Ch. 10
In the figure, the Arabic numeral (blank 1) corresponds to an extrafusal muscle fiber
4
A condition in which progressive degeneration of alpha motor neurons causes hypotonia and atrophy of skeletal muscles is termed ______ lateral ___
Amyotrophic lateral sclerosis
is also known as Lou Gehrig's disease.
Amyotrophic lateral sclerosis
Looping parellel circuits that begin in and return to the sensorimotor cortex through the _____ and the thalamus facilitate some movements and inhibit others.
Basal nuclei
Some of the fibers of the descending pathways affect afferent systems. They do this via (1) presynaptic synapses on the terminals of afferent neurons as these fibers enter the (blank 1) (blank2), system or (2) synapses on (blank 3) in the ascending pathways
Blank 1: central Blank 2: nervous Blank 3: interneurons
The muscle spindles are attached by connective tissue in parallel to the (blank 1) fibers. Thus, an external force stretching the muscle also pulls on the (blank 2) fibers, stretching the, and activating their receptor endings
Blank 1: extrafusal Blank 2: intrafusal
The building blocks for all movements are motor units, each comprising one motor (blank 1 ) together with all the (blank 2) muscle fibers that it innervates
Blank 1: neuron Blank 2: skeletal
The two major groups of descending spinal cord tracts or pathways are the (blank 1) and the (blank 2) tracts
Blank 1: pyramidal or corticospinal Blank 2: extrapyramidal or brainstem
The afferent fibers carry information from sensory receptors located in three places: 1.) in the (BLANK 1) muscles controlled by the neurons; 2.) in other muscles, such as those with (BLANK 2) actions; and 3.) in the tendons, joints, and (BLANK 3) of body parts affected by the action of the muscle
Blank 1: skeletal Blank 2: antagonistic Blank 3: skin
Local control systems use information carried by afferent fibers from sensory receptors in the muscles, (blank 1), (blank 2), and skin of the body parts to be moved
Blank 1: tendons or tendon Blank 2: joints or joint
Middle-level neurons of the motor control hierarchy receive input from the
Brain stem and spinal cord interneurons Command neurons Vestibular apparatus and the eyes
extrapyramidal tracts originate in the
Brainstem
What structure receives information from the sensorimotor cortex, the vestibular system, eyes, skin, muscles, joints, and tendons, and provides timing signals that coordinate execution of complex movements involving several joints?
Cerebellum
During walking, when the extensor muscles are activated in the leg supporting the body's weight, which of the following simultaneously occurs?
Contralateral extensor muscles and ipsilateral flexor muscles are inhibited.
Prolonged and painful involuntary muscle contractions are called
Cramps
The category of skeletal muscle fibers that are NOT part of the muscle spindle and which constitute the greatest mass and generate the force and movement of the muscle are called (blank) muscle fibers
Extrafusal
Axons of most of the brainstem pathways cross over to influence contralateral muscles.
False
The knee-jerk reflex is active in posture control.
False
The spinal cord has three major descending pathways to the motor neurons and the interneurons that affect them.
False
True or false: Afferent fibers that impinge on local interneurons controlling a muscle originate from sensory receptors found: 1. in the muscle being controlled, 2. in nearby muscles, such as those with antagonistic actions, and 3. in the vestibular apparatus of the inner ear.
False
Receptors that monitor tension in muscles,called (blank), consist of peripheral endings of nerve fibers that wrap around collagen bundles in the tissue that connects muscle to bone
Golgi tendon organs
Abnormally increased resistance that occurs when a joint is moved passively at high speeds is called
Hypertonia
An abnormally high muscle tone is denoted by the term
Hypertonia
What is the stimulus for Golgi tension organs?
Increased tension in the tendon
Stretching a skeletal muscle causes a(n) ______ in the tension on its tendon, which in turn _____ the Golgi tendon organs, which in turn via a spinal reflex causes ______ of the muscle
Increases, activates, inhibition
When golgi tendon organs are stimulated, contraction of the associated muscle is
Inhibited
Identify a true statement about amyotrophic lateral sclerosis (ALS).
