The particular set of olfactory neurons that respond to a given odor might

The particular set of olfactory neurons that respond

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The particular set of olfactory neurons that respond to a given odor might serve as a “fingerprint” the brain can use to identify the odor Internal chemoreceptors detect pH and other characteristics Sensory receptors within the body detect a variety of a chemical characteristics of the blood or fluids derived from the blood, including cerebrospinal fluid Included among these receptors are the peripheral chemoreceptors of the aortic and carotid bodies Are sensitive primarily to plasma pH Central chemoreceptors in the medulla oblongata of the brain Are sensitive to the pH of cerebrospinal fluid When the breathing rate is too low, the concentration of plasma carbon dioxide increases, producing more carbonic acid and causing a fall in the blood pH The carbon dioxide can also enter the cerebrospinal fluid and lower the pH, thereby stimulating the central chemoreceptors This stimulation indirectly affects the respiratory control center of the brainstem, which increases the breathing rate The aortic bodies can also respond to a lowering of blood oxygen concentrations This effect is normally not significant unless a person goes to a high altitude where the partial pressure of oxygen is lower
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44.5 Vision The ability to perceive objects at a distance is important to most animals Predators locate their prey, and prey avoid their predators, based on the three long- distance sense of hearing, smell, and vision Vision can act most distantly With a naked eye, humans can see stars thousands of light years away A single photon is sufficient to stimulate a cell of the retina to send an action potential Vision senses light and light changes at a distance Vision begins with the capture of light energy by photoreceptors Because light travels in a straight light and arrives virtually instantaneously regardless of distance, visual information can be used to determine both the direction and the distance of an object Other stimuli, which spread out as they travel and move more slowly, provide much less precise information Structure of the vertebrate eye Sclera The white of the eye Formed of tough connective tissue Cornea Transparent front part of the eye that covers the iris, pupil, and anterior chamber Light enters the eye through the cornea which begins to focus the light Focusing occurs because light is refracted or bent when it travels into a medium of different density Iris Colored portion of the eye Contraction of the iris muscles in bright light decreases the size of its opening, the pupil Pupil Back portion of the eye Light passes through the pupil to the lens Lens
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Transparent structure that completes the focusing of the light onto the retina at the back of the eye Attached by the suspensory ligament to the ciliary muscles The shape is influenced by the amount of tension in the suspensory ligament Surrounds the lens and attaches it to the circular ciliary muscle When the ciliary muscle contracts, it puts slack in the suspensory ligament, and the lens becomes more rounded and bends light more strongly o This rounding is required for close vision
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