Neurophysiology Practice Questions

Q: Which of the following is the primary excitatory neurotransmitter in the central nervous system?

Glutamate. ***Glutamate*** - **Glutamate** is the primary **excitatory neurotransmitter** in the central nervous system - It acts on ionotropic receptors (AMPA, NMDA, kainate) and metabotropic receptors to **depolarize** the postsynaptic membrane - Increases the likelihood of postsynaptic neuron firing by opening ligand-gated ion channels - Plays a crucial role in **synaptic plasticity**, learning, and memory *GABA* - **GABA (gamma-aminobutyric acid)** is the primary **inhibitory neurotransmitter** in the CNS - Hyperpolarizes the postsynaptic membrane by opening chloride channels - Reduces neuronal excitability throughout the brain *Glycine* - **Glycine** is the primary **inhibitory neurotransmitter** in the spinal cord and brainstem - Acts via glycine receptors (chloride channels) leading to hyperpolarization - Important for motor and sensory processing in the spinal cord *Aspartate* - **Aspartate** is also an **excitatory neurotransmitter** acting on NMDA receptors - However, it is **much less abundant** and less important than glutamate - Glutamate is considered the main excitatory neurotransmitter due to its widespread distribution and predominant role

Q: 'C' fibers carry sensations through which pathway?

Lateral spinothalamic tract. ***Lateral spinothalamic tract*** - **C fibers** are unmyelinated nerve fibers that transmit **slow, dull, burning, or aching pain**, as well as **temperature** sensations. - The **lateral spinothalamic tract** is the primary ascending pathway responsible for conveying these **pain and temperature** sensations from the spinal cord to the brain. *Posterior column* - The **posterior column-medial lemniscus pathway** is primarily responsible for transmitting **fine touch, vibration, conscious proprioception, and two-point discrimination**. - It consists of thickly myelinated A-beta fibers, which are distinct from the unmyelinated C fibers involved in pain transmission. *Anterior spinothalamic tract* - The **anterior spinothalamic tract** mainly carries crude touch and pressure sensations. - While it is a part of the anterolateral system, it does not primarily transmit the pain and temperature signals carried by C fibers. *All of the options* - This option is incorrect because C fibers specifically transmit sensations through the **lateral spinothalamic tract**, not all the listed pathways. - Each pathway has distinct roles in sensory transmission, and C fibers are not associated with the posterior column or exclusively with the anterior spinothalamic tract for their primary functions.

Q: Dull visceral pain is carried by which type of neurons?

C fibres. ***C fibres*** - **C fibres** are unmyelinated, small-diameter nerve fibres that conduct impulses slowly (0.5-2 m/s). - They are primarily responsible for transmitting **dull, aching, burning, and chronic pain**, including the diffuse, visceral pain often associated with internal organs. - Visceral pain is typically poorly localized and carried predominantly by C fibers. *A delta* - **A-delta (Aδ) fibres** are thinly myelinated, small-diameter nerve fibres that conduct impulses at moderate speeds (5-30 m/s). - They transmit **sharp, localized, and acute pain** (fast pain or "first pain"), which is different from the dull visceral pain described. - These fibers are responsible for the initial sharp sensation of pain. *Aa* - **Aα (alpha) fibres** are large-diameter, heavily myelinated nerve fibres that conduct impulses very rapidly (70-120 m/s). - They are primarily involved in transmitting **proprioception** (sense of body position) and **motor information to skeletal muscles**, not pain. *B* - **B fibres** are lightly myelinated, small-diameter nerve fibres (3-15 m/s), predominantly found in the autonomic nervous system. - They typically transmit **preganglionic autonomic signals** and are not directly involved in the sensation of somatic or visceral pain.

Q: Which type of fibers carry warmth sensation?

C fibers. ***C fibers*** - **C fibers** are **unmyelinated**, slow-conducting nerve fibers responsible for transmitting **dull, aching pain** and **warmth sensations**. - They are also involved in conveying **itching** and some types of **light touch**. *Aα fibers* - **Aα fibers** are **large**, **myelinated** and are primarily involved in transmitting **proprioception** (sense of body position) and **motor information** to skeletal muscles. - They have the **fastest conduction velocity** among peripheral nerve fibers. *Aβ fibers* - **Aβ fibers** are **medium-sized**, **myelinated** fibers that primarily transmit **light touch**, **pressure**, and **vibration** sensations. - They are responsible for discriminative touch and tactile sensations. *Aδ fibers* - **Aδ fibers** (not Aγ) are **small**, **myelinated** fibers that transmit **fast, sharp pain** and **cold** sensations. - They conduct more rapidly than C fibers due to myelination.

