summary of all the integrative portions of the lectures, comprises sensory (vision, pain/touch, taste, hearing), muscles (smooth and striated), effects of Ca+

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Department
Biology
Course
BIO304H5
Professor
B Stewart
Semester
Fall

Description
Activation of sensory receptors Different type of receptors vision paintouch taste touchThe way sensory neurons work stimulus activatesa specific sensory receptor which leads to direct or indirect through protein interactions and second messengers opening of the ion channel Once the ion channels are open it generates a ionic current which causes a change in Vm and spreads to spike initiation zone where AP starts and propagates downward and causes changes in the amount of NTThe above bolded event are graded event and contain sensory energyHowever after a change in Vm and NT levels this results in electrical energy and AP specifically influences the number and frequency of AP in the sensory neuronwhen pain or senses such as vision400nm700nm and hearingare experienced it can vary in range that it can respond to dynamic rangeThere is an upperlimit set by the refractory period according to the intensity of the stimulus and to overcome this in our body we have individual receptors that specialize in a specific portion of the large rangeReceptive field the region of the skin in which a stimulus evokes a response in a single sensory neuron where discrimination depends on the density of receptors ex Fingers 14mm Thigh 45mm means smaller the receptive field more sensitive the area will beEyes and Hearing have specific receptive fieldABOVE INFO IS FOR ALL SENSORY RECEPTORSPAINNOTE this is a reflex and therefore info goes through the Spinal cord and not the brain There are a lot of receptors that take in sensory input on the skin sensory neuronsFor pain its mechanical So it includes mechanically gated channelsFor pain specifically the receptor in the skin is Free nerve endings these also detect temperature aka nociceptorsFree nerve ending carried by nonmyelinated slow conduction C fiber sensory neuronsPain is elicited by heat acid mechanical damage and these activate nonspecific cation channels In the event of damage the cells release ATP Bradykinin Substance P and these activate nonspecific cation channelsTOUCHit is based on tactile sensory input which responds to pressure and movement of the skinspecialized receptors that respons to particular types of inputsThese inputs maybePacinian corpuscle heavy pressure deep touch rapid vibration 300HzMeissnerscorpuscle light pressure slow vibration 50 HzaPacinian corpuscle the mechanical stimulus open ion channel leading to the formation of receptor currents which flow passively within the axon IF receptor potential is large enough APs produced MAIN DIFF btw pain and touch is Pain is NONMYELINATED while touch is MYELINATEDadditionally it is an on and off system meaning it only responds when pressure is added to removed pressure changes and no responses when it is in between refer to diagramit is a Phasic receptor type of rapidly adapting receptorexplains diagramPacinian corpuscle is made up of epithelial layers which serve to filter out stead pressure but transfer rapid changes in pressureInformation from touch is eventually sent to BRAINVISION
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