Exam 3 Study Guide What are are somatosensation kinesthesis proprioception What are the types of proprioceptive receptors Where are they and what kind of info do they convey o Somatosensation a collective term for sensory signals from the body Touch mechanical deformation of skin Proprioception perception mediated by kinesthetic and vestibular receptors Kinesthesis the perception of the position and movement of our limbs in space internal sensations that arise from muscles tendons and joints part of broader system proprioception o Kinesthetic receptors tell us where our limbs are and what kind of movements were making in muscle spindles and golgi tendon organs Muscle spindles convey rate at which muscle fibers are changing in length fires upon stretch of a muscle reflex leads to contraction of a muscle senses tension Golgi tendon organs receptors in tendons that connect muscle to bone info about tension in muscle which pulls on tendon involved in reflexes o Fast adapting receptors responds with bursts of action potentials first when its preferred stimulus is applied and then again when it is removed does not respond during the steady state between stimulus onset and offset o Slow adapting receptors remains active through the period during which the stimulus is in contact with its receptive field 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 o Haptic perception knowledge of the world that is derived from sensory receptors in skin muscles tendons and joints usually involving active exploration 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 we then use this perception to act Perception for action Example aligning the arrows and opening a child proof aspirin bottle in the dark Feeling an object to learn about it difference procedures tell you different things action for perception Perception for action using somatosensation to grasp and manipulate objects in a stable and coordinated manner and to maintain proper balance and posture If the skin is anesthetized but proprioceptive kinesthetic receptors are intact can you still grasp manipulate an object Why or why not o You can not maintain a stable grasp of objects because touch receptors don t work What do you know about haptic search What features of an object hat you are touching pop out and what features do not o You can detect before using selective attention to identify a particular feature called preattentive feature detection o Haptic recognition relies on material properties not object contours o Works for texture rough smooth temperature hard soft o Does not work for horizontal and vertical lines feeling raised contours of a drawing of an object Can we perceive patterns with the skin What are the limitations on this capability How does this capability compare to looking w blurred vision o We aren t great at it but we can do it if the pattern is small enough to fit on 1 fingertip we also cant read more than 1 finger at a time o Touch acts like blurred vision when the fingertip explores a raised pattern we do equally well and make the same mistakes when identifying patterns with 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 o Touch receptors embedded in outer layer epidermis and underlying layer dermis all over body in hairy and hairless glabrous skin o Tactile receptors are called mechanoreceptors because they respond to mechanical stimulation or pressure have wide diameters that permit fast neural conduction Types of stimulation pressure vibration or temp changes Size of receptive field part of the body that activates that receptor Very sensitive area of body small and densely packed receptive fields more cortical area processing touch from that area Rate of adaptation how quickly or slowly the receptor stops firing to a given stimulus o Mechanoreceptors Thermoreceptors Chemoreceptors o 4 main types of mechanoreceptors Merkel Cells SA1 slow adapting Type 1 Texture and pattern perception Sustained pressure very low frequency Small receptor fields Meissner Corpuscles FA1 fast adapting Type 1 Low frequency vibration movement across skin Temporal changes in skin deformation Small receptor fields Ruffini Endings SA2 slow adapting type 2 Sustained pressure skin slip or stretch stable grasp Finger position stable grasp Large receptor fields Pacinian Corpuscles FA2 fast adapting type 2 High frequency vibration initial touch or change in pressure Temporal changes in skin deformation Large receptor fields receptors with small receptor fields are closest to surface both start with M corpuscles meissner pacinian are always fast adapting How do pacinian corpuscles work o Force neuron s membrane is deflected channels become leaky to sodium receptor potential mechanoreceptors The greater the deflection the greater the receptor potential Only sudden or vibrating force can deflect membrane Onion like outer membrane provides mechanical support so it is resistant to gradual or constant pressure rapidly adapting The other rapidly adapting receptor Meissner corpuscle works in a similar way o Press on Pacinian corpuscle deform lamellae which press on tip of sensory neuron deforms neuron s plasma membrane makes it leaky to Na ions can t depolarize membrane site of deformation bc it lacks voltage gated Na channels so it is like a large amplitude EPSP 1st part of sensory neuron that does have voltage gated Na channels required for AP is 1st node of ranvier depolarizes starts generating AP to go toward brain as long as tip of neuron is depolarized will continue to depolarize 1st node of ranvier because as soon as it recovers from generating an AP the depolarized neuron tip depolarizes it back to its threshold as soon as the depolarized 1st node of ranvier gets out of its absolute refractory period it generates another action potential this continues as long as the nruon tip remains depolarized o 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 o They respond to changes in
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