Question 1

Which of the following best describes the function of gap junctions in intercellular communication?

Accepted Answer

They allow direct passage of ions and small molecules between adjacent cells, enabling very fast, bidirectional signaling.

Question 2

A patient is given a drug that blocks gap junctions in cardiac muscle. What is the most likely physiological effect?

Accepted Answer

Disrupted electrical conduction between cardiac cells, potentially leading to arrhythmias.

Question 3

Which of the following is TRUE regarding paracrine chemical messengers?

Accepted Answer

They signal nearby cells by diffusion through interstitial fluid.

Question 4

Which chemical messenger is produced by neurons and released into the extracellular fluid of the synaptic cleft?

Accepted Answer

Neurotransmitter

Question 5

Which of the following statements about lipophilic chemical messengers is CORRECT?

Accepted Answer

They easily cross the cell membrane and typically bind to intracellular receptors.

Question 6

A hormone has a half-life of 90 minutes. If its initial concentration is 100 units, what will its concentration be after 180 minutes?

$$C = C_0$ 	imes \left(\frac{1}{2}\$$right)^{\frac{t}$${t_{1/2}}}$$

Accepted Answer

25 units

Question 7

Which of the following is a correct example of a neurohormone?

Accepted Answer

Antidiuretic hormone (ADH)

Question 8

What is the effect of up-regulation of receptors on a target cell?

Accepted Answer

Increased sensitivity to the chemical messenger due to a higher number of receptors.

Question 9

Which of the following best describes the action of an antagonist?

Accepted Answer

It binds to a receptor but does not produce a response, blocking the normal ligand.

Question 10

A patient receives morphine for pain relief. Later, naloxone is administered. What is the physiological basis for naloxone's effect?

Accepted Answer

Naloxone acts as an antagonist at opioid receptors, blocking morphine-induced analgesia.

Question 11

Which of the following factors does NOT directly affect the magnitude of a target cell's response to a chemical messenger?

Accepted Answer

The affinity of the receptor for the messenger.

Question 12

Which statement about the transport of hydrophilic (lipophobic) messengers is correct?

Accepted Answer

They dissolve in plasma and are transported freely in the blood.

Question 13

If a cell is exposed to high concentrations of a chemical messenger for a prolonged period, what is the most likely cellular response?

Accepted Answer

Down-regulation of receptors, leading to decreased sensitivity.

Question 14

Which of the following is TRUE regarding the specificity of receptor binding?

Accepted Answer

A receptor may bind to multiple types of messengers, but each messenger binds only to specific receptor types.

Question 15

Which equation correctly represents the calculation of messenger concentration after a given time, based on half-life?

$$C = C_0$ 	imes \left(\frac{1}{2}\$$right)^{\frac{t}$${t_{1/2}}}$$

Accepted Answer

$$C = C_0$ 	imes \left(\frac{1}{2}\$$right)^{\frac{t}$${t_{1/2}}}$$

Question 16

Which of the following is a property of lipophilic messengers?

Accepted Answer

They are usually bound to carrier proteins in the blood and have a longer half-life.

Question 17

Which scenario best illustrates autocrine signaling?

Accepted Answer

A cell releases a chemical messenger that binds to receptors on its own surface, triggering a response.

Question 18

Which of the following is NOT a characteristic of direct intercellular communication via gap junctions?

Accepted Answer

Unidirectional signaling

Question 19

Which of the following is most likely to have the shortest half-life in the body?

Accepted Answer

A hydrophilic messenger dissolved in plasma

Chemical Messengers and Intercellular Communication: Principles of Human Physiology (Chapter 5 Study Notes)

Study Guide - Practice Questions