General Physiology Practice Questions

Q: What is the ratio of ions moving out of the cell to the number of ions moving inside the cell via the Na:K ATPase pump?

3:2. ### Explanation **1. Why Option D is Correct:** The **Na⁺-K⁺ ATPase pump** (also known as the Sodium-Potassium pump) is a primary active transport mechanism located in the plasma membrane of almost all animal cells. For every single molecule of ATP hydrolyzed, the pump undergoes a conformational change that transports **3 Sodium (Na⁺) ions out** of the cell and **2 Potassium (K⁺) ions into** the cell. Therefore, the ratio of ions moving out to ions moving in is **3:2**. **2. Why Other Options are Incorrect:** * **Option A (2:3):** This is the inverse of the correct ratio. While 2 and 3 are the correct numbers, the direction is wrong (2 K⁺ move in, not out). * **Option B (3:1):** This ratio is seen in the **Sodium-Calcium Exchanger (NCX)**, which typically moves 3 Na⁺ ions into the cell in exchange for 1 Ca²⁺ ion out. * **Option C (1:3):** This does not correspond to any major physiological transport pump ratio in general physiology. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Electrogenic Nature:** Because it moves 3 positive charges out for every 2 positive charges in, the pump creates a net deficit of positive ions inside the cell. This contributes to the **negative Resting Membrane Potential (RMP)**. * **Energy Consumption:** This pump accounts for approximately **30% to 70%** of the total ATP consumption in many cells, especially neurons. * **Pharmacology Link:** **Cardiac Glycosides (e.g., Digoxin, Ouabain)** specifically inhibit the Na⁺-K⁺ ATPase. This inhibition increases intracellular Na⁺, which subsequently slows the Na⁺-Ca²⁺ exchanger, leading to increased intracellular Ca²⁺ and increased cardiac contractility (positive inotropy). * **Insulin & Potassium:** Insulin stimulates Na⁺-K⁺ ATPase activity, shifting K⁺ into cells. This is why insulin/glucose infusion is used to treat **hyperkalemia**.

Q: What does the PR interval on an ECG represent in terms of electrical conduction time from the SA node to the AV node?

PR interval. **Explanation:** The **PR interval** represents the time taken for electrical impulses to travel from the onset of atrial depolarization (SA node) to the onset of ventricular depolarization. It encompasses the conduction through the atria, the AV node (where the physiological delay occurs), the Bundle of His, and the Purkinje system. * **Why Option A is correct:** The PR interval specifically measures the time from the beginning of the P wave to the beginning of the QRS complex. Since the AV node is the primary site of conduction delay, the PR interval is the clinical marker used to assess the speed of conduction from the atria to the ventricles. * **Why Option B is incorrect:** The **ST segment** represents the period when the ventricles are completely depolarized (plateau phase of the action potential) and is used to identify myocardial ischemia or infarction. * **Why Option C is incorrect:** The **QT interval** represents the total time for ventricular depolarization and repolarization (electrical systole). * **Why Option D is incorrect:** While the ECG cannot visualize the SA node firing directly, the PR interval is the standard indirect measurement for this conduction time. **High-Yield NEET-PG Pearls:** 1. **Normal Duration:** 0.12 to 0.20 seconds (3-5 small squares). 2. **AV Nodal Delay:** The majority of the PR interval is due to the slow conduction in the AV node (0.09s), which allows for optimal ventricular filling (atrial kick). 3. **Clinical Correlation:** A PR interval >0.20s indicates **First-degree Heart Block**, whereas a short PR interval (<0.12s) is characteristic of **Wolff-Parkinson-White (WPW) syndrome** due to accessory pathways (Bundle of Kent).

Q: Who coined the term "Milieu intérieur"?

