Neurophysiology — MCQs

A 25-year-old male gets into a brawl outside a bar. During the altercation, someone pulls out a gun and shoots him in the head. The bullet enters the man's temple and severes his right optic nerve completely. He is quickly transported to a nearby emergency room and an emergency physician tests his pupillary response by shining a light in the right eye. What will the physician most likely find?

Q685

Pain and temperature in the thalamus are controlled by which nucleus?

Q686

The mechanism of hearing and memory, include all, EXCEPT:

Q687

Stimulation of which of the following areas of brain is experimentally used to control intractable pain -

Q688

Orexins, which control appetite and food intake, are secreted from neurons located in:

Q689

A viral infection causes damage to both hippocampi in a patient. This damage would cause the patient to exhibit functional deficits in

Q690

All of the following are carried by the dorsal column except?

Neurophysiology Indian Medical PG Practice Questions and MCQs

Question 681: Sensations which are appreciated in the thalamus -

A. Tactile sensations
B. Proprioception
C. Pressure
D. Pain & temperature (Correct Answer)

Explanation: ***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.

Question 682: EEG pattern of person at rest with eyes closed

A. Beta
B. Alpha (Correct Answer)
C. Delta
D. Gamma

Explanation: ***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 683: Voluntary movement of eye ball is controlled by

A. Visual cortex area
B. Frontal eye field (Correct Answer)
C. Cerebellum
D. Superior colliculus

Explanation: ***Frontal eye field*** - The **frontal eye field (Brodmann area 8)** plays a crucial role in the generation of voluntary eye movements, particularly **saccades**, which are rapid movements that direct the fovea to a new point of interest. - It works in conjunction with other cortical and subcortical areas to plan and execute these movements. *Visual cortex area* - The **visual cortex (primarily Brodmann areas 17, 18, 19)** is responsible for processing visual information, perceiving objects, and interpreting visual stimuli. - While it processes the visual input that guides eye movements, it does not directly initiate or control voluntary eye movements itself. *Cerebellum* - The **cerebellum** is involved in the coordination and motor learning aspects of eye movements, ensuring smooth pursuits and accurate saccades. - It refines these movements and corrects errors but is not the primary center for initiating voluntary eye movement. *Superior colliculus* - The **superior colliculus** is a subcortical structure primarily involved in directing eye and head movements towards salient visual, auditory, and somatosensory stimuli, especially for **reflexive gaze shifts**. - While it plays a role in generating saccades, its involvement is more in response to external stimuli rather than purely voluntary commands.

Question 684: A 25-year-old male gets into a brawl outside a bar. During the altercation, someone pulls out a gun and shoots him in the head. The bullet enters the man's temple and severes his right optic nerve completely. He is quickly transported to a nearby emergency room and an emergency physician tests his pupillary response by shining a light in the right eye. What will the physician most likely find?

A. Pupillary constriction followed by pupillary dilatation in both eyes
B. Pupillary constriction in the right eye, and no pupillary constriction in the left eye
C. No pupillary constriction in the right eye, and no pupillary constriction in the left eye (Correct Answer)
D. No pupillary constriction in the right eye, but pupillary constriction in the left eye

Explanation: ***No pupillary constriction in the right eye, and no pupillary constriction in the left eye*** - The **afferent limb** of the **pupillary light reflex** is carried by the **optic nerve**. Complete transection of the right optic nerve means the right eye cannot detect light. - When light is shone into the blind right eye, the brain receives no sensory input, so neither the right pupil (direct response) nor the left pupil (consensual response) will constrict. *Pupillary constriction followed by pupillary dilatation in both eyes* - This scenario would imply an initial detection of light by the right eye, which is impossible with a **severed optic nerve**. - A subsequent dilation might suggest a different neurological issue or drug effect, not a primary pupillary light reflex to light in a blind eye. *Pupillary constriction in the right eye, and no pupillary constriction in the left eye* - This is incorrect because a **severed optic nerve** means the right eye cannot send the signal for constriction, neither directly nor consensually. - Furthermore, pupillary constriction *only* in the right eye (direct response) without a consensual response in the left eye would suggest an issue with the efferent pathway to the left eye, not a unilateral afferent lesion. *No pupillary constriction in the right eye, but pupillary constriction in the left eye* - This response pattern would occur if there was a lesion *after* the **optic chiasm** affecting the nerve fibers going to the right side, but the information from the right eye was still able to cross and activate the left pupil. - With a completely severed right optic nerve, no light stimulus can be transmitted from the right eye to initiate any reflex, therefore no constriction would occur in either eye.

