Neurophysiology Practice Questions

Q: Which of the following does not have sympathetic noradrenergic fibers?

Sweat gland. ***Sweat gland*** - While sweat glands are innervated by the **sympathetic nervous system**, their postganglionic fibers are **cholinergic**, releasing **acetylcholine** rather than noradrenaline. - This is an important exception where sympathetic stimulation leads to acetylcholine release, causing sweating. *Blood vessels* - Most blood vessels, particularly resistance vessels such as **arterioles**, receive substantial **sympathetic noradrenergic innervation** that causes vasoconstriction. - This sympathetic tone is crucial for regulating **blood pressure** and distributing blood flow. *Heart* - The heart is richly innervated by **sympathetic noradrenergic fibers** that increase **heart rate**, **contractility**, and **conduction velocity** via beta-1 adrenergic receptors. - This makes noradrenaline a key neurotransmitter in the sympathetic regulation of cardiac function. *Eye* - The eye receives sympathetic noradrenergic innervation primarily to the **dilator pupillae muscle**, causing **mydriasis** (pupil dilation) upon activation. - These fibers also contribute to the sympathetic control of the **tarsal muscle** (Müller's muscle) in the eyelid.

Q: Spinal pathway mainly regulating fine motor activity?

Lateral corticospinal tract. ***Lateral corticospinal tract*** - This pathway contains **85-90% of corticospinal fibers** that cross at the medullary pyramids and descend in the **lateral funiculus** of the spinal cord - It is the **primary pathway for fine, precise, voluntary movements** of **distal extremities**, particularly the hands, fingers, feet, and toes - Enables intricate skilled movements like writing, buttoning, and fine manipulation due to direct monosynaptic connections to motor neurons - Damage results in loss of fine motor control and skilled movements *Anterior corticospinal tract* - Contains only **10-15% of corticospinal fibers** that descend uncrossed in the anterior spinal cord - Controls **bilateral movements of axial and proximal muscles** (neck, trunk, shoulders) - Not specialized for fine motor control of distal limbs *Vestibulospinal tract* - Regulates **posture and balance** by modulating extensor muscle tone - Coordinates head position and maintains upright posture - Does not control fine voluntary movements *Reticulospinal tract* - Modulates **muscle tone, posture, and locomotion** - Provides general motor control and autonomic regulation - Not specialized for precise, intricate fine motor movements

Q: Pelvic pain is mediated by ?

Autonomic nerves. ***Autonomic nerves*** - Pelvic pain, especially **visceral pelvic pain**, is predominantly mediated by the **autonomic nervous system**, specifically the **sympathetic and parasympathetic fibers** that innervate pelvic organs. - These nerves transmit sensations like ache, pressure, and cramp from the uterus, bladder, and bowel, which are characteristic of diffuse pelvic pain. *Pudendal nerve* - The pudendal nerve primarily mediates **somatic sensation** and motor function of the perineum and external genitalia. - While it can be involved in localized pelvic pain (e.g., pudendal neuralgia), it does not mediate diffuse, visceral pelvic pain. *Sciatic nerve* - The sciatic nerve is responsible for motor and sensory innervation of the **lower limb** and is not directly involved in mediating visceral pelvic pain. - Sciatic pain typically presents as **radicular pain** radiating down the leg, distinct from generalized pelvic discomfort. *None of the options* - This option is incorrect because **autonomic nerves** are clearly involved in mediating pelvic pain, as described above. - Various nerve types contribute to different aspects of pelvic sensation, but autonomic fibers are key for visceral pain.

Q: What type of reflex is the righting reflex?

Postural reflex. ***Postural reflex*** - The **righting reflex** is a mechanism that helps an animal or human maintain or regain their upright body position or head orientation in space, which is a key component of **postural control**. - It involves complex inputs from the **vestibular system**, visual system, and proprioceptors to adjust muscle tone and body position against gravity. - Examples include **neck righting reflex**, **body righting reflex**, and **labyrinthine righting reflex**. *Stretch reflex* - A **stretch reflex** is a monosynaptic reflex that causes a muscle to contract in response to being stretched, primarily to maintain muscle length and tone. - It does not encompass the complex, multi-sensory integration required for maintaining overall body orientation. *Spinal reflex* - A **spinal reflex** is any reflex arc whose neural circuit passes through the spinal cord, and it can be either monosynaptic or polysynaptic. - While the righting reflex involves spinal cord components, it is a broader, more integrated reflex that extends beyond a simple spinal cord circuit. *Ocular reflex* - **Ocular reflexes** are involuntary eye movements or responses, such as pupillary light reflex or vestibulo-ocular reflex, that primarily control eye position or pupil size. - They do not directly relate to the maintenance of the entire body's upright posture.

Q: Cell bodies of orexigenic neurons are present in?

