Cardiac and Smooth Muscle

Interactive Lecture

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Cardiac and Smooth Muscle

Open Ended

Differentiate between the structural characteristics of skeletal, cardiac, and smooth muscle tissues.

Multiple Choice

Where is cardiac muscle located in the human body, and what is its primary function?

• In the skeletal muscles; to support movement

• In the walls of blood vessels; to regulate blood flow

• In the heart; to pump blood throughout the body

• In the digestive tract; to aid in digestion

Multiple Select

Which of the following are key structural characteristics of cardiac muscle fibers?

• Branched

• Multinucleated

• Striated

• Intercalated discs

Multiple Choice

What is the primary function of intercalated discs in cardiac muscle cells?

• To generate electrical impulses

• To provide energy for muscle contraction

• To serve as junctions between cardiac muscle cells

• To store calcium ions

Multiple Select

Which of the following structures are found within intercalated discs?

• Mitochondria

• Desmosomes

• Sarcolemma

• Gap junctions

Fill in the Blank

Intercalated discs contain two important structures: desmosomes, which provide mechanical strength, and gap junctions, which facilitate __________.

Multiple Choice

What is the primary role of pacemaker cells in the heart?

• To supply oxygen to the heart muscle

• To generate electrical impulses that control heart rate

• To provide structural support to cardiac muscle cells

• To transport nutrients to cardiac muscle cells

Multiple Select

Which of the following can alter the rate of cardiac muscle contraction? (Select all that apply)

• Autonomic nervous system (ANS)

• Skeletal muscles

• Hormones

• Digestive enzymes

Multiple Choice

What are pacemaker cells in the heart?

• Cells that provide energy for heart contraction

• Cells that control the heart rate through self-excitation

• Cells that store calcium for muscle contraction

• Cells that supply nutrients to the cardiac muscle

Fill in the Blank

Pacemaker cells excite contractile cardiac muscle cells via __________, allowing the heart to contract in a coordinated manner.

Multiple Choice

From which two sources does calcium (Ca²⁺) required for cardiac muscle contraction come?

• Blood plasma and mitochondria

• Extracellular fluid and sarcoplasmic reticulum

• Cytoplasm and sarcolemma

• Sarcolemma and mitochondria

Multiple Choice

What happens when calcium binds during cardiac muscle contraction?

• It generates electrical impulses

• It stores energy for contraction

• It facilitates the binding of myosin to actin by moving tropomyosin

• It increases the production of ATP

Multiple Choice

Where are smooth muscles commonly found in the human body?

• Heart

• Skeletal muscles

• Walls of hollow organs (e.g., intestines, blood vessels)

• Skin

Multiple Select

Which of the following are key characteristics of smooth muscle fibers? (Select all that apply)

• Spindle-shaped

• Multinucleated

• Striated

• Uninucleated

Multiple Choice

What is the primary function of dense bodies in smooth muscle fibers?

• To store calcium ions

• To anchor thin filaments

• To generate electrical impulses

• To produce energy for muscle contraction

Multiple Choice

Which structures in skeletal and cardiac muscle are analogous to dense bodies in smooth muscle?

• T-tubules

• Sarcomeres

• Z discs

• Myofibrils

Multiple Choice

Does smooth muscle contain sarcomeres?

• Yes, smooth muscle contains sarcomeres like skeletal muscle

• No, smooth muscle does not contain sarcomeres

• Only during contraction

• Only in certain parts of the body

Multiple Choice

How are thick and thin filaments arranged in smooth muscle fibers?

• Longitudinally

• Transversely

• Diagonally

• Radially

Multiple Choice

What structure do smooth muscle cells have instead of T tubules to sequester calcium in the extracellular fluid?

• Sarcomeres

• Caveolae

• Myofibrils

• Z discs

Multiple Choice

Compared to skeletal muscle, how is the sarcoplasmic reticulum (SR) in smooth muscle?

• More elaborate

• Less elaborate

• Equally elaborate

• Non-existent

Multiple Choice

How does the autonomic nervous system (ANS) stimulate smooth muscle fibers?

• Through neuromuscular junctions directly connected to each muscle fiber

• By releasing neurotransmitters from varicosities that diffuse to multiple cells

• By generating electrical impulses within the muscle fibers

• By directly synapsing with each individual smooth muscle cell

Multiple Choice

Which of the following is NOT a mechanism for exciting smooth muscle fibers?

• Neural stimulation by the ANS

• Pacemaker cells

• Hormones

• Direct stimulation by skeletal muscle fibers

Multiple Choice

From which two sources does calcium (Ca²⁺) required for smooth muscle contraction come?

• Mitochondria and Golgi apparatus

• Extracellular fluid and sarcoplasmic reticulum

• Cytoplasm and sarcolemma

• Endoplasmic reticulum and lysosomes

Multiple Choice

In smooth muscle fibers, calcium (Ca²⁺) binds to which protein to initiate contraction?

• Troponin

• Tropomyosin

• Calmodulin

• Myosin

Multiple Choice

What happens when calcium (Ca²⁺) binds to calmodulin in smooth muscle fibers?

• It directly causes muscle contraction

• It activates myosin kinase

• It inhibits ATP production

• It deactivates myosin heads

Multiple Choice

Once myosin kinase is activated in smooth muscle, what is its next role?

• It deactivates calmodulin

• It phosphorylates myosin heads

• It breaks down ATP to ADP

• It releases calcium back into the extracellular fluid

Multiple Choice

How is smooth muscle contraction terminated?

• By the binding of calcium to troponin

• By the pumping of Ca²⁺ back into the sarcoplasmic reticulum (SR) and extracellular fluid (ECF)

• By the dephos-phorylation of actin

• By the continuous activation of myosin kinase

Poll

How prepared do you feel for the exam tomorrow?