Neurophysiology Practice Questions

Q: Agnosia is caused by a lesion of which of the following?

The representative hemisphere, right. ### Explanation **Concept Overview** In neurophysiology, the cerebral hemispheres are functionally specialized. The **Categorical Hemisphere** (usually the left) is responsible for sequential-analytic processes like language and mathematics. The **Representative Hemisphere** (usually the right) handles visuospatial relations, pattern recognition, and musical ability. **Why Option C is Correct** **Agnosia** is the inability to recognize objects, faces, or symbols despite intact sensory pathways. It typically results from lesions in the **Representative (Right) Hemisphere**, specifically the posterior parietal cortex. Because this hemisphere is specialized for "representing" the world in a spatial context, a lesion here disrupts the integration of sensory inputs into a meaningful whole. A classic example is **Prosopagnosia** (inability to recognize familiar faces), often linked to right-sided lesions in the fusiform gyrus. **Analysis of Incorrect Options** * **Options A & B (Left Hemisphere):** Lesions in the categorical (left) hemisphere primarily result in **Aphasias** (language disorders) or **Acalculia**. While the left hemisphere processes the "names" of objects, the "recognition" of their form and spatial orientation is a right-hemisphere function. * **Option D:** This is a contradiction in terms for most individuals. In 95% of right-handed people, the right hemisphere is the representative one, not the categorical one. **NEET-PG High-Yield Pearls** * **Astereognosis:** Inability to identify an object by touch (Right parietal lesion). * **Hemispatial Neglect:** A patient ignores the left side of their body or environment; classic sign of a **Right (Representative) Parietal Lobe** lesion. * **Wernicke’s Area:** Located in the Categorical (Left) hemisphere; lesion causes sensory aphasia. * **Dominance:** In almost all right-handed and 70% of left-handed individuals, the left hemisphere is categorical.

Q: Which of the following decreases in a fight and flight situation?

Airway resistance. **Explanation:** The "fight or flight" response is mediated by the **Sympathetic Nervous System (SNS)**. During this state, the body prioritizes oxygen delivery and energy mobilization to vital organs and skeletal muscles. **Why Airway Resistance Decreases:** Sympathetic stimulation leads to the release of epinephrine and norepinephrine, which act on **$\beta_2$-adrenergic receptors** located on the bronchial smooth muscles. This causes **bronchodilation**, which increases the diameter of the airways. According to Poiseuille’s Law, resistance is inversely proportional to the fourth power of the radius ($R \propto 1/r^4$); therefore, bronchodilation significantly **decreases airway resistance**, allowing for maximum airflow to meet increased metabolic demands. **Analysis of Incorrect Options:** * **A. Pupillary diameter:** SNS causes contraction of the iris dilator muscle ($\alpha_1$ receptors), leading to **mydriasis** (pupillary dilation) to enhance peripheral vision. * **B. Blood pressure:** SNS increases heart rate and contractility ($\beta_1$ receptors) and causes peripheral vasoconstriction ($\alpha_1$ receptors), leading to an **increase** in both systolic and diastolic blood pressure. * **C. Blood glucose:** To provide immediate energy, the SNS promotes **glycogenolysis** and **gluconeogenesis** in the liver, resulting in an **increase** in blood glucose levels. **High-Yield Clinical Pearls for NEET-PG:** * **Receptor Specificity:** Remember "$\beta_2$ for 2 lungs" (bronchodilation) and "$\beta_1$ for 1 heart" (tachycardia). * **Clinical Application:** Salbutamol, a $\beta_2$ agonist, is used in asthma to mimic this sympathetic effect and decrease airway resistance during an acute attack. * **Exception:** While SNS generally causes vasoconstriction, it causes **vasodilation in skeletal muscle vessels** (via $\beta_2$ receptors) to redirect blood flow during exercise.

Q: K-complexes and sleep spindles are characteristic EEG findings during which stage of sleep?

