Finals: Motor & Reflex Physio Flashcards
The Bell-Magendie Law states that?
The Bell-Magendie Law states that the anterior part of the spinal cord is responsible for motor functions, while the posterior part is responsible for sensory functions.
Which type of motor neuron innervates the extrinsic muscle fibers?
Alpha motor neurons innervate the extrinsic muscle fibers.
The principle of size recruitment in motor units refers to?
The principle of size recruitment in motor units refers to the recruitment of smaller motor units first before larger motor units during muscle contraction.
What are the two functions of alpha motor neurons?
sensory (proprioception, muscle stretch)
motor (innervation of skeletal muscles).
What is the function of gamma motor neurons?
Gamma motor neurons innervate the intrafusal muscle fibers of muscle spindles, playing a role in regulating muscle spindle sensitivity and maintaining muscle tone.
What distinguishes lower motor neurons from upper motor neurons in terms of their location and function?
Lower motor neurons are located in the anterior horn of the spinal cord and directly innervate muscles, while upper motor neurons originate in the brain and influence lower motor neurons.
What is the primary function of interneurons in the spinal cord?
Interneurons in the spinal cord connect various areas and are responsible for integrative functions, transmitting impulses between neurons.
How do Renshaw cells contribute to motor control?
Renshaw cells provide lateral inhibition by inhibiting adjacent motor neurons, sharpening motor signals and controlling movement specificity.
Name two types of muscle sensory receptors and describe their functions.
Muscle sensory receptors include muscle spindles (detect muscle length and stretch) and Golgi tendon organs (detect muscle tension), providing feedback necessary for motor control.
What role do propriospinal fibers play in spinal cord function?
Propriospinal fibers connect different segments of the spinal cord, facilitating multi-segmental reflexes and coordinating movements between forelimbs and hind limbs.
What are the requirements for proper motor control?
Requirements include excitation of muscles from anterior motor neurons, continuous feedback from muscle sensory receptors, and proprioception for muscle length and tension modulation.
Describe the symptoms associated with lesions in lower motor neurons.
Lesions in lower motor neurons result in symptoms such as flaccidity and hypotonia, leading to muscle weakness and atrophy.
How do lesions in upper motor neurons affect muscle tone?
Lesions in upper motor neurons cause spasticity, resulting in increased muscle tone that is velocity-dependent due to loss of inhibition to gamma motor neurons.
What are muscle spindles primarily composed of?
Muscle spindles are primarily composed of intrafusal muscle fibers.
Explain the importance of proprioception in muscle control.
roprioception provides feedback on muscle length, tension, and position, crucial for adjusting muscle contractions and maintaining balance and coordination.
What is lateral inhibition, and how does it contribute to motor function?
Lateral inhibition is the process by which certain neurons inhibit adjacent neurons, enhancing the specificity of sensory impulses and motor signals.
What type of nerve fibers innervate the central region of the muscle spindle?
Large diameter myelinated afferent nerve fibers, specifically group Ia (primary endings) and group II (secondary endings), innervate the central region of the muscle spindle.
What are the two types of large diameter myelinated afferent nerve fibers, and what do they innervate?
Group Ia fibers innervate both nuclear bag and nuclear chain fibers, while group II fibers innervate only nuclear chain fibers.
What is the role of intrafusal muscle fibers in muscle spindles?
Intrafusal muscle fibers do not contribute to overall contractile force but serve as sensory receptors.
Name the two types of intrafusal muscle fibers and describe their functions.
The two types of intrafusal muscle fibers are nuclear bag fibers (provide dynamic and static responses) and nuclear chain fibers (provide static response only).
How do dynamic and static gamma motor neurons differ in their function?
Dynamic gamma motor neurons increase sensitivity with muscle movement, while static gamma motor neurons maintain muscle tone and prevent afferent silencing.
Describe the function of gamma motor neurons in muscle spindle function.
Gamma motor neurons modulate the sensitivity and function of muscle spindles.
What is the role of the central region of the muscle spindle during contraction?
During contraction, the central region of the muscle spindle stretches, increasing receptor sensitivity.
How does denervation affect muscle tone in muscle spindles?
Denervation results in the loss of muscle tone in muscle spindles.
