Motor Neurons
These four components make up the Motor Unit.
What are the
-Motor Cell bodies
-Efferent fibers (axons)
-Motor end plate/neuromuscular junction (NMJ)
-Innervated muscle fibers
This neuron supplies input to the spinal cord from primary and premotor cortices.
What is the UMN?
These types of LMNs are the primary motor neurons of the spinal cord. They innervate skeletal muscle directly for voluntary movement and skeletal muscle reflexes. These folks are super mighty and ALL MOTOR IMPULSES of the CNS must pass through them before innervating muscles! One of these neurons can innervate more than 200 muscle fibers!
What are alpha motor neurons? AKA Final common pathway because all efferent impulses from CNS must pass through these cells before activating muscles.
T/F: The cerebellum is an initiation system, you need it to initiate balance.
What is false? The cerebellum coordinates and regulates motor output, modification system.
Patient B was submitted into the emergency room and presented with imprecise articulation, failure of the finger to nose test, he was seen bumping into furniture and others in the waiting room, and had difficulty picking up his wallet after dropping it on floor. A possible explanation could be.....
What is alcohol intoxication? Patient B had too much to drink and his cerebellum is compromised!
T/F: Lower motor neurons synapse on UMN.
What is false? UMN synapse on LMN.
These neurons are innervated by the ventral horn of the spinal cord and are efferent fibers carrying signals to the muscle.
What are the LMNs?
This refers to an enlarged fluid-filled central canal cavity where fluid can dissect into white matter. This causes an interruption of pain/temperature pathways and can lead to loss of these sensations bilaterally.
What is syringomyelia?
The cerebellum receives input from these structures...
What are the sensory cortex, brainstem, spinal cord, and extrapyramidal system.
This injury can result in bilateral paralysis and sensory loss. After some time, the patient may regain reflex activity below the lesion.
What is complete transection of the spinal cord?
Pyramidal means this...
Extrapyramidal?
Pyramidal refers to the cells that fibers in this motor tract arise from. There is a direct involvement in movement. Projects from the motor cortices (primary/premotor) to the spinal cord and brain stem. Includes corticospinal and corticobulbar tracts.
Extrapyramidal refers to fine tuning of movement which happens in the Basal Ganglia and Cerebellum. Includes Vestibular tract, and nigrostriatal pathway.
Damage to this neuron can cause paresis/paralysis, atrophy of muscles, spasticity, and can lead to hyperactivity of spinal reflexes.
What are UMN?
During withdrawal reflexes this happens to the antagonistic muscles.
What is they are inhibited from contracting through reciprocal inhibition?
Briefly describe cerebellar Anatomy.
There are two cerebellar hemispheres, it is divided transversely and longitudinally.
There are deep cerebellar nuclei (embedded in white matter)
There are 3 lobes
•Anterior lobe (paleocerebellum)
•Posterior lobe (neocerebellum)
•Flocculonodular lobe (archicerebellum)
•3 peduncles- superior, middle, inferior.
Dysmetria.....
What is a cerebellar lesion symptom-difficulty accurately gauging appropriate range of movement of distance to target?
These are the motor nerves that innervate skeletal muscles.
What are the lower motor neurons?
Alpha and Gamma are two types of...
What are LMNs?
These are the steps to muscle contraction....
•Alpha motor neurons release acetylcholine (ACh) at neuromuscular junction
•ACh produces large excitatory postsynaptic potential in muscle fibers
•Excitatory postsynaptic potential evokes action potential
•Action potential triggers calcium (Ca2+) release at NMJ, Leads to fiber contraction
•Ca2+ levels eventually lowered by reuptake, Muscle relaxes
This cerebellar lobe receives input from CN VIII...
What is the Flocculonodular AKA archibellum/vestibulocerebellum?
CN8 is vestibulocochlear. Helps with regulating muscle tone to maintain equilibrium.
This symptom is characterized by floppiness of muscle/flaccidity.
What is hypotonicity?
Muscles will do this if the neuromuscular junction is damaged.
What is degenerate?
These neurons connect adjacent spinal cord cells.
What are interneurons?
These motor neurons are slow, small, and less numerous. They control the sensitivity of muscle fibers, lie alongside alpha cells in the spinal ventral horns, and mediate alpha motor neurons by adjusting the rate of change of muscles.
What are Gamma motor neurons?
These are the 3 cerebellar peduncles...
What are the Superior, Middle, and Inferior peduncles.
Patient A presents with a brain lesion after suffering a CVA. She exhibited difficulty with rapid repeating of the sounds "pa, ta, ka." What might be a possible explanation for her difficulties. She appears to have normal muscle tone and strength at rest.
What is possible damage to the cerebellum/ataxia?