Smooth and Cardiac Muscle

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Questions and Answers

What type of smooth muscle contracts independently, with each muscle fiber contracting on its own?

Syncytial smooth muscle
Single-unit smooth muscle
Visceral smooth muscle
Multi-unit smooth muscle (correct)

Which type of smooth muscle responds to neural, hormonal, and stretch stimuli?

Single-unit smooth muscle (correct)
Visceral smooth muscle
Unitary smooth muscle
Syncytial smooth muscle

Where is single-unit smooth muscle commonly found in the body?

Heart
Brain
Skeletal muscles
Gastrointestinal tract (correct)

Which of the following is a characteristic of multi-unit smooth muscle?

Each muscle fiber contracts independently (A) Signup and view all the answers

What is one of the functions of smooth muscle in the body?

Regulation of blood flow (D) Signup and view all the answers

Which type of smooth muscle has fibers that are connected by many gap junctions?

Single-unit smooth muscle (B) Signup and view all the answers

What is a distinguishing feature of fusiform smooth muscle?

Does not contain sarcomeres (D) Signup and view all the answers

What neurotransmitter is associated with the function of single-unit smooth muscles?

Acetylcholine (C) Signup and view all the answers

What distinguishes the smooth muscle of each organ?

Organization into bundles or sheets (A) Signup and view all the answers

Which types of stimuli can the smooth muscle respond to?

Local factors such as O2 levels (C) Signup and view all the answers

How does the physical structure of smooth muscle vary in different organs?

Adjusts to the specific organs it is in (C) Signup and view all the answers

What type of nervous system provides signals to the smooth muscle?

Sympathetic and Parasympathetic nervous system (C) Signup and view all the answers

What enables coordinated contractions in smooth muscle?

Organization into bundles or sheets (D) Signup and view all the answers

Which factors can stimulate smooth muscle contraction?

Local factors like O2, CO2, and H2 (D) Signup and view all the answers

What role do intercalated disks play in cardiac muscle function?

Facilitate coordinated contractions (B) Signup and view all the answers

How does smooth muscle's response differ from cardiac muscle's response?

'Smooth muscle responds to local factors, while cardiac muscle does not' (A) Signup and view all the answers

What type of muscle contracts involuntarily without conscious control?

Smooth muscle (A) Signup and view all the answers

Where is smooth muscle commonly found in the body?

In the walls of blood vessels (A) Signup and view all the answers

Which type of muscle exhibits slower contraction and relaxation times compared to skeletal muscle?

Smooth muscle (D) Signup and view all the answers

What type of cells make up the myocardium in the heart?

Cardiomyocytes (B) Signup and view all the answers

What is the primary function of smooth muscle in the body?

Regulating blood pressure (C) Signup and view all the answers

What is the purpose of the heart in the cardiovascular system?

Pumping blood to facilitate exchange of substances between cells and environment (B) Signup and view all the answers

Which type of muscle tissue is specifically found only in the heart?

Cardiac muscle tissue (C) Signup and view all the answers

What is the function of the myocardium?

To contract and pump blood throughout the body (D) Signup and view all the answers

What specialized cell structure is responsible for cell-to-cell adhesion in cardiac muscle?

Desmosomes (A) Signup and view all the answers

What type of muscle is cardiac muscle?

Involuntary muscle (C) Signup and view all the answers

What allows cell-to-cell conduction of electrical currents in cardiac muscle?

Gap junctions (C) Signup and view all the answers

Which type of ions enter the cardiac myocytes through long-lasting Calcium channels during the action potential?

$Ca^{2+}$ ions (A) Signup and view all the answers

What provides mechanical strength and stability in tissues subjected to mechanical forces?

Desmosomes (A) Signup and view all the answers

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

To connect adjacent cells electrically (D) Signup and view all the answers

Which structure in cardiac muscle serves as low-resistance pathways between cells?

$Gap$ junctions (B) Signup and view all the answers

What type of conduction occurs in cardiac muscle?

