Neurophysiology Practice Questions

Q: The non-dominant hemisphere is responsible for all of the following functions, except:

Parallel thinking. **Explanation:** In most individuals (95% of right-handers and 70% of left-handers), the **left hemisphere** is the dominant hemisphere. It is primarily responsible for **analytical, sequential, and linear processing**, which includes language, mathematical calculations, and **parallel thinking** (the ability to process multiple logical threads simultaneously to reach a conclusion). Since parallel thinking is a function of the dominant (usually left) hemisphere, it is the correct "except" choice. The **non-dominant hemisphere** (usually the right) is characterized by its **holistic and spatial processing** capabilities. It excels in non-verbal functions: * **Identification of objects by form (Stereognosis):** While both hemispheres process sensory input, the non-dominant hemisphere is superior at appreciating three-dimensional shapes and spatial relationships. * **Recognition of musical themes:** The right hemisphere processes the melody, pitch, and emotional intonation (prosody) of music and speech. * **Recognition of faces:** Facial recognition is a specialized function of the fusiform gyrus, with a heavy reliance on the non-dominant hemisphere for holistic pattern matching. **Clinical Pearls for NEET-PG:** * **Aphasia:** Damage to the dominant hemisphere leads to Broca’s or Wernicke’s aphasia. * **Agnosia & Neglect:** Damage to the non-dominant parietal lobe often results in **hemispatial neglect** (ignoring the left side of the world) and **astereoagnosia**. * **Prosopagnosia:** The inability to recognize faces, often linked to bilateral or right-sided lesions in the fusiform gyrus. * **Categorical vs. Representational:** The dominant hemisphere is "Categorical" (logic/language); the non-dominant is "Representational" (visuospatial/creative).

Q: Which function is primarily associated with the spinocerebellum?

Smoothening and coordination of movements. **Explanation:** The cerebellum is functionally divided into three parts: the Vestibulocerebellum, the Spinocerebellum, and the Neocerebellum (Cerebrocerebellum). **Why Option B is Correct:** The **Spinocerebellum** (comprising the vermis and intermediate zones) primarily receives sensory input from the spinal cord (proprioception) and motor commands from the cortex. Its main function is **"Comparator" action**: it compares the intended movement with the actual performance and provides real-time corrective feedback. This ensures the **smoothening and coordination of movements**, preventing tremors and ensuring accuracy (synergy). **Analysis of Incorrect Options:** * **Option A (Maintenance of postural balance):** This is the primary function of the **Vestibulocerebellum** (Flocculonodular lobe), which maintains equilibrium and controls eye movements via connections with the vestibular apparatus. * **Option C (Planning and programming of movements):** This is the hallmark of the **Neocerebellum/Cerebrocerebellum** (Lateral hemispheres). It works with the premotor and sensory cortex to plan complex motor sequences before they are executed. * **Option D (Initiation of skilled voluntary movements):** Initiation is primarily a function of the **Basal Ganglia** and the **Motor Cortex**. The cerebellum coordinates movement once initiated but does not start it. **High-Yield Clinical Pearls for NEET-PG:** * **Lesion of Spinocerebellum:** Results in **Ataxia** (uncoordinated gait) and **Action/Intention Tremors**. * **Lesion of Vestibulocerebellum:** Results in **Trunkal Ataxia** and Nystagmus. * **Lesion of Neocerebellum:** Results in **Dysmetria** (past-pointing) and **Dysdiadochokinesia** (inability to perform rapid alternating movements). * **Memory Aid:** **S**pinocerebellum = **S**moothing/Execution; **C**erebrocerebellum = **C**onception/Planning.

Q: What is the root value of the plantar reflex?

