NEET-PG 2022 - Physiology PYQs Practice Questions

Q: Some cells secrete chemicals into the extracellular fluid that act on cells in the same tissue. Which of the following refers to this type of regulation?

Paracrine. ***Paracrine*** - **Paracrine signaling** involves chemical messengers, or **paracrine factors**, that act on **neighboring cells** within the **same tissue** without entering the bloodstream. - This type of regulation is crucial for local communication and coordination, such as in wound healing or immune responses. *Neural* - **Neural regulation** involves communication via **neurons** that transmit **electrical signals** (action potentials) and release **neurotransmitters** at synapses. - Neurotransmitters act on target cells, which can be distant from the neuron, for rapid and precise responses throughout the body. *Endocrine* - **Endocrine regulation** involves glands that secrete **hormones** directly into the **bloodstream**, which then travel to distant target cells in other tissues or organs. - This form of signaling leads to widespread and long-lasting effects, such as growth regulation or metabolic control. *Neuroendocrine* - **Neuroendocrine regulation** is a hybrid system where specialized **neurons** (neurosecretory cells) release **hormones** into the **bloodstream**, rather than releasing neurotransmitters into a synapse. - An example is the hypothalamus secreting ADH and oxytocin, which act on distant target organs. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following statements about the O2-Hb dissociation curve is correct?

It demonstrates cooperative binding.. ***It demonstrates cooperative binding.*** - **Cooperative binding** describes how the binding of one oxygen molecule to hemoglobin increases the affinity of the remaining binding sites for oxygen. - This property gives the O2-Hb dissociation curve its characteristic **sigmoid (S-shaped)** appearance, allowing for efficient oxygen loading in the lungs and unloading in the tissues. *The curve is a straight line.* - The O2-Hb dissociation curve is **sigmoid or S-shaped**, not a straight line, due to the phenomenon of cooperative binding. - A straight line would imply a constant affinity of hemoglobin for oxygen, which is not the case. *It is 100% saturated at a PO2 of 100 mmHg.* - Hemoglobin is typically around **97-98% saturated** at a PO2 of 100 mmHg (arterial blood). - Complete 100% saturation is rarely achieved under physiological conditions. *A hemoglobin molecule can carry 4 molecules of O2.* - While this statement is factually true (one hemoglobin molecule has **four heme groups** and can bind up to **four molecules of oxygen**), it describes the structure and oxygen-carrying capacity of hemoglobin rather than a characteristic of the dissociation **curve itself**. - The question asks about features of the O2-Hb dissociation curve, and cooperative binding is the key property that defines the curve's behavior and sigmoid shape. [Practice more Physiology PYQs on OnCourse]

Question 1

Some cells secrete chemicals into the extracellular fluid that act on cells in the same tissue. Which of the following refers to this type of regulation?

Accepted Answer

Paracrine

Answer

Neural

Answer

Endocrine

Answer

Neuroendocrine

Question 2

Which of the following statements is true regarding the given cystometrogram?

Accepted Answer

Segment Ib reflects the bladder's ability to accommodate increasing volume without a significant rise in pressure.

Answer

Micturition occurs in segment II; failure to micturate is not characteristic of this segment.

Answer

Segment Ia represents the initial phase of bladder filling, not residual urine.

Answer

The dotted line represents a reference point, not the occurrence of micturition.

Question 3

Which of the following statements about the O2-Hb dissociation curve is correct?

Accepted Answer

It demonstrates cooperative binding.

Answer

The curve is a straight line.

Answer

It is 100% saturated at a PO2 of 100 mmHg.

Answer

A hemoglobin molecule can carry 4 molecules of O2.

NEET-PG 2022 — Physiology