Anatomy
1 questionsWhich Brodmann's area is primarily associated with motor speech?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 191: Which Brodmann's area is primarily associated with motor speech?
- A. Area 1, 2, 3
- B. Area 4, 6
- C. Area 40
- D. Area 44 (Correct Answer)
Explanation: Area 44 - **Brodmann Area 44** is primarily known as **Broca's area**, which is critical for **motor speech production** and language processing [1]. - Damage to this area typically results in **Broca's aphasia**, characterized by non-fluent speech and difficulty forming complete sentences [1]. Area 1, 2, 3 - These Brodmann areas constitute the **primary somatosensory cortex**, responsible for processing **tactile and proprioceptive information** from the body. - They are involved in sensory perception, not directly with motor speech production. Area 4, 6 - **Brodmann Area 4** is the **primary motor cortex**, involved in executing voluntary movements [2]. **Brodmann Area 6** is the **premotor and supplementary motor cortex**, involved in planning and coordinating movements [2]. - While these areas are crucial for motor control, they are not specifically associated as the primary center for motor speech in the same way Broca's area is. Area 40 - **Brodmann Area 40**, also known as the **supramarginal gyrus**, is part of the **parietal lobe** and is involved in phonological processing, language perception, and spatial cognition. - While it plays a role in language, it is not the primary area for motor speech production.
Physiology
9 questionsEPSP is due to?
What is the typical resting membrane potential (RMP) of smooth muscle cells?
During the sympathetic fight-or-flight response, what is the primary cardiovascular effect of epinephrine and norepinephrine on skeletal muscle vasculature?
Maximum density of muscle spindle is found in?
Damage to pneumotaxic center along with vagus nerve causes which type of respiration?
Broca's area is primarily involved in which of the following functions?
The ST Segment of an ECG corresponds to which phase of the action potential?
Which of the following receptors is stimulated by sustained pressure?
Vital capacity is measured by:
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 191: EPSP is due to?
- A. Sodium ion influx (Correct Answer)
- B. Potassium ion influx
- C. Sodium ion efflux
- D. Calcium ion influx
Explanation: ***Sodium ion influx*** - An **Excitatory Postsynaptic Potential (EPSP)** is caused primarily by the binding of an **excitatory neurotransmitter** to its receptor, leading to the opening of **ligand-gated ion channels** permeable to sodium (Na+) ions. - The **influx of positively charged sodium ions** into the postsynaptic neuron causes a **depolarization** of the membrane potential, making it more likely to reach the threshold for an action potential. *Potassium ion influx* - **Potassium (K+) influx** is not the primary mechanism for generating an EPSP; instead, **potassium efflux** (movement out of the cell) is typically involved in **repolarization** after an action potential or in generating **Inhibitory Postsynaptic Potentials (IPSPs)**. - The movement of K+ into the cell would make the membrane potential more negative, leading to **hyperpolarization** or preventing depolarization. *Sodium ion efflux* - **Sodium (Na+) efflux** is mediated by the **Na+/K+ pump** and is crucial for maintaining the resting membrane potential, but it does **not directly cause an EPSP**. - Pumping Na+ out of the cell would **hyperpolarize** the cell or oppose depolarization, making an action potential less likely. *Calcium ion influx* - While **calcium (Ca2+) influx** is vital for many neuronal processes, including **neurotransmitter release** from the presynaptic terminal, it is **not the primary ionic basis** for generating an EPSP in the postsynaptic neuron itself. - Significant Ca2+ influx can occur during an **action potential** or lead to intracellular signaling, but it's not the main depolarizing current responsible for an EPSP.
Question 192: What is the typical resting membrane potential (RMP) of smooth muscle cells?
- A. -90 mV
- B. -70 mV
- C. -60 mV (Correct Answer)
- D. -40 mV
Explanation: ***-60 mV*** - Smooth muscle cells typically have a **resting membrane potential of -55 to -60 mV**, which is **less negative** compared to skeletal muscle (-90 mV) or neurons (-70 mV). - This relatively depolarized RMP allows them to be **more easily excited** and enables **spontaneous slow wave depolarizations** and pacemaker activity in some smooth muscle types. - The less negative potential is due to higher resting permeability to Na+ and Ca2+ compared to skeletal muscle. *-90 mV* - This is the typical resting membrane potential for **skeletal muscle cells** and **large myelinated nerve fibers**. - Such a highly negative RMP provides a **larger buffer against accidental excitation** and ensures precise voluntary control. - This value is maintained by high K+ permeability and active Na+/K+ ATPase activity. *-70 mV* - This is the characteristic resting membrane potential of **most neurons**, allowing for efficient generation and propagation of action potentials. - It represents a balance between depolarizing and hyperpolarizing influences, optimal for neuronal signaling. - This is more negative than smooth muscle but less negative than skeletal muscle. *-40 mV* - This value is **too depolarized** to be a stable resting potential for smooth muscle and would be **near threshold potential**. - At -40 mV, voltage-gated calcium channels would be significantly activated, causing sustained contraction rather than a resting state. - This might represent a **partially depolarized state** or the RMP of specialized pacemaker cells like cardiac SA node cells, but **not typical smooth muscle**.
