A&P 12 Somatic and Special Senses

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Sensation The conscious or subconscious awareness of changes in the external or internal environment. For a sensation to occur, four conditions must be met: A stimulus, sensory receptor, nerve impulses, a region in the brain (receive and integrate)
Sensation: Stimulus Stimulus- change in the environment, capable of activating certain sensory neurons must occur (light, heat, pressure, mechanical or chemical energy)
Sensation: Sensory Receptor Must convert the stimulus to an electrical, which produces one or more nerve impulses if it is large enough.
Sensation: Nerve Impulse & Region of Brain Nerve impulse- must be conducted along a neural pathway from the sensory receptor to the brain. Region of the brain must receive and integrate the nerve impulses into a sensation.
Tactile Sensations Touch- stimulation of tactile receptors in skin or subcutaneous layer. Pressure- sustained sensation deeper tissues widely distributed in the body. Vibration- sensory signles from tactile receptors, itch and tickle.
Thermal Sensations Free nerve endings, cold and warmth are mediated by different receptors.
Pain Sensations Called nociceptors are free nerve endings, fast and slow
Special Senses Includes smell, taste, sight, hearing, and equilibrium housed in complex sensory organs such as the eyes and ears.
Olfaction Nose contains 10-100million receptors for the sense of smell, or olfaction. Nerve impulses for smell and taste propagate
Taste Aversion Strong link between taste and pleasure or unpleasant emotions. Sweet foods evoke reactions of pleasure while bitter one’s cause expressions of disgust. Animals quickly learn to avoid food that upsets the digestive system.
Vision Rods/Cones; constricts due to light (bright light), Expands in the dark
Presbyopia A condition associated with aging of the eye that results in progressively worsening ability to focus clearly on close objects.
Colour Blindness & Night Blindness Difficulty distinguishing certain colours and inherited condition. Night blindness poor vision in low light
Structure of the Ear The ear is a multifaceted organ that connects the CNS to the external head and neck. This structure as a whole can be thought of as 3 separate organs that work in a collective to coordinate certain functions (hearing/balance)
Physiology of Hearing Outer ear collects sound waves, eardrum vibrate; inner ear send to brain
Equilibrium Two types of equilibrium (balance). Static equilibrium maintenance of the position of the body. Dynamic equilibrium maintenance of body position.
Cataracts Lenses become cloudy due to changes in the structure of proteins, surgical removal of lenses and implantation of an artificial one.
Glaucoma Most common cause of blindness, a buildup of aqueous humor within the anterior cavity causes an abnormality high intraocular pressure.
Deafness Significant or total hearing loss
Meniere’s Disease Increase in amount of endolymph that enlarges the membranous labyrinth. Symptoms are fluctuating hearing loss and roaring tinnitus (rigging).
Otitis Media An acute infection of the middle ear caused primarily by bacteria and associated with infections of the nose and throat.

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