Question 1

Which of the following best explains why cardiac muscle cells are able to contract as a functional syncytium?

Accepted Answer

They are connected by intercalated discs containing gap junctions.

Question 2

A patient is given a drug that blocks slow calcium channels in cardiac muscle. What is the most likely effect on the cardiac action potential?

Accepted Answer

The action potential will be shortened, reducing contraction duration.

Question 3

Which structure in smooth muscle is functionally analogous to the T-tubules in skeletal muscle?

Accepted Answer

Caveolae

Question 4

During smooth muscle contraction, which molecule directly activates myosin light chain kinase (MLCK)?

Accepted Answer

Ca2+-calmodulin complex

Question 5

Which of the following best describes the role of calcium in skeletal muscle contraction?

Accepted Answer

Calcium binds to troponin, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 6

A patient with a mutation that disrupts gap junctions in cardiac muscle would most likely experience which of the following?

Accepted Answer

Impaired synchronous contraction of the heart muscle

Question 7

Which of the following is a key difference between the contraction mechanisms of smooth and skeletal muscle?

Accepted Answer

Smooth muscle contraction is regulated by Ca2+-calmodulin activation of MLCK, while skeletal muscle contraction is regulated by Ca2+ binding to troponin.

Question 8

Which of the following best explains why smooth muscle contraction is slower and more sustained than skeletal muscle contraction?

Accepted Answer

Ca2+ is removed from the cytoplasm more slowly in smooth muscle.

Question 9

Which of the following statements about the SA node is correct?

Accepted Answer

It is the pacemaker of the heart, located in the right atrium near the superior vena cava.

Question 10

Which of the following best describes the arrangement of smooth muscle fibers in the wall of the gastrointestinal tract?

Accepted Answer

Two layers: an inner circular layer and an outer longitudinal layer

Question 11

Which neurotransmitters are commonly released by varicosities in smooth muscle tissue?

Accepted Answer

Acetylcholine and norepinephrine

Question 12

A muscle that stabilizes the origin of the agonist muscle so that it can move efficiently is called a:

Accepted Answer

Fixator

Question 13

Which of the following best describes the function of the Achilles (calcaneal) tendon?

Accepted Answer

It attaches the gastrocnemius, soleus, and plantaris muscles to the calcaneus, enabling plantar flexion.

Question 14

Which of the following is true regarding the origin and insertion of a muscle?

Accepted Answer

The origin is the less movable attachment, while the insertion is the more movable attachment.

Question 15

Which of the following best explains why cardiac muscle is considered involuntary?

Accepted Answer

It is controlled unconsciously by regions of the brain stem and hypothalamus.

Question 16

Which of the following best describes the process of smooth muscle contraction?

Accepted Answer

Ca2+ binds to calmodulin, activating MLCK, which phosphorylates myosin and allows cross-bridge cycling.

Question 17

Which of the following is a characteristic unique to cardiac muscle tissue?

Accepted Answer

Branching chains of cells with intercalated discs

Question 18

Which of the following best explains why skeletal muscle cannot contract as a syncytium like cardiac muscle?

Accepted Answer

Skeletal muscle cells lack gap junctions.

Question 19

Which of the following best describes the function of a synergist muscle?

Accepted Answer

It assists the agonist by adding extra force or reducing undesirable movements.

Muscle Tissue Types: Cardiac and Smooth Muscle Structure and Function

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