Afferent S1, Efferent L5, S1. **Explanation:** The **Plantar Reflex** is a superficial (polysynaptic) reflex elicited by stroking the lateral aspect of the sole of the foot. Understanding its reflex arc is crucial for localizing spinal cord lesions. 1. **Why Option B is Correct:** * **Afferent (Sensory) Limb:** The stimulus is carried from the skin of the S1 dermatome (lateral sole) via the **Tibial nerve** to the **S1 spinal segment**. * **Efferent (Motor) Limb:** The motor response involves the contraction of the flexor muscles of the toes. These muscles are primarily innervated by the **Tibial nerve (S1)** and the **Peroneal nerve (L5)**. Specifically, the Great Toe flexion involves L5, while the other toes involve S1. Thus, the complete reflex arc is **Afferent S1, Efferent L5, S1**. 2. **Why Other Options are Incorrect:** * **Options A & C:** These include **L3** in the efferent limb. L3 is primarily involved in the **Knee Jerk (Patellar reflex)** and supplies the quadriceps; it has no role in toe flexion. * **Options C & D:** These suggest **S2** as the primary afferent. While S2 provides some sensation to the foot, the classic dermatomal trigger point for the plantar reflex on the lateral sole is specifically **S1**. **NEET-PG High-Yield Pearls:** * **Babinski Sign:** An abnormal plantar reflex (extensor response) indicating an **Upper Motor Neuron (UMN) lesion**. It is physiological (normal) in infants up to 1–2 years due to incomplete myelination of the corticospinal tracts. * **Receptor:** Nociceptors in the skin (not muscle spindles). * **Reflex Center:** S1 segment of the spinal cord. * **Quick Recall for Deep Tendon Reflexes:** * Ankle (Achilles): S1, S2 * Knee (Patellar): L2, L3, L4 * Biceps: C5, C6 * Triceps: C7, C8

Q: When a stretch reflex occurs, the muscles that antagonize the action of the involved muscle relax. This phenomenon is known as:

Reciprocal innervation. ### Explanation **Correct Answer: B. Reciprocal Innervation** **Why it is correct:** Reciprocal innervation (or reciprocal inhibition) is a fundamental spinal reflex mechanism. When a muscle spindle is stretched, it triggers a reflex contraction of that same muscle (the agonist). Simultaneously, the afferent impulses (Group Ia fibers) branch out in the spinal cord to stimulate **inhibitory interneurons**. These interneurons inhibit the alpha motor neurons of the **antagonist muscles**, causing them to relax. This coordination prevents muscles from working against each other, ensuring smooth and efficient movement. **Why other options are incorrect:** * **A. Inverse stretch reflex:** This is a protective reflex mediated by **Golgi Tendon Organs (GTO)**. When a muscle experiences excessive tension, it causes the muscle itself to relax to prevent injury. * **C. Autogenic inhibition:** This is the mechanism underlying the inverse stretch reflex. It refers to the inhibition of the *same* muscle that is experiencing high tension, mediated by Ib afferents from the GTO. * **D. Lengthening reaction:** This is a clinical manifestation of the inverse stretch reflex, often seen in "clasp-knife" spasticity. When a hypertonic muscle is stretched forcefully, it suddenly gives way and relaxes due to GTO activation. **High-Yield Clinical Pearls for NEET-PG:** * **Afferent Fiber Types:** Stretch reflex (Muscle Spindle) uses **Ia fibers**; Inverse stretch reflex (GTO) uses **Ib fibers**. * **The "Clasp-Knife" Phenomenon:** This is a classic example of the lengthening reaction/inverse stretch reflex seen in Upper Motor Neuron (UMN) lesions. * **Renshaw Cells:** These are inhibitory interneurons in the spinal cord that provide **recurrent inhibition** to the same motor neuron that fired, acting as a "limiter" to prevent over-activity.

Q: All of the following are signs of cerebellar disease EXCEPT—

Resting tremors. The cerebellum is responsible for the coordination of voluntary movements, maintenance of posture, and balance. It acts as an "error-correction" center, comparing intended movement with actual performance. **Why "Resting Tremors" is the correct answer:** Resting tremors are a hallmark of **Basal Ganglia** disorders, specifically Parkinson’s disease. They occur when muscles are relaxed and typically disappear during voluntary movement. In contrast, cerebellar lesions cause **Intention Tremors**, which are absent at rest but appear and worsen as the limb approaches a target during a voluntary task. **Explanation of Incorrect Options:** * **Past pointing (Dysmetria):** This is a classic sign of cerebellar dysfunction where a patient overshoots (hypermetria) or undershoots (hypometria) a target due to the inability to control the range and force of movement. * **Nystagmus:** Damage to the vestibulocerebellum (flocculonodular lobe) disrupts the coordination of eye movements, leading to involuntary, rhythmic oscillation of the eyeballs. * **Ataxic gait:** Cerebellar ataxia is characterized by a wide-based, "drunken" gait. It results from the loss of muscle coordination and the inability to maintain truncal equilibrium. **High-Yield Clinical Pearls for NEET-PG:** * **DANISH Mnemonic:** Common cerebellar signs include **D**ysdiadochokinesia, **A**taxia, **N**ystagmus, **I**ntention tremor, **S**lurred speech (Scanning speech), and **H**ypotonia. * Cerebellar lesions always manifest **ipsilaterally** (on the same side as the lesion) because the fibers double-decussate. * **Romberg’s Test:** It is negative in cerebellar ataxia (the patient is unstable even with eyes open) but positive in sensory ataxia (posterior column loss).

