Neurophysiology Practice Questions

Q: Which of the following statements is true regarding post-ganglionic parasympathetic fibers?

They release acetylcholine at the target organs.. ***They release acetylcholine at the target organs.*** - Post-ganglionic parasympathetic fibers are **cholinergic**, meaning they release the neurotransmitter **acetylcholine** at their effector organs. - This action mediates the characteristic "rest and digest" responses of the parasympathetic nervous system. *They originate from the spinal cord.* - **Pre-ganglionic parasympathetic fibers** originate from the **brainstem** (cranial nerves III, VII, IX, X) and the **sacral spinal cord** (S2-S4). - Post-ganglionic fibers originate in ganglia located near or within their target organs, not the spinal cord directly. *They are part of the sympathetic nervous system.* - Post-ganglionic parasympathetic fibers are a component of the **parasympathetic nervous system**, not the sympathetic nervous system. - The sympathetic and parasympathetic systems are distinct divisions of the autonomic nervous system with generally opposing functions. *They are responsible for 'fight or flight' responses.* - The **'fight or flight' response** is characteristic of the **sympathetic nervous system**, which prepares the body for stressful situations. - The parasympathetic nervous system is responsible for **'rest and digest' functions**, promoting energy conservation and maintenance activities.

Q: Lesion of globus pallidus causes

Athetosis. ***Athetosis*** - **Athetosis** is the **classic movement disorder** associated with lesions of the **globus pallidus**, often occurring with **putamen** involvement. - It is characterized by **slow, writhing, involuntary movements**, particularly affecting the **distal extremities** (hands and feet). - Commonly seen in **kernicterus** (bilirubin-induced damage to basal ganglia), **cerebral palsy**, and **status marmoratus** of the basal ganglia. - When combined with chorea, it forms **choreoathetosis**. *Chorea* - **Chorea** is predominantly associated with dysfunction of the **caudate nucleus** and **putamen**, as seen in **Huntington's disease**. - It involves brief, irregular, unpredictable, **involuntary movements** that flow from one body part to another. *Hemibalismus* - **Hemibalismus** is most commonly caused by a lesion in the **subthalamic nucleus** (nucleus of Luys), often due to a **lacunar stroke**. - It involves large-amplitude, **involuntary flinging movements** of the limbs on **one side of the body**. *Dystonia* - **Dystonia** involves sustained or repetitive muscle contractions leading to twisting movements or abnormal fixed postures. - It results from dysfunction of **multiple basal ganglia structures** including the globus pallidus internal segment, putamen, and thalamus, but is **not the classic presentation** of isolated globus pallidus lesions.

Q: Narcolepsy is due to abnormality in ?

Hypothalamus. **Hypothalamus** - Narcolepsy is primarily caused by the loss of **orexin (hypocretin)** producing neurons in the **hypothalamus**, which are crucial for maintaining wakefulness. - This deficiency leads to dysregulation of **sleep-wake cycles**, causing excessive daytime sleepiness and other narcolepsy symptoms. *Neocortex* - The neocortex is involved in higher-level cognitive functions, sensory perception, and voluntary movement, but it is not the primary site of pathology in narcolepsy. - While sleep stages involve cortical activity, the core deficit in narcolepsy does not originate here. *Cerebellum* - The cerebellum is mainly responsible for motor control, coordination, and balance. - Its dysfunction is associated with ataxic gait and coordination problems, not the sleep disturbances characteristic of narcolepsy. *Medulla oblongata* - The medulla oblongata controls vital autonomic functions like breathing, heart rate, and blood pressure. - While involved in sleep regulation pathways, it is not the primary anatomical location affected in narcolepsy.

Q: Which tract is responsible for the loss of proprioception and fine touch?

Dorsal column. ***Dorsal column*** - The **dorsal column-medial lemniscus pathway** is responsible for transmitting **fine touch**, **vibration**, and **proprioception** from the body to the cerebral cortex. - Damage to this tract (e.g., in **tabes dorsalis** or **vitamin B12 deficiency**) leads to a loss of these sensations. *Anterior spinothalamic tract* - This tract primarily conveys crude touch and pressure sensations. - While it carries tactile information, it does not transmit the fine discriminative touch or proprioception associated with the dorsal columns. *Lateral spinothalamic tract* - This pathway is responsible for transmitting **pain** and **temperature** sensations. - It does not play a role in proprioception or fine touch. *Corticospinal tract* - The **corticospinal tract** is a **motor pathway** responsible for voluntary movement. - It has no role in transmitting sensory information such as proprioception or fine touch.

Q: Which of the following statements is true regarding the function of the spinocerebellar tract?

