Podcast
Questions and Answers
Which type of tracts deliver information to the brain?
Which type of tracts deliver information to the brain?
What is the function of the posterior funiculus?
What is the function of the posterior funiculus?
Which tract delivers information from the spinal cord to the cerebellum?
Which tract delivers information from the spinal cord to the cerebellum?
What is the role of the lateral funiculus?
What is the role of the lateral funiculus?
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Where are the fibers of the ascending tracts derived from?
Where are the fibers of the ascending tracts derived from?
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What is a characteristic of funiculus in the spinal cord?
What is a characteristic of funiculus in the spinal cord?
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How are tracts named in relation to the spinal cord?
How are tracts named in relation to the spinal cord?
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Where is the cell body of the second-order neuron in the spinothalamic tract located?
Where is the cell body of the second-order neuron in the spinothalamic tract located?
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Which sensations are carried by the lateral spinothalamic tract?
Which sensations are carried by the lateral spinothalamic tract?
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What is the clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
What is the clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
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Which tracts carry discriminative touch, joint position sense, vibration, and pressure sensation?
Which tracts carry discriminative touch, joint position sense, vibration, and pressure sensation?
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What is the function of the spinocerebellar tracts?
What is the function of the spinocerebellar tracts?
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Which tract carries tactile, pressure, and proprioceptive input from muscle spindles and GTO to the cerebellum for monitoring and modulating movements?
Which tract carries tactile, pressure, and proprioceptive input from muscle spindles and GTO to the cerebellum for monitoring and modulating movements?
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What is astereognosis associated with?
What is astereognosis associated with?
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Which sensory receptor is imbedded in tendons of skeletal muscles and monitors the degree of tension and force placed on the skeletal muscle?
Which sensory receptor is imbedded in tendons of skeletal muscles and monitors the degree of tension and force placed on the skeletal muscle?
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Which pathway is responsible for reflex postural movements in response to visual stimuli?
Which pathway is responsible for reflex postural movements in response to visual stimuli?
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Lesions above the decussation of the corticospinal tract result in weakness seen in muscles on which side of the body?
Lesions above the decussation of the corticospinal tract result in weakness seen in muscles on which side of the body?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
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What is the function of the Rubrospinal Tract?
What is the function of the Rubrospinal Tract?
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Which descending pathway facilitates activity of extensor muscles and inhibits activity of flexor muscles?
Which descending pathway facilitates activity of extensor muscles and inhibits activity of flexor muscles?
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Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
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Which fibers control autonomic systems and originate from the cortex, hypothalamus, amygdala, and reticular formation?
Which fibers control autonomic systems and originate from the cortex, hypothalamus, amygdala, and reticular formation?
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Which descending tract in the spinal cord carries afferent information for spinovisual reflexes?
Which descending tract in the spinal cord carries afferent information for spinovisual reflexes?
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Which tract in the spinal cord carries afferents influencing levels of consciousness?
Which tract in the spinal cord carries afferents influencing levels of consciousness?
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Which descending tract in the spinal cord carries balance and unconscious proprioceptive afferent information to the cerebellum?
Which descending tract in the spinal cord carries balance and unconscious proprioceptive afferent information to the cerebellum?
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Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
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Where are the cell bodies of UMN located?
Where are the cell bodies of UMN located?
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Which reflex is the simplest and involves only one synapse between 1 sensory and 1 motor neuron?
Which reflex is the simplest and involves only one synapse between 1 sensory and 1 motor neuron?
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Which tract is responsible for the voluntary innervation of skeletal muscle, descending through the brain stem?
Which tract is responsible for the voluntary innervation of skeletal muscle, descending through the brain stem?
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Which type of tracts carry discriminative touch, joint position sense, vibration, and pressure sensation?
Which type of tracts carry discriminative touch, joint position sense, vibration, and pressure sensation?
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Where are the cell bodies of upper motor neurons (UMNs) located?
Where are the cell bodies of upper motor neurons (UMNs) located?
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What is the function of the rubrospinal tract?
What is the function of the rubrospinal tract?
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Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Which descending tract in the spinal cord carries afferent information for spinovisual reflexes?
Which descending tract in the spinal cord carries afferent information for spinovisual reflexes?
