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Questions and Answers
What is the fate of the second-order neurons in the ventral (anterior) spinocerebellar tract once they have crossed to the opposite side?
What is the fate of the second-order neurons in the ventral (anterior) spinocerebellar tract once they have crossed to the opposite side?
In which disorder mentioned is the spinocerebellar tract affected, leading to specific symptoms such as incoordination and tremors?
In which disorder mentioned is the spinocerebellar tract affected, leading to specific symptoms such as incoordination and tremors?
What characteristic does the posterior spinocerebellar tract possess regarding decussation?
What characteristic does the posterior spinocerebellar tract possess regarding decussation?
Which of the following is a function attributed to the spinotectal tract?
Which of the following is a function attributed to the spinotectal tract?
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Where are the cell bodies of second-order neurons located in the spinocerebellar tract?
Where are the cell bodies of second-order neurons located in the spinocerebellar tract?
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Which type of sensory receptor is responsible for detecting pain and temperature?
Which type of sensory receptor is responsible for detecting pain and temperature?
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What is the primary function of ascending tracts in the spinal cord?
What is the primary function of ascending tracts in the spinal cord?
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Which part of the nervous system do the first-order neurons enter through?
Which part of the nervous system do the first-order neurons enter through?
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What distinguishes graded receptor potentials from action potentials?
What distinguishes graded receptor potentials from action potentials?
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Which type of sensory information is primarily associated with mechanoreceptors?
Which type of sensory information is primarily associated with mechanoreceptors?
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What is the main pathway for sensory transmission in the spinal cord?
What is the main pathway for sensory transmission in the spinal cord?
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Where do the primary sensory neurons synapse with the second-order neurons?
Where do the primary sensory neurons synapse with the second-order neurons?
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What type of receptors are responsible for conscious proprioception?
What type of receptors are responsible for conscious proprioception?
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What type of joint condition is characterized by disorganization without discomfort?
What type of joint condition is characterized by disorganization without discomfort?
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Which pathways are included in the Dorsal Column-Medial Lemniscal system?
Which pathways are included in the Dorsal Column-Medial Lemniscal system?
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What is the primary function of the Fasciculus Gracilis?
What is the primary function of the Fasciculus Gracilis?
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Where do the axons of the second-order neurons in the Dorsal Column-Medial Lemniscal pathways decussate?
Where do the axons of the second-order neurons in the Dorsal Column-Medial Lemniscal pathways decussate?
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Which condition is associated with dorsal column lesions due to syphilitic infection?
Which condition is associated with dorsal column lesions due to syphilitic infection?
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What is the primary function of the lateral spinothalamic tract?
What is the primary function of the lateral spinothalamic tract?
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What sensation is primarily disturbed in syringomyelia due to the involvement of spinothalamic fibers?
What sensation is primarily disturbed in syringomyelia due to the involvement of spinothalamic fibers?
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What deficiency leads to Subacute Combined Degeneration of the spinal cord?
What deficiency leads to Subacute Combined Degeneration of the spinal cord?
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Where are the cell bodies of the second-order neurons located for the lateral spinothalamic tract?
Where are the cell bodies of the second-order neurons located for the lateral spinothalamic tract?
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What specific sensory loss occurs in individuals with multiple sclerosis at T6 or above?
What specific sensory loss occurs in individuals with multiple sclerosis at T6 or above?
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Which function is NOT primarily attributed to the Dorsal Column-Medial Lemniscal pathways?
Which function is NOT primarily attributed to the Dorsal Column-Medial Lemniscal pathways?
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What happens to sensations below the level of a lesion in syringomyelia?
What happens to sensations below the level of a lesion in syringomyelia?
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The anterior spinothalamic tract is primarily responsible for carrying which type of sensations?
The anterior spinothalamic tract is primarily responsible for carrying which type of sensations?
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Which pathway carries pain information from the opposite side of the body following a spinal cord injury?
Which pathway carries pain information from the opposite side of the body following a spinal cord injury?
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What is the primary role of the spinocerebellar tracts?
What is the primary role of the spinocerebellar tracts?
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Which neuron is responsible for transmitting information from the thalamus to the somatosensory cortex?
Which neuron is responsible for transmitting information from the thalamus to the somatosensory cortex?
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Where do the second order neurons of the posterior spinocerebellar tract arise?
Where do the second order neurons of the posterior spinocerebellar tract arise?
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What is a consequence of a lesion in the anterior spinothalamic tract?
What is a consequence of a lesion in the anterior spinothalamic tract?
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What is the term for the phenomenon where touch sensation is preserved while pain sensation is lost on opposite sides after a spinal injury?
What is the term for the phenomenon where touch sensation is preserved while pain sensation is lost on opposite sides after a spinal injury?
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Where do the axons of the second-order neurons of the lateral spinothalamic tract decussate?
Where do the axons of the second-order neurons of the lateral spinothalamic tract decussate?
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What type of cells comprise the first-order neurons of the anterior spinothalamic tract?
What type of cells comprise the first-order neurons of the anterior spinothalamic tract?
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What type of information do the spinocerebellar tracts transmit to the cerebellum?
What type of information do the spinocerebellar tracts transmit to the cerebellum?
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What characterizes the axons of the second order neurons in the posterior spinocerebellar tract?
What characterizes the axons of the second order neurons in the posterior spinocerebellar tract?
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What is the location of the spinocerebellar tracts in the spinal cord?
What is the location of the spinocerebellar tracts in the spinal cord?
