Neurophysiology Practice Questions

Q: Which receptor binds to Brain-Derived Neurotrophic Factor (BDNF)?

TrK-B. ### Explanation **Neurotrophins** are a family of proteins essential for the survival, development, and function of neurons. They exert their effects by binding to specific high-affinity transmembrane tyrosine kinase receptors known as **TrK (Tropomyosin receptor kinase)** receptors. **Why TrK-B is the Correct Answer:** Each neurotrophin has a specific affinity for a particular TrK receptor. **Brain-Derived Neurotrophic Factor (BDNF)** and **Neurotrophin-4/5 (NT-4/5)** specifically bind to **TrK-B**. Upon binding, BDNF triggers dimerization and autophosphorylation of the receptor, activating downstream signaling pathways (like MAPK and PI3K) that promote neuronal plasticity, long-term potentiation (LTP), and cell survival. **Analysis of Incorrect Options:** * **Option A (TrK-A):** This is the primary receptor for **Nerve Growth Factor (NGF)**. It is crucial for the survival of sympathetic and sensory neurons. * **Option C (TrK-C):** This receptor specifically binds to **Neurotrophin-3 (NT-3)**. NT-3 is unique because it can also bind to TrK-A and TrK-B with lower affinity, but TrK-C is its primary target. **High-Yield NEET-PG Pearls:** 1. **p75NTR Receptor:** All neurotrophins (NGF, BDNF, NT-3, NT-4/5) bind with low affinity to the **p75 neurotrophin receptor**, which often mediates apoptosis (cell death) rather than survival. 2. **BDNF & Memory:** BDNF is highly expressed in the **hippocampus** and is a key molecular mediator of synaptic plasticity and memory formation. 3. **Clinical Correlation:** Reduced levels of BDNF are implicated in the pathogenesis of **Depression** and **Alzheimer’s disease**. Antidepressants often work by increasing BDNF expression. 4. **Mnemonic:** * **A**-NGF (A comes first, like NGF discovery) * **B**-BDNF (B for B) * **C**-NT-3 (C is the 3rd letter)

Q: The raphe nuclei located in the lower pons and medulla secrete which neurotransmitter?

Serotonin. **Explanation:** The **Raphe Nuclei** are a cluster of nuclei found in the brainstem (midbrain, pons, and medulla) and are the primary source of **Serotonin (5-HT)** in the Central Nervous System. Neurons from these nuclei project widely to the cerebral cortex, thalamus, and spinal cord. In the lower pons and medulla, these projections descend to the spinal cord to modulate pain signals in the dorsal horn (part of the descending pain inhibitory pathway). **Analysis of Options:** * **A. Norepinephrine:** Primarily secreted by the **Locus Coeruleus** located in the upper pons. It regulates arousal, attention, and the sleep-wake cycle. * **B. Dopamine:** Produced mainly in the **Substantia Nigra** (pars compacta) and the **Ventral Tegmental Area (VTA)** of the midbrain. It is crucial for motor control and the reward pathway. * **D. Acetylcholine:** Major sources in the brain include the **Basal Nucleus of Meynert** and the **Pedunculopontine nucleus**. It is vital for memory and cognitive function. **High-Yield Clinical Pearls for NEET-PG:** * **Pain Modulation:** Serotonergic neurons from the *Nucleus Raphe Magnus* (medulla) project to the enkephalin-releasing interneurons in the spinal cord to inhibit pain (Gate Control Theory). * **Sleep:** Serotonin from the Raphe nuclei is a precursor to melatonin and plays a role in inducing sleep; lesions here can lead to insomnia. * **Psychiatry:** Most Selective Serotonin Reuptake Inhibitors (SSRIs) work by increasing the availability of serotonin produced by these nuclei, used in treating depression and anxiety.

Q: Inability to perform rapid alternating movements is termed as?

Dysdiadochokinesia. **Explanation:** The correct answer is **Dysdiadochokinesia**. This clinical sign refers to the inability to perform rapid, alternating movements (e.g., rapid supination and pronation of the forearms or tapping the palm with the fingers). **1. Why Dysdiadochokinesia is correct:** This condition is a hallmark of **cerebellar dysfunction**, specifically involving the **cerebrocerebellum** (lateral hemispheres). The cerebellum is responsible for the "timing" and "sequencing" of muscle contractions. In dysdiadochokinesia, the normal coordination between agonist and antagonist muscles is lost, leading to movements that are clumsy, irregular, and slow. **2. Why other options are incorrect:** * **Past-pointing (Option A):** Also known as hypermetria, this occurs when a patient overshoots a target during a coordinated movement (e.g., finger-to-nose test). It is a component of dysmetria. * **Dysmetria (Option C):** This refers to the inability to control the distance, power, and speed of a muscular act. It results in overshooting (hypermetria) or undershooting (hypometria) a target. While related to cerebellar lesions, it specifically describes the "range" of movement rather than the "alternating rhythm." **3. High-Yield Clinical Pearls for NEET-PG:** * **Cerebellar Lesions:** Always remember the mnemonic **VANISHED** (Vertigo, Ataxia, Nystagmus, Intentional tremor, Slurred speech/Scanning speech, Hypotonia, Exaggerated gait, Dysmetria/Dysdiadochokinesia). * **Ipsilateral Presentation:** Cerebellar signs occur on the **same side** as the lesion because of the double decussation of pathways. * **Decomposition of Movement:** This is when a complex movement is broken down into individual, jerky steps rather than one smooth motion.