Smoothens and coordinates movements. ***Smoothens and coordinates movements*** - The spinocerebellar tract provides the cerebellum with **unconscious proprioceptive information** from muscle spindles and Golgi tendon organs. - This information allows the cerebellum to compare intended movements with actual movements, thereby **smoothing and coordinating voluntary motor activity**. *Involved in planning and programming motor activities* - This function is primarily attributed to the **cerebral cortex** (e.g., premotor and supplementary motor areas) and the **basal ganglia**. - While the cerebellum is involved in motor learning and fine-tuning, the initial **planning and programming** of complex movements are cortical functions. *Involved in maintaining equilibrium* - Maintaining equilibrium and balance is primarily a function of the **vestibulocerebellum** (flocculonodular lobe), which receives input from the vestibular system. - While the spinocerebellum indirectly influences balance by coordinating limb movements, its direct role is less pronounced than that of the vestibulocerebellum. *Facilitates learning through vestibulo-ocular reflex changes* - This function is specific to the **vestibulocerebellum** and is crucial for adapting the vestibulo-ocular reflex (VOR) to maintain visual stability during head movements. - The spinocerebellar tract's primary role is proprioception for limb coordination, not VOR adaptation.

Q: Neurotransmitter involved in nigrostriatal pathway is?

Dopamine. ***Dopamine*** - The **nigrostriatal pathway** is a major dopaminergic pathway in the brain, originating in the **substantia nigra pars compacta** and projecting to the striatum. - It is crucial for the control of voluntary movement, and its degeneration is a hallmark of **Parkinson's disease**. *Serotonin* - Serotonin (5-HT) is primarily involved in mood, sleep, appetite, and cognition, and is not the primary neurotransmitter of the **nigrostriatal pathway**. - Serotonergic pathways originate in the **raphe nuclei** and project widely throughout the brain. *Acetylcholine* - Acetylcholine is a key neurotransmitter in the periphery (neuromuscular junction, autonomic nervous system) and in the central nervous system, involved in learning and memory. - Cholinergic neurons in the **basal forebrain** project to the cortex and hippocampus, but acetylcholine is not the neurotransmitter of the **nigrostriatal pathway**. *Norepinephrine* - Norepinephrine (noradrenaline) is involved in arousal, attention, and the fight-or-flight response, with pathways originating in the **locus coeruleus**. - While it plays a role in modulating motor circuits, it is not the main neurotransmitter of the **nigrostriatal pathway**.

Q: Damage to the striatum primarily affects which type of memory?

Memory of how to perform tasks. ***Memory of how to perform tasks*** - The **striatum**, a component of the **basal ganglia**, is crucial for **procedural memory**, which is the memory of how to perform skills and habitual tasks. - Damage to this area can impair the ability to learn new motor skills or execute previously learned ones, even if the person remembers the task explicitly. *Memory for recent events* - This type of memory, often referred to as **episodic memory**, relies heavily on the **hippocampus** and medial temporal lobe structures. - Damage to the striatum typically does not directly affect the recall of recent events or experiences. *Memory for past experiences* - **Autobiographical memory**, which includes past experiences, primarily involves widespread cortical networks, particularly in the **temporal and frontal lobes**. - While broad brain damage can affect this, the striatum's primary role is not in the storage or retrieval of experiential memories. *Memory for facts and events* - This describes **declarative memory**, which is subdivided into **semantic memory** (facts) and **episodic memory** (events). - These are largely mediated by the **hippocampus**, **medial temporal lobes**, and various cortical areas, not primarily the striatum.

Q: Which of the following is the MOST accurate statement about CSF?

Formed by the choroid plexus in the ventricles.. ***Formed by the choroid plexus in the ventricles.*** * The **choroid plexus**, located in the ventricles of the brain, is primarily responsible for the production of **cerebrospinal fluid (CSF)**. * Specialized epithelial cells of the choroid plexus filter blood plasma to produce CSF, which then circulates through the central nervous system. *Normally contains no neutrophils* * Normal CSF should contain **virtually no neutrophils**; their presence typically indicates an inflammatory or infectious process, such as **bacterial meningitis**. * While normal CSF doesn't have neutrophils, this option isn't as broadly accurate as the choroid plexus statement because the presence of other cell types like lymphocytes in small numbers is normal. *pH is less than that of plasma* * The pH of CSF is typically **slightly lower than that of plasma** (around 7.31 compared to 7.40), but the statement "less than" is broad and the degree of difference can be variable and is a less defining characteristic than its formation site. * This slight difference in pH is important for regulating **respiration** through chemoreceptors, but it's not the most accurate or fundamental statement about CSF properties. *Removal of CSF during dural tap can cause a headache due to the change in pressure.* * A **post-dural puncture headache** (PDPH) is a well-known complication of a dural tap (lumbar puncture), caused by the leakage of CSF from the puncture site, leading to **intracranial hypotension**, not simply a change in pressure. * This decrease in CSF volume and pressure causes a traction on pain-sensitive structures within the cranium, resulting in a headache that is typically **worse when upright** and relieved by lying down.

Q: Which sensory modalities are most directly affected by lesions of the primary somatosensory cortex?