Q: At what gestational age does the swallowing-breathing reflex first appear in the fetus?

16 weeks. ***16 weeks*** - The **swallowing-breathing reflex** is a crucial protective mechanism that ensures coordination between swallowing and breathing to prevent aspiration. - This reflex is considered to fully develop and become consistently observable in the fetus around **16 weeks of gestation**. *14 weeks* - While some rudimentary swallowing movements may be observed earlier, the integrated and mature **swallowing-breathing reflex** is not fully established at 14 weeks. - The coordination required for this reflex is still developing during this period. *12 weeks* - At 12 weeks, the fetal swallowing mechanism is even less mature, and the **swallowing-breathing reflex** is not yet present. - Fetal development at this stage is primarily focused on organogenesis and basic motor functions. *Appear in all above period* - This statement is incorrect because the **swallowing-breathing reflex** has a specific developmental timeline and is not consistently functional at all gestational ages mentioned. - Its full emergence is a hallmark of more mature neuromuscular coordination.

Q: Horizontal acceleration with forward movement in the sagittal plane is detected by ?

Macula of Utricle. ***Macula of Utricle*** - The **utricle** is primarily responsible for detecting **horizontal linear acceleration**, such as forward/backward and side-to-side movements in the **sagittal and coronal planes**. - Its **macula** is oriented **horizontally**, making it the ideal structure for sensing horizontal acceleration with forward movement in the sagittal plane. - The utricle contains otoliths (calcium carbonate crystals) that shift with linear acceleration, stimulating hair cells that signal movement direction. *Macula of Saccule* - The **saccule** is primarily responsible for detecting **vertical linear acceleration** of the head, such as moving up and down in an elevator. - Its macula is oriented **vertically**, not horizontally, making it unsuitable for detecting horizontal forward movement. - While it may have minor secondary roles in certain head positions, it is NOT the primary detector for horizontal sagittal plane movement. *Lateral semicircular canal* - The **lateral semicircular canal** detects **rotational acceleration** primarily in the **horizontal plane**, such as turning the head from side to side (yaw rotation). - It does **not** detect linear acceleration like forward movement—only angular/rotational movements. *Posterior semicircular canal* - The **posterior semicircular canal** detects **rotational acceleration** when the head moves in the **sagittal plane**, like nodding (pitch rotation). - It works in conjunction with the anterior semicircular canal to detect head rotations, not linear acceleration.

Q: Which is not an extrapyramidal tract?

Corticospinal tract. ***Corticospinal tract*** - The **corticospinal tract** is the primary component of the **pyramidal system**, directly mediating voluntary, skilled movements. - It originates in the cerebral cortex and descends through the medullary pyramids, distinguishing it from extrapyramidal tracts which primarily modulate movement indirectly. *Reticulospinal tract* - The reticulospinal tract is a major **extrapyramidal tract** involved in controlling **posture, balance**, and **muscle tone**. - It originates in the brainstem reticular formation, mediating movements below the level of conscious control. *Rubrospinal tract* - The rubrospinal tract is an **extrapyramidal tract** that originates in the **red nucleus** and contributes to the control of **flexor muscle tone** and fine motor movements. - It plays a role in coordinating upper limb movements, particularly in the distal musculature. *Tectospinal tract* - The tectospinal tract is an **extrapyramidal tract** originating in the **superior colliculus** of the midbrain. - It is primarily involved in mediating **reflexive head and neck movements** in response to visual and auditory stimuli.

Q: Which of the following sensations is carried by pathways that relay through the thalamus via the spinothalamic tract?

Pain & temperature. ***Pain & temperature*** - The **spinothalamic tracts** (lateral and anterior) are the primary pathways for relaying **pain** and **temperature** sensations from the periphery to the **thalamus**. - These sensations synapse in the **thalamus** before being projected to the somatosensory cortex for conscious perception. *Proprioception* - **Proprioception** (sense of body position) is primarily relayed through the **dorsal column-medial lemniscus pathway**, which also synapses in the thalamus. - However, the thalamic relay is crucial for all conscious somatic sensations, but pain and temperature are most *classically* and *exclusively* associated with dedicated spinothalamic tracts. *Tactile sensations* - **Crude touch** (general tactile sensation) is carried by the anterior spinothalamic tract, but **fine touch** and **discriminative touch** are primarily carried by the **dorsal column-medial lemniscus pathway**. - While tactile sensations involve thalamic relay, the pathways are more diverse compared to the distinct spinothalamic tracts for pain and temperature. *Pressure* - **Pressure sensation** is also primarily carried by the **dorsal column-medial lemniscus pathway**, similar to proprioception. - While it relays through the thalamus, it shares a pathway with other mechanoreceptive sensations rather than having a distinct, classic dedicated pathway like pain and temperature.

