Chapter 11 Flashcards

α-synuclein
A protein that has been implicated in Parkinson’s disease.
acetylcholine (ACh)
A neurotransmitter produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain.
actin
A protein that, along with myosin, mediates the contraction of muscle fibers. See Figure 11.7.
alpha motoneuron
A motoneuron that controls the main contractile fibers (extrafusal fibers) of a muscle. See Figure 11.9. Compare gamma motoneuron.
amyotrophic lateral sclerosis (ALS)
Also called Lou Gehrig’s disease. A disease in which motoneurons and their target muscles waste away.
antagonist
1. A molecule, usually a drug, that interferes with or prevents the action of a transmitter. Compare agonist (definition 1). 2. A muscle that counteracts the effect of another muscle. Compare agonist (definition 2) and synergist.
apraxia
An impairment in the ability to begin and execute skilled voluntary movements, even though there is no muscle paralysis. See also ideational apraxia and ideomotor apraxia.
ataxia
An impairment in the direction, extent, and rate of muscular movement; often caused by cerebellar pathology.
autoimmune disorder
A disorder caused when the immune system mistakenly attacks a person’s own body, thereby interfering with normal functioning.
ballistic movement
A rapid muscular movement that is often organized or programmed in the cerebellum. Compare ramp movement.
basal ganglia
A group of forebrain nuclei, including caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres. See Figures 2.13, 2.17, 11.19.
central pattern generator
Neural circuitry that is responsible for generating the rhythmic pattern of a behavior such as walking.
cerebrocerebellum
The lowermost part of the cerebellum, consisting especially of the lateral parts of each cerebellar hemispehere. It is implicated in planning complex movements. Compare spinocerebellum and vestibulocerebellum.
closed-loop control mechanism
A control mechanism that provides a flow of information from whatever is being controlled to the device that controls it. See Figure 11.3. Compare open-loop control mechanism.
corticospinal system
See pyramidal system.
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.
deep brain stimulation (DBS)
Mild electrical stimulation through an electrode that is surgically implanted deep in the brain.
dystrophin
A protein that is needed for normal muscle function. Dystrophin is defective in some forms of muscular dystrophy.
electromyography (EMG)
The electrical recording of muscle activity. See Figure 11.2.
extrafusal fiber
One of the ordinary muscle fibers that lie outside the spindles and provide most of the force for muscle contraction. See Figure 11.9. Compare intrafusal fiber.
extrapyramidal system
A motor system that includes the basal ganglia and some closely related brainstem structures.
fast-twitch muscle fiber
A type of striated muscle that contracts rapidly but fatigues readily. Compare slow-twitch muscle fiber.
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.
flaccid paralysis
A loss of reflexes below the level of transection of the spinal cord.
gamma motoneuron
Also called gamma efferent. A motor neuron that innervates the contractile tissue in a muscle spindle. See Figure 11.9. Compare alpha motoneuron.
Golgi tendon organ
One of the receptors located in tendons that send impulses to the central nervous system reporting muscle tension. See Figure 11.9.
huntingtin
A protein produced by a gene (called HTT) that, when containing too many trinucleotide repeats, results in Huntington’s disease in a carrier.
Huntington’s disease
Also called Huntington’s chorea. A progressive genetic disorder characterized by abrupt, involuntary movements and profound changes in mental functioning.
ideational apraxia
An impairment in the ability to carry out a sequence of actions, even though each element or step can be done correctly. Compare ideomotor apraxia.
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. Compare ideational apraxia.
innervation ratio
The ratio expressing the number of muscle fibers innervated by a single motor axon. The fewer muscle fibers an axon innervates (i.e., the lower the ratio), the finer the control of movements.
intrafusal fiber
One of the small muscle fibers that lie within each muscle spindle. See Figure 11.9. Compare extrafusal fiber.
l-dopa
The immediate precursor of the transmitter dopamine.
mirror neuron
A neuron that is active both when an individual makes a particular movement and when that individual sees another individual make that same movement.
motoneuron
Also called motor neuron. A neuron in the brain or spinal cord that transmits motor messages to a muscle. See Figure 11.8.
motor plan
Also called motor program. A plan for action in the nervous system.
motor unit
A single motor axon and all the muscle fibers that it innervates.