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Which neurons are used in the grey matter and tracts of axons in the grey matter of the spinal cord?
Which neurons are used in the grey matter and tracts of axons in the grey matter of the spinal cord?
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Which descending tract in the spinal cord carries afferent information for spinovisual reflexes?
Which descending tract in the spinal cord carries afferent information for spinovisual reflexes?
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Where do the corticospinal fibers descend through in the brain stem?
Where do the corticospinal fibers descend through in the brain stem?
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Which tract carries balance and unconscious proprioceptive afferent information to the cerebellum?
Which tract carries balance and unconscious proprioceptive afferent information to the cerebellum?
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Where do the corticospinal fibers cross at the decussation of the pyramids?
Where do the corticospinal fibers cross at the decussation of the pyramids?
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Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Which fibers control autonomic systems and originate from the cortex, hypothalamus, amygdala, and reticular formation?
Which fibers control autonomic systems and originate from the cortex, hypothalamus, amygdala, and reticular formation?
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Where is the cell body of the third-order neuron in the spinothalamic tract located?
Where is the cell body of the third-order neuron in the spinothalamic tract located?
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Which descending pathway is responsible for reflex postural movements in response to visual stimuli?
Which descending pathway is responsible for reflex postural movements in response to visual stimuli?
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Which tract carries information related to pain, temperature, tickle, itch, and sexual sensations?
Which tract carries information related to pain, temperature, tickle, itch, and sexual sensations?
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Where are the cell bodies of gamma motor neurons located?
Where are the cell bodies of gamma motor neurons located?
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Which tract is responsible for carrying discriminative touch, joint position sense (kinesthetic), vibration, and pressure sensation?
Which tract is responsible for carrying discriminative touch, joint position sense (kinesthetic), vibration, and pressure sensation?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Which tract carries tactile, pressure, and proprioceptive input from muscle spindles and GTO to the cerebellum for monitoring and modulating movements?
Which tract carries tactile, pressure, and proprioceptive input from muscle spindles and GTO to the cerebellum for monitoring and modulating movements?
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Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
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What is the clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
What is the clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
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Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
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What is astereognosis associated with?
What is astereognosis associated with?
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What is the function of the Vestibulospinal Tract?
What is the function of the Vestibulospinal Tract?
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Where do the fibers of the anterior spinocerebellar tract ultimately end?
Where do the fibers of the anterior spinocerebellar tract ultimately end?
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Where do the descending autonomic fibers controlling autonomic systems originate from?
Where do the descending autonomic fibers controlling autonomic systems originate from?
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What is the role of the 1b afferent neurons stimulated by Golgi tendon organs?
What is the role of the 1b afferent neurons stimulated by Golgi tendon organs?
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Which descending pathway gives multiple branches at each level and represents about 30% of fibers going to the muscle?
Which descending pathway gives multiple branches at each level and represents about 30% of fibers going to the muscle?
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Where is the cell body of the third-order neuron in the spinothalamic tract located?
Where is the cell body of the third-order neuron in the spinothalamic tract located?
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Where do the corticospinal fibers descend through in the brain stem?
Where do the corticospinal fibers descend through in the brain stem?
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What is astereognosis associated with?
What is astereognosis associated with?
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Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
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Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
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Where are the cell bodies of gamma motor neurons located?
Where are the cell bodies of gamma motor neurons located?
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What is the function of the spinocerebellar tracts?
What is the function of the spinocerebellar tracts?
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Which type of tracts primarily carry information to the brain?
Which type of tracts primarily carry information to the brain?
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What is the specific function of the rubrospinal tract?
What is the specific function of the rubrospinal tract?
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Where are the cell bodies of upper motor neurons (UMNs) located?
Where are the cell bodies of upper motor neurons (UMNs) located?
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Which sensory receptor is embedded in tendons of skeletal muscles and monitors the degree of tension and force placed on the skeletal muscle?
Which sensory receptor is embedded in tendons of skeletal muscles and monitors the degree of tension and force placed on the skeletal muscle?
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What is the clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
What is the clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
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Where do the corticospinal fibers cross at the decussation of the pyramids?
Where do the corticospinal fibers cross at the decussation of the pyramids?