Q: Major neurotransmitter in afferents to the nucleus tractus solitarius regulating the cardiovascular system?

Glutamate. ***Glutamate*** - **Glutamate** is the primary **excitatory neurotransmitter** in the central nervous system, and it plays a crucial role in the afferent nerve terminals of the **nucleus tractus solitarius (NTS)**. - Afferent signals from baroreceptors and chemoreceptors synapse in the NTS, where glutamate mediates the initial processing of these inputs to regulate **blood pressure** and heart rate. *Serotonin* - **Serotonin** (5-HT) has diverse roles in the brain, but its primary function in the **NTS** is not as the major fast-acting excitatory neurotransmitter for cardiovascular afferents. - While serotonin can modulate NTS activity, it is typically involved in slower, neuromodulatory effects rather than direct excitatory synaptic transmission from primary afferents. *Glycine* - **Glycine** is an important **inhibitory neurotransmitter**, primarily found in the spinal cord and brainstem. - It hyperpolarizes postsynaptic neurons, making them less likely to fire, which is the opposite effect of what is required for the initial excitatory transmission of cardiovascular afferent signals in the **NTS**. *Norepinephrine* - **Norepinephrine** is a **catecholamine neurotransmitter** involved in arousal, attention, and the fight-or-flight response. - While adrenergic neurons project to the **NTS** and can modulate its activity, norepinephrine is not the major neurotransmitter released by the primary afferent fibers that carry cardiovascular information to the NTS.

Q: While walking or standing, posture is maintained by?

Cerebellum. ***Cerebellum*** - The **cerebellum** plays a crucial role in maintaining **balance and posture** by coordinating muscular activity, regulating muscle tone, and integrating sensory input. - It receives information about planned movements from the motor cortex and current body position from sensory receptors, allowing it to make real-time adjustments for stable locomotion and standing. *Basal ganglia* - The **basal ganglia** are primarily involved in the **initiation and control of voluntary movements**, motor learning, and routine behaviors. - While they influence movement, their direct role in the instantaneous maintenance of posture is less prominent than that of the cerebellum. *Hypothalamus* - The **hypothalamus** is a key brain region for regulating **autonomic functions**, hormone release, and maintaining homeostasis (e.g., body temperature, hunger, thirst). - It does not have a direct or primary role in the control of conscious posture or balance during walking or standing. *Amygdala* - The **amygdala** is a central component of the **limbic system**, primarily involved in processing emotions, particularly fear, and emotional memory. - It has no direct involvement in the motor control mechanisms required for maintaining posture during locomotion.

Question 1

Which of the following is the primary excitatory neurotransmitter in the central nervous system?

Accepted Answer

Glutamate

Answer

GABA

Answer

Glycine

Answer

Aspartate

Question 2

'C' fibers carry sensations through which pathway?

Accepted Answer

Lateral spinothalamic tract

Answer

Posterior column

Answer

Anterior spinothalamic tract

Answer

All of the options

Question 3

Dull visceral pain is carried by which type of neurons?

Accepted Answer

C fibres

Answer

A delta

Answer

Aa

Answer

B

Question 4

Which type of fibers carry warmth sensation?

Accepted Answer

C fibers

Answer

Aα fibers

Answer

Aβ fibers

Answer

Aδ fibers

Question 5

At what gestational age does the swallowing-breathing reflex first appear in the fetus?

Accepted Answer

16 weeks

Answer

14 weeks

Answer

12 weeks

Answer

Appear in all above period

Question 6

Horizontal acceleration with forward movement in the sagittal plane is detected by ?

Accepted Answer

Macula of Utricle

Answer

Macula of Saccule

Answer

Lateral semicircular canal

Answer

Posterior semicircular canal

Question 7

Which is not an extrapyramidal tract?

Accepted Answer

Corticospinal tract

Answer

Reticulospinal tract

Answer

Tectospinal tract

Answer

Rubrospinal tract

Question 8

Which of the following sensations is carried by pathways that relay through the thalamus via the spinothalamic tract?

Accepted Answer

Pain & temperature

Answer

Proprioception

Answer

Tactile sensations

Answer

Pressure

Question 9

Major neurotransmitter in afferents to the nucleus tractus solitarius regulating the cardiovascular system?

Accepted Answer

Glutamate

Answer

Glycine

Answer

Norepinephrine

Answer

Serotonin

Question 10

While walking or standing, posture is maintained by?

Accepted Answer

Cerebellum

Answer

Basal ganglia

Answer

Hypothalamus

Answer

Amygdala

Neurophysiology — MCQs

Neurophysiology — MCQs

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