Anatomy and Pathophysiology PDF

Anatomy and Pathophysiology Marven R. Escano, RMT, MPH College of Nursing and Allied Health Sciences Manuel S. Enverga University Foundation Incorporated SENSES SENSES are the means by which the brain receives information about the environment and the body. SENSATION is the process initiated by...

Anatomy and Pathophysiology Marven R. Escano, RMT, MPH College of Nursing and Allied Health Sciences Manuel S. Enverga University Foundation Incorporated SENSES SENSES are the means by which the brain receives information about the environment and the body. SENSATION is the process initiated by stimulating sensory receptors, and PERCEPTION is the conscious awareness of those stimuli. A. SENSORY RECEPTORS are sensory nerve endings or specialized cells capable of responding to stimuli by developing action potentials. Several types of receptors are associated with both the general and the special senses, and each responds to a different type of stimulus: 1. Mechanoreceptors respond to mechanical stimuli, such as the bending or stretching of receptors. 2. Chemoreceptors respond to chemicals. For example, odor molecules bind to chemoreceptors, allowing us to perceive smells. 3. Photoreceptors respond to light. 4. Thermoreceptors respond to temperature changes. 5. Nociceptors respond to stimuli that result in the sensation of pain. GENERAL SENSES have sensory receptors that are widely distributed throughout the body. The general senses include the senses of: 1. TOUCH 2. PRESSURE 3. PAIN 4. TEMPERATURE 5. VIBRATION 6. ITCH 7. PROPRIOCEPTION, which is the sense of movement and position of the body and limbs. FREE NERVE ENDINGS - the simplest and most common types of sensory receptors. relatively unspecialized neuronal branches similar to dendrites. Receptors for temperature - cold receptors or warm receptors -12°C (54°F) 47°C (117°F). TOUCH RECEPTORS - are structurally more complex than free nerve endings. Many touch receptors are enclosed by capsules. 1. Merkel disks - are small, superficial nerve endings involved in detecting light touch and superficial pressure. 2. Hair follicle receptors - associated with hairs, are also involved in detecting light touch. Light touch receptors are very sensitive but not very discriminative, meaning that the point being touched cannot be precisely located. 3. Meissner corpuscles - receptors for fine, discriminative touch and are located just deep to the epidermis. These receptors are very specific in localizing tactile sensations. 4. Ruffini corpuscles - deeper tactile receptors and play an important role in detecting continuous pressure in the skin. 5. Pacinian corpuscles - the deepest receptors and are associated with tendons and joints. These receptors relay information concerning deep pressure, vibration, and body position (proprioception). PAIN characterized by a group of unpleasant perceptual and emotional experiences. There are two types of pain sensation: (1)localized, sharp, pricking, or cutting pain resulting from rapidly conducted action potentials, and (2)diffuse, burning, or aching pain resulting from action potentials that are propagated more slowly. REFERRED PAIN is perceived to originate in a region of the body that is not the source of the pain stimulus. OLFACTION – sense of smell occurs in response to airborne molecules, called odorants, that enter the nasal cavity. Olfactory neurons - are bipolar neurons within the olfactory epithelium, which lines the superior part of the nasal cavity The dendrites of the olfactory neurons extend to the epithelial surface, and their ends are modified with long, specialized cilia that lie in a thin mucous film on the epithelial surface. TASTE BUDS - sensory structures that detect taste stimuli. Each taste bud consists of two types of cells. Specialized epithelial cells form the exterior supporting capsule of each taste bud, and the interior consists of about 40 taste cells. Each taste cell contains hairlike processes, called taste hairs, that extend through a tiny opening in the surrounding stratified epithelium, called a taste pore. If the epithelial cells are only damaged, taste sensation returns within a few hours to a few days. If the cells die, it takes about 2 weeks for the epithelial cells to be replaced. The eyeball is a hollow, fluid-filled 1. The outer, fibrous tunic consists of the sphere. The wall of the eyeball is sclera and cornea. composed of three tissue layers, 2. The middle, vascular tunic consists of the choroid, ciliary body, and iris. or tunics 3. The inner nervous tunic consists of the retina. FIBROUS TUNIC The SCLERA is the firm, white, outer connective tissue layer of the posterior five-sixths of the fibrous tunic. helps maintain the shape of the eye, protects the internal structures, and provides attachment sites for the extrinsic eye muscles. A small portion of the sclera can be seen as the “white of the eye.” The CORNEA is the transparent anterior sixth of the eye, which permits light to enter. As part of the focusing system of the eye, the cornea also bends, or refracts, the entering light. VASCULAR TUNIC The middle tunic of the eye is called the vascular tunic because it contains most of the blood vessels of the eye. The posterior portion of the vascular tunic, associated with the sclera, is the choroid. This very thin structure consists of a vascular network and many melanin-containing pigment cells, causing it to appear black. The black color absorbs light, so that it is not reflected inside the eye. If light were reflected inside the eye, the reflection would interfere with vision. The ciliary body is continuous with the anterior margin of the choroid. The ciliary body contains smooth muscles called ciliary muscles, which attach to the perimeter of the lens by suspensory ligaments. The lens is a flexible, biconvex, transparent disc IRIS is the colored part of the eye. attached to the anterior margin of the ciliary body, anterior to the lens. iris is a contractile structure consisting mainly of smooth muscle surrounding an opening called the pupil. Light passes through the pupil, and the iris regulates the diameter of the pupil, which controls the amount of light entering the eye. NERVOUS TUNIC The RETINA covers the posterior five-sixths of the eye and is composed of two layers: (1)an outer pigmented retina - with the choroid, keeps light from reflecting back into the eye (2)an inner sensory retina - contains photoreceptor cells as well as numerous interneurons Photoreceptor cells Rods are 20 times more common than cones. Rods can function in dim light because they are very sensitive, meaning they require lower levels of light to be stimulated. do not provide color vision. Cones require much more light, and they do provide color vision. There are three types of cones, each sensitive to a different color: blue, green, or red. Each ear is divided into three areas: (1)the external ear - part extending from the outside of the head to the tympanic membrane (eardrum). (2)the middle ear - an air- filled chamber medial to the tympanic membrane (3)the inner ear - set of fluid-filled chambers medial to the membrane The process of hearing involves two major steps: (1)conduction of sound waves (2)stimulation of hearing receptors. The sense of balance, or equilibrium, has two components: (1) static equilibrium - associated with the vestibule and is involved in evaluating the position of the head relative to gravity (2) dynamic equilibrium - associated with the semicircular canals and is involved in evaluating changes in the direction and rate of head movements.