Q: Which of the following acts as a neurotransmitter inhibitor?

GABA. **Explanation:** The correct answer is **GABA (Gamma-Aminobutyric Acid)**. In the central nervous system (CNS), neurotransmitters are classified as either excitatory or inhibitory based on their effect on the postsynaptic membrane potential. 1. **Why GABA is correct:** GABA is the primary **inhibitory neurotransmitter** in the adult brain. When GABA binds to its receptors (GABA-A or GABA-B), it typically causes an influx of chloride ions ($Cl^-$) or an efflux of potassium ions ($K^+$). This leads to **hyperpolarization** of the postsynaptic neuron, making it less likely to fire an action potential. 2. **Why the other options are incorrect:** * **Glutamate:** This is the major **excitatory** neurotransmitter in the CNS. It acts on NMDA and AMPA receptors to cause depolarization. * **Aspartic acid (Aspartate):** Similar to glutamate, aspartate is an **excitatory** neurotransmitter, particularly in the spinal cord and brainstem. * **Lysine:** While an essential amino acid, lysine does not function as a primary neurotransmitter in the CNS. **High-Yield Clinical Pearls for NEET-PG:** * **GABA-A vs. GABA-B:** GABA-A is **ionotropic** (fast-acting, $Cl^-$ channel), while GABA-B is **metabotropic** (slow-acting, G-protein coupled). * **Glycine:** Remember that Glycine is the major inhibitory neurotransmitter in the **spinal cord**, whereas GABA dominates the **brain**. * **Clinical Correlation:** Drugs like Benzodiazepines and Barbiturates work by potentiating the effects of GABA at the GABA-A receptor, leading to sedation and anxiolysis. * **Strychnine:** A potent convulsant that acts by antagonizing Glycine receptors.

Question 1

The non-dominant hemisphere is responsible for all of the following functions, except:

Accepted Answer

Parallel thinking

Answer

Identification of objects by their form

Answer

Recognition of musical themes

Answer

Recognition of faces

Question 2

Which of the following promotes rouleaux formation?

Accepted Answer

Fibrinogen

Answer

Zeta potential on RBC membrane

Answer

Albumin

Answer

Biconcave shape of RBC

Question 3

Which function is primarily associated with the spinocerebellum?

Accepted Answer

Smoothening and coordination of movements

Answer

Maintenance of postural balance

Answer

Planning and programming of movements

Answer

Initiation of skilled voluntary movements

Question 4

What is the root value of the plantar reflex?

Accepted Answer

Afferent S1, Efferent L5, S1

Answer

Afferent S1, Efferent L3, S1

Answer

Afferent S2, Efferent L3, S1

Answer

Afferent S2, Efferent L5, S1

Question 5

Which of the following blood transfusions will most likely result in a transfusion reaction, assuming the patient has never received a transfusion before?

Accepted Answer

Type A Rh-positive packed cells to an O Rh-positive patient

Answer

Type O Rh-negative packed cells to an AB Rh-positive patient

Answer

Type A Rh-positive packed cells to an A Rh-negative patient

Answer

Type AB Rh-positive packed cells to an AB Rh-positive patient

Question 6

Gamma motor neurons are mainly influenced by which of the following tracts?

Accepted Answer

Rubrospinal tract

Answer

Vestibulospinal tract

Answer

Anterior corticospinal tract

Answer

Tectospinal tract

Question 7

When a stretch reflex occurs, the muscles that antagonize the action of the involved muscle relax. This phenomenon is known as:

Accepted Answer

Reciprocal innervation

Answer

Inverse stretch reflex

Answer

Autogenic inhibition

Answer

Lengthening reaction

Question 8

Facilitation of flexor muscle tone is by which tract?

Accepted Answer

Rubrospinal tract

Answer

Vestibulospinal tract

Answer

Tectospinal tract

Answer

Reticulospinal tract

Question 9

All of the following are signs of cerebellar disease EXCEPT—

Accepted Answer

Resting tremors

Answer

Past pointing

Answer

Nystagmus

Answer

Ataxic gait

Question 10

Which of the following acts as a neurotransmitter inhibitor?

Accepted Answer

GABA

Answer

Glutamate

Answer

Aspartic acid

Answer

Lysine

Neurophysiology — MCQs

Neurophysiology — MCQs

On this page

Practice by Chapter

Want unlimited practice?