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abducens (VI) nerve: cranial nerve; axons innervate the lateral rectus muscle

abducens nucleus: contains lateral rectus motor neurons and internuclear neurons; located in pons

accessory cuneate nucleus: relays somatic sensory information from upper trunk, arm, and neck to the cerebellum; located in medulla

accessory (XI) nerve: cranial nerve that innervates the sternocleidomastoid muscle and the upper part of the trapezius muscle

accessory optic system: transmits visual information to brain stem nuclei for eye movement control

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

accommodation reflex: increase in lens curvature that occurs during near vision

acetylcholine: neurotransmitter used by motor neurons and neurons in several nuclei, including the basal nucleus and the pedunculopontine nucleus

acetylcholinesterase: enzyme that inactivates acetylcholine

acousticomotor function: motor behavioral response triggered or controlled by sound such as orienting towards a sound

adrenergic: neuron that uses adrenalin as a neurotransmitter or neuromodulator

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)

airway protective reflex: closure of the larynx to prevent fluid and food from entering the trachea

akinesia: impairment in initiating voluntary movement

alar plate: dorsal portion of the neuroepithelium that gives rise to sensory nuclei of the spinal cord and brain stem

allocortex: cortex having a variable number of layers, but always fewer than six

alveus: thin sheet of myelinated axons covering hippocampal formation; axons of pyramidal neurons in the hippocampus and subiculum

Alzheimer disease: presenile dementia

amacrine cells: retinal interneuron

amygdala: telencephalic structure that plays an essential role in emotions and their behavioral expression; has three component nuclear divisions: basolateral, central, and corticomedial

amygdaloid nuclear complex: another name for the amygdala

anastomosis: a network of interconnected arteries

aneurysm: an abnormal ballooning of a part of an artery due to weakening of the arterial wall

angiogram: radiological image of vasculature

anosmia: absence of the sense of smell

ansa lenticularis: output pathway of the internal segment of the globus pallidus; axons terminate in the thalamus

anterior: toward the abdomen; synonymous with ventral

anterior cerebral artery: supplies blood to the medial frontal lobes and underlying deep structures

anterior choroidal artery: supplies blood to the choroid plexus in the lateral ventricle and several deep structures

anterior cingulate gyrus: portion of the cingulate important for emotions; activated while experiencing ...

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