80 Questions
What type of smooth muscle contracts independently, with each muscle fiber contracting on its own?
Multi-unit smooth muscle
Which type of smooth muscle responds to neural, hormonal, and stretch stimuli?
Single-unit smooth muscle
Where is single-unit smooth muscle commonly found in the body?
Gastrointestinal tract
Which of the following is a characteristic of multi-unit smooth muscle?
Each muscle fiber contracts independently
What is one of the functions of smooth muscle in the body?
Regulation of blood flow
Which type of smooth muscle has fibers that are connected by many gap junctions?
Single-unit smooth muscle
What is a distinguishing feature of fusiform smooth muscle?
Does not contain sarcomeres
What neurotransmitter is associated with the function of single-unit smooth muscles?
Acetylcholine
What distinguishes the smooth muscle of each organ?
Organization into bundles or sheets
Which types of stimuli can the smooth muscle respond to?
Local factors such as O2 levels
How does the physical structure of smooth muscle vary in different organs?
Adjusts to the specific organs it is in
What type of nervous system provides signals to the smooth muscle?
Sympathetic and Parasympathetic nervous system
What enables coordinated contractions in smooth muscle?
Organization into bundles or sheets
Which factors can stimulate smooth muscle contraction?
Local factors like O2, CO2, and H2
What role do intercalated disks play in cardiac muscle function?
Facilitate coordinated contractions
How does smooth muscle's response differ from cardiac muscle's response?
'Smooth muscle responds to local factors, while cardiac muscle does not'
What type of muscle contracts involuntarily without conscious control?
Smooth muscle
Where is smooth muscle commonly found in the body?
In the walls of blood vessels
Which type of muscle exhibits slower contraction and relaxation times compared to skeletal muscle?
Smooth muscle
What type of cells make up the myocardium in the heart?
Cardiomyocytes
What is the primary function of smooth muscle in the body?
Regulating blood pressure
What is the purpose of the heart in the cardiovascular system?
Pumping blood to facilitate exchange of substances between cells and environment
Which type of muscle tissue is specifically found only in the heart?
Cardiac muscle tissue
What is the function of the myocardium?
To contract and pump blood throughout the body
What specialized cell structure is responsible for cell-to-cell adhesion in cardiac muscle?
Desmosomes
What type of muscle is cardiac muscle?
Involuntary muscle
What allows cell-to-cell conduction of electrical currents in cardiac muscle?
Gap junctions
Which type of ions enter the cardiac myocytes through long-lasting Calcium channels during the action potential?
$Ca^{2+}$ ions
What provides mechanical strength and stability in tissues subjected to mechanical forces?
Desmosomes
What is the function of intercalated discs in cardiac muscle cells?
To connect adjacent cells electrically
Which structure in cardiac muscle serves as low-resistance pathways between cells?
$Gap$ junctions
What type of conduction occurs in cardiac muscle?
$Ionic$ conduction
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
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
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%
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
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
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
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
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
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.
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.
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.
What is the main source of calcium ions for contraction in smooth muscle?
Release of calcium from the sarcoplasmic reticulum (SR).
Which type of smooth muscle has fibers that are connected by many gap junctions?
Single-unit smooth muscle.
What is the primary function of the dense bodies in smooth muscle cells?
They serve as anchoring points for actin filaments.
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.
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.
What is the primary difference in the mode of contraction between cardiac muscle and skeletal muscle?
Cardiac muscle contraction is involuntary
Which specialized cells are responsible for generating the cardiac action potential?
Pacemaker cells
What feature of cardiac muscle allows it to function as a single unit?
Intercalated disks connecting fibers
How does the development of cardiac muscle fibers differ from skeletal muscle fibers?
Cardiac myocytes fuse into multinucleated fibers
What differentiates the initiation of the cardiac action potential from nervous activity?
Pacemaker cells generate the action potential
Which structural feature contributes to the synchronized contractions in cardiac muscle?
Intercalated disks connecting myocytes
Why does cardiac muscle contract involuntarily?
Controlled via the autonomic nervous system
What characteristic feature distinguishes cardiac muscle fibers from skeletal muscle fibers?
Bifurcation and branching during cardiac fiber development
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
In which organs of the body is single-unit smooth muscle commonly found?
Gastrointestinal tract, bile ducts, ureters, and uterus
What is the primary function of multi-unit smooth muscle?
Finer control and independent contractions
Which of the following is a distinguishing feature of fusiform smooth muscle cells?
They have a central, single nucleus
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
Which of the following neurotransmitters is associated with the function of single-unit smooth muscle?
Acetylcholine
What is the primary source of calcium ions for contraction in smooth muscle?
Both extracellular fluid and intracellular stores
Which type of nervous system provides signals to the smooth muscle?
Autonomic nervous system
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.
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.
What is the primary source of calcium ions for contraction in smooth muscle?
The extracellular fluid
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%.
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.
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.
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.
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.
What is the primary function of intercalated discs in cardiac muscle?
To allow cell-to-cell conduction of electrical signals
What is the role of desmosomes in cardiac muscle?
They provide cell-to-cell adhesion and mechanical strength
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
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
What is the primary function of gap junctions in cardiac muscle?
To allow cell-to-cell conduction of electrical signals
Which of the following statements about cardiac muscle is correct?
Cardiac muscle contraction is controlled by the autonomic nervous system
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
Which type of muscle tissue exhibits a slower contraction and relaxation time compared to skeletal muscle?
Smooth muscle
This quiz covers the types, physical structures, and functions of smooth and cardiac muscles. Topics include differentiating between smooth muscle types, understanding the physical structure of muscles, and describing the importance of intercalated disks in cardiac muscle.
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