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Chapter 5

PSYB65 - chapter 5.docx

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Department
Psychology
Course Code
PSYB65H3
Professor
Ted Petit

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Chapter 5: The Sensorimotor System Sensorimotor System Why Sensorimotor? - The somatosensory information that your skin, joints, and muscles provide ensures that your brain makes accurate movements - Many of the adjustments that we make to our movements are guided by somatosensory feedback Somatosensory Receptors - Much of the somatosensory information that we receive about the world comes from sensory receptors in the skin. The 3 main types of receptors include:  Nociception: sensations of pain and temperature (Ventral Spinothalamic Tract)  Hapsis: sensations of fine touch and pressure (Dorsal Spinothalamic Tract)  Proprioception: awareness of the body and its position in space (Dorsal Spinothalamic Tract) - Most of the sensory receptors in the skin are mechanoreceptors, which react to distortion such as bending or stretching Somatosensory Pathways in the Brain - There are 2 main sensory pathways in the brain, which are named for their position in the spinal cord and the connections made:  The Dorsal Spinothalamic Tract  The Ventral Spinothalamic Tract Association Cortex - Hierarchical Organization of the Sensorimotor System: Association cortex, secondary motor cortex, primary motor cortex, brain stem motor nuclei, spinal motor circuits - Posterior Parietal Association Cortex: determines both the original position of the body and objects around the body in space (an association cortex because it receives input from a variety of sensory systems, including proprioception, hapsis, and vision) - Dorsolateral Prefrontal Cortex: involved with the decision to execute voluntary movements Secondary Motor Cortex - Areas of the secondary motor cortex include the:  Supplementary motor area Chapter 5: The Sensorimotor System  Premotor cortex  Cingulate motor areas Primary Motor Cortex - Primary motor cortex controls the movements of the muscles, and it plans out the coordinated activity of the muscles - Damage to the primary motor cortex does not lead to limb paralysis; rather, it reduces the speed, accuracy, and force with which an individual makes a movement - The Primary Somatosensory and motor Cortices from top to bottom: legs, hip, trunk, neck, head, shoulders, arms, hands, eyes, nose, face, lips, teeth, tongue, abdomen Basal Ganglia and Cerebellum - Basal Ganglia: subdivision of the telecephalon, and they are composed of: the caudate nucleus, the putamen, and the globus pallidus  Critically important for initiating movements and maintaining muscle tone  Huntington’s chorea results from damage to the striatum – both the caudate nucleus and the putamen - The Cerebellum: important role in the modulation of motor movements and the acquisition of motor skills. The cerebellum can be described in terms of 3 zones:  The lateral zone  The intermediate zone  The Vermis (lies between the hemispheres) Spinal Motor Pathways - There are 2 main systems of motor projections that descend from the brain to the spinal cord to initiate and control movement  Ventromedial System o The brainstem projections form 3 tracts, the vestibulospinal tract (balance), the reticulospinal tract (posture), and the tectospinal tract (head and eye movements) o The cortical projection form the ventral corticospinal tract (trunk/legs for walking)  Lateral System o Brainstem projections form the rubrospinal tract (limbs and hands movement) Chapter 5: The Sensorimotor System o Cortical projections form the lateral corticospinal tract (finger and toes movement) Sensorimotor Disorders Cortical Sensorimotor Disorders - Apraxia: “lack of action”, however apraxic individual are still capable of action, but their actions are often unorganized and inappropriate. It is a deficit in performing skilled voluntary movements. Possible problem with associating objects with movements (“motor agnosia”). Today, apraxia is generally regarded as a disorder of motor planning. Can be unilateral or bilateral, impairing 1 or both sides of the body. There is 4 major classes of apraxia:  Ideomotor apraxia: an individual cannot execute or imitate simple gestures in response to a command.  Ideational apraxia: some proposed that ideomotor apraxia is an inability to correctly form single movements, whereas ideational apraxia is the inability to correctly sequence a series of movements  Constructional apraxia: inability to construct a complex object, wherein one cannot arrange the elements of the object correctly (deficit in processing spatial aspects of the task, but
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