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An UMN lesion may in fact present with atrophy, but it does so over time.
With a LMN lesion, the muscle loses its innervation directly and thus will not be receiving any neurological stimulus at all. However, damage to an UMN leaves the corresponding LMN to that particular muscle intact, thus leaving it to fire somewhat irregularly, but firing nonetheless. Macroscopically the muscle is no longer under central control and thus can't perform proper function, but microscopically the muscle fibers are still receiving some neurological input, or signal from the LMN innervating it, thus the muscle integrity appear unaffected at first. Over time, the muscle will atrophy because of a lack of use, but this happens more gradually than with a direct LMN lesion.
-Onyx (Medical Student)
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What are motor neuron diseases?
Motor neuron diseases are a group of neurological conditions that affect the nerve cells responsible for controlling voluntary muscle movements. Examples include amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy. These diseases can lead to muscle weakness, atrophy, and eventually loss of motor function.
What is a motor neuron attached to?
A Motor neuron is a neuron that carries impulses from the spinal cord to muscle cells.A Motor neuron is a neuron that carries impulses from the spinal cord to muscle cells.
What is the difference between an upper motor neuron lesion and a lower motor neuron lesion?
LMNLIt is due to lesion of lower motor neurons i.e. the spinal and cranial motor neurons that directly innervate the muscles.Usually single or individual muscle is affected.Disuse atrophy of muscles.All reflexes are absent.flaccid paralysis occurs.Babinski planter response not elicited.2. UMNLIt is due to upper motor neuron lesion.It involves group of muscles.spastic paralysis occurs.muscle atrophy is not severe.reflexesdeep reflexes are hyperactive.superficial refle;xes;only abdominal,cremastric and anal reflexes are lost.Babinski sign:positive.AI'IGHT,UUUMMM HOPE THIS HELPS :) LOWER MOTOR NEURON LESION: vs UPPER MOTOR NEURON LESION:1)FLACCID MUSCLE SPASTICITY OF MUSCLE2)HYPO-TONIA HYPER-TONIA3)HYPO-REFLEXIA HYPER-REFLEXIA4)PROFOUND MUSCLE ATROPHY MINIMAL MUSCLE ATROPHY5)FASCICULATIONS("TWITCHING") PRESENT FASCICULATIONS ABSNTSO JUST REMEMBER: LOWER = HYPO- EVERYTHING ; UPPER = HYPER- EVERYTHING,WELL, EXCEPT OFCOURSE - THE TWITCHING AND MUSCLE ATROPHY (ITS REVERSED).
What is the difference between a motor unit and a motor neuron in the context of muscle movement?
A motor unit consists of a motor neuron and the muscle fibers it controls. The motor neuron sends signals to the muscle fibers to contract, while the motor unit refers to the combination of the neuron and the muscle fibers it innervates.
What are some of the better known motor neuron diseases?
Some of the better known motor neuron diseases include amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, spinal muscular atrophy (SMA), and primary lateral sclerosis (PLS). These diseases affect the motor neurons in the brain and spinal cord, leading to muscle weakness, atrophy, and impaired movement.
What type of neuron connects to a muscle?
A motor or efferent neuron.
The combination of a neuron and the muscle fibers it associates with is called?
The combination of a neuron and the muscle fibers it associates with is called a motor unit. Motor units work together to produce movement by having the neuron stimulate the muscle fibers it innervates to contract.
What motor neuron and all the muscle fibers it innervates called?
the motor unit
What is the name of the point at which motor neuron synapses motor end plate?
The point at which a motor neuron synapses with a muscle fiber's motor end plate is called the neuromuscular junction. This is where the nerve impulse is transmitted from the motor neuron to the muscle fiber, leading to muscle contraction.
What site where the motor neuron and muscle cell meet is called the?
The site where a motor neuron and muscle cell meet is called the neuromuscular junction. This is where the motor neuron releases neurotransmitters that signal the muscle cell to contract.
The motor neuron and the muscle fiber it controls constitute a what?
The motor neuron and the muscle fiber it controls constitute a motor unit. This functional unit is essential to the process of muscle contraction and movement in the body. When the motor neuron sends signals to the muscle fiber, it results in the activation and coordination of muscle fibers to produce movement.
Define motor unit?
A motor unit consists of a motor neuron and all the muscle fibers it innervates. When the motor neuron fires, all the muscle fibers in the motor unit contract simultaneously. This coordinated activation allows for precise control of muscle force and movement.