It has no cure
Which level of the motor control hierarchy makes adjustments in response to unexpected obstacles to movement and to painful stimuli in the environment?
Local level
The starting position of the body parts required to perform a desired movement as well as information about the nature of the space surrounding the body in which movement is to take place are communicated to and integrated in the (blank 1) level of the motor control hierarchy
Middle
Which level of the motor control hierarchy involves all five of the regions labeled in this image?
Middle
Which two of these are most helpful in maintaining upright posture and balance?
Muscle crossed-extensor reflexes Muscle stretch reflexes
In this figure, the letter A represents an apparatus called the
Muscle spindle
The nervous system receives information about the length of a muscle from the
Muscle spindle apparatus
An apparatus consisting of peripheral endings of afferent nerve fibers wrapped around modified muscle fibers, several of which are enclosed in a connective tissue capsule, is called a(n)
Muscle spindles
Relaxed skeletal muscles exhibit a slight, uniform resistance to passive stretch called
Muscle tone
Because basal ganglia are present within the central nervous system, it is more anatomically correct to refer to them as basal
Nuclei
A collection of cell bodies in the central nervous system is called a
Nucleus
After originating in one side of the cortex, most corticospinal tracts descend on the ______ side of the spinal cord.
Opposite
Which two are the main determinants of resting skeletal muscle tone?
Passive elastic properties of muscles and joints Ongoing alpha motor neuron activity
Which of the following statements is true about this figure of muscle action?
Passive stretch of the muscle by an external load activates the spindle stretch receptors and causes an increased rate of action potentials in the afferent nerve.
Consider the case of a sensory neuron stimulating a motor neuron and an interneuron leading to contraction of the agonist muscle and inhibit action of the antagonistic muscle group. This phenomenon is called
Reciprocal innervation
Stretch reflexes serve to
Return a muscle that has changed length back to its original length
The general intention of any movement is determined by neurons that originate in the..
Sensorimotor cortex Areas of the brain involved in memory, emotions, and motivation
Middle level structures of the motor control hierarchy include which of the following?
Sensorimotor cortex Cerebellum and thalamus Basal nuclei and brain stem
The correction description of the components and sequence of events in a monosynaptic reflex pathway is
Sensory receptor- sensory neuron- motor neuron - muscle contraction
Brief, involuntary muscle contractions are called
Spasms
Which of the following causes the greatest simulation of golgi tendon organ receptors
Stretching of a tendon by active muscle contraction
Which of these play a prominent role in establishing the programs that determine the specific sequence of movements needed to accomplish a desired action?
The brainstem and subcortical nuclei
True or false: Neurons of the descending pathways may synapse with and influence afferent signals at the local level.
True
Clinically, the descending pathways and neurons of the motor cortex are often referred to as the ______ motor neurons.
Upper
Neurons in the brain that contribute axons to descending motor tracts and act as facilitators and inhibitors to lower motor neurons are called ____ motor neurons
Upper
In what activity is the body allowed to repeatedly fall forward to an unstable position with each leg alternately moved forward and extensor muscles activated to bear the body's weight?
Walking
Which three locations contain sensory receptors that send input to local inter neurons that control a given skeletal muscle
Within the skeletal muscles controlled by the motor neurons Within other nearby muscles, such as those with antagonistic actions In the tendons, joints, and skin of body parts affected by actions of the muscle
Coactivation in muscle involves the simultaneous stimulation of both the (blank) motor neurons so that a muscle can contract while also providing information about its length to the CNS.
alpha and gamma
Suppose that the pathways indicated by #s 1 and 2 are activated simultaneously. This phenomenon would then be called (blank ) coactivation.