NREM Stage 2. ### Explanation **Correct Answer: B. NREM Stage 2** **Mechanism and Concept:** NREM Stage 2 (Light Sleep) is characterized by specific EEG patterns: **Sleep Spindles** and **K-complexes**. * **Sleep Spindles:** These are bursts of oscillatory brain activity (12–14 Hz) lasting 0.5–1.5 seconds. They are generated by the thalamic reticular nucleus and represent the brain's attempt to maintain tranquility by inhibiting gastrointestinal and sensory processing. * **K-complexes:** These are high-amplitude, long-duration biphasic waves. They serve as a mechanism to "gate" external stimuli (preventing arousal) and are involved in memory consolidation. **Analysis of Incorrect Options:** * **A. NREM Stage 1:** This is the transition from wakefulness to sleep. The EEG shows low-voltage, mixed-frequency activity with a predominance of **Theta waves** (4–7 Hz). Alpha waves disappear. * **C. NREM Stage 3:** Also known as Slow Wave Sleep (SWS) or Deep Sleep. It is characterized by high-voltage, low-frequency **Delta waves** (0.5–2 Hz). This is the stage where night terrors and sleepwalking (somnambulism) occur. * **D. REM Sleep:** The EEG shows "paradoxical" activity—low-voltage, high-frequency desynchronized waves similar to an awake state, often accompanied by **Sawtooth waves**. **High-Yield Clinical Pearls for NEET-PG:** * **Bruxism** (teeth grinding) typically occurs during NREM Stage 2. * **Growth Hormone** secretion is maximal during NREM Stage 3. * **REM Sleep** is associated with muscle atonia, vivid dreaming, and PGO (Ponto-Geniculo-Occipital) spikes. * **Benzodiazepines** increase NREM Stage 2 but decrease NREM Stage 3 and REM sleep.

Q: Which part of the cerebellum is responsible for the planning and programming of movements?

Neocerebellum. The cerebellum is functionally divided into three distinct zones, each responsible for specific aspects of motor control. **Explanation of the Correct Answer:** **D. Neocerebellum (Cerebrocerebellum):** This is the largest and phylogenetically newest part of the cerebellum, comprising the lateral cerebellar hemispheres. It receives input primarily from the cerebral cortex via the pontine nuclei. Its primary function is the **planning, programming, and timing of complex motor activities**. It "pre-calculates" movements before they are executed by communicating back to the motor cortex via the dentate nucleus and thalamus. **Explanation of Incorrect Options:** * **A & B. Vestibulocerebellum / Flocculonodular Lobe:** These terms are functionally synonymous. This primitive part of the cerebellum is primarily concerned with **vestibular functions**, including the maintenance of equilibrium, balance, and control of eye movements (vestibulo-ocular reflex). * **C. Spinocerebellum:** Consisting of the vermis and intermediate zones, it receives sensory input from the spinal cord. Its role is the **execution of movement** and the regulation of muscle tone. It acts as a "comparator," correcting errors in ongoing movements by comparing intended movement with actual performance. **High-Yield Clinical Pearls for NEET-PG:** * **Lesion of Neocerebellum:** Results in **appendicular ataxia**, intention tremors, dysmetria (past-pointing), and dysdiadochokinesia. * **Lesion of Vestibulocerebellum:** Results in **truncal ataxia**, swaying, and nystagmus. * **Deep Nuclei Mnemonic:** "Don't Eat Greasy Foods" (**D**entate, **E**mboliform, **G**lobose, **F**astigial) from lateral to medial. The **Dentate nucleus** is the output center for the Neocerebellum.

Q: Alpha waves are typically seen in which of the following states?

