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abducens (VI) nerve: cranial nerve; axons innervate the lateral rectus muscle
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abducens nucleus: contains lateral rectus motor neurons and internuclear neurons; located in pons
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accessory cuneate nucleus: relays somatic sensory information from upper trunk, arm, and neck to the cerebellum; located in medulla
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accessory (XI) nerve: cranial nerve that innervates the sternocleidomastoid muscle and the upper part of the trapezius muscle
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accessory optic system: transmits visual information to brain stem nuclei for eye movement control
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accommodation-convergence reaction: a complex response that prepares the eyes for near vision by (1) increasing lens curvature, (2) constricting the pupils, and (3) coordinating convergence of the eyes
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accommodation reflex: increase in lens curvature that occurs during near vision
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acetylcholine: neurotransmitter used by motor neurons and neurons in several nuclei, including the basal nucleus and the pedunculopontine nucleus
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acetylcholinesterase: enzyme that inactivates acetylcholine
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acousticomotor function: motor behavioral response triggered or controlled by sound such as orienting towards a sound
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adrenergic: neuron that uses adrenalin as a neurotransmitter or neuromodulator
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afferent: axons that transmit information toward a particular structure; afferent is not synonymous with sensory, which means related to processing information from a receptor sheet (eg, body surface or retina)
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airway protective reflex: closure of the larynx to prevent fluid and food from entering the trachea
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akinesia: impairment in initiating voluntary movement
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alar plate: dorsal portion of the neuroepithelium that gives rise to sensory nuclei of the spinal cord and brain stem
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allocortex: cortex having a variable number of layers, but always fewer than six
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alveus: thin sheet of myelinated axons covering hippocampal formation; axons of pyramidal neurons in the hippocampus and subiculum
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Alzheimer disease: presenile dementia
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amacrine cells: retinal interneuron
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amygdala: telencephalic structure that plays an essential role in emotions and their behavioral expression; has three component nuclear divisions: basolateral, central, and corticomedial
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amygdaloid nuclear complex: another name for the amygdala
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anastomosis: a network of interconnected arteries
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aneurysm: an abnormal ballooning of a part of an artery due to weakening of the arterial wall
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angiogram: radiological image of vasculature
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anosmia: absence of the sense of smell
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ansa lenticularis: output pathway of the internal segment of the globus pallidus; axons terminate in the thalamus
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anterior: toward the abdomen; synonymous with ventral
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anterior cerebral artery: supplies blood to the medial frontal lobes and underlying deep structures
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anterior choroidal artery: supplies blood to the choroid plexus in the lateral ventricle and several deep structures
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anterior cingulate gyrus: portion of the cingulate important for emotions; activated while experiencing ...