11 - Motor Control and Plasticity Flashcards
Reflex
A simple, highly stereotyped, and unlearned response to a particular stimulus (e.g., an eye blink in response to a puff of air)
Spinal animal
An animal whose spinal cord has been surgically disconnected from the brain to enable the study of behaviors that do not require brain control
Movement
A brief, unitary activity of a muscle or body part; less complex than an act.
Act
Also called action pattern. Complex behavior, as distinct from a simple movement
Motor plan
Also called motor program. A plan for action in the nervous system
Electromyography (EMG)
The electrical recording of muscle activity
Closed-loop control mechanism
A control mechanism that provides a flow of information from whatever is being controlled to the device that controls it
Ramp movement
Also called smooth movement. Slow, sustained motion that is often controlled by the basal ganglia
Open-loop control mechanism
A control mechanism in which feedback from the output of the system is not provided to the input control
Ballistic movement
A rapid muscular movement that is often organized or programmed in the cerebellum
Smooth muscle
A type of muscle fiber, as in the heart, that is controlled by the autonomic nervous system rather than by voluntary control
Tendon
Strong tissue that connects muscles to bone
Antagonist
A muscle that counteracts the effect of another muscle
Synergist
A muscle that acts together with another muscle
Muscle fiber
A collection of large cylindrical cells, making up most of a muscle, that can contract in response to neurotransmitter released from a motoneuron
Striated muscle
A type of muscle with a striped appearance, generally under voluntary control
Myosin
A protein that, along with actin, mediates the contraction of muscle fibers
Actin
A protein that, along with myosin, mediates the contraction of muscle fibers
Fast-twitch muscle fiber
A type of striated muscle that contracts rapidly but fatigues readily
Slow-twitch muscle fiber
A type of striated muscle fiber that contracts slowly but does not fatigue readily
Motoneuron
Also called motor neuron. A nerve cell in the spinal cord that transmits motor messages from the spinal cord to muscles.
Acetylcholine (ACh)
A neurotransmitter produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain
Neuromuscular junction (NMJ)
The region where the motoneuron terminal and the adjoining muscle fiber meet; the point where the nerve transmits its message to the muscle fiber
Motor unit
A single motor axon and all the muscle fibers that it innervates
Innervation ratio
The ratio expressing the number of muscle fibers innervated by a single motor axon
Final common pathway
The information processing pathway consisting of all the motoneurons in the body. Motoneurons are known by this collective term because they receive and integrate all motor signals from the brain and then direct movement accordingly
Size principle
The idea that, as increasing numbers of motor neurons are recruited to produce muscle responses of increasing strength, small, low-threshold neurons are recruited first, followed by large, high-threshold neurons
Proprioception
Body sense; information about the position and movement of the body that is sent to the brain
Muscle spindle
A muscle receptor that lies parallel to a muscle and sends impulses to the central nervous system when the muscle is stretched
Intrafusal fiber
One of the small muscle fibers that lie within each muscle spindle
Extrafusal fiber
One of the ordinary muscle fibers that lie outside the spindles and provide most of the force for muscle contraction
Primary sensory ending
Also called annulospiral ending. The axon that transmits information from the central portion of a muscle spindle
Secondary sensory ending
Also called flower spray ending. The axon that transmits information from the ends of a muscle spindle
Gamma motoneuron
Also called gamma efferent. A motor neuron that innervates the contractile tissue in a muscle spindle
Alpha motoneuron
A motoneuron that control the main contractile fibers (extrafusal fibers) of a muscle
Golgi tendon organ
One of the receptors located in tendons that send impulses to the central nervous system when a muscle contracts
Stretch reflex
The contraction of a muscle in response to stretch of that muscle
Central pattern generator
Neural circuitry that is responsible for generating the rhythmic pattern of a behavior such as walking
Pyramidal system or corticospinal system
The motor system that includes neurons within the cerebral cortex and their axons, which form the pyramidal tract
Primary motor cortex (M1)
The apparent executive region for the initiation of movement; primarily the precentral gyrus
Nonprimary motor cortex
Frontal lobe regions adjacent to the primary motor cortex that contribute to motor control and modulate the activity of the primary motor cortex
Supplementary motor area (SMA)
A region of non-primary motor cortex that receives input from the basal ganglia and modulates the activity of the primary motor cortex
Premotor cortex
A region of non-primary motor cortex just anterior to the primary motor cortex
Mirror neuron
A neuron that is active both when an individual makes a particular movement and when an individual sees another individual make that same movement
Extrapyramidal system
A motor system that includes the basal ganglia and some closely related brainstem structures
Reticular formation
An extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal (waking)
Reticulospinal tract
A tract of axons arising from the brainstem reticular formation and descending to the spinal cord to modulate movement
Red nucleus
A brainstem structure related to motor control
Rubrospinal tract
A tract of axons arising from the red nucleus in the midbrain and innervating neurons of the spinal cord
Basal ganglia
A group of forebrain nuclei, including caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres
Striatum
The caudate nucleus and putamen together
Muscular dystrophy (MD)
A disease that leads to degeneration of and functional changes in muscles
Dystrophin
A protein that is needed for normal muscle function
Myasthenia gravis
A disorder characterized by a profound weakness of skeletal muscles; caused by a loss of acetylcholine receptors
Autoimmune disorder
A disorder caused when the immune system mistakenly attacks a person’s own body, thereby interfering with normal functioning
Polioviruses
A class of viruses that destroy motoneurons of the spinal cord and brainstem
Amyotrophic lateral sclerosis (ALS)
Also called Lou Gehrig’s disease. A disease in which motoneurons and their target muscles waste away
Flaccid paralysis
A loss of reflexes below the level of transection of the spinal cord
Plegia
Paralysis, the loss of the ability to move
Paresis
Partial paralysis
Spasticity
Markedly increased rigidity in response to forced movement of the limbs
Apraxia
An impairment in the ability to begin and execute skilled voluntary movements, even though there is no muscle paralysis
Ideomotor apraxia
The inability to carry out a simple motor activity in response to a verbal command, even though this same activity is readily performed spontaneously
Ideational apraxia
An impairment in the ability to carry out the sequence of actions, even though each element or step can be done correctly
Parkinson’s disease
A degenerative neurological disorder, characterized by tremors at rest, muscular rigidity, and reduction in voluntary movement, that involves dopaminergic neurons of the substantia nigra
Substantia nigra
A brainstem structure in humans that innervates the basal ganglia and is named for its dark pigmentation
a-synuclein
A protein that has been implicated in Parkinson’s disease
Parkin
A protein that has been implicated in Parkinson’s disease
L-dopa
The immediate precursor of the transmitter dopamine
Huntington’s disease
Also called Huntington’s chorea. A progressive genetic disorder characterized by abrupt, involuntary movements and profound changes in mental functioning
Huntingtin
A protein produced by a gene (called HTT) that, when containing too many trinucleotide repeats, results in Huntington’s disease in a carrier
Trinucleotide repeat
Repetition of the same three nucleotides within a gene, which can lead to dysfunction, as in the cases of Huntington’s disease and fragile X syndrome
Spinocerebellum
The uppermost part of the cerebellum, consisting mostly of the vermis and anterior lobe
Ataxia
An impairment in the direction, extent, and rate of muscular movement, often caused by cerebellar pathology
Cerebrocerebellum
The lowermost part of the cerebellum, consisting especially of the lateral parts of each celebellar hemisphere
Decomposition of movement
Difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly; a symptom of cerebellar lesions
Vestibulocerebellum
The middle portion of the cerebellum, sandwiched between the spinocerebellum and and the cerebrocerebellum and consisting of the nodule and the flocculus
