EXAM II Flashcards
Are Renshaw cells excitatory or inhibitory? Where are they located?
Inhibitory cells = lateral inhibition
Located in the anterior horns of the spinal cord, enhances the fluidity of limb movement
Which feature describes a unique characteristic that distinguishes a motor unit from a motor neuron pool?
Motor units are composed in intrafusal fibers, whereas motor neuron pools are composed of extrafusal fibers
Motor unit is composed of a single motor neuron, whereas motor neuron pools are composed of a group of motor neurons
Motor units innervate fibers within the same muscle, while motor neuron pools innervates a different muscle
All of the features above are unique characteristics of a motor unit
Motor unit is composed of a single motor neuron, whereas motor neuron pools are composed of a group of motor neurons
Which of the following groups of neurons within the spinal cord contain alpha motor neurons that give rise to A alpha fibers?
a. Sensory
b. Anterior motor neurons
c. Interneurons
d. Ganglia
e. None of the above
Anterior motor neurons
T/F Large motor neurons within the motor unit are the first to fire during an action potential
False; small motor neurons are the first
Which of the following neurons are highly excitable?
a. Anterior motor neurons
b. Sensory
c. Interneurons
d. Motor neuron pool
e. Motor unit
Interneurons
More numerous than sensory and anterior motor neurons, smaller and highly excitable, capable of spontaneous activity, responsible for most spinal cord integrative function
What type of signals do free nerve endings detect?
a. Noxious stimuli
b. Vibration
c. Muscle tension
d. Both dynamic and static changes in muscle length
e. Pressure
Noxious stimuli; non-myelinated, smallest diameter, smallest velocity = slow
Which muscle sensor is arranged in parallel with extrafusal fibers?
a. Free nerve endings (Groups II and IV afferents)
b. Pacinian corpuscles (Group II afferents)
c. Golgi tendon organ (Group Ib afferents)
d. Muscle spindle (Group Ia and II afferents)
e. Merkel cells
Muscle spindle; Group Ia primary fibers and II secondary afferents
In parallel with extrafusal fibers
Group Ia = recruited during stretching; synapse directly on alpha-motor neurons of same muscle, relieving tension on muscle spindle
Which muscle sensor detects muscle tension, thereby protecting the muscle and is arranged in series with extrafusal fibers?
a. Pacinian Corpuscle (II afferents)
b. Free Nerve Endings (III, IV afferents)
c. Golgi Tendons (Ib afferents)
d. Muscle Spindle (Ia primary fibers, II secondary afferents)
Golgi Tendons; detect muscle tension = protects the muscle, arranged in series
Which muscle sensor is the slowest due to the fact that they are non-myelinated?
a. Golgi Tendon (Ib afferents)
b. Muscle Spindle (Ia and II afferents)
c. Free Nerve Endings (IV and III afferents)
d. Pacinian Corpuscles (II afferents)
Free Nerve Endings; Type IV afferents are the slowest and are non-myelinated
muscle Spindle = Stretch
golgi Tendon = Tension
Pacinian = Pressure
free nerve endings = pain
.
What type of fibers make up the muscle fibers, which are innervated by alpha motor neurons?
a. Intrafusal fibers
b. Extrafusal fibers
c. Innerfusal fibers
d. Interfusal fibers
e. Contractile fibers
Extrafusal fibers; innervated by alpha motor neurons
Which portion of the muscle spindle contain no contractile fibers?
a. Peripheral region
b. Central region
c. Inner region
d. Outer region
e. None of the above
Central region = functions as a sensory receptor = Ia primary fibers and group II secondary fibers
Stimulation results in stimulation of alpha-motor neurons = contraction and shortening of muscle
When muscle is stretched, spindle is stretched
What type of motor neurons innervated muscle spindles that are required for finer movements?
a. Alpha motor neurons
b. Beta motor neurons
c. Gamma motor neurons
d. Alpha-beta motor neurons
e. Epsilon motor neurons
Gamma motor neurons; group II afferents
Which type of intrafusal muscle fiber are innervated by group II afferents and static gamma efferents?
a. Nuclear bag fibers
b. Nuclear chain fibers
c. Nuclear rope fibers
d. Nuclear sac fibers
e. Nuclear bar fibers
Nuclear chain fibers; detect static change in muscle length, arranged in a single row
Nuclear bag fibers = detect RATE of change in muscle length; innervated by group Ia afferents and dynamic gamma efferents
Which gamma motor neuron excites nuclear bag intrafusal fibers?
a. A-gamma
b. Gamma-dynamic
c. Gamma-static
d. None of the above
Gamma-dynamic
All gamma motor neurons innervate intrafusal fibers and adjust sensitivity of muscle spindle
A-gamma = supplies small intrafusal fibers
Gamma static = excite nuclear chain intrafusal fibers (which detect static change in muscle length)
What are the 3 functions of the muscle spindle?
- Dynamic stretch reflex - opposes sudden change to muscle length (signals via primary nerve endings)
- Static reflex - causes the degree of muscle contraction to remain relatively constant (transmitted via both primary and secondary endings)
- Prevents jerkiness of body movements (damping)
Which area(s) of the cerebral cortex generate a plan for movement and generate more complex patterns of movement?
a. Premotor and Supplementary Motor
b. Primary Motor
c. Pre motor and primary motor
d. Supplementary motor and primary motor
e. Sensory motor
Pre-motor and supplementary motor
Pre-motor = develops a “motor image”
Supplementary motor = programs complex motor sequences and mental rehearsal for a movement
Which area(s) of the cerebral cortex excites each successive pattern of muscle activity required to achieve a motor image?
a. Premotor cortex
b. Primary motor cortex
c. Supplementary motor cortex
d. Posterior motor cortex
e. Sensory cortex
Posterior motor cortex; sends signals to (2 ways) the primary motor cortex and the the basal nuclei and thalamus then the primary motor cortex
Cells in motor cortex are organized into vertical columns, each column stimulates a group of synergistic muscles or even a single muscle, which layer receives input signals?
a. 5th layer
b. 2-4 layers
c. 6th layer
d. 1-4 layers
2-4 layers
Pyramidal cells = 5th layer
6th layer contains neurons that communicate with other regions of the cerebral cortex
Cells in motor cortex are organized into vertical columns, each column stimulates a group of synergistic muscles or even a single muscle, which layer contains neurons that communicate with other regions of the cerebral cortex?
a. 5th layer
b. 2-4 layers
c. 6th layer
d. 1-4 layers
6th layer
Pyramidal cells = 5th layer
Input signals received = 2-4 layers
Which neurons are made up of alpha motor neurons and make up spinal and cranial nerves?
a. Upper motor neurons
b. Lower motor neurons
c. Interneurons
d. Primary motor neurons
e. Secondary motor neurons
Lower motor neurons
UMN = entirely within CNS, originate in cerebral cortex, cerebellum and brainstem and form descending tracts
UMNs are classified according to where they synapse in the ventral horn, which activation system innervates postural and girdle muscles?
a. Medial activating system
b. Lateral activating system
c. Anterior activating system
d. Posterior activating system
e. Nonspecific activating system
Medial activating system
Lateral activating system = distally located muscle used for fine movements
Nonspecific activating system = facilitate local reflex arcs