Vogel 3 Flashcards
Four main CNS divisions
- cerebrum
- cerebellum
- brainstem
- spinal cord
Brainstem includes:
- diencephalon
- mesencephalon
(midbrain) - pons
- medulla oblongata
brain + spinal cord
Central Nervous System
cranial nerves + spinal nerves + ganglia
Peripheral Nervous System
In the CNS, neuron cell bodies reside in ____, and their axons (fibers) extend in _____. The CNS arises from the ______.
- Nuclei
- Tracts
- Neural tube
In the PNS, neuron cell bodies reside in _____, and their axons (fibers) extend in _____. The PNS arises from the _______ (motor neuron cell bodies reside in the CNS, and thus they arise from the neural tube).
- Ganglia
- Nerves
- Neural crest
The brain develops from the portion of the neural tube cranial (rostral) to the level of the fourth pair of somites. Initially, there are three primary brain vesicles:
- prosencephalon (forebrain)
- mesencephalon (midbrain)
- rhombencephalon (hindbrain)
During the fifth week of development, the prosencephalon becomes subdivided into the _______, and the rhombencephalon is subdivided into the ________- with the undivided mesencephalon, a total of five secondary brain vesicles.
- telencephalon and the diencephalon
- metencephalon and the myelencephalon
The neuroepithelial cells immediately adjacent to the central canal form the _________, which generates neuroblasts and macroglia.
ventricular zone (neuroepithelial layer)
Neuroblasts migrate and form the ________ which later becomes the gray matter of the spinal cord.
intermediate zone
The axons emerging from these neuroblasts make up the ________ and eventually become myelinated; this external layer will give rise to the white matter of the spinal cord.
marginal zone
As neuroblasts are added to the intermediate zone, each wall of the neural tube develops a ventral thickening, the _____, and a dorsal thickening, the _____, separated by a longitudinal groove, the ______.
- basal plate
- alar plate
- sulcus limitans
Neuroblasts in the basal plate are associated with _____ functions; neuroblasts in the alar plate are associated with _____ functions.
- motor
- sensory
Forms cerebral hemispheres and lateral ventricles
Telencephalon
Forms thalami and third ventricle
Diencephalon
Forms midbrain and aqueduct
Mesencephalon
Forms pons, cerebellum, and upper part of fourth ventricle
Metencephalon
Forms medulla and lower part of fourth ventricle
Myelencephalon
Enlargements
- cervical
* lumbosacral
Spinal nerves
31 pairs • cervical = 8 pairs • thoracic = 12 pairs • lumbar = 5 pairs • sacral = 5 pairs
Sulci, fissures, and septa
- dorsal (posterior) median sulcus
- dorsal intermediate sulcus
- dorsolateral (posterolateral) sulcus
- ventrolateral (anterolateral) sulcus
- ventral (anterior) median fissure
In general, the neuron cell bodies located in this region of the spinal cord gray matter are involved in the transmission and processing of pain and temperature sensory information.
Dorsal horn
Consists of neuron cell bodies that receive pain and temperature information from dorsal root ganglion (DRG) sensory neurons. Appears “bright white” in the spinal cord sections, and is present at all levels. (Rexed lamina II)
Substantia gelatinosa
The neuron cell bodies located in this region of spinal cord gray matter are involved in the transmission and processing of either autonomic information, or unconscious (non- conscious) proprioception (“position sense”) information.
Intermediate horn
cell bodies of preganglionic
sympathetic neurons, found at spinal cord levels T1-L2
Intermediolateral cell column (IMLCC)
cell bodies of preganglionic
parasympathetic neurons for innervation of pelvic viscera, found at spinal cord levels S2-S4
Sacral parasympathetic nucleus
cell bodies of neurons that project axons in the dorsal spinocerebellar tract. Found at levels T1-L2/L3
Nucleus dorsalis of Clarke
cell bodies of neurons that decussate, and project axons in the ventral spinocerebellar tract. Found at levels L1-S2
Spinal border cells
Most of the neuron cell bodies located in this region of the spinal cord are alpha motor neurons that innervate voluntary skeletal muscles in the trunk, limbs, and neck. These neurons receive information (“input”) from a variety of neurons located in higher regions of the CNS (e.g. cerebral cortex), and are thus often referred to as “lower motor neurons”.
Ventral Horn
Alpha motor neurons are not randomly arranged in the ventral horns: the locations of the cell bodies are correlated with the locations and functions of the muscles that they innervate. This principle of mapping body parts onto the neurons that innervate them, and maintaining this map throughout all the connections in the CNS, is referred to as __________.
somatotopic organization
The terms “funiculus”, “fasciculus”, and “tract” all refer to bundles, or cables, of axons; these appear as _______ because of the myelin insulation, produced by oligodendrocytes (CNS) and Schwann cells (PNS).
white matter
In the spinal cord, tracts are grouped into a ______ (between the dorsal median fissure and dorsolateral sulcus), a _______ (between the dorsolateral sulcus and ventrolateral sulcus), and a _______ (between the ventrolateral sulcus and ventral median fissure).
- dorsal funiculus
- lateral funiculus
- ventral funiculus
Axons _____ (project towards the brain) or _____ (project towards the caudal end of the spinal cord) within the funiculi.
- ascend
- descend
Ascending tract, consists of central axons of DRG neurons
transmitting discriminative touch, conscious (destined for the cerebral cortex) proprioception, and vibratory sense from the lower limbs and lower trunk. Present at all levels of the spinal cord.
Fasciculus gracilis
Ascending tract, consists of central axons of DRG neurons transmitting discriminative touch, conscious proprioception, and vibratory sense from the upper limbs and upper trunk. Present only above (rostral to) spinal cord level T6.
Fasciculus cuneatus
Consists of the axons of
neurons in the nucleus dorsalis of Clarke. Transmits unconscious proprioceptive information from the individual muscles of the lower limb, to the cerebellum.
Dorsal (posterior) spinocerebellar tract
Consists of the axons of spinal border cell neurons. Transmits unconscious proprioceptive information about the position and movement of the lower limbs to the cerebellum.
Ventral (anterior) spinocerebellar tract
Consists of the axons of dorsal horn neurons. Transmits pain, itch, temperature, tickle, and sexual sensation (“PITTS”) information from the body.
(Lateral) spinothalamic tract
Consists of the axons of cerebral cortical
neurons that transmit commands for movement to the alpha motor
neurons in the ventral horn.
Lateral corticospinal tract
Consists of the axons of neurons in the red nucleus
of the midbrain, which transmit modulatory information to alpha motor neurons that innervate axial and proximal flexor muscles. The functional and clinical significance of this tract is minimal; in fact, it may not be present in humans.
Rubrospinal tract
descending control of autonomic neurons (e.g. IMLCC) from the hypothalamus.
Hypothalamospinal axons
Contains several smaller motor tracts, descending from the cerebral cortex and brainstem.
Ventral Funiculus
Tracts of the Ventral Funiculus
a. Anterior corticospinal tract
b. Vestibulospinal tracts (medial and lateral)
c. Reticulospinal tracts (medial and lateral)
- All voluntary movement is abolished, completely and permanently.
- All sensation arising from below the level of the lesion is abolished, completely and permanently.
- All local reflexes involving spinal segments below the level of the lesion are temporarily abolished.
Transection of the Spinal Cord
- Spastic paralysis ipsilateral to the lesion.
- Loss of conscious proprioception, discriminative touch, and vibratory sense ipsilateral to the lesion.
- Loss of pain and temperature sensation contralateral to the lesion.
Hemisection of the Spinal Cord (Brown-Sequard Syndrome)
