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Foramen magnum
large opening at the base of the occipital bone through which the medulla is continuous with the spinal cord.
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Cauda equina
consists of a bundle of nerve roots of all of the spinal nerves caudal to the second lumbar vertebra
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Funiculus
a bundle containing one or more tracts, or fasciculi, in the spinal cord
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Gray commissure
a band of gray matter extending onto both sides of the spinal cord
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Renshaw cells
interneurons that make inhibitory (glycinergic) synapses of the alpha motor neurons and receive excitatory (cholinergic) collaterals from the same neurons
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Dermatome
the area of skin supplied by the right and left dorsal roots of a single spinal segment
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Fasciculus gracilis
first-order sensory neurons that project to the nucleus gracilis and conveys tactile sensation to the ipsilateral limb
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Fasciculus cuneatus
first-order sensory neurons contained in the dorsal funiculus that project to the nucleus cuneatus and conveys tactile sensation to the ipsilateral limb
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Cuneocerebellar tract
formed by axons arising from the accessory cuneate nucleus.
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Rostral Spinocerebellar tract
arises from the cervical cord and supplies the anterior lobe of the cerebellum, conveying whole limb movement to the anterior lobe from the upper limb.
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Spinothalamic tract
pathway from the spinal cord to the thalamus that mediates pain, temperature, and tactile sensation.
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Syringomyelia
developmental abnormality, characterized by expansion of the central canal of the spinal cord. Loss of pain and thermal sensation.
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Periaqueductal gray area
gray matter surrounding the cerebral aqueduct of the midbrain
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Corticospinal tract
major descending pathway from the cerebral cortex to the spinal cord that mediates voluntary control of motor activity.
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Tectospinal tract
pathway from the superior colliculus to cervical cord which mediates postural movements in response to visual stimuli reaching the superior colliculus.
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Inferior cerebellar peduncle
major afferent pathway to cerebellum from the medulla.
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Medulla
most caudal aspect of the brainstem extending from the pons to the spinal cord.
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Corticobulbar fibers
descending corticofugal fibers arising from lateral aspects of sensorimotor cortex. Also called corticonuclear fibers.
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Pyramidal tract
mediates voluntary control of movement of limbs and motor functions
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substantia gelatinosa
region of gray matter of the dorsal horn of spinal cord that reeives mainly pain and termperature inputs from the periphery.
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Reticular formation
- central core of the brainstem extending from the medulla through the midbrain. Functions include control of sensory, motor, and visceral processes and states
- of consciousness.
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Superior colliculus
rostral aspect of the tectum of midbrain associated with visual refplexes and tracking movements of the eyes.
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Inferior olivary nucleus
large nuclear structure situated in the ventrolateral medulla and relays transmission of impulses from the spinal cord and red nucleus to the cerebellum.
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Spino-olivary fibers
fibers originating in spinal cord that project to the inferior olivary nucleus
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Lateral medullary syndrome
(Wallenberg’s Syndrom) results from a vascular lesion of the veterbral and inferior posterior cerebellar artieries. Loss of pain and temperature, hoarseness, loss of gag relex, and difficulty swallowing.
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Midbrain
the most rostral aspect of the brainstem, situated between the forebrain and pons.
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pons
part of the brainstem extending from the midbrain to the medulla.
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Facial colliculus
a bulge found along the floor of the fourth ventricle formed from fibers of the facial nerve that pass over the dorsal aspect of the abducens nucleus.
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Abducens nucleus
general somatic efferent nucleus of the lower pons
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Facial nucleus
lies in the ventrolateral aspect of the tegmentum; innervates muscles controlling ipsilateral facial expression.
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Superior salivatory nucleus
located in lower pons and provides parasympathetic innervation to the salivary glands.
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Superior cerebellar peduncle
one of the three cerebellar peduncles constituting the major output pathway of the cerebellum.
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Mesencephalic nucleus of CN V
located in the upper pons that receives trigeminal inputs from the muscle spindles of the face region.
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Dentate nucleus
largest of deep cerebellar nuclei, axons project through the superior cerebellar peduncle to the ventrolateral nucleus of thalamus.
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Fastigial nucleus
deep cerebellar nucleus whose axons project to the reticular formation and vestibular nuclei.
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Corpora quadrigemina
superior and inferior colliculi.
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tectum
most dorsal part of the midbrain.
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tegmentum
dorsal aspect of the pons and midbrain containing the reticular formation and a variety of nuclear groups.
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substantia nigra
structure found in the ventral aspect of the midbrain associated with functions of the basal ganglia. Parts produce dopamine and gamma aminobutyric acid
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crus cerebri
ventral aspect of the midbrain containing principally corticospinal, coroticospinal, and corticopontine tracts
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Central tegmental area
region of the midbrain containing the reticular formation
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Pretectal region
most rostral region of the midbrain bordering n the diencephalon, part of the pathway mediating visual reflexes.
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Pupillary light reflex
- (pupillary constriction) the result of shining light into the eye which is the contraction
- of pupillary constrictor muscles and reduction of the size of the pupil
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Gaze palsy
(Parinaud’s syndrome) disorder characterized by an upward gaze paralysis, nystagmus with downward gaze, large pupil, abnormal elevation of the upper lid, from vascular lesion or pineal tumor.
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Benedikt’s syndrome
disorder affecting nerve fibers of cranial nerve III causing an oculomotor paralysis tremor of the contralateral limb, and somatosensory loss of the contralateral side of the body.