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Study Notes
Sensory Receptors
- Sensory receptors are specialized for different senses, categorized into:
- Specialized receptors (smell, vision, hearing, taste)
- Visceral receptors (viscera, smooth muscle, unconscious or autonomic responses)
- Somatic receptors (skin, striated muscle, joints)
Characteristics of Sensory Neurons
- Sensory neurons have shapes suited to their functions.
- Receptor type is specific to the sense.
- Sensory neurons utilize graded receptor potentials, not all-or-nothing action potentials.
F Sensory Receptors
- Photoreceptors: Rods and cones in the eye, stimulated by visible light.
- Chemoreceptors: Taste buds on the tongue (taste), olfactory receptors in the nose (smell), osmoreceptors in the hypothalamus and receptors in the carotid and aorta (internal senses detecting things like food particles, odor molecules, low blood volume, and blood pH).
- Mechanoreceptors: Receptors in the skin (touch/pressure/pain), hair cells in the inner ear (hearing), proprioceptors in muscles and tendons (balance and body position).
- Thermoreceptors: Heat and cold receptors in the skin, sensitive to changes in radiant energy.
Sense of Touch
- Mechanoreceptors in the skin and viscera detect varying degrees of pressure.
- Free nerve endings are pain receptors and thermoreceptors.
Cutaneous Receptors
- Various cutaneous receptors exist (e.g., Meissner's corpuscles, Merkel disks, Ruffini endings, Pacinian corpuscles), each responsive to different types of touch stimuli (light touch, pressure, pain, warmth, cold).
- Muscle and tendon receptors also exist (e.g., muscle spindles, Golgi tendon organs), enabling the detection of muscle length, tension, and movement.
Nerve Fibres
- Various types of nerve fibres (axons) form nociceptors (pain receptors)
- A-alpha fibres: proprioception, 80-120 m/s conduction
- A-beta fibres: touch, 35-90 m/s conduction
- A-delta fibres: pain/mechanical and thermal, 5-40 m/s conduction
- C fibres: pain/mechanical, thermal and chemical, 0.5-2 m/s conduction
Ascending Tracts
- The white matter of the spinal cord contains ascending and descending nerve fibers.
- It is divided into Dorsal, Lateral & Ventral Columns or Funiculi.
- Different ascending tracts carry various sensory information (e.g., pain, temperature, touch, proprioception).
- Lateral Spinothalamic Tract: Pain, thermal sensation
- Anterior Spinothalamic Tract: Crude (light) touch, pressure, tickle, itch
- Dorsal Column (lemniscus medialis): Fine touch, discriminative touch, graphaesthesia, stereogenesis, two-point discrimination, vibration, conscious proprioception
- Anterior Spinocerebellar Tract: Unconscious proprioception, gross movements
- Posterior Spinocerebellar Tract: Unconscious proprioception, fine movements
Spinothalamic Tracts
- Lateral spinothalamic tract: Carries pain and temperature sensations to the thalamus, then on to the sensory cortex; three neurons are involved.
- Anterior spinothalamic tract: Carries crude touch and pressure sensations to the thalamus, then on to the sensory cortex; three neurons are involved.
Dorsal Column-Medial Lemniscal Pathways
- The Posterior Column contains the fasciculus gracilis (FG) and fasciculus cuneatus (FC) tracts, carrying proprioception and discriminative touch information from the ipsilateral side of the body.
- The axons of these first-order neurons ascend to the medulla oblongata, where they synapse with second-order neurons.
- The axons of these second-order neurons decussate in the medulla and ascend as the medial lemniscus to the thalamus.
- The medial lemniscus terminates in the ventral posterior nucleus of the thalamus, with third-order neurons carrying the information to the somatosensory cortex.
Spinocerebellar Tracts
- Carry proprioceptive information to the cerebellum, important for coordination and posture control
- Anterior Spinocerebellar Tract: Ascends ipsilaterally (same side), crosses at the level of the medulla.
- Posterior Spinocerebellar Tract: Ascends and terminates on the same side of the cerebellum; contains only one decussation.
Spinotectal Tract
- Ascends within the anterolateral part, in close association with the spinothalamic system; involved in reflexive turning of the head and eyes toward a point of cutaneous stimulation
Spino-olivary tract
- Conveys sensory information to the cerebellum. This tract is important in contributing to movement coordination associated with balance.
- Originates at different spinal cord levels and carries impulses regarding proprioception
Spinoreticular Tract
- Carries information on dull aching (slow pain) to the cerebral cortex
Lesions Affecting Spinal Tracts
- Syringomyelia: Widening of the central canal of the spinal cord, which compresses adjacent nerve fibers, leading to selective loss of pain and temperature sensation.
- Tabes Dorsalis: Syphilitic infection affecting lumbosacral dorsal spinal roots and dorsal columns, resulting in sensory ataxia.
- Multiple Sclerosis: Affects the fasciculus cuneatus of the cervical region, leading to proprioceptive loss in hands and fingers (astereognosis).
Friedrich's Ataxia:
- Inherited disease affecting the spinocerebellar tracts, resulting in incoordination of arms, tremors, and an unsteady gait.
Additional Notes
- Specific receptors in tissues/structures
- Different types of nerve fibers conduct at varying speeds
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Description
Test your knowledge on the different types of sensory receptors and the characteristics of sensory neurons. This quiz will cover specialized, visceral, and somatic receptors, as well as the various sensory neuron functions. Perfect for students studying biology and human physiology.