$Ionic$ conduction (B) Signup and view all the answers

What is the main difference between the arrangement of actin and myosin filaments in smooth muscle compared to striated muscle?

Smooth muscle has myosin filaments inserted among the actin filaments, while striated muscle has actin and myosin filaments arranged in a regular pattern (D) Signup and view all the answers

What is unique about the arrangement of the myosin cross-bridges in smooth muscle?

The myosin cross-bridges are arranged in a bipolar fashion, with some bending in one direction and others bending in the opposite direction (B) Signup and view all the answers

What is the maximum contraction capability of smooth muscle compared to skeletal muscle?

Smooth muscle can contract up to 80% of their length, while skeletal muscle can contract up to 30% (A) Signup and view all the answers

What is the main source of calcium ions for contraction in smooth muscle?

Calcium ions from the extracellular fluid are the main source for smooth muscle contraction (B) Signup and view all the answers

What is the energy requirement for maintaining a tonic contraction in smooth muscle compared to skeletal muscle?

Smooth muscle requires 1/10 to 1/300 of the energy necessary to maintain a tonic contraction compared to skeletal muscle (B) Signup and view all the answers

What is the main advantage of the side-polar arrangement of myosin cross-bridges in smooth muscle?

It allows smooth muscle to contract over a wider range of lengths (D) Signup and view all the answers

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

The dense bodies serve as attachment sites for the actin filaments, similar to the Z-discs in striated muscle (B) Signup and view all the answers

What is the primary advantage of the low frequency of cross-bridge cycles in smooth muscle?

It allows smooth muscle to maintain a tonic contraction with less energy expenditure (C) Signup and view all the answers

What is the primary role of caveolae in smooth muscle cells?

They make contact with the surface of the sarcoplasmic reticulum (SR) and are believed to excite calcium release from the SR. (A) Signup and view all the answers

What is the primary advantage of the low frequency of cross-bridge cycles in smooth muscle?

It allows for more efficient energy utilization during sustained contractions. (B) Signup and view all the answers

What is the main difference between the arrangement of actin and myosin filaments in smooth muscle compared to striated muscle?

Smooth muscle has a side-polar arrangement of myosin cross-bridges, unlike the bipolar arrangement in striated muscle. (B) Signup and view all the answers

What is the main source of calcium ions for contraction in smooth muscle?

Release of calcium from the sarcoplasmic reticulum (SR). (D) Signup and view all the answers

Which type of smooth muscle has fibers that are connected by many gap junctions?

Single-unit smooth muscle. (C) Signup and view all the answers

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

They serve as anchoring points for actin filaments. (D) Signup and view all the answers

What is the main advantage of the side-polar arrangement of myosin cross-bridges in smooth muscle?

It allows for more efficient energy utilization during sustained contractions. (C) Signup and view all the answers

What is the primary role of calmodulin in the smooth muscle contraction process?

Calmodulin activates the enzyme myosin light chain kinase (MLCK), which then phosphorylates myosin. (B) Signup and view all the answers

What is the primary difference in the mode of contraction between cardiac muscle and skeletal muscle?

Cardiac muscle contraction is involuntary (D) Signup and view all the answers

Which specialized cells are responsible for generating the cardiac action potential?

Pacemaker cells (D) Signup and view all the answers

What feature of cardiac muscle allows it to function as a single unit?

Intercalated disks connecting fibers (C) Signup and view all the answers

How does the development of cardiac muscle fibers differ from skeletal muscle fibers?

Cardiac myocytes fuse into multinucleated fibers (B) Signup and view all the answers

What differentiates the initiation of the cardiac action potential from nervous activity?

Pacemaker cells generate the action potential (D) Signup and view all the answers

Which structural feature contributes to the synchronized contractions in cardiac muscle?

Intercalated disks connecting myocytes (C) Signup and view all the answers

Why does cardiac muscle contract involuntarily?

Controlled via the autonomic nervous system (D) Signup and view all the answers

What characteristic feature distinguishes cardiac muscle fibers from skeletal muscle fibers?

