NEET-PG 2015 - Physiology Practice Questions

Q: What is the typical pH range of intracellular fluid (ICF) compared to extracellular fluid (ECF)?

Typically around 7.0, slightly less than ECF. ***Typically around 7.0, slightly less than ECF*** - The **intracellular fluid (ICF)** tends to be slightly more acidic due to metabolic processes within cells that produce **acidic byproducts**. - This makes its pH typically around **7.0–7.2**, which is subtly lower than the extracellular fluid. *Typically around 7.4, slightly more than ICF* - A pH of approximately **7.4** is characteristic of **extracellular fluid (ECF)**, which includes plasma and interstitial fluid. - The ECF is maintained within a **narrow, slightly alkaline** range to support cellular function and enzyme activity throughout the body. *Approximately equal to ECF* - While both fluid compartments are maintained within a **narrow physiological range**, their pH values are not exactly equal. - This slight difference is essential for various biological processes, including maintaining **membrane potential** and **enzyme efficiency**. *Significantly higher than ECF* - The ICF pH is **not significantly higher** than ECF; in fact, it is slightly lower. - Maintaining too high a pH intracellularly would disrupt **cellular metabolism** and **protein structure**.

Q: Vibrations are detected by which types of receptors?

Rapidly adapting. ***Rapidly adapting*** - **Rapidly adapting mechanoreceptors**, such as **Pacinian corpuscles** and **Meissner's corpuscles**, are highly sensitive to changes in pressure and movement. - They fire at the **onset and offset of a stimulus**, making them ideal for detecting vibrations, which are rhythmic changes in pressure. *Slowly adapting* - **Slowly adapting mechanoreceptors**, such as **Merkel cells** and **Ruffini endings**, are responsible for sustained pressure and touch. - They continue to fire as long as the stimulus is present, making them less suited for detecting transient vibratory stimuli. *Non-adapting* - The human body does not typically have **truly non-adapting** sensory receptors; most receptors show some form of adaptation to continuous stimuli. - This term is not standard in the classification of mechanoreceptors based on their adaptation rates. *None of the above* - This option is incorrect because rapidly adapting receptors are indeed responsible for detecting vibrations.

Q: Which of the following statements is true regarding smooth muscle contraction?

Phosphorylation of myosin is essential for contraction.. **Phosphorylation of myosin is essential for contraction.** - In **smooth muscle**, the **myosin light chain (MLC)** must be phosphorylated by **myosin light chain kinase (MLCK)** to enable interaction with actin and initiate contraction. - This phosphorylation causes a conformational change in the **myosin head**, increasing its ATPase activity and allowing cross-bridge cycling. *Calmodulin plays no role in smooth muscle contraction.* - **Calmodulin (CaM)** is crucial for smooth muscle contraction, as it binds **calcium ions (Ca²⁺)** forming a Ca²⁺-CaM complex. - This complex then activates **myosin light chain kinase (MLCK)**, which phosphorylates myosin, triggering contraction. *None of the options.* - This statement is incorrect because one of the provided options, "Phosphorylation of myosin is essential for contraction," is indeed true. *Troponin plays a significant role in smooth muscle contraction.* - Unlike **striated muscle (skeletal and cardiac)**, **smooth muscle** does not contain **troponin**. - Regulation of smooth muscle contraction is primarily **calcium-calmodulin-dependent**, with roles for **MLCK** and **MLCP**, rather than troponin.

Q: Broca's area is primarily involved in which of the following functions?

Speech production. ***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.

Q: What does the transient response observed during the insertion of an electrode in electromyography (EMG) indicate?

Cell membrane disruption. **Cell membrane disruption** - The **transient response** observed during electrode insertion in **EMG** is caused by the mechanical trauma of the needle disrupting the **muscle fiber cell membranes**. - This disruption leads to a brief depolarization and subsequent repolarization of the affected fibers, generating characteristic electrical activity. *Spontaneous muscle activity* - **Spontaneous muscle activity**, such as **fibrillation potentials** or **positive sharp waves**, occurs independently of electrode insertion. - While observed during EMG, these are indicative of **denervation** or **myopathy** and are not directly caused by the act of insertion itself. *Voluntary muscle contraction* - **Voluntary muscle contraction** is recorded when the patient actively contracts the muscle and results in **motor unit action potentials (MUAPs)**. - This is a distinct process from the transient activity produced by electrode insertion. *Induced muscle contraction* - **Induced muscle contraction** typically refers to activity caused by **nerve stimulation** (e.g., in nerve conduction studies) or direct electrical stimulation of the muscle. - This is not the mechanism for the transient response during simple electrode insertion.

Q: During the sympathetic fight-or-flight response, what is the primary cardiovascular effect of epinephrine and norepinephrine on skeletal muscle vasculature?

Increased blood flow to muscles. ***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.

Q: What is the composition of epithelial sodium channels?