Relaxed awake. **Explanation:** The correct answer is **Relaxed awake (Option B)**. Electroencephalogram (EEG) waves are classified based on their frequency and amplitude, reflecting the level of cortical activity. **1. Why Relaxed Awake is Correct:** Alpha waves (8–13 Hz) are the characteristic rhythm of an adult who is **awake but in a quiet, relaxed state with eyes closed**. They are most prominent in the occipital region. The defining feature of alpha waves is that they disappear upon opening the eyes or focusing on a task—a phenomenon known as **Alpha Block** or Desynchronization. **2. Analysis of Incorrect Options:** * **Deep Sleep (Option A):** This state is characterized by **Delta waves** (0.5–4 Hz). These are high-amplitude, low-frequency waves seen in Stage 3 NREM sleep. * **Awake Alert / Highly Focused (Options C & D):** When a person is mentally active, alert, or solving a problem, the EEG shifts to **Beta waves** (13–30 Hz). These have lower voltage and higher frequency, representing a desynchronized cortical state. **3. High-Yield Facts for NEET-PG:** * **Mnemonic (Frequency High to Low):** **B**eta > **A**lpha > **T**heta > **D**elta (**B**at **A**t **T**he **D**oor). * **Theta Waves (4–7 Hz):** Seen in children, during emotional stress in adults, or in Stage 1 NREM sleep. * **Gamma Waves (30–80 Hz):** Associated with high-level information processing and "binding" of different sensory inputs. * **Clinical Correlation:** EEG is the gold standard for diagnosing epilepsy and classifying sleep stages. Absence of alpha waves when eyes are closed may indicate cortical dysfunction.

Question 1

Slow inhibitory postsynaptic potential (IPSP) in autonomic ganglia is generated by which of the following?

Accepted Answer

Gonadotropin-releasing hormone (GnRH)

Answer

Nicotinic cholinergic

Answer

Muscarinic cholinergic

Answer

Dopamine

Question 2

Agnosia is caused by a lesion of which of the following?

Accepted Answer

The representative hemisphere, right

Answer

The representative hemisphere, left

Answer

The categorical hemisphere, left

Answer

The categorical hemisphere, right

Question 3

Destruction of the anterior cerebellum in a decerebrate animal leads to what effect on rigidity?

Accepted Answer

Increased rigidity via alpha motor neurons

Answer

No effect on rigidity

Answer

Increased flexor muscle tone

Answer

Decrease in rigidity

Question 4

Evacuation of the urinary bladder and stool with profuse sweating is a feature of which of the following reflexes?

Accepted Answer

Mass reflex

Answer

Positive supportive reaction

Answer

Labyrinthine righting reflex

Answer

Stretch reflex

Question 5

Which of the following decreases in a fight and flight situation?

Accepted Answer

Airway resistance

Answer

Pupillary diameter

Answer

Blood pressure

Answer

Blood glucose

Question 6

K-complexes and sleep spindles are characteristic EEG findings during which stage of sleep?

Accepted Answer

NREM Stage 2

Answer

NREM Stage 1

Answer

NREM Stage 3

Answer

REM Sleep

Question 7

Which part of the cerebellum is responsible for the planning and programming of movements?

Accepted Answer

Neocerebellum

Answer

Vestibulocerebellum

Answer

Flocculonodular lobe

Answer

Spinocerebellum

Question 8

Alpha waves are typically seen in which of the following states?

Accepted Answer

Relaxed awake

Answer

Deep sleep

Answer

Awake alert

Answer

Highly focused

Question 9

Which of the following statements is true about presynaptic inhibition?

Accepted Answer

It occurs due to inhibition of the release of neurotransmitter from the presynaptic terminal.

Answer

It results due to failure of the action potential to reach the synapse.

Answer

It occurs due to hyperpolarization of the presynaptic membrane.

Answer

It occurs due to blockade of neurotransmitter receptors.

Question 10

Which of the following statements are true about the cerebellum?

Accepted Answer

Excitatory effect from deep nuclei.

Answer

The cerebral cortex has mostly inhibitory effects.

Answer

Coordination of movement.

Answer

Planning of motor movements.

Neurophysiology — MCQs

Neurophysiology — MCQs

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