NEET-PG 2020 - Physiology PYQs Practice Questions

Q: Which of the following techniques is used to study current flow across a single ion channel?

Patch clamp. ***Patch clamp*** - The **patch clamp** technique allows for the direct measurement of **ion current flow** through a single ion channel or a small group of channels. - It involves isolating a small patch of cell membrane with a micropipette to record the electrical activity. *Voltage clamp* - The **voltage clamp** technique is used to maintain a constant membrane potential while measuring the **total ionic current** across the entire cell membrane. - It is not typically used for studying current across a *single* ion channel, but rather for analyzing whole-cell currents. *Iontophoresis* - **Iontophoresis** is a method used to introduce ionized substances, such as drugs or neurotransmitters, into tissues using a small electric current. - It is a technique for drug delivery or localized stimulation, not for directly measuring ion channel current. *Galvanometry* - **Galvanometry** is a general term for the measurement of small electric currents using a galvanometer. - While ion channel activity involves electric currents, galvanometry is not a specific technique for isolating and studying single ion channels. [Practice more Physiology PYQs on OnCourse]

Q: A 35-year-old female experiences a tingling sensation in her arm after watching TV for long hours with her hands under her head. Which type of nerve fibers is most likely to be affected due to this position?

A-beta (Aβ) sensory nerve fibers. ***A-beta (Aβ) sensory nerve fibers*** - The tingling sensation (paresthesia) described is a classic symptom of **A-beta fiber compression**. - **A-beta fibers** are large, myelinated sensory fibers that transmit light touch, pressure, vibration, and proprioception. - These fibers are **most susceptible to mechanical compression** due to their position and structure. - Positioning the hands under the head for extended periods compresses superficial nerves, causing temporary A-beta fiber dysfunction, which manifests as the characteristic "pins and needles" sensation. *B-fibers (autonomic)* - **B-fibers** are preganglionic autonomic fibers that mediate visceral functions, such as organ control and glandular secretions. - Compression of these fibers would lead to symptoms related to autonomic dysfunction (e.g., changes in sweating, blood pressure), not a tingling sensation in the arm. *C-fibers (pain and temperature)* - **C-fibers** are unmyelinated fibers that transmit slow, dull, aching pain and contribute to temperature sensation. - They are **less susceptible to compression** than larger myelinated fibers. - The primary sensation described (tingling/paresthesia) is characteristic of large myelinated fiber (A-beta) dysfunction, not C-fiber involvement. *Sympathetic nerve fibers* - **Sympathetic nerve fibers** regulate involuntary functions like heart rate, blood pressure, and sweating. - Their compression would cause symptoms such as changes in skin temperature, altered sweating, or blood vessel constriction (Horner's syndrome if severe), not a tingling sensation. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following is an estrogen-dependent pubertal change?

Vaginal Cornification. ***Vaginal Cornification*** - Vaginal cornification refers to the **maturation and stratification of the vaginal epithelium** under the direct influence of **estrogen**. - Estrogen stimulates the **proliferation of vaginal epithelial cells**, leading to thickening of the vaginal mucosa and increased glycogen content in the superficial cells. - This is a **purely estrogen-dependent change** and is one of the key markers of estrogenic activity during puberty. - The vaginal maturation index increases with estrogen exposure, making this a reliable indicator of estrogenic stimulation. *Menstruation* - While estrogen is important for endometrial proliferation, menstruation requires the **coordinated action of both estrogen AND progesterone**. - Estrogen builds the endometrium during the proliferative phase, but **progesterone** is essential for the secretory transformation. - Menstruation occurs due to the **withdrawal of both hormones**, not estrogen alone, making it dependent on both hormones rather than purely estrogen-dependent. *Cervical mucus* - Cervical mucus characteristics are influenced by **both estrogen and progesterone** throughout the menstrual cycle. - Estrogen makes mucus thin, watery, and stretchy (spinnbarkeit), while progesterone makes it thick and viscous. - This **dual hormonal regulation** means it is not purely estrogen-dependent. *Hair growth* - Pubertal hair growth, including **pubic and axillary hair**, is primarily stimulated by **androgens** (testosterone, DHEA-S from the adrenal glands). - This process is called **adrenarche** and is androgen-dependent, not estrogen-dependent. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following is referred to as the "Window of the limbic system"?

