PSYC 2200 Reading 14

motor homunculus

map depicting the proportion of motor cortex areas devoted to certain body parts

corticospinal tracts

bundles of axons that descend from cerebral motor cortex and connects to the spinal cord, has 2 tracts, essential for voluntary control over skeletal muscles.

lateral corticospinal tract

majority of corticalspinal fibers in pyramidal area that cross over to the other side of the body, playing a integral role in the conscious motor control of distal limbs and digits

anterior/ventral corticospinal tract

smaller proportion of corticospinal fibers that do not cross over in the medulla, but decussate at the level of the lower motor neuron and control the muscles of the core or midline of the body

betz cells

giant pyramidal cells located in layer V of the primary cortex, in the lateral and anterior corticospinal tracts

corona radiata

projection of nerve fibers that connect the cerebral cortex to the brainstem and spinal cord

medullary pyramids

areas in the brainstem medulla containing the corticospinal tract, where the lateral corticospinal tracts cross over/decussate

upper motor neurons

bundles of axons extending from the cell bodies in the motor cortex that comprise the corticospinal tracts and project to the lower motor neurons of the anterior gray horns of the spinal cord

lower motor neurons

essential motor neurons in the gray matter of the spinal cord that specifically arise from the ventral horn of the spinal cord

spinal cord

transit system for motor neural signal

alpha motor neurons

lower motor neurons, axons of which exit the spinal cord via ventral roots, directly responsible for contractions of skeletal muscles

dorsal roots

carry sensory (afferent info)

ventral roots

carry motor (efferent) info

reflexes

very fast involuntary movement responses to stimuli

reflex arc

very fast neural network that processes a motor reaction to a sensory stimuli outside the domain of the cortex

cardiac muscle

heart muscle, involuntary control

smooth muscle

muscles located in the organs, such as the stomach, considered under involuntary control

skeletal (striatal) muscles

muscles found throughout the body, considered to depend on volition to be activated, voluntary control

biofeedback

training techniques to control physiological responses that are typically viewed as involuntary, such as heart rate or blood pressure

extrafusal fibers

muscle cells that contract to shorten a muscle

intrafusal fibers

muscle cells that detect changes in muscle length

motor unit

the alpha motor neuron in the ventral horn of the gray matter of the spinal cord, its axon, and the extrafusal muscle fibers it innervates

neuromuscular junction

synapse formed when the axon terminal of a motor neuron positions itself in the motor end plate (acetylcholine is the neurotransmitter released)

motor end plate

section of extrafusal muscle fiber that is highly excitable and appropriate for the initiation of action potentials; forms a synapse with the axon terminal of a motor neuron

antagonistic muscle

muscles that produce actions that are opposite of one another (bicep and tricep)

proprioception

ability to sense the position orientation, and movement of one’s own body

muscle spindle

intrafusal muscle sensory organ for detecting stretch in the muscle, with receptor endings that extend from gamma motor neurons in the spinal cord to wrap around the intrafusal muscle fibers

gamma motor neurons

efferent nerve cells in spinal cord that innervate muscle spindles

golgi tendon organ

sensory organ located in the tendon that sends a message back to the nervous system to initiate compensatory action if a muscle contract excessively

monosynaptic spinal reflex

a reflex arc containing a single synapse of one sensory neuron and one motor neuron (determined by knee-jerk test)

central pattern generators

networks of neurons that spontaneously generate patterns of activity such as walking

supplementary motor complex

cluster of cortical areas located in the dorsomedial frontal cortex that helps to guide the execution of complex voluntary movements

supplementary motor area

part of the motor cortex that activates when a person imagines performing a complex motor task, like finger movement sequences of a musician

presupplementary motor area

part of the motor cortex that is activated during tasks involving executive control, such as deciding to suppress a response or switch tasks, conducting a difficult procedure with constantly changing conditions

premotor cortex

located ventral to supplementary motor complex and directly in front of primary motor cortex, cortex activated for motor skills less dependent on self-initiation and more dependent on the external guidance of movement

basal ganglia

collection of nuclei that surround the thalamus and regulate movement

caudate nucleus

in basal ganglia, communicates with cerebral cortex to contribute to the efficient execution of appropriate movements

putamen

in basal ganglia, communicates with cerebral cortex to contribute to the efficient execution of appropriate movements

globus pallidus

in basal ganglia, critical for the regulation of movement; output typically inhibits unwanted movements

substancia nigra

“black substance,” pair in tegmentum in midbrain known for production of neurochemical important for smooth physical movement; communicates with the basal ganglia

striatum

caudate nucleus and putamen

vermis

in midline of cerebellum, thought to regulate muscle tone

lateral cerebellar hemispheres

largest portions of the cerebellum, containing deep nuclei that communicate with various motor and non-motor areas of the cerebral cortex

denate nucleus

communicates in a structured, maplike fashion with the various motor and nonmotor areas of the cerebral cortex

flocculonodular lobe

oldest part of the cerebellum, thought to support fundamental motor functions such as the maintenance of balance and posture

cerebellar peduncles

neural communication transit system at the foot of the cerebellum; connects to other brain areas such as the cerebral cortex

cerebellum

plays role in movements, coordination, balance, and muscle tone

cerebellar cognitive affective syndrome

clinical disorder characterized by the emergence of cognitive deficits following cerebellar damage, impairs executive function, language, sequencing events, and visuospatial abilities