Question 685: Pain and temperature in the thalamus are controlled by which nucleus?

A. Posterior
B. VPM
C. VPL (Correct Answer)
D. Anterior

Explanation: ***VPL*** - The **ventral posterolateral (VPL) nucleus** of the thalamus receives sensory input concerning **pain, temperature, touch, and proprioception** from the body via the **spinothalamic tracts** and **medial lemniscus**. This makes it crucial for processing these sensations. - After processing, the VPL projects this sensory information to the **primary somatosensory cortex**. *Posterior* - The **posterior nuclei** of the thalamus are generally involved in polymodal sensory processing, integrating information from various senses, but they are not the primary relay for segregated **pain and temperature** sensation. - These nuclei are less directly involved in relaying specific sensory modalities like pain and temperature to the **somatosensory cortex** compared to VPL. *VPM* - The **ventral posteromedial (VPM) nucleus** of the thalamus is responsible for processing **facial sensation**, including **pain and temperature** from the face, via the **trigeminal system**. - While it processes pain and temperature, it specifically handles inputs from the **head and face**, not the trunk and limbs, which are implied by the general question. *Anterior* - The **anterior nucleus** of the thalamus is primarily involved in functions related to **memory** and the **limbic system**, receiving input from the **mammillary bodies** and projecting to the **cingulate gyrus**. - It plays no direct role in the relay of general **pain and temperature** sensations from the body.

Question 686: The mechanism of hearing and memory, include all, EXCEPT:

A. Spatial Reorganization of synapse
B. Changes in level of neurotransmitter at synapse
C. Increasing protein synthesis
D. Recruitment by multiplication of neurons (Correct Answer)

Explanation: ***Recruitment by multiplication of neurons*** - The **brain's capacity for learning and memory** primarily involves changes in existing neural circuits, not the multiplication of neurons in the adult brain for new information processing. - While neurogenesis occurs in specific brain regions (e.g., hippocampus), it is not a widespread mechanism for acquiring or storing specific memories or the rapid processing involved in hearing. *Spatial Reorganization of synapse* - This refers to the **restructuring of synaptic connections**, which is a crucial mechanism for long-term potentiation and depression, fundamental to learning and memory formation. - Changes in the **number or location of synapses** can alter neural pathways and strengthen or weaken signal transmission. *Changes in level of neurotransmitter at synapse* - Alterations in the **amount of neurotransmitter released** or the **sensitivity of postsynaptic receptors** significantly impact synaptic strength and neuronal communication. - This short-term and long-term modulation is vital for processes like habituation, sensitization, and long-term potentiation, integral to memory and sensory processing. *Increasing protein synthesis* - **New protein synthesis** is essential for the consolidation of long-term memories and for the structural changes underlying synaptic plasticity. - These proteins can range from enzymes that modify synaptic transmission to structural proteins that alter dendritic spine morphology, enabling lasting changes in neural circuits.

Question 687: Stimulation of which of the following areas of brain is experimentally used to control intractable pain -

A. Mesencephalon
B. Subthalamic nucleus
C. Periaqueductal grey matter (Correct Answer)
D. Medial forebrain bundle

Explanation: ***Periaqueductal grey matter*** - The **periaqueductal grey (PAG)** is a key modulator of endogenous analgesia, and its stimulation activates descending pain inhibitory pathways. - Stimulation of the PAG leads to the release of **endogenous opioids** (e.g., endorphins, enkephalins) and other neurotransmitters that suppress pain transmission at the spinal cord level. *Mesencephalon* - While the PAG is located within the mesencephalon (midbrain), simply stimulating the broader mesencephalon is not as precise or effective for pain control. - The mesencephalon contains various structures with diverse functions, and non-specific stimulation could lead to unwanted side effects. *Subthalamic nucleus* - The **subthalamic nucleus (STN)** is primarily involved in motor control and is a common target for deep brain stimulation in Parkinson's disease. - Its direct stimulation is not a primary or established method for controlling intractable pain. *Medial forebrain bundle* - The **medial forebrain bundle (MFB)** is a complex pathway associated with reward, motivation, and pleasure, important in the limbic system. - While it plays a role in emotional aspects of pain, its direct stimulation is not a recognized technique for somatic pain management.

