biology

Upper motor neuron lesion

Upper motor neuron lesion is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Upper motor neuron lesion rather than just read about it. In short: An upper motor neuron lesion (also known as pyramidal insufficiency) Is an injury or abnormality that occurs in the neural pathway above the anterior horn cell of the spinal cord or motor nuclei of the cranial nerves. Conversely, a lower motor neuron lesion affects nerve fibers traveling from the anterior horn of the spinal cord or the cranial motor nuclei to the relevant muscle(s).

Key takeaways

Upper motor neuron lesion belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Upper motor neuron lesion to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Upper motor neuron lesion from memory before moving on to harder problems.

Reference excerpt

An upper motor neuron lesion (also known as pyramidal insufficiency) Is an injury or abnormality that occurs in the neural pathway above the anterior horn cell of the spinal cord or motor nuclei of the cranial nerves. Conversely, a lower motor neuron lesion affects nerve fibers traveling from the anterior horn of the spinal cord or the cranial motor nuclei to the relevant muscle(s). Upper motor neuron lesions occur in the brain or the spinal cord as the result of stroke, multiple sclerosis, traumatic brain injury, cerebral palsy, atypical parkinsonisms, multiple system atrophy, and amyotrophic lateral sclerosis.

Symptoms Changes in muscle performance can be broadly described as the upper motor neuron syndrome. These changes vary depending on the site and the extent of the lesion, and may include:

Muscle weakness. known as 'pyramidal weakness' Sloth sign. Decreased control of active movement, particularly slowness Spasticity, a velocity-dependent change in muscle tone Clasp-knife response where initial higher resistance to movement is followed by a lesser resistance Babinski sign is present, where the big toe is raised (extended) rather than curled downwards (flexed) upon appropriate stimulation of the sole of the foot. The presence of the Babinski sign is an abnormal response in adulthood. Normally, during the plantar reflex, it causes plantar flexion and the adduction of the toes. In Babinski's sign, there is dorsiflexion of the big toe and abduction of the other toes. Physiologically, it is normally present in infants from birth to 12 months. The presence of the Babinski sign after 12 months is the sign of a non-specific upper motor neuron lesion. Increased deep tendon reflex (DTR) Pronator drift

Corticospinal/pyramidal tract These are the neural tracts which descend in the ventral horn of the spinal cord, carrying signals for voluntary movement of skeletal muscle. From their origin in the primary motor cortex, these nerves pass via the corona radiata to gather in the internal capsule before crossing over to the opposite side (decussation) in the medullary pyramids and proceeding down the spinal cord to meet lower motor neurons in the anterior grey column.

Diagnosis During an exam, your doctor will look for signs of a nervous system problem by checking your:

Balance and coordination Movement Hearing, speech, and vision Memory and concentration

Tests for diagnosis Nerve conduction study Spinal tap or lumbar puncture Nerve biopsy

Treatment The treatment of an upper motor neuron lesion will be dependent on the underlying cause.

See also Upper motor neuron Lower motor neuron Lower motor neuron lesion

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Upper motor neuron lesion

Start with the simplest possible case. Write down what Upper motor neuron lesion claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Upper motor neuron lesion before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Upper motor neuron lesion ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Upper motor neuron lesion

In research: Upper motor neuron lesion appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Upper motor neuron lesion in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Upper motor neuron lesion is common in secondary-school and first-year university syllabi. It links to neighbouring topics Neurological disorders, so understanding it makes those chapters shorter.
In everyday life: Look for Upper motor neuron lesion outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Upper motor neuron lesion in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Upper motor neuron lesion means in your own words.
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Frequently asked questions

What is Upper motor neuron lesion in simple terms?

Why does Upper motor neuron lesion matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Upper motor neuron lesion?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Upper motor neuron lesion.