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Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
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Which tract carries afferent information for spinovisual reflexes and terminates by synapsing on neurons in the superior colliculus?
Which tract carries afferent information for spinovisual reflexes and terminates by synapsing on neurons in the superior colliculus?
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Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
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Where are the fibers of the ascending tracts derived from?
Where are the fibers of the ascending tracts derived from?
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What is the role of the lateral funiculus?
What is the role of the lateral funiculus?
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Which sensory receptor is embedded in tendons of skeletal muscles and monitors the degree of tension and force placed on the skeletal muscle?
Which sensory receptor is embedded in tendons of skeletal muscles and monitors the degree of tension and force placed on the skeletal muscle?
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What is astereognosis associated with?
What is astereognosis associated with?
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Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
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Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Where are the cell bodies of gamma motor neurons located?
Where are the cell bodies of gamma motor neurons located?
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Which descending pathway is responsible for reflex postural movements in response to visual stimuli?
Which descending pathway is responsible for reflex postural movements in response to visual stimuli?
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What is the role of the 1b afferent neurons stimulated by Golgi tendon organs?
What is the role of the 1b afferent neurons stimulated by Golgi tendon organs?
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Which descending pathway facilitates activity of extensor muscles and inhibits activity of flexor muscles?
Which descending pathway facilitates activity of extensor muscles and inhibits activity of flexor muscles?
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Where do the corticospinal fibers cross at the decussation of the pyramids?
Where do the corticospinal fibers cross at the decussation of the pyramids?
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Which tract carries tactile, pressure, and proprioceptive input from muscle spindles and GTO to the cerebellum for monitoring and modulating movements?
Which tract carries tactile, pressure, and proprioceptive input from muscle spindles and GTO to the cerebellum for monitoring and modulating movements?
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What is the function of the Rubrospinal Tract?
What is the function of the Rubrospinal Tract?
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Which type of tracts primarily carry information to the brain?
Which type of tracts primarily carry information to the brain?
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What is the role of the lateral funiculus?
What is the role of the lateral funiculus?
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Where are the cell bodies of gamma motor neurons located?
Where are the cell bodies of gamma motor neurons located?
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Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Where is the cell body of the third-order neuron in the spinothalamic tract located?
Where is the cell body of the third-order neuron in the spinothalamic tract located?
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What is the function of the Vestibulospinal Tract?
What is the function of the Vestibulospinal Tract?
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Where is the cell body of the third-order neuron in the spinothalamic tract located?
Where is the cell body of the third-order neuron in the spinothalamic tract located?
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Which tract carries pain, temperature, tickle, itch, and sexual sensations?
Which tract carries pain, temperature, tickle, itch, and sexual sensations?
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Where do the axons of the second neuron in the dorsal column-medial lemniscal pathway cross midline and ascend as the medial tract in the brain stem?
Where do the axons of the second neuron in the dorsal column-medial lemniscal pathway cross midline and ascend as the medial tract in the brain stem?
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Which spinocerebellar tract is responsible for conveying tactile, pressure, and proprioceptive information from muscle spindles and GTO to the cerebellum?
Which spinocerebellar tract is responsible for conveying tactile, pressure, and proprioceptive information from muscle spindles and GTO to the cerebellum?
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What is the characteristic clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
What is the characteristic clinical manifestation of a lesion in the spinothalamic tract in the brain stem or spinal cord?
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What is the clinical correlate of lesions in the dorsal column-medial lemniscal pathway?
What is the clinical correlate of lesions in the dorsal column-medial lemniscal pathway?
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Where do the second-order neurons in the spinothalamic tract have their cell bodies located?
Where do the second-order neurons in the spinothalamic tract have their cell bodies located?
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Which tract carries balance and unconscious proprioceptive afferent information to the cerebellum?
Which tract carries balance and unconscious proprioceptive afferent information to the cerebellum?
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Where do the corticospinal fibers cross at the decussation of the pyramids?
Where do the corticospinal fibers cross at the decussation of the pyramids?
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What is the primary motor cortex responsible for?
What is the primary motor cortex responsible for?
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Which neurons initiate involuntary motor responses to a sensory stimulus?
Which neurons initiate involuntary motor responses to a sensory stimulus?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the midbrain and facilitates activity of flexor muscles?
