KINES 360 Exam 3

Upper Motor Neurons

neuron that gives rise to a descending projection that controls the activity of lower motor neurons in the brainstem and spinal cord

Cerebellum

prominent hindbrain structure concerned with motor coordination, posture, and balance, composed of three-layered cortex and deep nuclei, attached to brainstem by the cerebellar penduncles

Primary Motor Cortex

major source of descending projections to motor neurons in the spinal cord and cranial nerve nuclei, located in the precentral gyrus (Broddman's area 4) and essential for the voluntary control of movement

Premotor Cortex

motor association areas in the frontal lobe anterior to the primary motor cortex, thought to be involved in planning or programming of voluntary movements

Basal Ganglia

group of nuclei lying deep in the subcortical white matter of the frontal lobes that organize motor behavior (caudate, putamen, and globus pallidus are the major components, subthalamic nucleus and substantia nigra are often included)

Alpha Motor Neurons

neurons in the ventral horn of the spinal cord that innervate skeletal muscle

Gamma Motor Neurons

class of spinal motor neurons specifically concerned with the regulation of muscle spindle length, these neurons innervate the intrafusal muscle fibers of the spindle

Motor Unit

motor neuron and the skeletal muscle fibers it innervates, more loosely, the collection of skeletal muscle fibers innervated by a single motor neuron

Size Principle

orderly recruitment of motor neurons by size to generate increasing amounts of muscle tension

Muscle Spindles

highly specialized sensory organs found in most skeletal muscles, provide mechanosensory information about muscle length

Muscle Tone

normal, ongoing tension in a muscle, measured by resistance of a muscle to passive stretching

Medullary Pyramids

longitudinal bulges on the ventral aspect of the medulla that signify the corticobulbar and corticospinal tracts at the level of the neuraxis

Corticospinal Tract

pathway carrying motor information from the primary and secondary motor cortices to the spinal cord (essential for performance of discrete voluntary movements, especially for those of the hands and feet)

Broca's Area

area in the left frontal lobe specialized for the production of speech

Reticular Formation

a network of neurons and axons that occupies the core of the brainstem, giving it a reticulated (net-like) appearance in myelin stained material, major functions include control of respiration and heart rate, posture, and state of consciousness

Superior Colliculus

laminated structure that forms part of the roof of the midbrain, plays an important role in orienting movements of the head and eyes

Rubospinal Tract

in non-human mammals, the pathways from the red nucleus of the midbrain to the spinal cord, essential for normal gait and motion, in humans however, the corticospinal tract serves this function and the rubospinal tract is vestigial (perhaps nonexistent)

Upper Motor Neuron Syndrome

signs and symptoms that result from damage to descending motor pathways, these include paralysis, spasticity, and a positive Babinski sign

Spinal Shock

initial flaccid paralysis that accompanies damage to descending motor pathways

Decerebrate Rigidity

excessive tone is extensor muscles as a result to damage to descending pathways at the level of the brainstem

Corpus Striatum

general term applied to the caudate and putamen, name derived from the striated (striped) appearance of these basal ganglia nuclei

Caudate

one of the three major components of the basal ganglia

Medium Spiny Neurons

principle projection neuron of the caudate and the putamen

Globus Pallidus

one of the three major nuclei that make up the basal ganglia in the cerebellar hemispheres, relays information from the caudate and putamen to the thalamus

Substantia Nigra

basal ganglionic nucleus at the base of the midbrain that receives input from several cortical and subcortical structures , the cells of the pars compacta send their output to the caudate/putamen and the cells of the pars reticulata send their output to the thalamus

Internal Segment

subdivision of the globus pallidus

External Segment

subdivision of the globus pallidus

Subthalamic Nucleus

in the ventral thalamus and receives input from the caudate/putamen and participates in the modulation of motor behavior

Parkinson's Disease

neurodegenerative disease of the substantia nigra that results in a characteristic tremor at rest and a general paucity of movement

Huntington's Disease

autosomal dominant genetic disorder in which a single gene mutation results in personality changes, progressive loss of control of voluntary movement, and eventually death, primary target is the basal ganglia

Hemiballismus

basal ganglia syndrome resulting from damage to the subthalamic nucleus and characterized by violent involuntary movement of the limbs

Cerebrocerebellum

part of the cerebellar cortex that receives input from the cerebral cortex via axons from the pontine relay nuclei

Vestibulocerebellum

part of the cerebellar cortex that receives direct input from the vestibular nuclei or vestibular nerve

Spinocerebellum

region of the cerebellar cortex that receives input from the spinal cord, particularly Clarke's nucleus in the thoracic spinal cord

Cerebellar Peduncles

three bilateral pairs of axon tracts that carry information to and from the cerebellum

Superior Cerebellar Peduncle

efferent motor pathway

Middle Cerebellar Peduncle

afferent pathway arising from the pontine nuclei

Pontine Nuclei

collections of neurons in the pons that receive input from the cerebral cortex and send their axons across the midline to the cerebellar cortex via the middle cerebellar peduncle

Inferior Cerebellar Peduncle

smallest but most complex, encompasses multiple pathways (afferent and efferent- mixed)

Red Nucleus

midbrain structure involved in motor coordination, especially in non-human mammals

Climbing Fibers

axons that originate in the inferior olive, ascend through the inferior cerebellar peduncle and make terminal arborizations that invest the dendrite tree of purkinje cells

Basket Cells

inhibitory interneurons in the cerebellar cortex whose cell bodies are located within the purkinje cell layer and whose axons make basketlike terminal arbors around purkinje cell bodies

Cerebellar Ataxia

pathological inability to make coordinated movements, associated with lesions to the cerebellum

Intention Tremors

tremors that occur while performing a voluntary motor act (characteristic of cerebellar pathology)

Dysmetria

inaccurate movements due to faulty judgement of distance, especially over or under reaching (characteristic of cerebellar pathology)

Dysdiadochokinesia

difficulty performing rapid alternating movements

Nystagmus

nodding, repetitive movements of the eyes normally elicited by large-scale movements of the visual field, absences of appropriate stimuli indicates brain stem or cerebellar pathology

Saccades

ballistic, conjugate eye movements that change the point of foveal fixation

Trochlear Nerve

cranial nerve IV, an efferent motor nerve that controls the superior oblique muscle of the eye

Abducens Nerve

cranial nerve VI, and efferent nerve that controls the later rectus muscle of the eye

Smooth Pursuit Movements

slow, tracking movements of the eyes designed to keep a moving object alligned with the fovea

Near Reflex Triad

reflexive response induced by changing binocular fixation to a closer target, comprises convergence, accommodation and pupillary constriction

Vestibulo-Ocular Reflex

involuntary movement of the eyes in response to displacement of the head (allows retinal images to remain stable while the head is moved)

Optokinetic Eye Movements

movements of the eyes that compensate for head movements, the stimulus for optokinetic movements is large scale motion of the visual field

Conjugate Eye Movements

paired movements of the two eyes in the same direction, as occurs in the vestibulo-ocular reflex

Disjunctive Eye Movements

movements of the two eyes in opposite directions (vergence movements)

Optokinetic Nystagmus

repeated reflexive responses of the eyes to ongoing large-scale movements of the visual scene

Medial Longitudinal Fasciculus

axon tract that carries excitatory projections from the abducens nucleus to the contralateral oculomotor nucleus, important in coordination conjugate eye movements

Frontal Eye Field

region of the frontal lobe that lies in a rostral portion of the premotor cortex and that contains cells that respond to visual and motor stimuli

Optic Tectum

the first central station of many non-mammalian vertebrates (analogous to the superior colliculus in mammals)