Adaptation:Action Potentials are slowly adapting, eventually adapt and sensation of feeling no longer there (slowly adaptingOthers adapt really swiftly, receptors stop responding swiftly (fast adapting)Pacinian Corpuscles are like thisReceptive FieldArea of skin that changes the neuron’s activityCan be excitatory or inhibitoryWill be different sizes depending on which neurons you are examiningDifferent receptors have different receptive fieldsSome small receptive field cells are slowly adapting and some are rapidly adaptingSame for cells with large receptive fieldsCombination of receptive field size and adaptation may be related to the perception evoked (see slide for chart of the corresponding field size/adaptation/perception)Small receptive fields near surface, large receptive fields deeper in skine.g., holding cup:SA1: fine details of bumps and ridges, etc. (e.g., Braille)FA1: activity when running fingers across cupSA2: stretch of hand caused by grasping cupFA2: motion or vibration of held object (cheers bump)Need all of these receptors because provide different percepts/information2 Pathways to CortexLemniscal System (see slide)Touch, pressure, vibrationE.g., Pacinian, hair follicle receptorsFast communication, good positional infoPathway:Enters spinal cord and ascends to brain steamIn brain stem, makes synapse there, and crosses over the midlineFrom there goes along pathway called medial lemniscusFrom there goes to Thalamus, makes a synapse, and then from there goes to CortexSpinothalamic SystemTissue damage, thermal, pain (not as localized information)Binary input: free nerve endings.Relatively slow, relatively broad positional info“Gated” at the spinal cordPathway:First cell (free nerve ending) enters spinal cord, makes synapses, crosses over and ascends on other sideMajor difference, makes synapse much earlier on.From “spine” to thalamus (hence, spinothalamic)From there, info goes to the cortexTogether: 2 paths to the cortexLemniscalSpinothalamicBoth are Contralateral (opposite side) reprsentationEXP 3202 Sensation and Perception AKA THE MOST BULLSHIT CLASS EVERStudy Guide for Exam 2 ESSAY QUESTIONS WILL BE (1) THE SYNAPSE QUESTION (2) ONE OF THE BELOW QUESTIONS WILL BE AN ESSAY QUESTION DIAGRAM: BE ABLE TO DRAW A SYNAPSE AND PARTS OF A NEURONLABELING & EXPLANATION: DON’T KNOW WHAT THOUGH Lecture study questions: 1. Compare a neuron-to-neuron synapse to a hair cell-to-neuron synapse. Draw a typical synapse. If an action potential reaches the terminal of the presynaptic cell, what sequence of events happens to result in a synaptic potential in the postsynaptic cell (be sure to use proper terms and the proper sequence of events)? Draw a typical hair cell. What happens when the stereocilia are deflected and then what sequence of events happens to result in an action potential being sent to the brain? - Neuron to neuron:- Voltage gated calcium channels open up at terminal. Important stepo Happens for any synapseo Calcium goes in and vesicles release neurotransmitter into gap. Some bind to particular receptor on post synaptic cell. Chemical interaction between the recepter and neurotransmitter opens up ligand gated channel. Ions go through the membrane. o Less negative in new cell because of the positive ions that come ino Channels are key. Proteins embedded in membrane. What opens them and what ions og through Is how they are classifiedo Ligand gates and neurotransimitter recepter are synonomas. They are one big unito Channels only let certain ions through but can onl do that if they are opened- Hair cello Potassium coming in because of the high concentrationo That depolarization doesn’t start action potential because no voltage gated channels. Opened by mechanical activity (by being opened)o Depolarization enough to open voltage gated calcum channels and calcium goes in neurotransimitter is releaseo Then biding to receptor, open gate, let sodium in. if enough goes in you get action potential same as with neuron Can hear better in the ear that is covered (when doing bone conduction theory) becauseoutside noise is not affecting the sound2. What is a cochlear implant and how does it work. What principle of cochlear function/neural coding does it taking advantage of? (tonotopic organization)!!- Used for profound hearing loss when hearing aid wont work- Cochlear implant comes from basic understanding of cochleao Hair cells are damaged but the auditory nerve fibers are still there but cant activate themo Brain doesn’t care how auditory nerve is stimulated, but if it is, you will hear sound (doctrine of specific nerve energy)o Electrically stimulate nerve fibers. Coils of electrodes placed inside cochleao Different electrodes can stimulate different places, so different frequencies are perceived (tonotopic organization: labeled line coding)- Hearing aid. Electrode array in cochlea. Coil up into the cochlea with places to stimulate along the wayo Receiver under skin with wire to implanto Transmitter worn outside provides commands to activate electrodes- Why have little tube go into ear?o Microphone placed in ear canal so you get to filter out sound through pinna still.- Very successfulo Many patients can go from profound deafness to talking on the telephone 3. What is tinnitus? What are some of the causes of tinnitus? What evidence suggests that some forms of tinnitus are not generated by the ear? What does tinnitus tell us about how perception relates to physical changes in the world around us? - Tinnitus is common disordero Perception of sound in the absence of an acoustic stimulus “Ringing in the ears” after a concert but some people have it as a chronic condition could cause depressiono 10-15% of all adultso Cause multiple: noise induced, some drugs (aspirin), aging related to hearing loss but not necessarily produced by damaged ear per se- can have tinnitus even when auditory nerve is cuto antidepressents used if its driving people crazyo its just central activity in the tinnitus patients if brain is ative, then perception…it doesn’t need to be started by sound MEG overlaid on MRI scan of subject with unilateral tinnititus o Leading hypo: loss of inhibition in the central auditory pathway. Excess ofactivity (debate of where gets started)o For most people this is transient and it comes and goeso Many returning vets will have this who were exposed to loud noises More common because more people have noise
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