Sensory and Motor Pathways PDF

Sensory and Motor Pathways Sensory pathways Acsending pathways carry sensory information Motor pathways Descending pathways carry motor commands Decussation Cross-over of pathways to the other side of the brain Ipsilateral: pathway does not cross over Contralateral: pathway crosses over S...

Sensory and Motor Pathways Sensory pathways Acsending pathways carry sensory information Motor pathways Descending pathways carry motor commands Decussation Cross-over of pathways to the other side of the brain Ipsilateral: pathway does not cross over Contralateral: pathway crosses over Somatic sensory pathways somatic sensory pathways consist of a series of neurons called the labeled line. 1st order neuron - receptor up to brainstem or spinal cord 2nd order neuron - runs from brainstem or spinal cord to thalamus 3rd order neuron - thalamus to sensory cortex collectively, these neurons are known as a labeled line Usually named for their origin or termination Sensory pathways Conscious awareness: sensations we are consciously aware of Anterior spinothalamic tract information transmitted: crude touch and pressure, itch and tickle ipsilateral or contralateral: contralateral destination: cerebral cortex Lateral spinothalamic tract information transmitted: pain and temperature to cerebral cortex ipsilateral or contralateral: contralateral destination: cerebral cortex Fasciculus Gracilis information transmitted: ne touch, pressure, vibration, and proprioception from the inferior half of body ipsilateral or contralateral: contralateral destination: cerebellum and cerebral cortex Fasciculus Cuneatus information transmitted: ne touch, pressure, vibration, and proprioception from the superior half of body ipsilateral or contralateral: contralateral fi fi destination: cerebellum and cerebral cortex Unconscious awareness: sensations we are not aware of Spinomesencephalic tract information transmitted: pain and touch to mesencephalon ipsilateral or contralateral: contralateral destination: mesencephalon Spinoreticular tract information transmitted: pain ipsilateral or contralateral: contralateral or ipsilateral destination: reticular formation Anterior spinocerebellar tract information transmitted: proprioceptive information from the lower trunk and lower limbs to cerebellum ipsilateral or contralateral: ipsilateral destination: cerebellum Posterior spinocerebellar tract information transmitted: proprioceptive information from the thoracic and upper lumbar areas, upper trunk and upper limbs to cerebellum ipsilateral or contralateral: ipsilateral destination: cerebellum Somatic motor pathways involuntary movements: re exes-mediated through spinal cord and brainstorm voluntary movements: consciously activated to achieve a speci c goal. occurs automatically once started upper motor neurons: cell bodies in cerebral cortex. Primary motor cortex to brainstem or spinal cord lower motor neurons: cell bodies in anterior gray horn or cranial nerve nuclei travel brainstem or spinal cord to skeletal muscles Voluntary movements require many steps: 1. primary motor cortex initiates movement 2. coordination via cerebellum and basal nuclei 3. upper motor neurons stimulated send action potentials to lower motor neurons 4. Lower motor neurons stimulate skeletal muscles Direct pathways: control voluntary, conscious pathways. involved in maintaining muscle tone. Controls speed and precision of skilled motor movements Anterior corticospinal pathway information transmitted: movement of neck and trunk fl fi ipsilateral or contralateral: contralateral Lateral corticospinal pathway information transmitted: moves neck, trunk and limbs, especially the ngers ipsilateral or contralateral: contralateral Corticobulbar pathway information transmitted: movement of head and face such as facial expressions and chewing ipsilateral or contralateral: contralateral fi