Question 688: Orexins, which control appetite and food intake, are secreted from neurons located in:

A. Lateral hypothalamus (Correct Answer)
B. Pons
C. Adrenal medulla
D. Central hypothalamus

Explanation: ***Lateral hypothalamus*** - The **lateral hypothalamus** contains neurons that produce **orexins** (also known as hypocretins), which are critical neuropeptides involved in the **regulation of appetite, wakefulness, and arousal**. - Stimulation of these orexin-producing neurons leads to feelings of **hunger and increased food intake**, playing a key role in energy homeostasis. *Pons* - The **pons** is a part of the brainstem primarily involved in relaying sensory information, regulating breathing, and sleep. - It does not contain the primary neurons responsible for secreting **orexins** related to appetite control. *Adrenal medulla* - The **adrenal medulla** is part of the adrenal gland and primarily secretes **catecholamines** (epinephrine and norepinephrine) in response to stress. - It has no role in the production or secretion of **orexins** or direct control of appetite. *Central hypothalamus* - While the hypothalamus is crucial for appetite regulation, the term "central hypothalamus" is not a specific anatomical region where orexin-producing neurons are primarily located. - The **arcuate nucleus** in the hypothalamus is involved in appetite regulation by producing other peptides like NPY/AgRP and POMC/CART, but orexins originate from the lateral hypothalamus.

Question 689: A viral infection causes damage to both hippocampi in a patient. This damage would cause the patient to exhibit functional deficits in

A. Forming a new short-term memory
B. Recalling an old procedural memory
C. Forming a new long-term memory (Correct Answer)
D. Recalling an old declarative memory

Explanation: ***Forming a new long-term memory*** - The **hippocampus** is crucial for the formation of **new declarative long-term memories** (both episodic and semantic). - Damage to both hippocampi would result in **anterograde amnesia**, specifically impacting the ability to create and consolidate new explicit memories. *Forming a new short-term memory* - **Short-term memory** (or working memory) is primarily associated with the **prefrontal cortex** and does not heavily rely on hippocampal function. - Patients with hippocampal damage can typically still maintain information in short-term memory for brief periods. *Recalling an old procedural memory* - **Procedural memories** (skills and habits) are a type of implicit memory predominantly mediated by the **basal ganglia**, cerebellum, and motor cortex. - The hippocampus is not essential for the recall of established procedural memories, as demonstrated by patients like H.M. *Recalling an old declarative memory* - While the hippocampus is involved in the initial formation and consolidation of declarative memories, **very old, well-established declarative memories** become progressively independent of the hippocampus. - These remote memories are thought to be stored diffusely in the **cerebral cortex**, so hippocampal damage would not primarily affect their recall.

Question 690: All of the following are carried by the dorsal column except?

A. Vibration
B. Touch
C. Pain (Correct Answer)
D. Proprioception

Explanation: ***Pain*** - Pain and temperature sensations are transmitted via the **spinothalamic tracts**, specifically the **lateral spinothalamic tract**, not the dorsal column. - The spinothalamic tracts decussate (cross) at the level of entry into the spinal cord, ascending contralaterally. *Vibration* - **Vibration sense** is a key modality carried by the dorsal column, along with proprioception and fine touch. - It involves receptors like **Pacinian corpuscles** and is crucial for detecting rapid changes in pressure and texture. *Touch* - **Fine discriminative touch** (two-point discrimination, precise localization, and tactile discrimination) is a primary function of the dorsal column-medial lemniscus pathway. - The dorsal column specifically carries fine touch, while crude touch has dual representation through both the dorsal column and the anterior spinothalamic tract. *Proprioception* - **Proprioception**, the sense of body position and movement, is heavily reliant on the dorsal column pathway. - Information from muscle spindles and Golgi tendon organs ascends through this pathway to the cerebral cortex for conscious awareness of limb position.

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Neurons and Glial Cells

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Synaptic Transmission

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Sensory Processing

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Motor Control Systems

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Hypothalamus and Limbic System

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Cerebral Cortex Functions

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Electroencephalography

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Neuroplasticity

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Sleep and Wakefulness

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