Most “voluntary” movements initiated by the cerebral cortex are achieved when the cortex activates “patterns” of function stored in lower brain areas—the cord, brain stem, basal ganglia, and cerebellum. These lower centers, in turn, send specific control signals to the…
Sensory information is integrated at all levels of the nervous system and causes appropriate motor responses that begin in the spinal cord with relatively simple muscle reflexes, extend into the brain stem with more complicated responses, and finally extend to…
The senses of taste and smell allow us to separate undesirable or even lethal foods from those that are pleasant to eat and nutritious. They also elicit physiological responses involved in the digestion and utilization of foods. The sense of…
This chapter describes the mechanisms whereby the ear receives sound waves, discriminates their frequencies, and transmits auditory information into the central nervous system, where its meaning is deciphered. Tympanic Membrane and the Ossicular System Conduction of Sound From the Tympanic…
Visual Pathways Figure 52-1 shows the principal visual pathways from the two retinas to the visual cortex . The visual nerve signals leave the retinas through the optic nerves . At the optic chiasm , the optic nerve fibers from…
The retina is the light-sensitive portion of the eye that contains the following: (1) the cones , which are responsible for color vision; and (2) the rods , which can detect dim light and are mainly responsible for black and…
Physical Principles of Optics Understanding the optical system of the eye requires familiarity with the basic principles of optics, including such factors as the physics of light refraction, focusing, and depth of focus. A brief review of these physical principles…
Many ailments of the body cause pain. Furthermore, the ability to diagnose different diseases depends to a great extent on a physician’s knowledge of the different qualities of pain. For these reasons, the first part of this chapter is devoted…
The somatic senses are the nervous mechanisms that collect sensory information from all over the body. These senses are in contradistinction to the special senses , which mean specifically vision, hearing, smell, taste, and equilibrium. Classification of Somatic Senses The…
Our perceptions of signals within our bodies and of the world around us are mediated by a complex system of sensory receptors that detect such stimuli as touch, sound, light, pain, cold, and warmth. In this chapter, we discuss the…