General Physiology Practice Questions

Q: The ductus venosus in fetal circulation primarily functions to:

Umbilical vein → IVC. ***Umbilical vein → IVC*** - The **ductus venosus** serves as a specialized vascular shunt that allows approximately 30-50% of the oxygenated, nutrient-rich blood from the **umbilical vein** to bypass the hepatic microcirculation. - By shunting blood directly into the **inferior vena cava (IVC)**, it ensures that highly oxygenated blood is preferentially directed toward the **fetal heart** and brain. *Umbilical vein → liver* - While the **umbilical vein** does provide some blood to the liver (via the left portal vein), the primary function of the **ductus venosus** specifically is to *bypass* the liver rather than supply it. - If all flow went to the liver, the resistance would be too high and fetal hepatic blood flow would be dangerously restricted. *Pulmonary artery → aorta* - This describes the **ductus arteriosus**, which shunts blood away from the high-resistance **fetal lungs** to the systemic circulation via the descending aorta. - The **ductus arteriosus** connects the pulmonary trunk to the aorta, not the IVC. *Right atrium → left atrium* - This describes the **foramen ovale**, an anatomical opening in the atrial septum that allows right-to-left shunting of blood. - It acts as a bypass to keep oxygenated blood from the IVC moving toward the **left atrium**, avoiding the pulmonary circulation.

Q: Which of the following statements about facilitated diffusion is true?

It requires a carrier protein. **Explanation:** **Facilitated diffusion** is a type of carrier-mediated transport that allows large or polar molecules (like glucose and amino acids) to cross the cell membrane down their electrochemical gradient without the expenditure of energy. 1. **Why Option B is Correct:** Unlike simple diffusion, facilitated diffusion requires specific **integral membrane proteins (carriers)**. These proteins undergo conformational changes to shuttle molecules across the lipid bilayer. Because it relies on a finite number of carrier proteins, this process exhibits **saturation kinetics** ($V_{max}$). 2. **Why Other Options are Incorrect:** * **Option A:** It is a form of **passive transport**, not active. It does not move substances against a gradient. * **Option C:** This is false due to **saturation**. In simple diffusion, the rate is directly proportionate to the gradient (Fick’s Law). In facilitated diffusion, the rate increases with the gradient only until all carrier binding sites are occupied ($V_{max}$), after which the rate plateaus. * **Option D:** It requires **no metabolic energy** (ATP or Creatine Phosphate). The driving force is the concentration gradient itself. **High-Yield NEET-PG Pearls:** * **Classic Example:** Glucose transport via **GLUT transporters** (e.g., GLUT4 in muscle/adipose tissue) is the most frequently tested example of facilitated diffusion. * **Key Characteristics:** It is specific, saturable (shows a $T_m$ or Transport Maximum), and can be competitively inhibited. * **Distinction:** Unlike Primary Active Transport (e.g., Na+-K+ ATPase) or Secondary Active Transport (e.g., SGLT), facilitated diffusion **cannot** create a concentration gradient; it can only dissipate one.

Q: Natural light causes all except?

Destruction of the organ of Corti. **Explanation:** The question asks for the physiological effect that is **NOT** caused by natural light. **1. Why "Destruction of the organ of Corti" is the correct answer:** The **organ of Corti** is the sensory organ for hearing located within the inner ear (cochlea). It is stimulated by mechanical sound waves, not electromagnetic radiation (light). Destruction of the organ of Corti is typically caused by chronic exposure to loud noise (noise-induced hearing loss), ototoxic drugs (e.g., aminoglycosides), or aging—not by exposure to natural light. **2. Analysis of Incorrect Options:** * **Vitamin D synthesis:** Ultraviolet B (UVB) radiation from natural sunlight triggers the conversion of 7-dehydrocholesterol in the skin into cholecalciferol (Vitamin D3). * **Decrease in bilirubin level:** Blue-green light (wavelength 460–490 nm) helps decompose bilirubin into water-soluble isomers (lumirubin) that can be excreted without conjugation. This is the physiological basis for **phototherapy** used in neonatal jaundice. * **Melanin synthesis:** Exposure to UV light stimulates melanocytes in the basal layer of the epidermis to produce melanin (melanogenesis), which acts as a protective pigment against DNA damage. **High-Yield Clinical Pearls for NEET-PG:** * **Pineal Gland Connection:** Natural light inhibits the secretion of **Melatonin** from the pineal gland via the suprachiasmatic nucleus (SCN), regulating the circadian rhythm. * **Phototherapy:** The most effective wavelength for treating neonatal hyperbilirubinemia is approximately **450 nm**. * **Vitamin D:** The skin is the primary source of Vitamin D; deficiency leads to Rickets in children and Osteomalacia in adults. * **Retinal Damage:** While light doesn't affect the ear, excessive UV/blue light can cause **photoretinitis** or damage to the macula.

Question 1

The ductus venosus in fetal circulation primarily functions to:

Accepted Answer

Umbilical vein → IVC

Answer

Umbilical vein → liver

Answer

Pulmonary artery → aorta

Answer

Right atrium → left atrium

Question 2

A 62-year-old woman eats a high carbohydrate meal. Her plasma glucose concentration rises, and this results in increased insulin secretion from the pancreatic islet cells. The insulin response is an example of

Accepted Answer

Negative feedback

Answer

Chemical equilibrium

Answer

End-product inhibition

Answer

Feed forward control

Question 3

Which of the following statements about facilitated diffusion is true?

Accepted Answer

It requires a carrier protein

Answer

It is a form of active transport

Answer

Rate of transport is proportionate to the concentration gradient

Answer

Requires creatine phosphate

Question 4

Which of the following is NOT an example of a feedforward control system?

Accepted Answer

Blood pressure regulation

Answer

Temperature regulation

Answer

Cephalic phase of gastric secretion

Answer

Increased heart rate before the start of exercise

Question 5

Natural light causes all except?

Accepted Answer

Destruction of the organ of Corti

Answer

Vitamin D synthesis

Answer

Decrease in bilirubin level

Answer

Melanin synthesis

General Physiology — MCQs

General Physiology — MCQs

On this page

Practice by Chapter

Want unlimited practice?