Question 193: During the sympathetic fight-or-flight response, what is the primary cardiovascular effect of epinephrine and norepinephrine on skeletal muscle vasculature?
- A. Increased blood flow to muscles (Correct Answer)
- B. Increased blood flow to the skin
- C. Bronchoconstriction
- D. Decreased heart rate
Explanation: ***Increased blood flow to muscles*** - **Epinephrine** and **norepinephrine** cause **vasodilation** in skeletal muscle arterioles, shunting blood toward tissues critical for immediate physical action. - This response ensures that muscles have adequate **oxygen** and **nutrients** to support intense activity, enabling a quick escape or confrontation. *Increased blood flow to the skin* - During fight-or-flight, the body prioritizes essential organs, causing **vasoconstriction** in the skin to redirect blood flow away from non-essential areas. - This redirection helps to conserve blood and reduce potential blood loss from surface injuries. *Bronchoconstriction* - **Epinephrine** and **norepinephrine** actually cause **bronchodilation**, leading to the relaxation of airway smooth muscles. - This effect increases the diameter of the airways, allowing more air to enter and exit the lungs, thereby enhancing **oxygen intake** and carbon dioxide expulsion. *Decreased heart rate* - The primary effect of **epinephrine** and **norepinephrine** is to **increase heart rate** and myocardial contractility. - This cardiac acceleration enhances **cardiac output**, ensuring rapid and efficient delivery of oxygenated blood throughout the body to meet the demands of stress.
Question 194: Maximum density of muscle spindle is found in?
- A. Calf muscle
- B. Lumbricals (Correct Answer)
- C. Triceps
- D. Quadriceps muscle
Explanation: ***Lumbricals*** - **Lumbricals** are small, intricate muscles in the hand, responsible for fine motor control and precise movements like grasping and manipulating objects. - The high density of **muscle spindles** in lumbricals allows for extremely accurate feedback on muscle length and tension, crucial for **proprioception** and delicate tasks. *Calf muscle* - **Calf muscles** (gastrocnemius and soleus) are large muscles primarily involved in powerful movements like walking and running. - While they do contain muscle spindles for proprioception, their density is lower compared to muscles involved in fine motor control. *Quadriceps muscle* - The **quadriceps femoris** is a large muscle group in the thigh responsible for knee extension and powerful leg movements. - They contain muscle spindles to monitor muscle stretch, but not with the extreme density seen in muscles with fine motor functions. *Triceps* - The **triceps brachii** is a large muscle on the back of the upper arm, primarily responsible for elbow extension. - It has a moderate density of muscle spindles, sufficient for coordinating arm movements but not as high as muscles designed for precision.
Question 195: Damage to pneumotaxic center along with vagus nerve causes which type of respiration?
- A. Cheyne-Stokes breathing
- B. Deep and slow breathing
- C. Shallow and rapid breathing
- D. Apneustic breathing (Correct Answer)
Explanation: ***Apneustic breathing*** - Damage to the **pneumotaxic center** prevents the normal inhibition of inspiration, leading to **prolonged inspiratory gasps**. - **Vagal nerve damage** further removes the inhibitory feedback from the lungs, exacerbating the inspiratory "holds" characteristic of apneustic breathing. *Cheyne-Stokes breathing* - This pattern is characterized by a **crescendo-decrescendo pattern** of breathing, interspersed with periods of **apnea**. - It is often associated with conditions like **heart failure**, stroke, or severe neurological damage, not specifically the pneumotaxic center and vagus nerve. *Deep and slow breathing* - This pattern can be seen in conditions like **Kussmaul breathing** (due to metabolic acidosis) or as a compensatory mechanism. - It does not directly result from the combined damage of the **pneumotaxic center** and the **vagus nerve**. *Shallow and rapid breathing* - This pattern is commonly seen in restrictive lung diseases, anxiety, or pain, where tidal volume is decreased and respiratory rate increased. - It does not reflect the **prolonged inspiration** that would result from a compromised pneumotaxic center and vagal input.