Q: Which one of the following nuclei is primarily excitatory in its function within the basal ganglia circuitry?

Subthalamic nucleus. ### Explanation The basal ganglia circuitry is a complex network of nuclei that modulates motor control through a balance of inhibitory and excitatory signals. **Why the Subthalamic Nucleus (STN) is correct:** The **Subthalamic Nucleus** is the only major nucleus within the basal ganglia that is **glutamatergic** and thus **excitatory**. In the **Indirect Pathway**, the STN receives inhibitory input from the Globus Pallidus externa (GPe) and, in turn, sends excitatory projections to the Globus Pallidus interna (GPi) and Substantia Nigra pars reticulata (SNr). By exciting these output nuclei (which are GABAergic), the STN ultimately increases the inhibition of the thalamus, leading to a decrease in motor activity. **Why the other options are incorrect:** * **Putamen, Caudate Nucleus, and Striatum:** These are essentially part of the same functional unit (the Striatum is composed of the Caudate and Putamen). The primary neurons in the striatum are **Medium Spiny Neurons (MSNs)**, which are **GABAergic (inhibitory)**. They inhibit the GPi/SNr (Direct Pathway) or the GPe (Indirect Pathway). **High-Yield NEET-PG Pearls:** * **Neurotransmitters:** Remember that almost all connections within the basal ganglia are inhibitory (GABA) *except* for the STN (Glutamate) and the Nigrostriatal pathway (Dopamine—which can be excitatory via D1 or inhibitory via D2 receptors). * **Clinical Correlation:** Lesions of the Subthalamic Nucleus (often due to a lacunar infarct) lead to **Hemiballismus**, characterized by violent, flinging movements of the contralateral limbs due to the loss of excitatory control over the "brakes" of the motor system. * **Surgical Target:** The STN is a primary target for **Deep Brain Stimulation (DBS)** in patients with advanced Parkinson’s Disease.

Q: Slow wave sleep is also known as which of the following?

NREM sleep. **Explanation:** Sleep is physiologically divided into two main stages: **Non-Rapid Eye Movement (NREM) sleep** and **Rapid Eye Movement (REM) sleep**. **Why NREM sleep is the correct answer:** NREM sleep is characterized by a progressive slowing of brain wave frequencies on an Electroencephalogram (EEG). It consists of three stages (N1, N2, and N3). Stage N3 is specifically characterized by high-amplitude, low-frequency **delta waves** (0.5–4 Hz). Because the overall brain activity is synchronized and slow compared to the waking state, the entire NREM phase is collectively referred to as **Slow Wave Sleep (SWS)**. During this phase, heart rate, blood pressure, and respiratory rate decrease, and the body undergoes restorative processes. **Why other options are incorrect:** * **REM sleep:** Also known as **Paradoxical Sleep** or **Desynchronized Sleep**. The EEG during REM shows high-frequency, low-voltage activity (beta-like waves) similar to an awake state, despite the person being in deep sleep with muscle atonia. * **Both REM and NREM:** These are distinct physiological states with opposing EEG patterns (synchronized vs. desynchronized); therefore, they cannot both be classified as slow wave sleep. **High-Yield Clinical Pearls for NEET-PG:** * **Growth Hormone:** Secretion peaks during Stage N3 (Slow Wave Sleep). * **Parasomnias:** Sleepwalking (somnambulism), sleep terrors, and bedwetting (enuresis) typically occur during **Stage N3 (NREM)**. * **Nightmares:** These occur during **REM sleep**, unlike night terrors. * **PGO Spikes:** (Pontine-Geniculate-Occipital) waves are the hallmark of the onset of REM sleep.

Q: Which EEG rhythm has the lowest frequency?

