Neurophysiology Practice Questions

Q: Dorsal column lesions are associated with loss of:

Loss of proprioception. ***Proprioception*** - The **dorsal column-medial lemniscus pathway** is responsible for transmitting fine touch, vibration, and **proprioception** from the body to the brain. - Damage to this pathway, such as in a **dorsal column lesion**, directly impairs the ability to sense the position and movement of body parts. *Loss of ankle jerk reflex* - The **ankle jerk reflex**primarily tests the integrity of the **S1 and S2 nerve roots** and the reflex arc involving the gastrocnemius and soleus muscles. - This reflex is generally not directly affected by isolated dorsal column lesions, as it is a **deep tendon reflex** that relies on sensory and motor neuron pathways distinct from the dorsal column. *Loss of superficial abdominal reflexes* - **Superficial abdominal reflexes** assess the integrity of the T7-T12 spinal cord segments and corresponding nerve pathways. - These reflexes involve different neurological pathways compared to the dorsal column, which is primarily sensory for conscious proprioception, vibration, and fine touch. *Loss of knee jerk reflex* - The **knee jerk reflex** (patellar reflex) tests the integrity of the **L2, L3, and L4 spinal nerve roots** and the quadriceps femoris muscle. - Like the ankle jerk, this is a **deep tendon reflex** whose arc is separate from the dorsal column's ascending sensory tracts.

Q: Which of the following statements is MOST accurate regarding REM sleep?

Low muscle tone. ***Low muscle tone*** - **Muscle atonia** (near-complete loss of skeletal muscle tone) is one of the **defining physiological characteristics** of **REM sleep**. - This **muscle paralysis** prevents individuals from acting out their dreams and is a consistent, measurable feature of REM sleep. - Along with rapid eye movements and desynchronized EEG, **muscle atonia** is one of the three hallmark features that define REM sleep. *Dreams* - While **vivid dreams** are commonly associated with **REM sleep** and dream recall is highest during this stage, not all REM periods result in recalled dreams. - Dream recall varies significantly between individuals and circumstances. - Dreams can also occur during **NREM sleep**, though they are typically less vivid and less frequently recalled. *Slow waves on EEG* - **Slow waves** are characteristic of **deep non-REM sleep (N3 stage)**, not REM sleep. - During REM sleep, the **EEG** shows a **low-voltage, mixed-frequency pattern** resembling wakefulness (desynchronized EEG). *Decrease in BP* - During **REM sleep**, blood pressure often **fluctuates** and can even **increase** due to autonomic instability, rather than consistently decreasing. - The cardiovascular system exhibits **irregularities** in both heart rate and blood pressure during REM sleep.

Q: Complete transection of the spinal cord at the C7 level produces all of the following effects except:

Areflexia below the level of the lesion. ***Areflexia below the level of the lesion*** - While immediate **spinal shock** after a complete transection would cause areflexia, over time, the segments below the lesion often develop **hyperreflexia** and spasticity due to the loss of descending inhibitory control. - Therefore, sustained areflexia is an *unlikely* long-term effect of a complete spinal cord transection at C7. *Limited respiratory effort* - A C7 lesion would affect the **intercostal muscles** (innervated by T1-T11) and the **abdominal muscles** (innervated by T7-L1), which are crucial for forceful exhalation and coughing. - While the diaphragm (C3-C5) would be spared, breathing would still be significantly compromised, leading to a limited respiratory effort. *Anesthesia below the level of the lesion* - Complete transection interrupts all ascending sensory pathways, including the **spinothalamic tracts** (pain and temperature) and the **dorsal columns** (fine touch, vibration, proprioception), resulting in a complete loss of sensation below the C7 dermatome. - This is a hallmark of a complete spinal cord injury. *Hypotension* - Complete transection at C7 would disrupt the **sympathetic nervous system** pathways originating in the thoracolumbar region (T1-L2). - This leads to a loss of sympathetic tone to blood vessels, causing **vasodilation** and subsequent neurogenic shock, characterized by severe hypotension and bradycardia.

Q: Which of the following is true regarding cerebrospinal fluid?

Is actively secreted by choroid plexus. **Is actively secreted by choroid plexus** - **Cerebrospinal fluid (CSF)** is primarily produced by the **choroid plexus** via a combination of active transport and ultrafiltration processes. - The epithelial cells of the **choroid plexus** actively secrete ions and water, contributing to the formation and composition of CSF. *Virtually glucose free* - CSF normally contains **glucose**, although its concentration is about two-thirds of the plasma glucose concentration. - Significant reduction or absence of glucose in CSF often indicates a pathological process, such as **bacterial meningitis**. *Has the same pH of arterial blood* - The pH of CSF is typically slightly lower than that of arterial blood, usually around **7.31-7.34**, compared to plasma pH of 7.35-7.45. - This difference is crucial for maintaining the delicate acid-base balance within the central nervous system. *It is a major source of brain nutrition* - While CSF provides some nutrients, the primary source of brain nutrition is the **blood supply** through the cerebral vasculature. - Its main roles include providing **buoyancy**, **protection**, and acting as a medium for metabolite exchange, rather than direct substantial nutrition.

