Ch. 10

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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


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