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BIOA02 MODULE 2 Lec 14 The Nervous System.doc

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University of Toronto Scarborough
Biological Sciences
Mary Olaveson

BIOA02 MODULE 2 Lec 14 The Nervous SystemsFebruary 09 2012early experiments on nervous systems was done on squids and wormsFUNCTION OF THE NERVOUS SYSTEMthere are nerves sensors in the external environment and internal environementexternal environmentodours light etc internal environmentblood pressure CO levels pH levels etc2transmission is sent to the central nervous systems and this transmission occurs along the afferent neurons or the sensory nervous systemthis information is then integrated by interneurons intermediates between in the in and out signals and there is a transmission out of the CNS through an efferent path to various organs glands muscles etc so they elicit an appropriate responseinsert Slide 1begin the whole processbegins with a sensing systems detects stimulithree types of receptors that sense stimuli externally or internally1chemoreceptor it can sense a variety of chemical stimuli ie oxygen levels odour molecules2mechanoreceptors senses pressure stimulus ie pressure applied to skin blood pressure pressure in lungs inflatedeflate3photoreceptor senses incoming lightin all of these systems there are molecules on the cell membrane ie receptor protein or transducer that senses the stimulusthis causes a signal transduction pathway to be activated which leads to intercellular changes or opens ion channels to move ions in and out of cellsoccurs in most nervesinsert slide 2 herewhen a stimuli has been sensed it has to be sent to the braintwo ways sensor cells can get a signal from the sensing sight to the brain1The sensing neuron itself can generate a nerve signal that goes directly to the brain2The sensing cell can deactivate itself and release a neurochemical onto a second cell which then sends a signal to the brainboth of these cases work with depolarizationdepolarizationincrease in membrane potentialthe electrical charge across a cell membrane
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