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Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
Which neural circuit is involved in initiating a voluntary contraction of skeletal muscle?
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Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
Which descending pathway originates from the red nucleus in the mid-brain and facilitates activity of flexor muscles?
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What is the characteristic response of an upper motor neuron (UMN) lesion?
What is the characteristic response of an upper motor neuron (UMN) lesion?
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Where are the cell bodies of gamma motor neurons located?
Where are the cell bodies of gamma motor neurons located?
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What is astereognosis associated with?
What is astereognosis associated with?
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Where do the descending autonomic fibers controlling autonomic systems originate from?
Where do the descending autonomic fibers controlling autonomic systems originate from?
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Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
Which descending pathway inhibits or facilitates voluntary movement and has some fibers that cross the midline at various levels?
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What is the function of the spinocerebellar tracts?
What is the function of the spinocerebellar tracts?
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Which type of tracts carry discriminative touch, joint position sense, vibration, and pressure sensation?
Which type of tracts carry discriminative touch, joint position sense, vibration, and pressure sensation?
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Where are the cell bodies of upper motor neurons (UMNs) located?
Where are the cell bodies of upper motor neurons (UMNs) located?
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Study Notes
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Friedreich's Ataxia: three descending tracts in the spinal cord: Spinotectal, Spinoreticular, and Spinoolivary
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Spinotectal tract: carries afferent information for spinovisual reflexes, terminates by synapsing on neurons in the superior colliculus
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Spinoreticular tract: carries afferents influencing levels of consciousness, terminates on neurons in the reticular formation
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Spinoolivary tract: carries balance and unconscious proprioceptive afferent information to the cerebellum, 3rd order neurons in the inferior olivary nuclei in the medulla, axons cross and enter the cerebellum
-
Sensory tracts: organization based on the site of origin, arranged in a somatotopic manner, medial-lateral rule: neurons that enter a lower level of the spinal cord are more medial, neurons that enter at a higher level are more lateral
-
Motor system: voluntary innervation of skeletal muscle, basic neural circuit: upper motor neuron (UMN) and lower motor neuron (LMN), initiating a voluntary contraction: an LMN must be innervated by a UMN, UMN: LMN: cell bodies in brain stem and cerebral cortex, cell bodies in the ventral horn of the spinal cord and cranial nerve nuclei in the brain stem, LMN (in spinal cord) axons exit the spinal cord in a ventral root, join and course with a spinal nerve, reach and synapse on a neuromuscular junction in skeletal muscle
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Motor neuron groups in the spinal cord: Anterior Grey Column, Alpha Efferents: large, multipolar LMN of brainstem and spinal cord, innervate extrafusal muscle fibers of skeletal muscle, present in most segments, innervate skeletal muscles of neck, trunk, intercostals, abdominals, present in some cervical and lumbosacral segments, innervate the diaphragm, accessory nucleus, lumbosacral nucleus, Corticospinal Tract: voluntary innervation of skeletal muscle, primary motor cortex: precentral gyrus of the frontal lobe, corticospinal fibers descend through the brain stem in the ventral portion of the mid brain, pons, and medulla, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, continue in the contralateral part of the spinal cord as the lateral corticospinal tract, descend full length of the cord in the lateral part of the white matter, as it descends axons leave and enter the gray matter of the ventral horn to synapse on a LMN, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, corticospinal tract reflex innervation of skeletal muscle: involuntary motor responses to a sensory stimulus, requires a minimum of 2 neurons: a sensory neuron that initiates a motor response and lower motor neurons, reflexes range from simple 2-neuron circuits to more complex reflexes, deep muscle stretch (myotatic) reflex: simplest of the reflexes, involves only one synapse between 1 sensory and 1 motor neuron, tests the integrity of the reflex in the limbs provides important clinical information when assessing different types of motor weaknesses and dysfunction, present in most skeletal muscles, provides the important physiological mechanism of regulating and maintaining proper muscle tone throughout the skeletal muscular system.
