Medical Terminology I Senses Chapter 17

Senses

Input Sensory input begins with sensors that react to stimuli in the form of energy that is transmitted into an action potential and sent to the CNS.

Five Senses Touch…Pain/Pressure/Temperature Vision Taste Smell Hearing & Balance

Somatic Senses Pain Temperature Pressure Senses that relate to tissue

Sensory Receptors Sensory receptors are classified according to the type of energy they can detect and respond to. Mechanoreceptors: hearing and balance, stretching. Photoreceptors: light. Chemoreceptors: smell and taste mainly, as well as internal sensors in the digestive and circulatory systems. Thermoreceptors: changes in temperature. Electroreceptors: detect electrical currents in the surrounding environment.

Ear From:wikipedia.com

Hearing Hearing involves the actions of the external ear, eardrum, ossicles, and cochlea. In hearing, sound waves in air are converted into vibrations of a liquid then into movement of hair cells in the cochlea. This is converted into action potentials in a sensory dendrite connected to the auditory nerve. Very loud sounds can cause violent vibrations in the membrane under hair cells, causing a shearing or permanent distortion to the cells, resulting in permanent hearing loss.

Balance, Orientation and Gravity Orientation and gravity are detected at the semicircular canals. Hair cells along three planes respond to shifts of liquid within the cochlea, providing a three-dimensional sense of equilibrium. Calcium carbonate crystals can shift in response to gravity, providing sensory information about gravity and acceleration.

Balance . From NIH Gray FIG. 920– Right osseous labyrinth. Lateral view.

Eye

Photoreceptor Cells Retina Two types of photoreceptors are located in this area Rods-light intensity more common near the edge of the eye Cones-color detection found in the fovea centralis center of the eye

Cross Section of the Eys http://webvision.med.utah.edu/imageswv/Sagschem.jpeg

Cones Humans have three types of cones, each sensitive to a different color of light: red blue Green Opsins are chemicals that bind with cone cells to make them sensitive to a particular wave length of light (color)

Vision Light reaching a photoreceptor causes the breakdown of the chemical rhodopsin, which in turn causes a membrane potential that is transmitted to an action potential. The action potential transfers to synapsed neurons that connect to the optic nerve. The optic nerve connects to the occipital lobe of the brain.

Electromagnetic Spectrum

Normal Vision 20/20 vision is normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.

Common Refractive Errors Hyperopia can see well at a distance(farsightedness) Presbyopia (loss of focusing ability Myopia can see items that are close, but cannot see those far away(nearsightedness). Astigmatism (distorted vision)- irregular cornea Amblyopia, a serious vision condition commonly known as lazy eye.

Hyperopia The eye is shorter than normal close objects are difficult to focus on.

Presbyopia The lens becomes rigid and doesn’t change shape as easily as it once did- this makes focusing difficult.

Myopia The eye is longer than normal- close objects look clear

Astigmatism Distorted Cornea

Eye Conditions Conjunctivitis (Pink Eye). This term describes a group of diseases that cause swelling, itching, burning, and redness of the conjunctiva Fuchs' dystrophy -endothelial cells gradually deteriorate without any apparent reason. The endothelium becomes less efficient at pumping water out of the stroma. This causes the cornea to swell and distort vision.

Eye Conditions Glaucoma-internal pressure in your eyes increases enough to damage the nerve fibers in your optic nerve and cause vision loss Cataract-clouding of all or part of the normally clear lens Macular Degeneration-changes to the macula, a portion of the retina that is responsible for clear, sharp vision

Eye Conditions Keratoconus-cornea (the front part of the eye) becomes thin and irregular (cone) shaped. This abnormal shape prevents the light entering the eye from being focused correctly on the retina and causes distortion of vision. Retinitis pigmentosa-damage the light-sensitive rods and cones Simulates eye disorders: http://www.nei.nih.gov/photo/sims/sims.htm

Assignments 17.01.01 17.01.02 17.01.03 Case Study Review Test 17

Assessment 17.01 Preview Tell how sensory input travels from the environment to the brain for each of the following. Auditory input to the ear: Visual input into the eye:

Assessment 17.02 Preview Provide the term for each of the given descriptions. Irregular muscle movement Discharge from the nose Ringing in the ears Discharge from the ear Dizziness Disease of the cornea Increased intraocular pressure Opaque lens of the eye Removal of the vitreous humor Age-related macular degeneration Collection of skin cells and cholesterol in the ear Elevated pressure in the cochlea & semicircular canals Inflammation of the retina Hardening of the bony tissue of the labyrinth of the ear Cystic mass on the eyelid Defective curvature of the cornea or lens Inflammation of the conjunctiva Impaired vision as the result of aging Abnormal deviation of the eye

Assessment 17.03 Preview HEET MDM CC HPI PMH/PMHX ROS SH FH BP TPR ROM Use the internet to find the meanings of each of the following abbreviations: HEET MDM CC HPI PMH/PMHX ROS SH FH BP TPR ROM ADOL Rx Dx Fx

Assessment 17.04 – Case Study Progressive Hearing Loss: A 68-year-old woman reported an 8-year history of progressive hearing loss of the left ear leading to anacusis. She also complained about left-sided tinnitus, intermittent trigeminal neuralgia and vertigo. Clinically, there were no additional neurological deficits and no signs of von Hippel-Lindau (VHL) disease. Cranial computed tomography (CCT) and magnetic resonance imaging (MRI) disclosed a tumor in the left cerebellopontine angle with destruction of the petrous bone and the internal acoustic meatus and involvement of the inner and middle ear and the jugular foramen. In MRI, the tumor was inhomogenously hyperintense in T2-weighted images and showed strong contrast enhancement in tT1-weighted images (Fig. 1). There was no brainstem compression. Radiological diagnosis was jugular paraganglioma. Angiographic embolization of the tumor was performed. It was fed through left-sided branches of the medial meningeal artery, of the occipital artery, of the pharyngeal and auricular artery and of the anterior inferior cerebellar artery. Intraoperatively, the tumor was highly vascularized and partly cystic. It infiltrated and destructed the petrous bone, and its intracranial portion showed a focally intradural location without leptomeningeal or brain infiltration. The left cranial nerves V, VII and VIII were adherent to the neoplasm. The intracranial tumor part was completely resected. 4 weeks later residual tumor in the petrous bone was removed.