Ch 8 Definitions: Movement Flashcards
smooth muscle
a type of muscle found in the lining of the digestive tract, within arteries, and in the reproductive system;
controlled by autonomic nervous system
striated muscle
a type of muscle named for its striped appearance including cardiac and skeletal muscles
cardiac muscle
a type of striated muscle found in the heart
skeletal muscle
a type of striated muscle that is attached to bones and is responsible for the majority of body movements
muscle fiber
an individual muscle cell
twitch
the contraction of a single muscle fiber
myofibril
a long fiber strand running the length of a muscle fiber that is responsible for contraction
sarcomere
a myofibril segment bound on either side by a Z line and spanned by thin filaments
Z line
a boundary line for each sarcomere within a myofibril
actin
a protein that makes up the thin filaments of the myofibril
myosin
a protein that makes up the thick filaments of the myofibril
M line
the middle of the sarcomere where myosin fibers are anchored
tropomyosin
a protein that covers actin binding sites in a resting muscle fiber, preventing actin from interacting with myosin
troponin
a protein that when bound by calcium displaces tropomyosin, allowing actin to interact with myosin
slow-twitch fiber
a muscle fiber containing type I myosin filaments and large numbers of mitochondria that contracts slowly using aerobic metabolism;
primarily responsible for movement requiring endurance
fast-twitch fiber
a muscle fiber containing type IIa or IIb myosin filaments that contains few mitochondria, uses anaerobic metabolism, and contracts rapidly;
primarily responsible for movement requiring explosive strength
aerobic metabolism
a chemical process that requires oxygen
anaerobic metabolism
a chemical process that does not require oxygen
alpha motor neuron
a spinal motor neuron directly responsible for signaling a muscle fiber to contract
neuromuscular junction
a synapse formed between an alpha motor neuron axon terminal and a muscle fiber
motor unit
the combination of a single alpha motor neuron and all the muscle fibers that it innervates
motor neuron pool
the collection of motor neurons that innervates a single muscle
rate code
variations in the firing rate of motor neurons to meet the need for a certain amount of contraction
tetanus
the point at which a muscle cannot contract further
recruitment
the process of gradually activating more motor units as an increasing load is placed on a muscle
muscle spindle
a sensory structure that provides feedback regarding muscle stretch
intrafusal muscle fiber
one of the fibers that makes up a muscle spindle
exrafusal muscle fiber
one of the fibers outside the muscle spindle that is responsible for contracting the muscle
nuclear chain fibers
a type of muscle spindle fiber that provides information about muscle length
static nuclear bag fibers
a type of muscle spindle that provides information about muscle length
dynamic nuclear bag fibers
a type of muscle spindle fiber that provides information about the velocity of change in the length of a muscle
Ia (1a) sensory fiber
a large and fast sensory axon that connects a muscle spindle to neurons in the spinal cord
group II sensory fiber
sensory fiber that provides information about muscle length
myotatic reflex
the contraction of a muscle in response to sensory information about its having been stretched
monosynaptic reflex
a spinal reflex, such as a patellar reflex, that requires the action of only one synapse between sensory and motor neurons
gamma (¥) motor neuron
a small spinal neuron that innervates the muscle spindles
Golgi tendon organ
a structure located in the tendons of muscles that provides information about muscle contraction
Ib (1b) sensory fibers
a small, slower Alpha-alpha (Aa) sensory axon that connects Golgi tendon organs to neurons in the spinal cord
polysynaptic reflex
a spinal reflex that requires interaction at more than one synapse
antagonistic pair
two opposing muscles, one a flexor and one an extensor, arranged at a joint
extensor
a muscle that acts to straighten a joint
flexor
a muscle that acts to bend a joint
reciprocal inhibition
a polysynaptic reflex that prevents the simultaneous contraction of flexors and extensors serving the same joint
flexor reflex
a polysynaptic spinal reflex that produces withdrawal of a limb from a partial stimulus
Babinski sign
a polysynaptic reflex present in infants and adults with neural damage, in which stroking the sole of the foot causes the toes to spread with the big toe pointing upward
corticobulbar tract
a pathway connecting primary motor cortex with brainstem cranial nerve nuclei to manage movement of head and neck
lateral pathway
a large collection of axons that originates in the cerebral cortex,
synapses on either the red nucleus or alpha motor neurons,
and controls voluntary movements
ventromedial pathway
a spinal motor pathway originating in the brainstem and carrying commands for subconscious, automatic movements of the neck and torso
corticospinal tract
a pathway connecting the motor cortex to alpha motor neurons in the spinal cord
rubrospinal tract
a pathway connecting the red nucleus of the midbrain to the alpha motor neurons of the spinal cord
tectospinal tract
a ventromedial pathway connecting the tectum of the midbrain to the alpha motor neurons in the spinal cord
vestibulospinal tract
a ventromedial pathway that connects the vestibular nuclei of the medulla to the alpha motor neurons of the spinal cord
pontine reticulospinal tract
a ventromedial pathway connecting the reticular formation in the pons to the alpha motor neurons of the spinal cord
medullary reticulospinal tract
a ventromedial pathway connecting the reticular formation in the medulla to alpha motor neurons of the spinal cord
supplementary motor area (SMA)
motor area located in the gyrus rostral to the precentral gyrus;
involved with managing complex sequences of movement
premotor cortex
a motor area located in the gyrus rostral to the precentral gyrus;
this area participates in holding a motor plan until it can be implemented;
formerly referred to as the premotor area (PMA)
pyramidal cell
a large, pyramid-shaped neuron found in the output layers (Layers III and V) of the cerebral cortex, including primary motor cortex
mirror neuron
a special motor neuron that responds to a particular action, whether that action is performed or simply observed
myasthenia gravis
an autoimmune condition caused by the degeneration if ACh receptors at the neuromuscular junction, resulting in muscle weakness and fatigue
muscular dystrophy
a group of diseases characterized by extreme muscle development followed by muscle wasting,
due to abnormalities in the protein dystrophin
polio
a contagious viral disease that attacks the spinal motor neurons,
producing paralysis
amyotrophic lateral sclerosis (ALS)
a disease in which motor neurons of the spinal cord, brainstem, and motor cortex progressively deteriorate, leading to death
Parkinson’s disease
a degenerative disease characterized by difficulty in moving, muscular tremors, and frozen facial expressions
Huntington’s disease
a genetic disorder beginning in middle age that results in jerky, involuntary movements and progresses to psychosis and premature death