-
Friedreich's Ataxia: three descending tracts in the spinal cord: Spinotectal, Spinoreticular, and Spinoolivary
-
Spinotectal tract: carries afferent information for spinovisual reflexes, terminates by synapsing on neurons in the superior colliculus
-
Spinoreticular tract: carries afferents influencing levels of consciousness, terminates on neurons in the reticular formation
-
Spinoolivary tract: carries balance and unconscious proprioceptive afferent information to the cerebellum, 3rd order neurons in the inferior olivary nuclei in the medulla, axons cross and enter the cerebellum
-
Sensory tracts: organization based on the site of origin, arranged in a somatotopic manner, medial-lateral rule: neurons that enter a lower level of the spinal cord are more medial, neurons that enter at a higher level are more lateral
-
Motor system: voluntary innervation of skeletal muscle, basic neural circuit: upper motor neuron (UMN) and lower motor neuron (LMN), initiating a voluntary contraction: an LMN must be innervated by a UMN, UMN: LMN: cell bodies in brain stem and cerebral cortex, cell bodies in the ventral horn of the spinal cord and cranial nerve nuclei in the brain stem, LMN (in spinal cord) axons exit the spinal cord in a ventral root, join and course with a spinal nerve, reach and synapse on a neuromuscular junction in skeletal muscle
-
Motor neuron groups in the spinal cord: Anterior Grey Column, Alpha Efferents: large, multipolar LMN of brainstem and spinal cord, innervate extrafusal muscle fibers of skeletal muscle, present in most segments, innervate skeletal muscles of neck, trunk, intercostals, abdominals, present in some cervical and lumbosacral segments, innervate the diaphragm, accessory nucleus, lumbosacral nucleus, Corticospinal Tract: voluntary innervation of skeletal muscle, primary motor cortex: precentral gyrus of the frontal lobe, corticospinal fibers descend through the brain stem in the ventral portion of the mid brain, pons, and medulla, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, continue in the contralateral part of the spinal cord as the lateral corticospinal tract, descend full length of the cord in the lateral part of the white matter, as it descends axons leave and enter the gray matter of the ventral horn to synapse on a LMN, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, corticospinal tract reflex innervation of skeletal muscle: involuntary motor responses to a sensory stimulus, requires a minimum of 2 neurons: a sensory neuron that initiates a motor response and lower motor neurons, reflexes range from simple 2-neuron circuits to more complex reflexes, deep muscle stretch (myotatic) reflex: simplest of the reflexes, involves only one synapse between 1 sensory and 1 motor neuron, tests the integrity of the reflex in the limbs provides important clinical information when assessing different types of motor weaknesses and dysfunction, present in most skeletal muscles, provides the important physiological mechanism of regulating and maintaining proper muscle tone throughout the skeletal muscular system.
-
Friedreich's Ataxia: three descending tracts in the spinal cord: Spinotectal, Spinoreticular, and Spinoolivary
-
Spinotectal tract: carries afferent information for spinovisual reflexes, terminates by synapsing on neurons in the superior colliculus
-
Spinoreticular tract: carries afferents influencing levels of consciousness, terminates on neurons in the reticular formation
-
Spinoolivary tract: carries balance and unconscious proprioceptive afferent information to the cerebellum, 3rd order neurons in the inferior olivary nuclei in the medulla, axons cross and enter the cerebellum
-
Sensory tracts: organization based on the site of origin, arranged in a somatotopic manner, medial-lateral rule: neurons that enter a lower level of the spinal cord are more medial, neurons that enter at a higher level are more lateral
-
Motor system: voluntary innervation of skeletal muscle, basic neural circuit: upper motor neuron (UMN) and lower motor neuron (LMN), initiating a voluntary contraction: an LMN must be innervated by a UMN, UMN: LMN: cell bodies in brain stem and cerebral cortex, cell bodies in the ventral horn of the spinal cord and cranial nerve nuclei in the brain stem, LMN (in spinal cord) axons exit the spinal cord in a ventral root, join and course with a spinal nerve, reach and synapse on a neuromuscular junction in skeletal muscle
-
Motor neuron groups in the spinal cord: Anterior Grey Column, Alpha Efferents: large, multipolar LMN of brainstem and spinal cord, innervate extrafusal muscle fibers of skeletal muscle, present in most segments, innervate skeletal muscles of neck, trunk, intercostals, abdominals, present in some cervical and lumbosacral segments, innervate the diaphragm, accessory nucleus, lumbosacral nucleus, Corticospinal Tract: voluntary innervation of skeletal muscle, primary motor cortex: precentral gyrus of the frontal lobe, corticospinal fibers descend through the brain stem in the ventral portion of the mid brain, pons, and medulla, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, continue in the contralateral part of the spinal cord as the lateral corticospinal tract, descend full length of the cord in the lateral part of the white matter, as it descends axons leave and enter the gray matter of the ventral horn to synapse on a LMN, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, corticospinal tract reflex innervation of skeletal muscle: involuntary motor responses to a sensory stimulus, requires a minimum of 2 neurons: a sensory neuron that initiates a motor response and lower motor neurons, reflexes range from simple 2-neuron circuits to more complex reflexes, deep muscle stretch (myotatic) reflex: simplest of the reflexes, involves only one synapse between 1 sensory and 1 motor neuron, tests the integrity of the reflex in the limbs provides important clinical information when assessing different types of motor weaknesses and dysfunction, present in most skeletal muscles, provides the important physiological mechanism of regulating and maintaining proper muscle tone throughout the skeletal muscular system.