Lateral hypothalamic area. ***Lateral hypothalamic area*** - The **lateral hypothalamic area** (LHA) contains neurons that produce **orexin (hypocretin)**, a neuropeptide critical for promoting appetite and wakefulness. - Stimulation of the LHA leads to increased food seeking and consumption, earning it the moniker "**feeding center**." *Dorsal raphe* - The **dorsal raphe nucleus** is a key source of **serotonin** in the brain, involved in mood, sleep-wake cycles, and appetite regulation (often promoting satiety). - It does not primarily house orexigenic neurons that directly stimulate appetite. *Locus coerulus* - The **locus coeruleus** is the primary source of **norepinephrine** in the brain, playing a significant role in arousal, attention, and stress response. - While it modulates appetitive behaviors indirectly, its neurons are not the primary orexigenic cell bodies. *Hippocampus* - The **hippocampus** is crucial for **learning, memory formation**, and spatial navigation. - It is not directly involved in the primary neural circuits that control hunger and satiety through orexigenic neuropeptides.

Q: Unable to consolidate long-term memory. Which lobe of the brain is involved?

Temporal. ***Temporal*** - The **temporal lobe**, particularly the **hippocampus** within it, is critically involved in the formation and consolidation of new long-term memories [1]. - Damage to the temporal lobe can result in **anterograde amnesia**, the inability to form new memories after the injury [1]. *Frontal* - The **frontal lobe** is primarily responsible for executive functions, **planning**, decision-making, and working memory [1]. - While it contributes to memory retrieval and strategic memory processes, it is not the primary site for the consolidation of long-term memories. *Parietal* - The **parietal lobe** is involved in processing **sensory information**, spatial awareness, and navigation. - It plays a role in attention and short-term memory, but not in the consolidation of long-term memory. *Occipital* - The **occipital lobe** is dedicated to **visual processing** and interpretation of visual information. - It has no direct primary role in the consolidation of long-term memories.

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: What is the normal range for the CSF/plasma glucose ratio?

0.6 - 0.8. ***Correct: 0.6 - 0.8*** - This ratio indicates that cerebrospinal fluid (CSF) glucose concentration is typically 60-80% of plasma glucose concentration - This range is crucial for identifying metabolic or infectious pathologies affecting the central nervous system - Normal CSF glucose is approximately 50-80 mg/dL when plasma glucose is 70-120 mg/dL *Incorrect: 0.2 - 0.4* - A ratio in this range indicates significantly low CSF glucose, suggesting conditions like bacterial meningitis or hypoglycorrhachia - This is well below the normal physiological proportion of glucose in the CSF relative to plasma - Seen in bacterial/tuberculous meningitis, fungal infections, or malignancy *Incorrect: 1.0 - 1.2* - A CSF/plasma glucose ratio close to or above 1.0 would imply that CSF glucose levels are equal to or higher than plasma levels, which is physiologically impossible under normal conditions - Glucose transport into the CSF is regulated by GLUT-1 transporters and typically results in lower concentrations than in plasma - The blood-brain barrier maintains this gradient *Incorrect: 1.2 - 1.6* - This range is even more exaggerated and physiologically impossible, as CSF glucose cannot exceed plasma glucose in a healthy individual - Such a high ratio would contradict the mechanisms of glucose transport across the blood-brain barrier - Would suggest laboratory error if observed

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.

Question 1

Which of the following does not have sympathetic noradrenergic fibers?

Accepted Answer

Sweat gland

Answer

Heart

Answer

Eye

Answer

Blood vessels

Question 2

Spinal pathway mainly regulating fine motor activity?

Accepted Answer

Lateral corticospinal tract

Answer

Vestibulospinal tract

Answer

Anterior corticospinal tract

Answer

Reticulospinal tract

Question 3

Pelvic pain is mediated by ?

Accepted Answer

Autonomic nerves

Answer

Sciatic nerve

Answer

Pudendal nerve

Answer

None of the options

Question 4

What type of reflex is the righting reflex?

Accepted Answer

Postural reflex

Answer

Spinal reflex

Answer

Ocular reflex

Answer

Stretch reflex

Question 5

Cell bodies of orexigenic neurons are present in?

Accepted Answer

Lateral hypothalamic area

Answer

Dorsal raphe

Answer

Locus coeruleus

Answer

Hippocampus

Question 6

Unable to consolidate long-term memory. Which lobe of the brain is involved?

Accepted Answer

Temporal

Answer

Frontal

Answer

Parietal

Answer

Occipital

Question 7

Lesion of globus pallidus causes

Accepted Answer

Athetosis

Answer

Chorea

Answer

Hemibalismus

Answer

Dystonia

Question 8

Narcolepsy is due to abnormality in ?

Accepted Answer

Hypothalamus

Answer

Neocortex

Answer

Cerebellum

Answer

Medulla oblongata

Question 9

What is the normal range for the CSF/plasma glucose ratio?

Accepted Answer

0.6 - 0.8

Answer

1.2 - 1.6

Answer

0.2 - 0.4

Answer

1.0 - 1.2

Question 10

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

Neurophysiology — MCQs

Neurophysiology — MCQs

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