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Weber’s syndrome
disorder affecting the ventromedial midbrain, damaging oculomotor nerve fibers and axons causing ipsilateral oculomotor paralysis and upper motor neuron paralysis of the limbs.
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Medial geniculate nucleus
thalamic relay nucleus that transmits auditory information from inferior colliculus to the superior temporal gyrus
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Diencephalon
region of the forebrain which lies below the fornix and consists of the thalamus and hypothalamus.
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thalamus
dorsal and largest part of the diencephalon consistes of varieties of nuclie that project mainly to the cerebral cortex
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Hypothalamus
- ventral aspect of the diencephalon; concerns a variety of cell groups associated with
- diverse visceral functions – endocrine release of the pituitary, temperature
- regulation, feeding, drinking, sexual behavior, aggression, and rage.
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epithalamus
group of structures forming the roof of the diencephalon, includes habenular complex, stria medullaris, and pineal gland.
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subthalamus
group of structures in the posterior third of the diencephalon, including the subthalamic nucleus and the zona incerta
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Dorsomedial nucleus
nucleus situated in the dorsomedial aspect of the middle third of the thalamus; receives inputs from the limbic structures and is reciprocally connected with the prefrontal cortex
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Lateral geniculate nucleus
thalamic relay nucleus transmitting visual signals from the retina to the visual cortex
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Substantia innominate
region of the basal forebrain situated immediately lateral to the proptic region; linked to amygdala and projects to widespread regions of the cerebral cortex.
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Habenular commissure
commissure connecting the habenular complex on both sides of the epithalamus
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pineal gland
conical shaped structure attached to the roof of the posterior aspect of the third ventricle and displays a circadian rhythm
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Infundibular stalk
connecting link between the hypothalamus and pituitary gland
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vasopressin
antidiuretic hormone released from the posterior pituitary and causes water retention by decreasing kidney’s urine production
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Lenticular fasciculus
major efferent pathway of basal ganglia
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H field of Forel
region immediately rostral to the red nucleus where fibers of the lenticular fasciculus and ansa lenticularis merge and begin to course rostrally.
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Special visceral afferent neurons
components of afferent fibers of cranial nerves that are associated with the transmission of chemical sensation
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Special sensory afferent
neurons
afferent components of cranial nerves associated with the transmission of visual, auditory, and vestibular impulses
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Special visceral efferent neurons
cell groups that are derived from mesenchyme of the brachial arches
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Sulcus limitans
landmark in the developing nervous system that separates sensory from motor regions
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hypoglossal nerve
mainly a motor nerve which innervate the tongue and control the shape and position of it.
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Spinal accessory nerve (CN XI)
motor cranial nerve arising from ventral horn cells in the first 6 cervical segments that mediate turning and lifting the head
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Vagus nerve(CN X)
consists of various afferent and efferent fibers innervating thoracic and abdominal viscera and special visceral efferent fibers innervating the larynx and pharynx.
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Glossopharyngeal nerve (CN IX)
contains fibers which innervate the otic ganglion and special visceral efferent fibers which innervate the stylopharyngeus muscle.
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Vestibulochlear nerve (CN VIII)
special sensory afferent nerves mediating auditory and vestibular inputs through separate receptors inputs through separate receptors and neural pathways
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Facial Nerve (CN VII)
mixed cranial nerve of the lower pons that affects salivary, lacrimal, and pterygopalitine glands; also taste signals from the tongue, and innervates muscles of facial expression
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Trigerminal nerve (CN V)
supplies muscles of mastication to produce biting and chewing; sensation from palate, teeth, gum, face, and cornea.
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neuralgia
supporting cells located in the central nervous system; nonexcitable and more numerous than neurons
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jaw-jerk reflex
monosynaptic stretch reflex, occurring after stimulation of muscle spindles in the masseter muscle of the lower jaw causing a jaw closing response
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Tic douloureux
trigeminal neuralgia (severe pain in the face)
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flower-spray endings
secondary afferents arising from intrafusal fibers located on nuclear chain and nuclear bag fibers on each of the annulosprial endings
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Pacinian corpuscles
low-threshold, rapidly adapting receptors sensitive to rapid indentation of the skin caused by high frequency vibrations; located in dermis layer of hairy and glabrous skin
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Intrafural fibers
eight to ten specialized muscle fibers in the connective tissue capsule of a muscle spindle
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Extrafusal fibers
large skeletal muscle fibers surrounding the connective tissue capsule of a muscle spindle; involved in the movement of the limb.
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gamma-motor neurons
neurons interspersed between alpha-motor neurons in the ventral horn of the spinal cord; regulate the sensitiviey of muscle spindles.
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Annulospiral endings
primary afferents arising from intrafusal fibers; located on the central part of the nuclear bag and nuclear chain fibers
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Neospinothalamic tract
major ascending pathway involved in conveying pain signals to higher centers
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Hyperalgesia
enhancement of the pain sensation.
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causalgia
characterized by burning sensation caused by increased sympathetic efferent activity after a peripheral nerve injury
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Substance P
an undecapeptide (composed of 11 amino acids); a neurotransmitter or neuromodulator.
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glutamate
major excitatory amino acid neurotransmitter in the central nervous system synthesized from glutamine in presence of the enzyme glutaminase
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Noradrenergic pathway
descending pathway that inhibits dorsal horn neurons that relay pain sensation by activating enkephalingeric interneurons
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