Bifurcation and branching during cardiac fiber development (A) Signup and view all the answers

Which type of smooth muscle is characterized by muscle fibers that are connected via gap junctions, allowing them to contract together as a single unit?

Single-unit smooth muscle (C) Signup and view all the answers

In which organs of the body is single-unit smooth muscle commonly found?

Gastrointestinal tract, bile ducts, ureters, and uterus (B) Signup and view all the answers

What is the primary function of multi-unit smooth muscle?

Finer control and independent contractions (B) Signup and view all the answers

Which of the following is a distinguishing feature of fusiform smooth muscle cells?

They have a central, single nucleus (D) Signup and view all the answers

What is the primary advantage of the side-polar arrangement of myosin cross-bridges in smooth muscle?

It reduces the energy required for maintaining tonic contractions (B) Signup and view all the answers

Which of the following neurotransmitters is associated with the function of single-unit smooth muscle?

Acetylcholine (C) Signup and view all the answers

What is the primary source of calcium ions for contraction in smooth muscle?

Both extracellular fluid and intracellular stores (D) Signup and view all the answers

Which type of nervous system provides signals to the smooth muscle?

Autonomic nervous system (C) Signup and view all the answers

What is the primary advantage of the low frequency of cross-bridge cycles in smooth muscle?

It enables smooth muscle to maintain tonic contractions for extended periods with low energy expenditure. (D) Signup and view all the answers

Which of the following statements about the arrangement of myosin filaments in smooth muscle is correct?

Myosin filaments have side-polar cross-bridges that allow them to pull actin filaments in opposite directions simultaneously. (D) Signup and view all the answers

What is the primary source of calcium ions for contraction in smooth muscle?

The extracellular fluid (C) Signup and view all the answers

What is the maximum contraction capability of smooth muscle compared to skeletal muscle?

Smooth muscle can contract up to 80% of its length, while skeletal muscle can contract up to 30%. (B) Signup and view all the answers

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

They serve as attachment points for actin filaments, similar to Z-discs in skeletal muscle. (D) Signup and view all the answers

How does the energy requirement for maintaining a tonic contraction in smooth muscle compare to that of skeletal muscle?

Smooth muscle requires 1/10 to 1/300 of the energy necessary for skeletal muscle. (D) Signup and view all the answers

Which of the following statements about the sarcoplasmic reticulum in smooth muscle is correct?

The sarcoplasmic reticulum is slightly developed and is not the major source of calcium ions for contraction. (A) Signup and view all the answers

What is the primary function of smooth muscle in the body?

To control the movement of substances within the body and regulate the diameter of various passages. (D) Signup and view all the answers

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

To allow cell-to-cell conduction of electrical signals (B) Signup and view all the answers

What is the role of desmosomes in cardiac muscle?

They provide cell-to-cell adhesion and mechanical strength (D) Signup and view all the answers

How does calcium ion entry during contraction differ in cardiac muscle compared to skeletal muscle?

Calcium ions enter through both the sarcoplasmic reticulum and long-lasting calcium channels (D) Signup and view all the answers

What is a key structural difference between cardiac muscle cells and skeletal muscle cells?

Cardiac muscle cells are connected by intercalated discs, while skeletal muscle cells lack such connections (C) Signup and view all the answers

What is the primary function of gap junctions in cardiac muscle?

To allow cell-to-cell conduction of electrical signals (C) Signup and view all the answers

Which of the following statements about cardiac muscle is correct?

Cardiac muscle contraction is controlled by the autonomic nervous system (C) Signup and view all the answers

What is a key difference between smooth muscle and cardiac muscle in terms of contraction regulation?

Smooth muscle contraction is regulated by both neural and hormonal factors, while cardiac muscle contraction is primarily regulated by neural factors (C) Signup and view all the answers

Which type of muscle tissue exhibits a slower contraction and relaxation time compared to skeletal muscle?

Smooth muscle (C) Signup and view all the answers

Flashcards

Multi-unit smooth muscle

Type of smooth muscle where each fiber contracts independently.

Single-unit smooth muscle

Smooth muscle that contracts as a whole unit due to gap junctions.