Claude Bernard. **Explanation:** The correct answer is **Claude Bernard**. **1. Why Claude Bernard is correct:** Claude Bernard, a French physiologist often called the "Father of Modern Physiology," introduced the concept of **"Milieu intérieur"** (Internal Environment) in the mid-19th century. He proposed that for an organism to remain healthy and independent of the external environment, its internal fluids (interstitial fluid and plasma) must remain constant. This concept laid the foundational groundwork for what we now understand as physiological regulation. **2. Analysis of Incorrect Options:** * **Walter Cannon:** He is the most common distractor. While Bernard coined "Milieu intérieur," Walter Cannon later (1926) coined the term **"Homeostasis"** to describe the processes by which this internal constancy is maintained. He also described the "Fight or Flight" response. * **Knut Schmidt-Nielsen:** A prominent figure in comparative physiology known for his work on how animals survive in extreme environments (e.g., camels in deserts) and scaling in biology. * **George Bartholomew:** A pioneer in physiological ecology who focused on the relationship between an animal's physiology and its natural environment. **3. NEET-PG High-Yield Pearls:** * **Claude Bernard:** Coined "Milieu intérieur"; discovered the glycogenic function of the liver. * **Walter Cannon:** Coined "Homeostasis"; "Fight or Flight" response; "Emergency theory" of the adrenal glands. * **Homeostasis:** Maintenance of a nearly constant internal environment. Most systems use **Negative Feedback** (e.g., blood pressure regulation). * **Positive Feedback:** Usually pathological (e.g., heart failure), but physiological in specific cases: **LH surge** (ovulation), **Oxytocin** (childbirth), and **Blood clotting cascade**.

Q: Skeletal muscle primarily utilizes which glucose transporter for uptake?

GLUT-4 transporter. **Explanation:** The correct answer is **GLUT-4 transporter**. **1. Why GLUT-4 is correct:** GLUT-4 is the primary glucose transporter found in **skeletal muscle** and **adipose tissue**. It is unique because it is **insulin-dependent**. In the resting state, GLUT-4 molecules are stored in intracellular vesicles. Upon insulin stimulation (or during exercise), these vesicles translocation to the cell membrane, allowing glucose to enter the cell via facilitated diffusion. This mechanism is crucial for post-prandial glucose lowering. **2. Why other options are incorrect:** * **GLUT-1:** This is an insulin-independent transporter found in almost all tissues, but it is the primary transporter for the **Blood-Brain Barrier (BBB)** and **RBCs**. It maintains basal glucose uptake. * **GLUT-2:** A high-capacity, low-affinity transporter found in the **Liver, Pancreas (beta cells), and Kidney**. It acts as a "glucose sensor" in the pancreas and allows bidirectional transport in the liver. * **GLUT-3:** Found primarily in **Neurons** and the placenta. It has a very high affinity for glucose, ensuring the brain receives priority supply even during hypoglycemia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Exercise & GLUT-4:** Muscle contraction during exercise can trigger GLUT-4 translocation *independent* of insulin. This is why exercise is a key management strategy for Type 2 Diabetes. * **GLUT-5:** This is a specialized transporter for **Fructose**, located primarily in the small intestine and spermatozoa. * **SGLT vs. GLUT:** Remember that SGLT (Sodium-Glucose Linked Transporters) perform **active transport** (secondary), whereas all GLUT transporters perform **facilitated diffusion** (passive).

Q: What is the hardest tissue in the human body?

Enamel. **Explanation:** **1. Why Enamel is the Correct Answer:** Enamel is the most highly mineralized and hardest substance in the human body. Its extreme hardness is attributed to its composition: it consists of approximately **96% inorganic material**, primarily in the form of **hydroxyapatite crystals** (calcium phosphate). Unlike other tissues, enamel is acellular and does not contain collagen in its mature state. It is designed to withstand the significant mechanical stresses of mastication (chewing) and to protect the underlying dentin and pulp. **2. Why Other Options are Incorrect:** * **Bone:** While bone is a rigid connective tissue, it is significantly less mineralized than enamel (containing about 65-70% inorganic matter). The presence of organic collagen fibers provides bone with flexibility and tensile strength, but reduces its overall hardness compared to enamel. * **Muscle:** Muscle is a soft tissue composed of contractile proteins (actin and myosin). It has no mineralization and is flexible. * **Skin:** Skin is the largest organ of the body, composed of epithelial and connective tissue. It is soft, pliable, and lacks the mineral density required to be considered "hard." **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Embryological Origin:** Enamel is derived from **Ectoderm** (specifically from the Enamel Organ/Ameloblasts), whereas dentin, cementum, and bone are derived from Mesoderm/Ectomesenchyme. * **Regeneration:** Because **Ameloblasts** are lost after tooth eruption, enamel cannot regenerate or repair itself biologically. * **Fluoride Action:** Fluoride prevents dental caries by replacing the hydroxyl group in hydroxyapatite to form **Fluorapatite**, which is even more resistant to acid dissolution. * **Hardness Scale:** On the Mohs scale of mineral hardness, enamel ranks around 5, while bone is significantly lower.