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. See Figure 11.7. See also extrafusal fiber and intrafusal fiber.
muscle spindle
A muscle receptor that lies parallel to a muscle and sends impulses to the central nervous system when the muscle is stretched. See Figure 11.9.
muscular dystrophy (MD)
A disease that leads to degeneration of and functional changes in muscles.
myasthenia gravis
A disorder characterized by a profound weakness of skeletal muscles; caused by a loss of acetylcholine receptors.
myosin
A protein that, along with actin, mediates the contraction of muscle fibers. See Figure 11.7.
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.
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. See Figure 11.17.
open-loop control mechanism
A control mechanism in which feedback from the output of the system is not provided to the input control. Compare closed-loop control mechanism.
paresis
Partial paralysis. Compare plegia.
parkin
A protein that has been implicated in Parkinson’s disease.
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.
plegia
Paralysis, the loss of the ability to move. Compare paresis.
polioviruses
A class of viruses that destroy motoneurons of the spinal cord and brainstem.
premotor cortex
A region of nonprimary motor cortex just anterior to the primary motor cortex. See Figure 11.17.
primary motor cortex (M1)
The apparent executive region for the initiation of movement; primarily the precentral gyrus.
primary sensory ending
Also called annulospiral ending. The axon that transmits information from the central portion of a muscle spindle. See Figure 11.9. Compare secondary sensory ending.
proprioception
Body sense; information about the position and movement of the body that is sent to the brain.
pyramidal system
Also called corticospinal system. The motor system that includes neurons within the cerebral cortex that sends axons to form the pyramidal tract. See Figure 11.13.
red nucleus
A brainstem structure related to motor control.
reflex
A simple, highly stereotyped, and unlearned response to a particular stimulus (e.g., an eye blink in response to a puff of air). See Figures 3.17, 11.11.
reticular formation
An extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal (waking) and motor control. See Figure 14.28.
reticulospinal tract
A tract of axons arising from the brainstem reticular formation and descending to the spinal cord to modulate movement. Compare rubrospinal tract.
rubrospinal tract
A tract of axons arising from the red nucleus in the midbrain and innervating neurons of the spinal cord. Compare reticulospinal tract.
secondary sensory ending
Also called flower spray ending. The axon that transmits information from the ends of a muscle spindle. Compare primary sensory ending.
slow-twitch muscle fiber
A type of striated muscle fiber that contracts slowly but does not fatigue readily. Compare fast-twitch muscle fiber.
smooth muscle
A type of muscle fiber, as in the heart, that is controlled by the autonomic nervous system rather than by voluntary control. Compare striated muscle.
spasticity
Markedly increased rigidity in response to forced movement of the limbs.
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.
spinocerebellum
The uppermost part of the cerebellum, consisting mostly of the vermis and anterior lobe. It receives sensory information about the current spatial location of the parts of the body and anticipates subsequent movement. Compare cerebrocerebellum and vestibulocerebellum.
stretch reflex
The contraction of a muscle in response to stretch of that muscle. See Figure 11.10.
striated muscle
A type of muscle with a striped appearance, generally under voluntary control. Compare smooth muscle.
striatum
The caudate nucleus and putamen together.
substantia nigra
Literally, “black spot.” A group of pigmented neurons in the midbrain that provides dopaminergic projections to areas of the forebrain, especially the basal ganglia.
supplementary motor area (SMA)
A region of nonprimary motor cortex that receives input from the basal ganglia and modulates the activity of the primary motor cortex. See Figure 11.17.
synergist
A muscle that acts together with another muscle. See also agonist (definition 2). Compare antagonist (definition 2).
tendon
Strong tissue that connects muscles to bone.
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.
vestibulocerebellum
The middle portion of the cerebellum, sandwiched between the spinocerebellum and the cerebrocerebellum and consisting of the nodule and the flocculus. It helps the motor systems to maintain posture and appropriate orientation toward the external world. See Figure 11.25.
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