Localization and two-point discrimination. ***Localization and two-point discrimination*** - Lesions in the **primary somatosensory cortex** (S1) lead to profoundly impaired **discriminative touch**, which includes the ability to precisely localize tactile stimuli and distinguish between two closely spaced points. - These are the **most characteristic deficits** of S1 lesions, representing the cortex's unique role in processing **spatial discrimination and fine sensory analysis**. - S1 is essential for the **integrative functions** that allow precise spatial mapping of sensory inputs. *Pain, temperature, and touch* - Basic touch perception is affected, but **pain and temperature** are primarily mediated by the **spinothalamic tracts** with substantial processing in the thalamus, insular cortex, and anterior cingulate cortex rather than S1. - Crude touch sensation remains relatively preserved with S1 lesions; it is the **discriminative quality** that is lost. - These modalities are NOT the most directly affected by isolated S1 lesions. *Vibration and proprioception* - **Vibration** and **proprioception** are indeed significantly impacted by S1 lesions as S1 receives thalamic projections from the **dorsal column-medial lemniscus (DCML) pathway**. - However, these modalities have substantial **subcortical representation** in the thalamus and can be partially preserved even with cortical damage. - In contrast, **localization and two-point discrimination** are purely cortical functions with no subcortical processing, making them the MOST directly and exclusively dependent on S1 integrity. *All of the options* - This is incorrect because pain and temperature perception is NOT most directly affected by S1 lesions—these are primarily processed by other pathways and cortical areas (spinothalamic system, insular cortex).

Q: Which part of the brain is responsible for setting posture before planned movement?

Supplementary motor cortex. ***Supplementary motor cortex*** - The **supplementary motor cortex (SMA)** is responsible for **anticipatory postural adjustments** that occur before voluntary movements - It plays a key role in **internal generation and planning of complex motor sequences** - SMA activation precedes movement, ensuring **postural stability and coordination** - Essential for **bilateral coordination** and **motor programming** *Premotor cortex* - The **premotor cortex** is primarily involved in **externally guided movements** and selection of movements based on sensory cues - While it participates in motor planning, it is more focused on **sensory-motor integration** rather than anticipatory postural control *Motor cortex* - The **primary motor cortex** executes voluntary movements by sending signals directly to spinal motor neurons - Responsible for **fine motor control** and determining the **force and direction** of muscle contractions - Functions in **movement execution** rather than preparatory postural adjustments *Frontal eye fields* - The **frontal eye fields** control **voluntary saccadic eye movements** and visual attention - Not involved in trunk or limb **postural preparation** for planned movements

Question 1

Which of the following statements is true regarding post-ganglionic parasympathetic fibers?

Accepted Answer

They release acetylcholine at the target organs.

Answer

They originate from the spinal cord.

Answer

They are part of the sympathetic nervous system.

Answer

They are responsible for 'fight or flight' responses.

Question 2

Lesion of globus pallidus causes

Accepted Answer

Athetosis

Answer

Chorea

Answer

Hemibalismus

Answer

Dystonia

Question 3

Narcolepsy is due to abnormality in ?

Accepted Answer

Hypothalamus

Answer

Neocortex

Answer

Cerebellum

Answer

Medulla oblongata

Question 4

Which tract is responsible for the loss of proprioception and fine touch?

Accepted Answer

Dorsal column

Answer

Anterior spinothalamic tract

Answer

Lateral spinothalamic tract

Answer

Corticospinal tract

Question 5

Which of the following statements is true regarding the function of the spinocerebellar tract?

Accepted Answer

Smoothens and coordinates movements

Answer

Involved in planning and programming motor activities

Answer

Involved in maintaining equilibrium

Answer

Facilitates learning through vestibulo-ocular reflex changes

Question 6

Neurotransmitter involved in nigrostriatal pathway is?

Accepted Answer

Dopamine

Answer

Acetylcholine

Answer

Serotonin

Answer

Norepinephrine

Question 7

Damage to the striatum primarily affects which type of memory?

Accepted Answer

Memory of how to perform tasks

Answer

Memory for recent events

Answer

Memory for past experiences

Answer

Memory for facts and events

Question 8

Which of the following is the MOST accurate statement about CSF?

Accepted Answer

Formed by the choroid plexus in the ventricles.

Answer

Normally contains no neutrophils

Answer

pH is less than that of plasma

Answer

Removal of CSF during dural tap can cause a headache due to the change in pressure.

Question 9

Which sensory modalities are most directly affected by lesions of the primary somatosensory cortex?

Accepted Answer

Localization and two-point discrimination

Answer

Pain, temperature, and touch

Answer

Vibration and proprioception

Answer

All of the options

Question 10

Which part of the brain is responsible for setting posture before planned movement?

Accepted Answer

Supplementary motor cortex

Answer

Motor cortex

Answer

Frontal eye fields

Answer

Premotor cortex

Neurophysiology — MCQs

Neurophysiology — MCQs

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