Q: Passive transfer of solvent occurs in which process?

Osmosis. **Explanation:** The correct answer is **Osmosis (Option C)**. **Why Osmosis is correct:** Osmosis is defined as the net movement of **solvent molecules** (usually water in biological systems) across a semi-permeable membrane. This movement occurs from a region of lower solute concentration (higher water potential) to a region of higher solute concentration (lower water potential). It is a passive process, meaning it requires no energy (ATP) and is driven solely by the osmotic pressure gradient. **Why other options are incorrect:** * **Diffusion (Option A):** This refers to the passive movement of **solute particles** (not solvent) from an area of higher concentration to lower concentration. * **Active Transport (Option B):** This process moves molecules against their concentration gradient and requires **energy (ATP)**. It is not a passive process. * **Pinocytosis (Option D):** Also known as "cell drinking," this is a form of endocytosis where the cell membrane invaginates to engulf extracellular fluid. It is an **active process** involving vesicle formation. **High-Yield NEET-PG Pearls:** * **Aquaporins:** These are specialized water channels (integral membrane proteins) that facilitate rapid osmosis in tissues like the renal collecting ducts (regulated by ADH). * **Osmotic Pressure vs. Oncotic Pressure:** While osmotic pressure is exerted by all solutes, **Oncotic pressure** (Colloid Osmotic Pressure) is specifically exerted by plasma proteins (mainly Albumin) and is crucial in preventing edema. * **Van’t Hoff’s Law:** Osmotic pressure is proportional to the molar concentration of the solute and the absolute temperature. * **Gibbs-Donnan Effect:** Describes the behavior of charged particles near a semi-permeable membrane that sometimes fails to distribute evenly, influencing osmotic balance.

Question 1

What is the ratio of ions moving out of the cell to the number of ions moving inside the cell via the Na:K ATPase pump?

Accepted Answer

3:2

Answer

2:3

Answer

3:1

Answer

1:3

Question 2

What is the primary function of the basement membrane?

Accepted Answer

Filtration

Answer

Excitation

Answer

Contraction

Answer

Transport of anions

Question 3

What does the PR interval on an ECG represent in terms of electrical conduction time from the SA node to the AV node?

Accepted Answer

PR interval

Answer

ST segment

Answer

QT interval

Answer

Cannot be determined by ECG

Question 4

Who coined the term "Milieu intérieur"?

Accepted Answer

Claude Bernard

Answer

Knut Schmidt-Nielsen

Answer

George Bartholomew

Answer

Walter Cannon

Question 5

Skeletal muscle primarily utilizes which glucose transporter for uptake?

Accepted Answer

GLUT-4 transporter

Answer

GLUT-1 transporter

Answer

GLUT-2 transporter

Answer

GLUT-3 transporter

Question 6

Across the cell membrane of a skeletal muscle cell in the resting state with a non-electrogenic pump, what is the relationship between the rates of ion movement?

Accepted Answer

The rate of sodium influx is equal to the rate of potassium efflux.

Answer

Both sodium and potassium are in electrochemical equilibrium.

Answer

The rate of sodium influx is much less than the rate of potassium efflux.

Answer

The rate of sodium influx is much greater than the rate of potassium efflux.

Question 7

What is the hardest tissue in the human body?

Accepted Answer

Enamel

Answer

Bone

Answer

Muscle

Answer

Skin

Question 8

Which of the following would cause a decrease in stroke volume when compared with the normal resting value?

Accepted Answer

Electrical pacing to a heart rate of 200 beats/min

Answer

Reduction in afterload

Answer

An increase in end-diastolic pressure

Answer

Stimulation of the vagus nerves

Question 9

All of the following are true regarding the Donnan effect EXCEPT?

Accepted Answer

A non-diffusible ion on one side of a membrane affects the distribution of other diffusible ions.

Answer

The Donnan effect helps prevent cell rupture.

Answer

There is no Donnan effect on diffusible ion movement across the capillary wall.

Answer

The Donnan effect causes a decrease in both the concentrations of cations and the colloid osmotic pressure in the capillary lumen.

Question 10

Passive transfer of solvent occurs in which process?

Accepted Answer

Osmosis

Answer

Diffusion

Answer

Active transport

Answer

Pinocytosis

General Physiology — MCQs

General Physiology — MCQs

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