astronomy

Startle-evoked movement

Startle-evoked movement is a astronomy 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 Startle-evoked movement rather than just read about it. In short: Startle-evoked movement (SEM or startReact) is the involuntary initiation of a planned action in response to a startling stimulus. While the classic startle reflex involves involuntary protective movements, SEMs can be a variety of arm, hand and leg actions including wrist flexion, and rising onto tiptoes.

Key takeaways

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

Reference excerpt

Startle-evoked movement (SEM or startReact) is the involuntary initiation of a planned action in response to a startling stimulus. While the classic startle reflex involves involuntary protective movements, SEMs can be a variety of arm, hand and leg actions including wrist flexion, and rising onto tiptoes. SEMs are performed faster than voluntary movements, but retain the same muscle activation characteristics. SEM has been used to study how the brain, spinal cord and brainstem can interact to produce movement, and provides a potential avenue of exploration for rehabilitation strategies for those with neurological impairments.

Neurophysiology

Reticulospinal tract connection Muscles lacking reticulospinal tract inputs are not susceptible to SEM. The ability to elicit SEM has been used as evidence for reticulospinal tract connections to the muscles governing grasp of the human hand.

Neurological impairment People who have suffered cortical damage such as a stroke are capable of performing SEM. In one experiment, SEM caused stroke survivors to perform arm movements as fast as unimpaired people, despite being slower when performing the same action voluntarily. Furthermore, people with pure hereditary spastic paraplegia, a condition effecting the corticospinal tract, are susceptible to SEM as well.

Involuntary initiation SEM is typified by a reduction in the time to perform an action. Voluntary arm extension, for example, occurs roughly 170 milliseconds after a "Go" signal, while SEMs for arm extension occur between 65 and 77 milliseconds. Due to this faster reaction time, and considering conduction velocity, cortical involvement for these movements is unlikely. Furthermore, movement-related cortical potentials which typically precede voluntary movement execution are absent in SEM.

Movement preparation In order for SEM to occur, a subject must be waiting to perform an action when a startling stimuli is encountered. Typically, this is achieved by first presenting the subject with a "Ready" signal, indicating that the subject should prepare to conduct a specified action; then playing a startling acoustic stimuli (SAS) before the "Go" signal the subject is anticipating.

References

Illustrations

Worked examples

Example 1 — a first encounter with Startle-evoked movement

Start with the simplest possible case. Write down what Startle-evoked movement claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, 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 Startle-evoked movement 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 Startle-evoked movement 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 Startle-evoked movement

In research: Startle-evoked movement appears in astronomy 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 Startle-evoked movement 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: Startle-evoked movement is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ethology, Neurophysiology, Reflexes, so understanding it makes those chapters shorter.
In everyday life: Look for Startle-evoked movement 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Startle-evoked movement” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Startle-evoked movement in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Startle-evoked movement means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Startle-evoked movement out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Startle-evoked movement in simple terms?

Why does Startle-evoked movement matter?

Because it connects several astronomy 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 Startle-evoked movement?

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 Startle-evoked movement.