Q: Delta waves are seen in which stage of sleep?

Deep sleep. ***Deep sleep*** - **Delta waves** are characteristic of **Stage N3 sleep**, also known as **deep sleep** or **slow-wave sleep**. - This stage is crucial for **physical restoration** and is the deepest stage of non-REM sleep, exhibiting the slowest brain activity. *Awake with mental activity* - This state is typically associated with **beta waves**, which are high-frequency, low-amplitude waves indicative of an **alert and active mind**. - Mental activity such as problem-solving or focused attention does not involve the prominent slow waves seen in deep sleep. *Awake while resting* - When awake but resting with eyes closed, the brain typically produces **alpha waves**, characterized by a relaxed and calm state. - While alpha waves are slower than beta waves, they are still distinct from the very slow delta waves of deep sleep. *Sleeping* - This option is too general, as "sleeping" encompasses multiple stages, including light sleep (N1, N2), deep sleep (N3), and REM sleep. - While deep sleep is a stage of sleeping, the term itself doesn't specify the unique **EEG pattern** of delta waves.

Q: Positive Romberg test with eyes closed detects a defect in -

Proprioceptive pathway. Proprioceptive pathway - A positive Romberg test indicates a loss of proprioception, meaning the patient cannot maintain balance when visual cues are removed, relying solely on somatosensory input [2]. - This suggests damage to the dorsal columns of the spinal cord or peripheral nerves that transmit proprioceptive information to the brain [1], [3]. Cerebellum - While cerebellar dysfunction also causes ataxia and balance problems, it would typically present as difficulty maintaining balance even with eyes open, referred to as cerebellar ataxia [2]. - A Romberg test primarily assesses the integrity of the proprioceptive system, distinguishing it from cerebellar issues where balance problems are evident regardless of visual input [2]. Peripheral nerve - Peripheral neuropathy can indeed lead to a positive Romberg test if the sensory nerves responsible for proprioception are affected [1]. - However, "Proprioceptive pathway" is a more direct and encompassing answer, as peripheral nerves are a component of this pathway, which also includes spinal cord tracts [3]. Spinothalamic tract - The spinothalamic tract primarily transmits sensations of pain and temperature, not proprioception [3]. - Damage to this tract would result in deficits in these specific sensory modalities, rather than a positive Romberg test [1].

Q: A lesion of ventrolateral part of spinal cord will lead to loss of which of the following sensation below the level of lesion?

Pain sensation on the contralateral side. ***Pain sensation on the contralateral side*** - The **ventrolateral part of the spinal cord** contains the **spinothalamic tract**, which transmits **pain and temperature** sensations. - Fibers of the spinothalamic tract **decussate (cross over)** at the level of entry into the spinal cord, meaning a lesion will cause loss of pain sensation on the **contralateral side** below the lesion. *Proprioception on the contralateral side* - **Proprioception** is primarily carried by the **dorsal columns**, which are located more posteriorly in the spinal cord. - Fibers for proprioception from the dorsal columns **decussate in the medulla**, not at the spinal cord level, so a spinal cord lesion would generally affect ipsilateral proprioception. *Proprioception on the ipsilateral side* - While proprioception is indeed carried primarily by the **dorsal columns** (located dorsally), a lesion limited to the ventrolateral part of the spinal cord would primarily affect the spinothalamic tract, not the dorsal columns. - Therefore, isolated **ventrolateral damage** would spare ipsilateral proprioception. *Pain sensation on the ipsilateral side* - This is incorrect because the **spinothalamic tract** fibers transmitting pain sensation **decussate** in the spinal cord close to their entry point. - Therefore, a lesion in the ventrolateral spinal cord would affect the already-crossed fibers, leading to **contralateral**, not ipsilateral, pain loss.

Q: Sweat glands are supplied by only:

Sympathetic nerves. ***Sympathetic nerves*** - Sweat glands (both eccrine and apocrine) are primarily innervated by the **sympathetic nervous system**. - While sympathetic fibers typically release **norepinephrine**, the sympathetic innervation of sweat glands is unique as it releases **acetylcholine**, acting on muscarinic receptors. *Sensory nerves* - **Sensory nerves** transmit information *from* the periphery *to* the central nervous system, detecting stimuli like touch, temperature, and pain. - They do not directly control the function or secretion of sweat glands. *Motor nerves* - **Motor nerves** innervate muscles, causing contraction, and some glands, but are not the primary innervation for sweat glands. - Their main role is in mediating voluntary and involuntary muscle movements. *Parasympathetic nerves* - The **parasympathetic nervous system** is primarily involved in "rest and digest" functions, such as stimulating digestion and reducing heart rate. - It plays a very limited role, if any, in the direct innervation and control of sweat gland secretion.

