astronomy

Startle response

Startle response 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 response rather than just read about it. In short: In animals, including humans, the startle response is a largely unconscious defensive response to sudden or threatening stimuli, such as sudden noise or sharp movement, and is associated with negative affect. Usually the onset of the startle response is a startle reflex reaction.

Key takeaways

Startle response 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 response to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Startle response from memory before moving on to harder problems.

Reference excerpt

In animals, including humans, the startle response is a largely unconscious defensive response to sudden or threatening stimuli, such as sudden noise or sharp movement, and is associated with negative affect. Usually the onset of the startle response is a startle reflex reaction. The startle reflex is a brainstem reflectory reaction (reflex) that serves to protect vulnerable parts, such as the back of the neck (whole-body startle) and the eyes (eyeblink) and facilitates escape from sudden stimuli. It is found across many different species, throughout all stages of life. A variety of responses may occur depending on the affected individual's emotional state, body posture, preparation for execution of a motor task, or other activities.

Startle reflex

Neurophysiology

A startle reflex can occur in the body through a combination of actions. A reflex from hearing a sudden loud noise will happen in the primary acoustic startle reflex pathway consisting of three main central synapses, or signals that travel through the brain. First, there is a synapse from the auditory nerve fibers in the ear to the cochlear root neurons (CRN). These are the first acoustic neurons of the central nervous system. Studies have shown a direct correlation to the amount of decrease of the startle to the number of CRNs that were killed. Second, there is a synapse from the CRN axons to the cells in the nucleus reticularis pontis caudalis (PnC) of the brain. These are neurons that are located in the pons of the brainstem. A study done to disrupt this portion of the pathway by the injection of PnC inhibitory chemicals has shown a dramatic decrease in the amount of startle by about 80 to 90 percent. Third, a synapse occurs from the PnC axons to the motor neurons in the facial motor nucleus or the spinal cord that will directly or indirectly control the movement of muscles. The activation of the facial motor nucleus causes a jerk of the head while an activation in the spinal cord causes the whole body to startle. During neuromotor examinations of newborns, it is noted that, for a number of techniques, the patterns of the startle reaction and the Moro reflex may significantly overlap, the notable distinction being the absence of arm abduction (spreading) during startle responses.

Reflexes There are many various reflexes that can occur simultaneously during a startle response. The fastest reflex recorded in humans happens within the masseter muscle or jaw muscle. The reflex was measured by electromyography which records the electrical activity during movement of the muscles. This also showed the response latency, or the delay between the stimulus and the response recorded, was found to be about 14 milliseconds. The blink of the eye which is the reflex of the orbicularis oculi muscle was found to have a latency of about 20 to 40 milliseconds. Out of larger body parts, the head is quickest in a movement latency in a range from 60 to 120 milliseconds. The neck then moves almost simultaneously with a latency of 75 to 121 milliseconds. Next, the shoulder jerks at 100 to 121 milliseconds along with the arms at 125 to 195 milliseconds. Lastly the legs respond with a latency of 145 to 395 milliseconds. This type of cascading response correlates to how the synapses travel from the brain and down the spinal cord to activate each motor neuron.

Acoustic startle reflex The acoustic startle reflex is thought to be caused by an auditory stimulus greater than 80 decibels. The reflex is typically measured by electromyography, brain imaging or sometimes positron emission tomography. There are many brain structures and pathways thought to be involved in the reflex. The amygdala, hippocampus, bed nucleus of the stria terminalis (BNST) and anterior cingulate cortex are all thought to play a role in modulating the reflex. The anterior cingulate cortex in the brain is largely thought to be the main area associated with emotional response and awareness, which can contribute to the way an individual reacts to startle-inducing stimuli. Along with the anterior cingulate cortex, the amygdala and the hippocampus are known to have implications in this reflex. The amygdala is known to have a role in the "fight-or-flight response", and the hippocampus functions to form memories of the stimulus and the emotions associated with it. The role of the BNST in the acoustic startle reflex may be attributed to specific areas within the nucleus responsible for stress and anxiety responses. Activation of the BNST by certain hormones is thought to promote a startle response. The auditory pathway for this response was largely elucidated in rats in the 1980s. The basic pathway follows the auditory pathway from the ear up to the nucleus of the lateral lemniscus (LLN) from where it activates a motor centre in the reticular formation. This centre sends descending projections to lower motor neurones of the limbs. In slightly more detail this corresponds to ear (cochlea) → cranial nerve VIII (auditory) → cochlear nucleus (ventral/inferior) → LLN → caudal pontine reticular nucleus (PnC). The whole process has a less than 10ms latency. There is no involvement of the superior/rostral or inferior/caudal colliculus in the reaction that "twitches" the hindlimbs, but these may be important for adjustment of pinnae and gaze towards the direction of the sound, or for the associated blink.

Application in occupational settings A study undertaken in 2005 by researchers at the Department of Aviation and Logistics, University of Southern Queensland, looked at the performance of aircraft pilots following unexpected critical events. Analysing a number of recent aircraft accidents, the authors identified the negative impact of the startle response as causal or contributory in these accidents. The authors argued that fear resulting from threat, especially if life-threatening, prompted startle effects which had a serious negative impact on pilots' performances. The study considered training strategies to address this, including exposing pilots to unexpected critical events more often, enabling them to improve their responses.

See also Startle-evoked movement Escape response Jumping Frenchmen of Maine Jump scare Prepulse inhibition – attenuation of the startle response after a weaker preceding prepulse stimulus Surprise (emotion)

References

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Startle response

Start with the simplest possible case. Write down what Startle response 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 response 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 response 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 response

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

Affiliate

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

How to study Startle response in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Startle response 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 response out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Startle response in simple terms?

Why does Startle response 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 response?

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 response.