1α, 1β, 1γ. ***1α, 1β, 1γ*** - Epithelial sodium channels (**ENaCs**) are heterotrimeric complexes composed of one **alpha (α)**, one **beta (β)**, and one **gamma (γ) subunit**. - This specific subunit composition is essential for the channel's proper function in **sodium reabsorption** across epithelial tissues. *2α, 1β* - This composition is incomplete as it lacks the **gamma (γ) subunit**, which is a crucial component of the functional ENaC. - While alpha and beta subunits are present, the absence of the gamma subunit would impair the channel's ability to efficiently transport sodium. *2α, 1β, 2γ* - This composition is incorrect because a functional ENaC typically includes only **one gamma (γ) subunit**, not two. - An imbalance in subunit stoichiometry can lead to misfolding or improper assembly, affecting channel function. *2α, 1β, 1γ* - This combination correctly includes all three types of subunits (alpha, beta, gamma) but incorrectly states there are **two alpha (α) subunits**. - A functional ENaC has a single alpha subunit, making this option incorrect.

Q: Which of the following neurons in the cerebellar cortex is primarily excitatory?

Granule cells. ***Granule cells*** - **Granule cells** are the only neurons in the cerebellar cortex that are **excitatory**, utilizing glutamate as their neurotransmitter. - They receive input from **mossy fibers** and project their parallel fibers to Purkinje cells and other interneurons. *Purkinje* - **Purkinje cells** are the primary output neurons of the cerebellar cortex and are **inhibitory**, releasing GABA. - They integrate vast amounts of information and project to the **deep cerebellar nuclei**. *Basket* - **Basket cells** are **inhibitory interneurons** located in the molecular layer of the cerebellum. - They synapse on the somata of **Purkinje cells**, providing potent inhibition. *Golgi* - **Golgi cells** are **inhibitory interneurons** found in the granular layer of the cerebellum. - They receive excitatory input from **parallel fibers** and inhibit granule cells, forming an important feedback loop.

Q: What is one of the specific functions of the primary motor cortex located on the anterior edge of the pre-central gyrus?

Control of voluntary movement. ***Control of voluntary movement*** - The **primary motor cortex (M1)**, located in the **precentral gyrus**, is critically involved in generating neural impulses that control the execution of **voluntary movements**. - It plays a key role in **planning and executing complex, skilled movements**, especially of the distal musculature. *Increase extensor muscle tone* - While motor pathways influence muscle tone, the primary motor cortex's most specific role is not simply increasing extensor tone; rather, it coordinates a wide range of movements involving both flexors and extensors. - **Spasticity** or increased muscle tone (often extensor) is more commonly associated with damage to the **corticospinal tracts (upper motor neuron lesions)**, which *prevents* the fine-tuning inhibitory control from the cortex. *Perception of pain* - **Pain perception** is primarily processed in the **somatosensory cortex** (postcentral gyrus), limbic system, and insula, not the primary motor cortex. - The primary motor cortex is responsible for **motor output**, not sensory interpretation. *Inhibition of stretch reflex* - While descending motor pathways can modulate spinal reflexes, the direct and primary function of the primary motor cortex is not the specific inhibition of the stretch reflex. - The **gamma motor system** and other spinal interneurons are more directly involved in modulating the sensitivity of the stretch reflex.

Q: What is the typical resting membrane potential (RMP) of smooth muscle cells?

-60 mV. ***-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 1

What is the typical pH range of intracellular fluid (ICF) compared to extracellular fluid (ECF)?

Accepted Answer

Typically around 7.0, slightly less than ECF

Answer

Typically around 7.4, slightly more than ICF

Answer

Approximately equal to ECF

Answer

Significantly higher than ECF

Question 2

Vibrations are detected by which types of receptors?

Accepted Answer

Rapidly adapting

Answer

Slowly adapting

Answer

Non-adapting

Answer

None of the above

Question 3

Which of the following statements is true regarding smooth muscle contraction?

Accepted Answer

Phosphorylation of myosin is essential for contraction.

Answer

None of the options.

Answer

Calmodulin plays no role in smooth muscle contraction.

Answer

Troponin plays a significant role in smooth muscle contraction.

Question 4

Broca's area is primarily involved in which of the following functions?

Accepted Answer

Speech production

Answer

Language comprehension

Answer

Language repetition

Answer

Reading ability

Question 5

What does the transient response observed during the insertion of an electrode in electromyography (EMG) indicate?

Accepted Answer

Cell membrane disruption

Answer

Spontaneous muscle activity

Answer

Voluntary muscle contraction

Answer

Induced muscle contraction

Question 6

During the sympathetic fight-or-flight response, what is the primary cardiovascular effect of epinephrine and norepinephrine on skeletal muscle vasculature?

Accepted Answer

Increased blood flow to muscles

Answer

Increased blood flow to the skin

Answer

Bronchoconstriction

Answer

Decreased heart rate

Question 7

What is the composition of epithelial sodium channels?

Accepted Answer

1α, 1β, 1γ

Answer

2α, 1β, 1γ

Answer

2α, 1β

Answer

2α, 1β, 2γ

Question 8

Which of the following neurons in the cerebellar cortex is primarily excitatory?

Accepted Answer

Granule cells

Answer

Purkinje

Answer

Basket

Answer

Golgi

Question 9

What is one of the specific functions of the primary motor cortex located on the anterior edge of the pre-central gyrus?

Accepted Answer

Control of voluntary movement

Answer

Increase extensor muscle tone

Answer

Perception of pain

Answer

Inhibition of stretch reflex

Question 10

What is the typical resting membrane potential (RMP) of smooth muscle cells?

Accepted Answer

-60 mV

Answer

-90 mV

Answer

-70 mV

Answer

-40 mV

NEET-PG 2015 — Physiology