Question 1

Which of the following statements best describes the arrangement of smooth muscle layers in most hollow organs?

Accepted Answer

They are organized into sheets with fibers oriented at right angles to each other.

Question 2

What is the primary effect of contraction of the longitudinal layer of smooth muscle in a hollow organ?

Accepted Answer

It causes the organ to shorten along its long axis.

Question 3

Which of the following is NOT a location where smooth muscle is typically found?

Accepted Answer

Heart

Question 4

Smooth muscle fibers differ from skeletal muscle fibers in all of the following ways EXCEPT:

Accepted Answer

Smooth muscle fibers contain only endomysium.

Question 5

Which structure in smooth muscle stores and releases neurotransmitters into a wide synaptic cleft?

Accepted Answer

Varicosities

Question 6

What is the main source of calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$for contraction in smooth muscle?

Accepted Answer

Extracellular space

Question 7

Which protein does $$\mathrm{Ca$$^{2+}$$}$$ bind to in smooth muscle to initiate contraction?

Accepted Answer

Calmodulin

Question 8

What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?

Accepted Answer

It phosphorylates myosin heads, activating them for cross-bridge formation.

Question 9

Which of the following best explains why smooth muscle can contract in a corkscrew manner?

Accepted Answer

The thick and thin filaments are arranged diagonally and spirally.

Question 10

During relaxation of smooth muscle, which of the following steps is required?

Accepted Answer

Active transport of $$\mathrm{Ca$$^{2+}$$}$$ into the SR and extracellular space

Question 11

Gap junctions in smooth muscle serve which primary function?

Accepted Answer

They allow depolarization to spread from cell to cell.

Question 12

Which of the following is TRUE regarding the ratio of thick to thin filaments in smooth muscle compared to skeletal muscle?

Accepted Answer

Smooth muscle has a lower ratio (1:13) than skeletal muscle (1:2).

Question 13

A patient is given a drug that blocks calmodulin activation. What is the most likely effect on smooth muscle contraction?

Accepted Answer

Contraction will be inhibited because myosin light chain kinase will not be activated.

Question 14

Which of the following best describes the neural regulation of smooth muscle contraction?

Accepted Answer

Neurotransmitter binding can cause either graded or action potentials, depending on the receptor type.

Question 15

Which of the following is a correct sequence of events in smooth muscle contraction?

Accepted Answer

$$\mathrm{Ca$$^{2+}$$}$$ enters cell $$\rightarrow$$ binds to calmodulin $$\rightarrow$$ activates MLCK $$\rightarrow$$ myosin phosphorylation $$\rightarrow$$ cross-bridge formation

Question 16

Which of the following chemical factors can stimulate smooth muscle contraction?

Accepted Answer

Hormones, high $$\mathrm{CO_2$}$$, low pH, and low oxygen

Question 17

A researcher observes that a smooth muscle cell contracts even though it lacks direct nerve supply. What is the most likely explanation?

Accepted Answer

The cell depolarizes spontaneously or in response to chemical stimuli.

Question 18

Which of the following is a function of dense bodies in smooth muscle?

Accepted Answer

They anchor filaments to the sarcolemma and correspond to Z discs in skeletal muscle.

Question 19

Which of the following is required for smooth muscle relaxation?

Accepted Answer

Dephosphorylation of myosin to inactivate it

Question 20

A patient with low extracellular $$\mathrm{Ca$$^{2+}$$}$$ levels is likely to experience which effect on smooth muscle function?

Accepted Answer

Reduced contraction due to insufficient $$\mathrm{Ca$$^{2+}$$}$$ influx

Chapter 9 part 3 notes

Guida di studio - Domande di pratica

Study guide - Flashcard