Question 196: Broca's area is primarily involved in which of the following functions?
- A. Speech production (Correct Answer)
- B. Language comprehension
- C. Language repetition
- D. Reading ability
Explanation: ***Speech production*** - **Broca's area** is a region in the frontal lobe of the dominant hemisphere, typically the left, that is crucial for the formation of coherent and grammatically correct speech. - Damage to this area leads to **Broca's aphasia**, characterized by **non-fluent speech**, difficulty retrieving words, and impaired syntax. *Language comprehension* - **Wernicke's area**, located in the temporal lobe, is primarily responsible for **language comprehension**. - Patients with **Wernicke's aphasia** can produce fluent speech but have difficulty understanding spoken and written language. *Language repetition* - The **arcuate fasciculus**, a bundle of nerve fibers connecting Broca's and Wernicke's areas, is essential for **language repetition**. - Lesions in this pathway result in **conduction aphasia**, where comprehension and fluency are relatively preserved, but repetition is severely impaired. *Reading ability* - Reading ability involves a complex network of brain regions, including the **angular gyrus** and **visual cortex**, in addition to language areas. - While Broca's area contributes to the motor planning aspects of reading aloud, it is not its primary function.
Question 197: The ST Segment of an ECG corresponds to which phase of the action potential?
- A. Rapid repolarization
- B. Final repolarization
- C. Plateau phase (Correct Answer)
- D. Rapid depolarization
Explanation: ***Plateau phase*** - The **ST segment** of the ECG represents the period when the ventricles are completely depolarized and corresponds to the **plateau phase (phase 2)** of the ventricular myocardial action potential. - During this phase, there is a balance between **calcium influx** and **potassium efflux**, maintaining the depolarized state and contributing to the sustained contraction of the ventricles. *Rapid depolarization* - This phase, represented by the **QRS complex** on the ECG, signifies the rapid influx of sodium ions into the ventricular cells. - It corresponds to **phase 0** of the action potential, where there is a sharp upstroke. *Rapid repolarization* - This corresponds to **phase 3** of the ventricular action potential, where potassium ions rapidly exit the cell, leading to repolarization. - On the ECG, this phase is represented by the **T wave**. *Final repolarization* - This is **not a standard electrophysiological term** in cardiac action potential nomenclature. - The complete repolarization process is represented by the **T wave** (phase 3), which returns the ventricle to its resting potential (phase 4). - The term may cause confusion as it doesn't correspond to a specific phase or ECG component.
Question 198: Which of the following receptors is stimulated by sustained pressure?
- A. Ruffini's end organ (Correct Answer)
- B. Merkel's disc
- C. Hair cells
- D. Meissner Corpuscles
Explanation: ***Ruffini's end organ*** - These are **slowly adapting mechanoreceptors** located deep in the dermis and subcutaneous tissue. - They are responsible for detecting **sustained pressure**, stretch, and position sense. *Merkel's disc* - These are **slowly adapting mechanoreceptors** found in the basal epidermis. - They are crucial for sensing **light touch** and **two-point discrimination**. *Hair cells* - These are **mechanoreceptors** primarily found in the inner ear, responsible for hearing and balance. - They are not involved in the perception of somatosensory stimuli like pressure on the skin. *Meissner Corpuscles* - These are **rapidly adapting mechanoreceptors** located in the dermal papillae, close to the skin surface. - They are primarily involved in detecting **light touch** and **discriminative touch**, especially changes in texture.
Question 199: Vital capacity is measured by:
- A. Plethysmography
- B. Nitrogen washout technique
- C. Spirometer (Correct Answer)
- D. Gas-dilution method
Explanation: ***Spirometer*** - A **spirometer** is a device used to measure lung volumes and capacities, including **vital capacity**. - It measures the volume of air inspired and expired by evaluating mechanical changes in the volume of air in the lungs. *Plethysmography* - **Plethysmography** is primarily used to measure **residual volume** and **total lung capacity**, not vital capacity directly. - This method measures changes in body volume to infer changes in lung volume. *Gas-dilution method* - The **gas-dilution method**, typically using helium, is used to measure the **functional residual capacity (FRC)** and subsequently calculate residual volume and total lung capacity. - It involves rebreathing a known concentration of gas to determine the volume of gas already in the lungs. *Nitrogen washout technique* - The **nitrogen washout technique** is also used to measure **functional residual capacity (FRC)** and detect uneven ventilation. - It involves breathing 100% oxygen to wash out all nitrogen from the lungs, allowing for calculation of lung volumes.