lecture 10

lecture 10 - Sensory systems The CNS consists of discrete...

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Sensory systems The CNS consists of discrete systems for each of the modalities of sensation (touch, vision, hearing, taste, smell). Each functional system involves several brain regions that carry out different types of information processing. IdentiFable pathways link the components of a functional system. Each part of the brain projects in an orderly fashion onto the next, thereby creating topographic maps. Neural maps not only re±ect the position of receptors but also their density. ²unctional systems on one side of the body generally control the other side of the body.
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Somatic Sensory System Touch, vibration, pressure, position of limbs (sense of self), pain, temperature. • Leads to the ability to identify shapes and textures of objects. • Monitors the internal and external forces acting on the body at any moment. • Detects potentially harmful circumstances.
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Overview of somatic sensory system • SpeciFc receptor neurons located in skin or joints receive stimuli. • Information is carried to brain via the spinal cord, brainstem, thalamus, to the post central gyrus of the parietal lobe, which in turn sends out info to higher order cortical areas. • Projections are topographic with respect to body region, and the amount of cortical space allocated to various body parts is proportional to the density of sensory receptors in that area.
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General Organization of the Somatic Sensory System Touch and Pain have different routes to the brain.
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Different sensory receptors can be classiFed based on different properties • Based on function- Pain, temp, touch, muscle length. • Based on morphology- free nerve endings or encapsulated. Nociceptors and thermoceptors have free nerve endings, most others are encapsulated. • Differ in conduction velocities, fast vs. slow • Differ in location: skin, muscle, tendon, hair • Differ in rate of adaptation slow vs. fast
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Slowly Adapting and Rapidly Adapting Mechanoreceptors Respond Differently to Stimulation
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• stimuli applied to skin, deforms or changes the nerve endings, produces a receptor potential that triggers an action potential • quality of stimulus (what it represents and where it is) is determined by the relevant receptor, and neuron’s targets in the brain. • quantity or strength of stimulus is
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This document was uploaded on 02/28/2011.

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lecture 10 - Sensory systems The CNS consists of discrete...

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