Q: Sensations which are appreciated in the thalamus -

Pain & temperature. ***Pain & temperature*** - The **thalamus** serves as a crucial relay station for all sensory input, including crude **pain** and **temperature** sensations, before they reach the cerebral cortex for detailed interpretation. - While the cortex is responsible for precise localization and discrimination of these stimuli, the thalamus is where the *feeling* of pain and temperature is initially appreciated in a more generalized sense. *Tactile sensations* - **Crude touch** is appreciated in the thalamus, but **fine discriminative touch** (tactile sensations) requires cortical processing for detailed localization and discrimination. - The thalamus acts as a relay, but the cerebral cortex is essential for the higher-order processing of tactile information. *Proprioception* - **Proprioception**, or the sense of body position and movement, is relayed through the thalamus, but its complex integration and conscious awareness occur in the **somatosensory cortex**. - The cerebellum also plays a critical role in unconscious proprioception for motor coordination. *Pressure* - **Crude pressure** can be registered in the thalamus, but the fine discrimination of pressure (e.g., varying degrees of force, texture) is primarily a function of the **somatosensory cortex**. - The thalamus acts as an initial processing and relay center for general pressure sensations.

Q: EEG pattern of person at rest with eyes closed

Alpha. ***Alpha*** - **Alpha waves** are characteristic of a relaxed, wakeful state with **eyes closed**, typically originating from the **occipital lobe**. - They have a frequency range of **8 to 13 Hz** and are suppressed when the eyes open or during mental exertion. *Beta* - **Beta waves** are associated with **active thinking**, problem-solving, and during the **eyes-open waking state**. - These waves have a higher frequency, typically **above 13 Hz**, and signify an alert or engaged brain. *Delta* - **Delta waves** are the **slowest brain waves**, ranging from **0.5 to 4 Hz**, and are characteristic of **deep, dreamless sleep (NREM stage 3)**. - Their presence in a wakeful adult can indicate a significant **brain pathology** or **brain injury**. *Gamma* - **Gamma waves** represent the **highest frequency brain waves**, typically **above 30 Hz**, and are associated with **high-level cognitive functions** such as learning, memory, and perception. - They are observed during tasks requiring **focused attention** and simultaneous processing of information from different brain regions.

Question 1

Dorsal column lesions are associated with loss of:

Accepted Answer

Loss of proprioception

Answer

Loss of ankle jerk reflex

Answer

Loss of superficial abdominal reflexes

Answer

Loss of knee jerk reflex

Question 2

Which of the following statements is MOST accurate regarding REM sleep?

Accepted Answer

Low muscle tone

Answer

Slow waves on EEG

Answer

Decrease in BP

Answer

Dreams

Question 3

Complete transection of the spinal cord at the C7 level produces all of the following effects except:

Accepted Answer

Areflexia below the level of the lesion

Answer

Limited respiratory effort

Answer

Anesthesia below the level of the lesion

Answer

Hypotension

Question 4

Which of the following is true regarding cerebrospinal fluid?

Accepted Answer

Is actively secreted by choroid plexus

Answer

Virtually glucose free

Answer

Has the same pH of arterial blood

Answer

It is a major source of brain nutrition

Question 5

Delta waves are seen in which stage of sleep?

Accepted Answer

Deep sleep

Answer

Awake with mental activity

Answer

Awake while resting

Answer

Sleeping

Question 6

Positive Romberg test with eyes closed detects a defect in -

Accepted Answer

Proprioceptive pathway

Answer

Cerebellum

Answer

Peripheral nerve

Answer

Spinothalamic tract

Question 7

A lesion of ventrolateral part of spinal cord will lead to loss of which of the following sensation below the level of lesion?

Accepted Answer

Pain sensation on the contralateral side

Answer

Proprioception on the contralateral side

Answer

Proprioception on the ipsilateral side

Answer

Pain sensation on the ipsilateral side

Question 8

Sweat glands are supplied by only:

Accepted Answer

Sympathetic nerves

Answer

Sensory nerves

Answer

Motor nerves

Answer

Parasympathetic nerves

Question 9

Sensations which are appreciated in the thalamus -

Accepted Answer

Pain & temperature

Answer

Tactile sensations

Answer

Proprioception

Answer

Pressure

Question 10

EEG pattern of person at rest with eyes closed

Accepted Answer

Alpha

Answer

Beta

Answer

Delta

Answer

Gamma

Neurophysiology — MCQs

Neurophysiology — MCQs

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