Delta. **Explanation:** Electroencephalogram (EEG) rhythms are classified based on their frequency (measured in Hertz, Hz) and amplitude. The frequency of these waves is inversely proportional to the level of cortical activity and alertness. **1. Why Delta is the Correct Answer:** **Delta waves** have the **lowest frequency (0.5 – 4 Hz)** and the highest amplitude. They represent the most synchronized brain activity. In adults, they are the hallmark of **Stage 3 Non-REM (Deep/Slow-wave) sleep**. Their presence in an awake adult is always pathological, indicating generalized encephalopathy or deep midline lesions. **2. Analysis of Incorrect Options:** * **Theta (4 – 7 Hz):** These are the second slowest waves. They are normal in children and in adults during drowsiness or Stage 1 sleep. * **Alpha (8 – 13 Hz):** These are moderate-frequency waves seen in a relaxed, awake state with **eyes closed**. They are most prominent in the occipital region and disappear (alpha block) upon opening the eyes or mental concentration. * **Beta (13 – 30 Hz):** These have the **highest frequency** and lowest amplitude. They are seen during active thinking, mental concentration, or states of high alertness (desynchronized rhythm). **3. NEET-PG High-Yield Clinical Pearls:** * **Mnemonic for Frequency (Highest to Lowest):** **B**eta > **A**lpha > **T**heta > **D**elta (**B**at **A**nd **T**he **D**og). * **Alpha Block (Berger Effect):** The replacement of alpha rhythm by beta rhythm when eyes are opened. * **Sleep Spindles & K-complexes:** Characteristic features of **Stage 2 NREM sleep**. * **Sawtooth waves:** Characteristic of **REM sleep**. * **Drug Effect:** Benzodiazepines and Barbiturates typically increase Beta activity.

Q: Which of the following neurotransmitters acts on both the sympathetic and parasympathetic divisions of the autonomic nervous system?

Acetylcholine. The correct answer is **Acetylcholine (ACh)**. To understand why, one must look at the functional anatomy of the Autonomic Nervous System (ANS). Acetylcholine is the universal neurotransmitter for **all preganglionic neurons** in both the sympathetic and parasympathetic divisions [1]. It acts on nicotinic receptors at the autonomic ganglia. Additionally, it is the neurotransmitter for all **parasympathetic postganglionic** fibers and a specific subset of sympathetic postganglionic fibers (those supplying sweat glands). **Analysis of Options:** * **A. Atropine:** This is a competitive antagonist of muscarinic acetylcholine receptors, not a neurotransmitter [2]. It is a drug used to block parasympathetic effects. * **B. Pilocarpine:** This is a cholinergic agonist (parasympathomimetic drug) used clinically (e.g., in glaucoma), not an endogenous neurotransmitter [2]. * **D. Adrenaline (Epinephrine):** While it is a primary hormone/neurotransmitter of the sympathetic system (released by the adrenal medulla), it does not play a role in the parasympathetic division [1]. **NEET-PG High-Yield Pearls:** 1. **The "Exception" Rule:** All sympathetic postganglionic neurons release Norepinephrine **except** those to eccrine sweat glands and some blood vessels in skeletal muscle, which release Acetylcholine. 2. **Receptor Types:** ACh acts on **Nicotinic (Nn)** receptors at all autonomic ganglia and **Muscarinic (M)** receptors at parasympathetic effector organs [2]. 3. **Adrenal Medulla:** Consider the adrenal medulla a "modified sympathetic ganglion"; it is stimulated by preganglionic sympathetic fibers using Acetylcholine to release Adrenaline into the blood [1].

Q: In the brain, which cells are responsible for converting glutamate to glutamine?

Astrocytes. ### Explanation The correct answer is **Astrocytes**. This process is a critical component of the **Glutamate-Glutamine Cycle**, which prevents excitotoxicity in the central nervous system (CNS). **Why Astrocytes are correct:** Glutamate is the primary excitatory neurotransmitter in the brain. After its release into the synaptic cleft, it must be rapidly removed to prevent overstimulation of neurons. Astrocytes take up excess glutamate via excitatory amino acid transporters (EAATs). Inside the astrocyte, the enzyme **Glutamine Synthetase** converts glutamate into **glutamine**, a non-toxic, electrochemically neutral amino acid. This glutamine is then transported back to neurons, where it is converted back into glutamate by the enzyme *glutaminase*, completing the cycle. **Why the other options are incorrect:** * **Oligodendrocytes:** These cells are responsible for the myelination of axons in the CNS. They do not play a primary role in the metabolic recycling of glutamate. * **Ependymal cells:** These ciliated epithelial cells line the ventricles of the brain and the central canal of the spinal cord, primarily aiding in the production and circulation of Cerebrospinal Fluid (CSF). * **Microglia:** These are the resident macrophages of the CNS. Their primary role is immune surveillance and phagocytosis, not neurotransmitter metabolism. **High-Yield Clinical Pearls for NEET-PG:** * **Hyperammonemia:** In liver failure (Hepatic Encephalopathy), excess ammonia crosses the blood-brain barrier. Astrocytes use this ammonia to convert glutamate to glutamine. The resulting accumulation of glutamine causes osmotic swelling of astrocytes, leading to **cerebral edema**. * **Marker:** Glial Fibrillary Acidic Protein (GFAP) is a specific intermediate filament used as a marker for astrocytes. * **Blood-Brain Barrier (BBB):** Astrocytes contribute to the integrity of the BBB via their "foot processes."