alpha-gamma
Neurons in the sensorimotor cortex and regions of the brain involved with memory, emotions, and motivation are part of the highest level of the motor control hierarchy. They
are involved in forming the general intention of a planned movement
A closely-related group of nuclei deep within the subcortical area of the cerebrum and which integrate motor commands are called the ____ nuclei
basal nuclei
During walking, the extensor muscles are activated on the supported side of the body to bear the body's weight. This is simultaneously accompanied by inhibition of the —— extensors to allow the nonsupporting limb to flex and swing forward.
contralateral
Higher centers of the brain, also known as "command" neurons, include (blank) areas involved with memory, emotions, and motivation
cortical and subcortical
The two major descending motor pathways are called the
corticospinal and brainstem pathways
The subcortical and brain stem nuclei play a major role in
executive functions such as planning and monitoring
The category of skeletal muscle fibers that are NOT part of the muscle spindle and which constitute the greatest mass and generate the force and movement of the muscle are called (blank) muscle fibers.
extrafusal
Tension on the stretch receptors is maintained during muscle contraction by activation of (blank) motor neurons to the spindle intrafusal muscle fibers
gamma
During muscle contraction, tension and stretch in the central region of an instrafusal fiber is maintained by action potentials in
gamma motor neurons
During muscle shortening, tension and stretch in the central region of an intrafusal fiber is maintained by action potentials in
gamma motor neurons
Action potentials from muscle spindle stretch receptors (blank) frequency as a result of increasing muscle length
increase in
intrafusal muscle fibers are those that form (blank) of the muscle spindle
inside
Modified skeletal muscle fibers within a muscle spindle apparatus are called (blank) fibers
instrafusal
In the schematic, the two arrows are pointing the (blank) muscle fibers
intrafusal
The terms reflex, unconscious, and automatic often serve as synonyms for
involuntary
The result of stretching the muscle spindle when the patellar tendon is struck is known as the (blank) reflex
knee jerk
When neurons of the descending pathways synapse on interneurons in the brainstem and spinal cord, the effect on alpha motor neurons
maybe excitatory or inhibitory
The motor neuron and all the muscle fibers it innervates is called a ______
motor unit
most stretch reflexes are examples of _____ feedback loops:
negative
The spinal cord tracts primarily involved with skill in moving the hands or the body are the ________ tracts.
pyramidal
Many movements, including the knee-jerk reflex, involve the activation of neurons to one muscle and simultaneous inhibition of neurons to antagonistic muscles. The pattern of activating neurons to one muscle with simultaneous inhibition of neurons to an antagonist muscle is called
reciprocal innervation
In a motor system, a (blank) is an involuntary, stereotypical response to a specific stimulus
reflex
Muscle spasms and muscle cramps ______.
result from dysfunction of muscle and not nervous tissue are forms of hypertonia
All areas of the cerebral cortex that play a role in the control of skeletal muscle are referred to as the
sensorimotor cortex
The only type of muscle reflex known to have a mono synaptic reflex arc is the (blank) arc
stretch
Two major reflex pathways involved in maintenance of upright posture are ____ reflexes and crossed-____ reflexes
stretch extensors
Different muscles which, when contracting, cause the same movement around a joint (for example flexion of the elbow) are referred to a
synergistic
Different muscles which, when contracting, cause the same movement around a joint (for example flexion of the elbow) are referred to as Blank______ muscles.
synergistic
In the knee-jerk reflex that results from tapping the patellar tendon, monosynaptic activation of both the stretched and ____ (synergistic or antagonistic?) muscles results in extension of the leg
synergistic
Muscles whose contraction assists the intended motion are called (blank) muscles. In the example of the knee-jerk reflex, this would include other muscles that extend the leg.
synergistic
Golgi tendon organs monitor what?
tension
A reflex arc that is initiated by a painful stimulus, such as touching something very hot, is called ____ reflex
withdrawal
Stimulation of nociceptors in the skin of a limb activates flexor muscles and inhibits ipsilateral extensor muscles, a negative feedback loop that is a component of a reflex called ___________________ reflex
withdrawal