-
Friedreich's Ataxia: three descending tracts in the spinal cord: Spinotectal, Spinoreticular, and Spinoolivary
-
Spinotectal tract: carries afferent information for spinovisual reflexes, terminates by synapsing on neurons in the superior colliculus
-
Spinoreticular tract: carries afferents influencing levels of consciousness, terminates on neurons in the reticular formation
-
Spinoolivary tract: carries balance and unconscious proprioceptive afferent information to the cerebellum, 3rd order neurons in the inferior olivary nuclei in the medulla, axons cross and enter the cerebellum
-
Sensory tracts: organization based on the site of origin, arranged in a somatotopic manner, medial-lateral rule: neurons that enter a lower level of the spinal cord are more medial, neurons that enter at a higher level are more lateral
-
Motor system: voluntary innervation of skeletal muscle, basic neural circuit: upper motor neuron (UMN) and lower motor neuron (LMN), initiating a voluntary contraction: an LMN must be innervated by a UMN, UMN: LMN: cell bodies in brain stem and cerebral cortex, cell bodies in the ventral horn of the spinal cord and cranial nerve nuclei in the brain stem, LMN (in spinal cord) axons exit the spinal cord in a ventral root, join and course with a spinal nerve, reach and synapse on a neuromuscular junction in skeletal muscle
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Motor neuron groups in the spinal cord: Anterior Grey Column, Alpha Efferents: large, multipolar LMN of brainstem and spinal cord, innervate extrafusal muscle fibers of skeletal muscle, present in most segments, innervate skeletal muscles of neck, trunk, intercostals, abdominals, present in some cervical and lumbosacral segments, innervate the diaphragm, accessory nucleus, lumbosacral nucleus, Corticospinal Tract: voluntary innervation of skeletal muscle, primary motor cortex: precentral gyrus of the frontal lobe, corticospinal fibers descend through the brain stem in the ventral portion of the mid brain, pons, and medulla, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, continue in the contralateral part of the spinal cord as the lateral corticospinal tract, descend full length of the cord in the lateral part of the white matter, as it descends axons leave and enter the gray matter of the ventral horn to synapse on a LMN, corticospinal tract in the lower medulla: 80-90% of fibers cross at the decussation of the pyramids, corticospinal tract reflex innervation of skeletal muscle: involuntary motor responses to a sensory stimulus, requires a minimum of 2 neurons: a sensory neuron that initiates a motor response and lower motor neurons, reflexes range from simple 2-neuron circuits to more complex reflexes, deep muscle stretch (myotatic) reflex: simplest of the reflexes, involves only one synapse between 1 sensory and 1 motor neuron, tests the integrity of the reflex in the limbs provides important clinical information when assessing different types of motor weaknesses and dysfunction, present in most skeletal muscles, provides the important physiological mechanism of regulating and maintaining proper muscle tone throughout the skeletal muscular system.
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Test your knowledge of ascending sensory pathways in the nervous system with this quiz. Explore the spinotectal tract, spinoreticular tract, and spinoolivary tract, and understand their roles in transmitting afferent information for various reflexes and functions.
