INI-CET 2024 - Physiology PYQs Practice Questions

Q: Sarcomere is the area between which two Z lines?

Two adjacent Z lines. ***Two adjacent Z lines*** - A **sarcomere** is defined as the fundamental contractile unit of muscle, extending from one **Z line** to the next. - The **Z lines** anchor the **actin (thin) filaments**, and their proximity helps delineate the functional sarcomere unit. *Two consecutive I bands* - The **I band** contains only **thin (actin) filaments** and is bisected by a Z line. It is not a boundary that defines a sarcomere. - A sarcomere encompasses parts of two I bands, plus an A band in the middle. *A band and I band* - The **A band** contains **thick (myosin) filaments** and overlapping thin filaments, while the **I band** contains only thin filaments. - These bands are components within a sarcomere, not boundaries that define its extent. *Two H zones* - The **H zone** is a region within the A band that contains only **thick (myosin) filaments** and is visible in relaxed muscle. - It is located in the center of the A band and does not serve as a boundary for the entire sarcomere. [Practice more Physiology PYQs on OnCourse]

Q: The interpretation of the following ABG value is: pH = 7.5, pCO2 = 50 mm Hg, HCO3 = 30 mEq/L

Metabolic alkalosis. ***Metabolic alkalosis (partially compensated)*** - The **pH of 7.5** indicates **alkalosis**, and the elevated **bicarbonate (HCO3) of 30 mEq/L** is the primary driver of this high pH. - The elevated **pCO2 of 50 mm Hg** represents **partial respiratory compensation**, where the body retains CO2 to lower the pH toward normal. - Since the pH remains elevated (not normalized to 7.35-7.45), this is **partially compensated** rather than fully compensated. *Respiratory acidosis* - This would be characterized by a **low pH** and an **elevated pCO2**, which is not seen here as the pH is high. - Although pCO2 is elevated, the **high pH** and **high bicarbonate** rule out primary respiratory acidosis. *Metabolic acidosis* - This would present with a **low pH** and a **low bicarbonate** concentration. - The given values show a **high pH** and **high bicarbonate**, which is the opposite of metabolic acidosis. *Normal acid-base balance* - A normal acid-base balance would have a **pH between 7.35-7.45**, a **pCO2 between 35-45 mm Hg**, and an **HCO3 between 22-26 mEq/L**. - All three values are outside of their normal ranges, indicating an acid-base disturbance. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following statements about cardiac muscle is incorrect?

Cardiac muscle has a short refractory period.. ***Cardiac muscle has a short refractory period.*** - This statement is **incorrect** because cardiac muscle has a **long refractory period** (~250 ms), which prevents summation and tetanus by ensuring that the muscle relaxes completely before another action potential can be initiated. - The long refractory period is crucial for maintaining the heart's **pumping efficiency** and preventing arrhythmias. *Cardiac muscle obeys the all or none law.* - This statement is **correct**. Individual **cardiac muscle cells** obey the **all-or-none law**; when a stimulus reaches threshold, the cell contracts fully. - The heart as a whole organ can grade its contraction force through recruitment of more fibers and the Frank-Starling mechanism, but at the cellular level, the all-or-none principle applies. *Cardiac muscle exhibits the Frank-Starling mechanism* - This statement is **correct**. The **Frank-Starling mechanism** describes the heart's ability to increase its force of contraction and stroke volume in response to an increase in **venous return** or end-diastolic volume. - This intrinsic regulatory mechanism allows the heart to match its output to the venous return, optimizing cardiac efficiency. *Cardiac muscle has automaticity and rhythmicity* - This statement is **correct**. **Automaticity** refers to the ability of specialized cardiac cells (e.g., in the sinoatrial node) to spontaneously generate action potentials without external nervous stimulation. - **Rhythmicity** is the regular, cyclical discharge of these action potentials, which drives the rhythmic beating of the heart. [Practice more Physiology PYQs on OnCourse]

Q: Erythropoietin is secreted by which of the following organs?

