science

Ventrobasal complex

Ventrobasal complex is a science 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 Ventrobasal complex rather than just read about it. In short: The ventrobasal complex (VB) is a relay nucleus of the thalamus for nociceptive stimuli received from nociceptive nerves. The VB consists of the ventral posteromedial nucleus (VPM) and the ventral posterolateral nucleus (VPL).

Key takeaways

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Reproduce the core statement of Ventrobasal complex from memory before moving on to harder problems.

Reference excerpt

The ventrobasal complex (VB) is a relay nucleus of the thalamus for nociceptive stimuli received from nociceptive nerves. The VB consists of the ventral posteromedial nucleus (VPM) and the ventral posterolateral nucleus (VPL). In some species, the ventral posterolateral nucleus, pars caudalis is also a part of the VB. The VB gets inputs from the spinothalamic tract, medial lemniscus, and corticothalamic tract. The main output of the VB is the primary somatosensory cortex. The VB serves as the main relay for nociceptive stimuli and the modulation of that stimuli to the primary somatosensory cortex. The modulation occurs through different types of receptors present in the VB.

VB Inputs Spinothalamic tract (STT) cells that project from laminae I and V in the lumbosacral area of the spinal cord project to the VPL in the VB. STT cells located in the cervical area of the spinal cord are the densest and project from the neck of the dorsal horn to the VPL of the VB. Most projections to the VB are contralateral while only a few projections to the VB are ipsilateral. Excitatory inputs to the VB are medial lemniscal (ML) and corticothalamic (CT) glutamatergic synapses. The ML is a sensory afferent input and the CT is from layer VI of the primary sensory cortex. The VB also gets inputs from areas in the brain stem which release acetylcholine (ACh) that can modulate activity in the VB.

VB Outputs The VB has outputs to the primary somatosensory cortex.

VB Neurons There are two types of nociceptive neurons that provide input to the VB: nociceptive specific (NS) neurons and wide dynamic range neuron (WDR). NS neurons respond specifically to a noxious mechanical stimulus, whereas WDR neurons respond to a graded mechanical stimulus. NS and WDR neurons within the VB are somatotopically organized. NS neurons are located more caudally in the VB, while WDR neurons are located more rostrally. All inputs into the VB are contralateral and have two different receptive fields within the VB. The VPM receptive field receives input from the contralateral trigeminal nerve and the VPL receptive field receives input from the contralateral spinal nerve. Each have NS and WDR neurons but terminate either caudally or rostrally respectively.

VB Modulation

Nicotinic ACh Receptors Nicotinic acetylcholine receptors (nAChRs) are present in the VB. Each nAChR can be made up of different subunits which can cause the receptor to respond to different stimuli. In the VB, nAChRs can contain the subunits α4, α5, α7, and β2. nAChRs that are made up of (α4β2)2α5 are of interest because they decrease neurotransmitter release for corticothalamic (CT) synapses. When nAChRs are activated there is a decrease in synaptic transmission of glutamate from CT neurons. When CT synaptic transmission is decreased by activation of the nAChRs then the activated nAChRs in the VB can selectively enhance information to the somatosensory cortex through the medial lemniscal tract.

Mu-opioid Receptors

μ-opioid receptor (MORs) are inhibitory receptors that can cause a decrease in pain if activated and are expressed in the VB especially in the VPL. When MORs are activated, by an agonist like DAMGO for example, pain-related behaviors are decreased for a certain amount of time. After 45 minutes rats that were given DAMGO show signs of increased pain behaviors suggesting that opiates activate a pronociceptive system which can lead to increased pain sensitivity after only having one dose of opiates administered. Decrease in pain-related behaviors can be attributed to the activation of MORs in the VB which activates an inhibitory circuit for pain by decreasing the amount or quality of information relayed to the somatosensory cortex. However, there is a complex mechanism between MORs and other receptors in the VB that can lead to a decrease in pain-related behaviors and thus further research is needed to understand exactly how this mechanism works.

GABAB Receptors GABAB receptors are located in the VB. If a receptor is located presynaptically when activated it causes the suppression of neurotransmitter release. If the receptor is located postsynaptically then when activated it causes inhibitory postsynaptic potential. When GABAB receptors are activated or blocked by baclofen (agonist) or CGP35348 (antagonist) respectively there is a decrease in pain-related behaviors in a dose-dependent manner. That is, there is less pain-related behavior if a higher dose is given. It is not known if this mechanism is occurring presynaptically or postsynaptically. Further research is needed to distinguish between where the inhibition is being mediated.

References

Worked examples

Example 1 — a first encounter with Ventrobasal complex

Start with the simplest possible case. Write down what Ventrobasal complex claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Ventrobasal complex 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 Ventrobasal complex 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 Ventrobasal complex

In research: Ventrobasal complex appears in science 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 Ventrobasal complex 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: Ventrobasal complex is common in secondary-school and first-year university syllabi. It links to neighbouring topics Sensory systems, Thalamus, so understanding it makes those chapters shorter.
In everyday life: Look for Ventrobasal complex 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 Ventrobasal complex in 20 minutes

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

Frequently asked questions

What is Ventrobasal complex in simple terms?

Why does Ventrobasal complex matter?

Because it connects several science 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 Ventrobasal complex?

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 Ventrobasal complex.