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BIOL373L Notes and Study Questions.docx

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Bruce Wolff

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LAB 1 Neural and Sensory Function oSensory cells respond to factors such as light pressure and the chemical nature of certain molecules by creating electrical signals which are sent to the central nervous system CNS oSpecial Senses vision taste smell equilibrium and hearing depend on complex organs which contain large numbers of individual sensory receptor cellsoSomatic senses involve sensory receptor cells which are not concentrated in sensory organs but widely distributed in the skin and in the muscles and joints oReflex Any longdistance pathway that receives input about a change integrates the information and uses the nervous system endocrine system or both to react appropriatelyoBoth reflexes and the fine control of muscle contractions rely on information from sensory cells The Special Senses 1Vision aVision AcuityoSnellen chart used to determine visual acuity oVisual acuity the degree of detail the eye can distinguish oStand 6 meters from the chart without corrective glasses Cover on eye and read successively smaller lines of print until the letters are hard to distinguish othe last line without mistakes represents the approximate visual acuity for that eye oMyopia near sighted light focuses in front of the retina Unable to see far distant objects are out of focus oHypertopia farsighted hard to focus objects close to the eye bAstigmatism oAstigmatism is the blurring or distortion of the visual image caused by a defective curvature of the refractive surfaces of the eye osome light rays are not sharply focused but spread diffusely over a broad area oAstigmatism test chart view from a distance of 3 meters with one eye at a time no glasses focus on the middle of the chart Normal all the bars will be sharp and evenly dark Astigmatic eye some lines are thick and dark while others will be lighter and blurredcColour Vision oColour blindness a diminished ability to sense colour accurately ocaused by a deficiency in the retinas systems for converting red blue or green light into receptor potentials by the sensory cells commonly called cones oIchikawa colour vision testmeasures the perception of colour a series of coloured plates is used to detect and identify the commonest type of colour blindness hereditary redgreen deficiency Normal 8 out of 10 plates Colour deficiency 3 or more abnormal responses2Tasteotaste buds consist of barrelshaped groupings of sensory cells located on the tongue and in the epithelial lining of the mouth otaste buds are not uniformly distributed and not tasted equally everywhere inside the mouth 3Olfaction othe type of response of a sensory cell to prolonged stimulation allows it to be classified as either tonic or phasic oTonic or slowlyadapting sensors produce a continuous sequence of action potentials as long as the stimulus lastoPhasic or rapidly adapting receptors detect a stimulus of constant strength they send a stream of action potentials of steadily decreasing frequency to the CNS 4Hearing othe sensation of hearing normally involves the vibration of the oval window in response to sound waves conducted through the air osound waves transmitted through the skull bones can also be detected and this ability may be used to diagnose hearing problems of the middle and inner ear aRinnes Test oplace a vibrating tuning fork against the mastoid process of the temporal bone with the tuning fork pointed down and behind the ear oas soon as the sound dies away move the tuning fork so that its stillvibrating arms are close to the external auditory opening oif there is no damage or blockage in the middle ear the sound will reappear othe ear is more efficient at detecting sound waves that are conducted through bone than air bbWebers Test ohold the handle of a vibrating fork on the midline of the top of the skull oPlugged earlouder sounds othe external noise on the perceived loudness of the sound that originates from the tuning fork is not as loud cAuditory Acuity oClose eyes plug one ear with fingeroStrike arm of tuning fork place it close to the open ear and slowly move it away until the sound can longer be heardoRepeat with different sized tuning forks and test the other ear oLower frequencies can be hear further away compared to higher frequencies 5Equilibrium the Romberg Test oMaintenance of an upright posture while standing or moving depends on input from a number of different sensesoThe information is integrated in the brain which responds by sending signals to the muscles of the legs back and other locations oProcedure subjects stands with back close to the blackboard with arms hanging at the sidesoStand there for 2 minutes while observer monitors the degree of sidetoside swaying oRepeat with subjects eyes closed oRepeat with the subject turned 90 degrees oProprioceptors sends sensory information to the brain regarding the tension of the skeletal muscles and the positions of the limbs oEars also provides the brain with information to help maintain balance The Somatic Senses oLike the proprioceptors the receptor cells of the skin are widespread not grouped into organs oThere are a variety of sensory neurons in the skin each sensitive to one type of stimulus TouchPressureVibration PainHeat or cold
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