Kidney. ***Kidney*** - The **kidneys** are the primary site of erythropoietin production in adults, particularly the **peritubular interstitial cells**. - Erythropoietin's main function is to stimulate **red blood cell production** in the bone marrow in response to hypoxia. *Muscle* - Muscles are involved in movement and metabolism but do not produce **erythropoietin**. - They primarily store glycogen and generate force through contraction. *Liver* - The liver produces erythropoietin during **fetal development** but contributes minimally to its production in adulthood. - Its main functions include metabolism, detoxification, and protein synthesis. *Heart* - The heart is responsible for **pumping blood** throughout the body and does not produce **erythropoietin**. - It primarily consists of cardiac muscle tissue. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following neurotransmitters is primarily released from the sympathetic nervous system to increase heart rate in response to a DECREASE in blood pressure?

Norepinephrine. ***Norepinephrine*** - **Norepinephrine** is the primary neurotransmitter released by **postganglionic sympathetic neurons** directly onto the heart to increase heart rate and contractility in response to a drop in blood pressure. - It acts on **beta-1 adrenergic receptors** in the sinoatrial (SA) node, atria, and ventricles, leading to increased chronotropy (heart rate) and inotropy (contractility). *Dopamine* - While **dopamine** can have cardiovascular effects, particularly at high doses, it is not the primary neurotransmitter released by the sympathetic nervous system for direct heart rate regulation. - Dopamine is a precursor to norepinephrine and epinephrine, but its main physiological roles involve **renal blood flow regulation** and central nervous system functions. *Acetylcholine* - **Acetylcholine** is the primary neurotransmitter of the **parasympathetic nervous system**, which generally acts to **decrease heart rate** (bradycardia) through muscarinic receptors. - It is also released by **preganglionic sympathetic fibers**, but these do not directly innervate the heart to produce the desired effect of increasing heart rate. *Epinephrine* - **Epinephrine** (adrenaline) is primarily a **hormone** released from the **adrenal medulla** into the bloodstream, not directly from postganglionic sympathetic nerve terminals to the heart. - Although it has strong effects on beta-1 receptors in the heart, its release is more generalized and slower than the direct neuronal release of norepinephrine. [Practice more Physiology PYQs on OnCourse]

Question 1

Sarcomere is the area between which two Z lines?

Accepted Answer

Two adjacent Z lines

Answer

A band and I band

Answer

Two H zones

Answer

Two consecutive I bands

Question 2

The interpretation of the following ABG value is: pH = 7.5, pCO2 = 50 mm Hg, HCO3 = 30 mEq/L

Accepted Answer

Metabolic alkalosis

Answer

Respiratory acidosis

Answer

Metabolic acidosis

Answer

Normal acid-base balance

Question 3

Which of the following statements about cardiac muscle is incorrect?

Accepted Answer

Cardiac muscle has a short refractory period.

Answer

Cardiac muscle obeys the all or none law.

Answer

Cardiac muscle exhibits the Frank-Starling mechanism

Answer

Cardiac muscle has automaticity and rhythmicity

Question 4

Erythropoietin is secreted by which of the following organs?

Accepted Answer

Kidney

Answer

Muscle

Answer

Liver

Answer

Heart

Question 5

Which of the following neurotransmitters is primarily released from the sympathetic nervous system to increase heart rate in response to a DECREASE in blood pressure?

Accepted Answer

Norepinephrine

Answer

Dopamine

Answer

Acetylcholine

Answer

Epinephrine

Question 6

All of the following are true about the adrenal gland EXCEPT:

Accepted Answer

Medulla produces mineralocorticoids

Answer

Zona fasciculata secretes cortisol

Answer

Zona glomerulosa produces aldosterone

Answer

Zona reticularis secretes androgens

INI-CET 2024 — Physiology