cochlea and vestibular apparatus. The spiral organ is most directly responsible for the sense of hearing  Hearing -> pressure waves-> transmitted form the middles ear to the fluid within the cochlea-> basilar membrane moves up and down.-> activate hair cells that stimulate the nerves -> impulse carried to the brain. The more hair cells stimulated, the louder the sound. Vestibular System (rotation & balance) - Vestibular apparatus – a fluid-filled maze of chambers and canals within the inner ear, is responsible for monitoring the position and movement of the head. The receptors in thevestibular apparatus. It consists of semicircular canals and the vestibule. The semicircular canals are thee canals in each ear that contain sensory receptors and help us stay balanced as we move. Lecture 3 (Blood) - Functions of blood  Transportation – carries vital materials to all body cells, carries wastes away from cells.  Temperature regulation – absorbs heart metabolically active regions, distribute heat to cooler areas and to the skin Protection – against disease-causing organisms, against blood loss after vessel damage. - Components of blood  Plasma makes up 55% of blood, nutrients, gases, hormones, wastes/products of cells, proteins, electrolytes.  Three formed elements: 1. Erythrocytes – 4.5- 5.5 million. 2. Leukocytes – 4,8000-10,800. Basophil, eosinophil, neutrophil, lymphocyte, monocyte 3. Platelets – 1500,000- 400.000Bed cells come from stem cells: red blood cells also called erythrocytes – transport oxygen to the cells, carry away carbon dioxide, shaped like biconcave disks and are very flexible, no nucleus or organelles, constitute 45% of blood volume. Each cell is packed with hemoglobin: red pigment, iron- containing protein that transports oxygen needed for cells respiration. Hemoglobin has a much greater affinity for carbon monoxide: odorless and tastless, an insidious poison.  Anemia – several types, the bloods ability to carry oxygen is reduced, can result from too little hemoglobin, too few red blood cells, or both: blood loss. o Symptoms – fatigues, headaches, dizziness, paleness, breathlessness, and heart palpitations.  Iron deficiency anemia- most common, leads to inadequate hemoglobin production. o Causes – a diet that contains too little iron, an inability to absorb iron from the digestive system, blood loss. Sickle-cell anemia- caused by genetically abnormal hemoglobin. RBC’s form a sickle shape when the blood’s oxygen content is low. Results in RBCs that are fragile and rupture easily, clogging small blood vessels and promoting clot formation. - Platelets ( thrombocytes)  150,000-400,000, from megakaryocytes, important in blood clotting, not cells, but cell fragments  sometimes called thrombocytes (clot cells), fragments of larger parent cells, essential to