Thalamus. ***Thalamus*** - The thalamus is often referred to as the **"relay station"** of the brain, processing and relaying most **sensory information** (except smell) to the cerebral cortex. - Due to its extensive connections with various limbic structures and its role in integrating and filtering emotional and motivational information before it reaches conscious awareness, it's considered the **"window of the limbic system"**. *Hypothalamus* - The hypothalamus primarily controls **autonomic functions** and maintains **homeostasis**, such as regulating temperature, hunger, thirst, and sleep cycles. - While it has strong connections with the limbic system, its main role is executive autonomic control rather than sensory integration. *Amygdala* - The amygdala is critically involved in processing **emotions**, particularly **fear** and **aggression**, and plays a key role in emotional memory. - It's a central component *within* the limbic system, but it doesn't serve as a general window or relay for the entire system's input. *Hippocampus* - The hippocampus is primarily responsible for **memory formation** (especially new episodic memories) and spatial navigation. - It is an important limbic structure, but its function is more specific to memory rather than being a gateway for broader limbic system activity. [Practice more Physiology PYQs on OnCourse]

Q: Among the following, prolactin secretion is maximum:

24 hrs after delivery. ***Correct: 24 hrs after delivery*** - Prolactin levels are highest in the initial **24 hours postpartum**, especially during and after **breastfeeding sessions**, which act as a powerful stimulus for prolactin release. - This peak prolactin level is crucial for initiating and maintaining **lactation** following childbirth. - The postpartum prolactin surge represents the **maximum physiological level** of this hormone under normal circumstances. *Incorrect: During REM sleep* - While prolactin secretion does exhibit a **circadian rhythm** with nocturnal peaks, the highest levels do not specifically occur during **REM sleep**; rather, they are elevated throughout the sleep cycle. - Though prolactin does rise during sleep, the magnitudes are **not comparable** to the surges seen postpartum or after intense suckling. *Incorrect: After 2 hours of running* - Exercise, particularly prolonged and intense physical activity, can cause a transient increase in prolactin levels due to **stress response** and hormonal changes. - However, this exercise-induced increase is generally **modest** compared to the physiological surge observed after delivery. *Incorrect: 24 hours after ovulation* - Prolactin levels show a slight increase during the **luteal phase** of the menstrual cycle, which follows ovulation, primarily due to rising progesterone levels. - This elevation is significantly **lower** than the dramatic rise seen immediately postpartum needed for milk production. [Practice more Physiology PYQs on OnCourse]

Question 1

Which of the following techniques is used to study current flow across a single ion channel?

Accepted Answer

Patch clamp

Answer

Galvanometry

Answer

Voltage clamp

Answer

Iontophoresis

Question 2

A 35-year-old female experiences a tingling sensation in her arm after watching TV for long hours with her hands under her head. Which type of nerve fibers is most likely to be affected due to this position?

Accepted Answer

A-beta (Aβ) sensory nerve fibers

Answer

B - fibers (autonomic)

Answer

C - fibers (pain and temperature)

Answer

Sympathetic nerve fibers

Question 3

Which of the following is an estrogen-dependent pubertal change?

Accepted Answer

Vaginal Cornification

Answer

Cervical mucus

Answer

Menstruation

Answer

Hair growth

Question 4

Which of the following is referred to as the "Window of the limbic system"?

Accepted Answer

Thalamus

Answer

Hypothalamus

Answer

Hippocampus

Answer

Amygdala

Question 5

Among the following, prolactin secretion is maximum:

Accepted Answer

24 hrs after delivery

Answer

During REM sleep

Answer

After 2 hours of running

Answer

24 hours after ovulation

Question 6

When the value of V/Q is infinity, it means?

Accepted Answer

Dead space

Answer

The PO2 of alveolar air is 159mmHg and PCO2 is 0mmHg

Answer

Partial pressure of O2 and CO2 are equal

Answer

No O2 goes from alveoli to blood and no CO2 goes from blood to alveoli

Question 7

In multiple sclerosis, slow conduction of motor and sensory pathways is due to?

Accepted Answer

Loss of myelin sheath

Answer

Dysfunction of sodium channels

Answer

Dysfunction of calcium channels

Answer

Defect in the nodes of Ranvier

Question 8

What is the main feature of chemotaxis as observed in white blood cells?

Accepted Answer

Unidirectional locomotion of neutrophils

Answer

Increased random movement of neutrophils

Answer

Increased adhesiveness to intima

Answer

Increased phagocytosis

Question 9

What is the reflex in which there is inhibition of gastric emptying when there is acid and hypertonic solution in the duodenum?

Accepted Answer

Enterogastric

Answer

Gastroileal

Answer

Gastrocolic

Answer

Myenteric

Question 10

A 33-year-old man presents with a 5-week history of calf pain, swelling, and low-grade fever. Serum levels of creatinine kinase are elevated. A muscle biopsy reveals numerous eosinophils and he also has peripheral blood eosinophilia. Which of the following interleukins is primarily responsible for the increase in eosinophils in this patient?

Accepted Answer

IL-5

Answer

IL-4

Answer

IL-6

Answer

IL-2

NEET-PG 2020 — Physiology