Coronal View Of Brain Showing Spinal Cord

Shingles and Herpes Zoster Virus

Herpes zoster virus, commonly known as chicken pox, preferentially infects neurons of the peripheral nervous system, particularly dorsal root ganglion cells. Individuals infected with the virus during childhood usually display red, itchy spots on the skin for approximately 1 week and are symptom free thereafter. However, the virus may remain dormant, usually residing in a single dorsal root ganglion, and can become reactivated in some individuals decades later to produce a condition known as shingles. The revived virus increases the excitability of sensory cells in the ganglion so that sensory nerves have lower thresholds as well as spontaneous activity. This activity triggers burning or stabbing sensations that are agonizingly painful. The reactivation phase of the infection may last months or years, during which time the skin first becomes inflamed, then blisters, and finally appears scaly. Because the infection is restricted to a single dorsal root ganglion, the affected areas of the skin reflect the dermatomal distribution of the affected ganglion. Thoracic and facial areas are most commonly involved, although instances of infection of every dermatome have been reported. In fact, the observations of many shingles patients and their infected areas helped to provide the currently used map of dermatomal distributions of individual dorsal root ganglia. Antiviral agents and steroids are used as treatment for this condition.

A. Cross sections of B. Coronal view of C. Lateral view of the nervous system the nervous system the nervous system left cerebral cortex

Brain Coronal Cross Section Spinal Cord

FIGURE 4 Dorsal column-lateral lemniscal pathway; neuronal pathways of proprioception and light, discriminatory touch: (A) cross section, (B) coronal view, and (C) lateral view of spinal cord and brain stem with associated body part. Sensory fibers enter the spinal cord and ascend in the dorsal columns to the dorsal column nuclei. Secondary neurons project from the nuclei, cross the midline, and ascend contralaterally in the medial lemniscus to the ventral posterior lateral nucleus of the thalamus. Tertiary neurons project to the post-central gyrus of the cerebral cortex. Tactile information from the face enters the trigeminal nerve (V) and synapses in the trigeminal main sensory nucleus. Axons from secondary neurons cross the midline, form the trigeminal lemniscus, join the medial lemniscus to form the sensory lemniscus, and ascend to the ventral posterior medial nucleus of the thalamus. Tertiary neurons project to the lower part of the post-central gyrus.

FIGURE 4 Dorsal column-lateral lemniscal pathway; neuronal pathways of proprioception and light, discriminatory touch: (A) cross section, (B) coronal view, and (C) lateral view of spinal cord and brain stem with associated body part. Sensory fibers enter the spinal cord and ascend in the dorsal columns to the dorsal column nuclei. Secondary neurons project from the nuclei, cross the midline, and ascend contralaterally in the medial lemniscus to the ventral posterior lateral nucleus of the thalamus. Tertiary neurons project to the post-central gyrus of the cerebral cortex. Tactile information from the face enters the trigeminal nerve (V) and synapses in the trigeminal main sensory nucleus. Axons from secondary neurons cross the midline, form the trigeminal lemniscus, join the medial lemniscus to form the sensory lemniscus, and ascend to the ventral posterior medial nucleus of the thalamus. Tertiary neurons project to the lower part of the post-central gyrus.

A. Cross sections of B. Coronal view of C. Lateral view of the nervous system the nervous system the nervous system left cerebral cortex

Frontal Section Brain And Spinal Cord

FIGURE 5 Anterolateral path to the brain; neuronal pathways of pain: (A) cross section, (B) coronal view, and (C) lateral view of spinal cord and brain stem with associated body parts. Nociceptive information is carried by two paths: the neo-anterolateral path (heavy lines), which carries information about sharp, pricking pain; and the paleo-anterolateral path (light lines), which carries information about dull aversive pain. Both enter the spinal cord and make synaptic connections in the dorsal horn of the spinal cord. Projection neurons from the dorsal horn ascend contralaterally in the anterolateral tract to the thalamus. These sensory neurons from the face have cell bodies in the trigeminal ganglia; their fibers enter the brain in the middle of the pons and descend to the spinal trigeminal nucleus. After synapsing, the projection neurons cross and ascend contralaterally in the trigeminal lemniscus to the thalamus. The neo-tracts project to the ventral posterior lateral nuclei (body) and ventral posterior medial nuclei (face) of the thalamus and from there to the post central gyrus of the cerebral cortex. The paleo-tracts terminate in the intralaminar nuclei of the thalamus. Both systems send information to the reticular formation. Temperature and crude touch follow similar paths to the cerebral cortex.

FIGURE 5 Anterolateral path to the brain; neuronal pathways of pain: (A) cross section, (B) coronal view, and (C) lateral view of spinal cord and brain stem with associated body parts. Nociceptive information is carried by two paths: the neo-anterolateral path (heavy lines), which carries information about sharp, pricking pain; and the paleo-anterolateral path (light lines), which carries information about dull aversive pain. Both enter the spinal cord and make synaptic connections in the dorsal horn of the spinal cord. Projection neurons from the dorsal horn ascend contralaterally in the anterolateral tract to the thalamus. These sensory neurons from the face have cell bodies in the trigeminal ganglia; their fibers enter the brain in the middle of the pons and descend to the spinal trigeminal nucleus. After synapsing, the projection neurons cross and ascend contralaterally in the trigeminal lemniscus to the thalamus. The neo-tracts project to the ventral posterior lateral nuclei (body) and ventral posterior medial nuclei (face) of the thalamus and from there to the post central gyrus of the cerebral cortex. The paleo-tracts terminate in the intralaminar nuclei of the thalamus. Both systems send information to the reticular formation. Temperature and crude touch follow similar paths to the cerebral cortex.

A. Cerebral cortex central sulcus

2 deep pressure, joint rotation (size & shape) 1 rapid adapting cutaneous (texture) 3b rapid and slow adapting cutaneous 3a muscle stretch 4 motor

B. column organization and layers in the 3b region of the cerebral cortex s^

FIGURE 6 Modular organization of the somatosensory cortex. (A) Organization of the primary receptive areas (darker blue; Brodmann's areas 1, 2, and 3, also called collectively S1) on the post-central gyrus of the cerebral cortex. Note that area 3 (both 3a and 3b) lies on the posterior wall of the central sulcus. Each area receives specific types (submodalities) of touch information from designated areas of the body in a somatotopic manner. (B) Detail of the 3b cortical area receiving information from mechanical receptors in three left-hand fingers. Projection neurons from the thalamus synapse in layer 4, within columns devoted to rapidly adapting (RA) and slowly adapting (SA) receptors. Fibers that project from the cortex segregate into five layers based on their destination.

1 local communications

2 to association cortex

3 to association to cortex

4 neurons from thalamus

5 down to sub cortical areas

6 back to thalamus

FIGURE 6 Modular organization of the somatosensory cortex. (A) Organization of the primary receptive areas (darker blue; Brodmann's areas 1, 2, and 3, also called collectively S1) on the post-central gyrus of the cerebral cortex. Note that area 3 (both 3a and 3b) lies on the posterior wall of the central sulcus. Each area receives specific types (submodalities) of touch information from designated areas of the body in a somatotopic manner. (B) Detail of the 3b cortical area receiving information from mechanical receptors in three left-hand fingers. Projection neurons from the thalamus synapse in layer 4, within columns devoted to rapidly adapting (RA) and slowly adapting (SA) receptors. Fibers that project from the cortex segregate into five layers based on their destination.

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