PSYC 304 - Chapter 11: Motor Control and Plasticity

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 behaviour such as walking.

Flaccid Paralysis

A loss of reflexes below the level of transection of the spinal cord.

Polloviruses

A class of viruses that destroy motor neurons of the spinal cord and brainstem.

Acute Flaccid myelitis

A sudden weakness or paralysis in limb(s) with(s) with decreased or absent reflexes.

Amyotrophic Lateral Sclerosis (ALS)

Also called Lou Gehrig’s disease. A disease in which motor neurons and their target muscles waste away.

Pyramidal System

Also called corticospinal system. The motor system that includes neurons within the cerebral cortex that send axons to 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 nonprimary motor cortex that receives input from the basal ganglia and modulates the activity of the primary motor cortex.

Premotor Cortex

A region of nonprimary 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 that individual sees another individual make that same movement.

Extrapyramidal System

A motor system that includes the basal ganglia and some closely related brainstem structures.

Reticulospinal Tract

A tract of axons arising from the brainstem reticular formation and descending to the spinal cord to modulate movement.

Reticular Formation

An extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal and motor control.

Rubrospinal Tract

A tract of axons arising from the red nucleus in the midbrain and innervating neurons of the spinal cord.

Red Nucleus

A brainstem structure related to motor control.

Basal Ganglia

A group of forebrain nuclei, including caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres.

Substantia Nigra

A brainstem structure in humans that innervates the basal ganglia and is named for its dark pigmentation.

Subthalamic Nucleus

A nucleus just ventral to the thalamus that interacts with the basal ganglia. It is a favoured site for deep brain stimulation to treat Parkinson’s disease.

Striatum

The caudate nucleus and putamen together.

Spinocerebellum

The central part of the cerebellum, consisting mostly of the vermis and anterior lobe.

Ataxia

An impairment in the direction, extent, and rate of muscular movement. It is often caused by cerebellar pathology.

Cerebrocerebellum

The lateral portions of each cerebellar hemisphere.

Decomposition of Movement

Difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly. It is a symptom of cerebellar lesions.

Vestibulocerebellum

The portion of the cerebellum tucked next to the brainstem, consisting of the nodule and the flocculus.

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 a 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.

Prion

A protein that can become improperly folded and thereby become an infectious agent, spreading diseases such as bovine spongiform encephalopathy.

Bovine Spongiform Encephalopathy (BSE)

Also called mad cow disease; a disorder caused by improperly formed prion proteins, leading to altered behaviour and death.

Creutzfeldt-Jakob Disease (CJD)

A brain disorder in humans, leading to abnormal behaviour and death, that is caused by improperly folded prion proteins; the human equivalent of mad cow disease.

L-Dopa

The immediate precursor of the transmitter dopamine.

Deep Brain Stimulation (DBS)

Mild electrical stimulation through an electrode that is surgically implanted deep in the brain.

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 may contain too many trinucleotide repeats. When it does, the protein causes 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.

Smooth Muscle

A type of muscle fibre, that is controlled by the autonomic nervous system rather than by voluntary control.

Tendon

Strong tissue that connects muscle to bone.

Antagonist

Here, a muscle that counteracts the effect of another muscle.

Synergist

Here, a muscle that acts together with another muscle.

Motor Neuron

Also motoneuron; a neuron in the brain or spinal cord that transmits motor messages to a muscle.

Muscle Fiber

A large cylindrical cell that can contract in response to neurotransmitter released from a motor neuron.

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.

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.

Acetylcholine (ACh)

A neurotransmitter produced and released by parasympathetic ganglionic neurons, by motor neurons, and by neurons throughout the brain.

Neuromuscular Junction (NMJ)

The region where the motor neuron 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 motor neurons in the body. Motor neurons are known by this collective term because they receive and integrate all motor signals from the brain and then direct movement accordingly.

Myasthenia Gravis

A disorder characterized by a profound weakness of skeletal muscles. It is 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.

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 action potentials to the central nervous system when the muscle is stretched.

Intrafusal Fiber

One of the small muscle fibers that lie within each muscle spindle, controlling its length.

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 Aging

Also called flower spray ending. The axon that transmits information from the ends of a muscle spindle.

Gamma Motor Neuron

Also called gamma efferent. A motor neuron that innervates the contractile tissue (the intrafusal fiber) in a muscle spindle.

Alpha Motor Neuron

A motor neuron that controls the main contractile fibers (extrafusal fibers) of a muscle.

Golgi Tendon Organ

One of the receptors located in tendons that send action potentials to the central nervous system reporting muscle tension.

Spinal Animal

An animal whose spinal cord has been surgically disconnected from the brain to enable the study of behaviours that do not require brain control.

Reflex

A simple, highly stereotyped, and unlearned response to a particular stimulus (I.e., an eye blink in response to a puff of air).

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.

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 generally preprogrammed.