Somatosensation What are are somatosensation kinesthesis proprioception What are the types of kinesthesis receptors Where are they and what kind of info do they convey Somatosensation A collective term for sensory signals from the body Kinesthesis The perception of the position and movement of our limbs in space Muscle spindles Golgi tendons Proprioception Perception mediated by kinesthetic and vestibular receptors Position of your body in space What is haptic perception What is perception for action What is action for perception In the latter what types of exploratory procedures do we use to give us info about an object and what type of info do those procedures yield Haptic perception muscles tendons and joints usually involving active exploration Knowledge of the world that is derived from sensory receptors in skin This is an active process Action for perception Touch relies on action to get info as opposed to vision or audition which are more passive in a moment We then use this perception to act Perception for action Example of haptic perception For instance aligning the arrows and opening a child proof aspirin bottle in the dark Perception for action Using somatosensation to grasp manipulate objects in a stable coordinated manner to maintain proper balance and posture Anesthetize skin kinesthetic receptors work touch receptors don t subject can t maintain stable grasp of objects he she must manipulate Example grabbing a baseball Action for perception Exploratory procedure feel an object to learn about it Different procedures tell you different things If the skin is anesthetized but proprioceptive kinesthetic receptors are intact can you still grasp manipulate an object Why or why not Not very great at this we can if pattern is small enough to fit 1 fingertip can t read more than 1 finger at a time narrow haptic field of view the area of skin we can take in all at once Touch acts like blurred vision when the fingertip explores a raised pattern do equally well and make same mistakes when identifying patterns with blurred vision of hectically What do you know about haptic search What features of an object that you are touching pop out and what features do not You can detect before using selective attention to identify a particular feature this is called preattentive feature detection No need to compare in order to detect some features just pop out No need to think about it just jumps out on them You can rotate it so you can have different surfaces Works for texture rough vs smooth temperature hard soft Doesn t work for horizontal vs vertical lines Haptic recognition relies on material properties not object contours Good for handling objects to identify them Bad for feeling raised contours of a drawing of the object This is opposite visual system which would be good at horizontal vs vertical We use this in the visual system too red pops out with greens for example Also horizontal versus vertical Not good at understanding contours through the touch system This is the reason that braille is dots not letter Your fingers are only good at small limited patterns Can we perceive patterns with the skin What are the limitations on this capability How does this capability compare to looking w blurred vision We can do it if the pattern is small enough to fit on 1 fingertip Also can t read more than 1 finger at a time suggests narrow haptic field of view the area of skin we can take in all at once Touch acts like blurred vision when the fingertip explores a raised pattern Do equally well and make same mistakes when identifying patterns w blurred vision or haptically What are the 4 main types of touch receptors How do they differ in terms of adaptation receptive field size What tactile functions do they subserve What does it mean that they are mechanoreceptors Generally in the lower layers of the epidermis and within the dermis Axons that are ending in the skin and go into the spinal cord There is a fancy encapsulation that causes axons to be stimulated Merkel Meissner Ruffini Differences Pacinian 1 Type of stimulation to which the receptor responds pressure vibration temperature damage etc Depends on anatomy of receptor 2 Size of the receptive field part amount of body that activates that receptor How much of the skin can actually cause a change in the action potentials Depends on the location of touch receptor deeper in the skin the larger the receptive fields 3 Rate of adaptation fast versus slow Depends on the anatomy of the receptor Very sensitive area of body small and densely packed receptive fields more cortical area processing touch from that area like finger tips or parts of the face Mechanoreceptor stimulated by mechanical deformation They are detecting a physical change How do pacinian corpuscles work These are really deep in the skin and most ubiquitous you have them everywhere so they have larger receptive fields They respond to vibration and are rapidly adapting Stimulated by touch they are deflected down through the membranes and deflect the membrane of the axon The membrane then becomes leaky to sodium Force neuron s membrane is deflected channels become leaky to sodium receptor potential mechanoreceptors The greater the deflection the greater the receptor potential threshold AP Only sudden or vibrating force can deflect membrane Onion like outer membrane provides mechanical support so it is resistant to gradual or constant pressure so rapidly adapting BTW the other rapidly adapting receptor Meissner corpuscle works in a similar way The What are thermoreceptors and what kinds are there What type of channel do they use Understand that these are free nerve endings know what that means w TRP receptors in the membrane Warmth fibers cold fibers Free nerve endings nociceptors In dermis epidermis Polkadot distribution Warmth receptors deeper than cold receptors Respond to changes in skin temp Normal is 30 36C 86 96F neither type of fiber fires much in this range Respond if temp is higher or lower than neutral or higher or lower than what skin is used to So feeling temp is relative try the hand in the bucket experiment TRP channels transient receptor potential channels non selective cation channels in cell membrane These channels are able to respond to various ranges of temperatures Allows positive charged ions to go through which are depolarizing To detect such a large range of temps probably need more than 1 turns out we have at least 6 different TRP channels for temp all tuned
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