Q: What is the root value of the supinator jerk?

C5C6. **Explanation:** The **supinator jerk** (also known as the brachioradialis reflex) is a deep tendon reflex elicited by tapping the distal end of the radius. This stretch reflex primarily tests the **C5 and C6 nerve roots** via the radial nerve. **Why C5C6 is Correct:** The brachioradialis muscle is innervated by the radial nerve. The primary spinal segments responsible for this motor output are C5 and C6. When the tendon is struck, the sensory impulse travels to these spinal levels, and the resulting motor response causes flexion and slight supination of the forearm. **Analysis of Incorrect Options:** * **C3C4:** These roots primarily contribute to the **phrenic nerve** (diaphragm) and sensory innervation of the neck and upper shoulder. They do not mediate any major limb reflexes. * **C4C5:** While C5 is involved in the supinator and biceps jerks, C4 is not a primary component of these distal limb reflexes. * **C8T1:** These roots form the lower trunk of the brachial plexus and mediate the **finger jerk** (C8) and the intrinsic muscles of the hand. **High-Yield Clinical Pearls for NEET-PG:** * **Inverted Supinator Jerk:** A crucial clinical sign where tapping the radius results in finger flexion instead of elbow flexion. This indicates a **C5-C6 cord lesion** (lower motor neuron lesion at C5-C6) with an associated upper motor neuron lesion affecting levels below (hyperreflexia of C8-innervated finger flexors). * **Reflex Quick-Reference:** * Biceps Jerk: C5, C6 (Musculocutaneous nerve) * Supinator Jerk: C5, C6 (Radial nerve) * Triceps Jerk: C7, C8 (Radial nerve) * Knee Jerk: L2, L3, L4 (Femoral nerve) * Ankle Jerk: S1, S2 (Tibial nerve)

Question 1

Which receptor binds to Brain-Derived Neurotrophic Factor (BDNF)?

Accepted Answer

TrK-B

Answer

TrK-A

Answer

TrK-C

Answer

None of the above

Question 2

The raphe nuclei located in the lower pons and medulla secrete which neurotransmitter?

Accepted Answer

Serotonin

Answer

Norepinephrine

Answer

Dopamine

Answer

Acetylcholine

Question 3

Inability to perform rapid alternating movements is termed as?

Accepted Answer

Dysdiadochokinesia

Answer

Past-pointing

Answer

Dysmetria

Answer

None of the above

Question 4

Which one of the following nuclei is primarily excitatory in its function within the basal ganglia circuitry?

Accepted Answer

Subthalamic nucleus

Answer

Putamen

Answer

Caudate nucleus

Answer

Striatum

Question 5

Which of the following statements regarding memory is FALSE?

Accepted Answer

The primary site for the storage of long-term memory is the temporal lobe.

Answer

Structural changes occur in synapses during the development of long-term memory.

Answer

Short-term memory lasts as long as the person continues to think about it.

Answer

Bilateral loss of hippocampal function leads to the inability to encode recent events into long-term memory.

Question 6

Slow wave sleep is also known as which of the following?

Accepted Answer

NREM sleep

Answer

REM sleep

Answer

Both REM and NREM sleep

Answer

None of the above

Question 7

Which EEG rhythm has the lowest frequency?

Accepted Answer

Delta

Answer

Alpha

Answer

Beta

Answer

Theta

Question 8

Which of the following neurotransmitters acts on both the sympathetic and parasympathetic divisions of the autonomic nervous system?

Accepted Answer

Acetylcholine

Answer

Atropine

Answer

Pilocarpine

Answer

Adrenaline

Question 9

In the brain, which cells are responsible for converting glutamate to glutamine?

Accepted Answer

Astrocytes

Answer

Oligodendrocytes

Answer

Ependymal cells

Answer

Microglia

Question 10

What is the root value of the supinator jerk?

Accepted Answer

C5C6

Answer

C3C4

Answer

C4C5

Answer

C8T1

Neurophysiology — MCQs

Neurophysiology — MCQs

On this page

Practice by Chapter

Want unlimited practice?