12-L1

Where are smooth muscle fibers mainly found?

In the walls of hollow organs (correct)

In association with bones

In the skeletal muscles

In the walls of the heart

What is the plasma membrane of muscle cells called?

Myofibril

Sarcomere

Sarcolemma (correct)

Myofilament

What type of muscle contractions are voluntary?

Smooth

Skeletal (correct)

All muscle types

Cardiac

What percentage of body weight is attributed to skeletal muscle?

40% Signup and view all the answers

Which type of muscle cell has obvious striations?

Skeletal muscle Signup and view all the answers

What is the main characteristic of the sarcoplasmic reticulum in cardiac muscle fibers compared to skeletal muscle?

It is less organized Signup and view all the answers

Where do cardiac T tubules occur in the muscle fibers?

At the Z line Signup and view all the answers

What type of cell is a mature smooth muscle fiber?

Spindle-shaped Signup and view all the answers

What ratio of thin to thick filaments is observed in smooth muscle?

12:1 Signup and view all the answers

What is a key characteristic of smooth muscle cytoplasm?

Full of actin and myosin filaments Signup and view all the answers

What is the cytoplasm of a muscle fiber also known as?

Sarcoplasm Signup and view all the answers

Which type of filament is found in the A-bands of myofibrils?

Myosin Signup and view all the answers

What is the function of the titin protein in muscle tissues?

Providing elasticity Signup and view all the answers

How many molecules of myosin are typically found in a thick myofilament?

200-500 Signup and view all the answers

What main proteins are found in the thin filaments?

F-actin, tropomyosin, troponin Signup and view all the answers

What type of muscle is cardiac muscle?

striated involuntary muscle Signup and view all the answers

What role do collagen fibers play at the muscle-tendon junction?

They blend with the epimysium and perimysium to prevent muscle tear. Signup and view all the answers

Which structure in cardiac muscle cells appears as dark lines?

intercalated discs Signup and view all the answers

What is a motor unit?

A single axon and all the muscle fibers it innervates. Signup and view all the answers

Where are mitochondria located in cardiac muscle cells?

Both A and B Signup and view all the answers

What prevents detachment of cardiac muscle fibers from one another during contraction?

Macula adherens Signup and view all the answers

Which component of the motor end-plate contains mitochondria and synaptic vesicles?

The terminal bouton Signup and view all the answers

Which of these lies directly beneath the presynaptic membrane?

Continuation of the muscle fiber's basal lamina Signup and view all the answers

What provides electronic coupling between adjacent cardiac muscle fibers?

gap junctions Signup and view all the answers

What does the postsynaptic membrane contain?

Receptors for acetylcholine Signup and view all the answers

Which structure is composed of alpha-actinin and is located in the center of the I band?

Z line Signup and view all the answers

Which type of myofilament is 5-nm wide and composed primarily of actin?

Thin filament Signup and view all the answers

What is the primary function of the sarcoplasmic reticulum in striated muscle cells?

Sequester calcium ions Signup and view all the answers

Which band is located in the center of the A band and represents the area where actin is not present?

H band Signup and view all the answers

Which component encircles every myofibril near the aligned A-I band boundaries of sarcomeres?

Transverse tubule Signup and view all the answers

What is the function of the transverse (T) tubule system in skeletal muscles?

To bring action potentials into the interior of muscle fibers Signup and view all the answers

What is the primary characteristic of red fibers (Type I) in skeletal muscles?

High myoglobin content and ability to sustain slow, steady contractions Signup and view all the answers

Which type of skeletal muscle fiber is predominant in extraocular muscles?

White fibers (Type IIb) Signup and view all the answers

How do intermediate fibers (Type IIa) in skeletal muscles differ from red and white fibers?

They are a mix of structural and functional characteristics of red and white fibers Signup and view all the answers

What is the triad in the skeletal muscle fiber structure?

Specialized complex of two sarcoplasmic reticulum (SR) components and a T tubule Signup and view all the answers

What type of connective tissue surrounds an entire skeletal muscle?

Epimysium Signup and view all the answers

Which of the following connective tissues surrounds each bundle of muscle fibers?

Perimysium Signup and view all the answers

Which type of connective tissue is known for its delicate and very thin structure?

Endomysium Signup and view all the answers

What structures does loose connective tissue carry to muscle?

Blood vessels, nerve fibers, and lymphatics Signup and view all the answers

What cells are responsible for new skeletal muscle fiber formation following muscle injury?

Satellite cells Signup and view all the answers

How are the connective tissues in skeletal muscle organized?

Epimysium around entire muscle, perimysium around fascicles, endomysium around individual fibers Signup and view all the answers

What is a distinguishing feature of Purkinje fibers under histological preparations?

Clear empty appearance Signup and view all the answers

Which muscle type has little regenerative ability beyond early childhood?

Cardiac muscle Signup and view all the answers

Which of the following is TRUE regarding smooth muscle repair?

Smooth muscle contains undifferentiated precursors Signup and view all the answers

What function are Purkinje fibers specialized for?

Transmission of excitation Signup and view all the answers

What is the primary role of Purkinje fibers in the heart?

Conducting an electrical stimulus to enable coordinated contraction Signup and view all the answers

Where are Purkinje fibers located?

In the inner ventricular walls of the heart Signup and view all the answers

How do Purkinje fibers influence heart rate?

They do not have a known role in setting heart rate Signup and view all the answers

What happens when Purkinje fibers generate action potentials faster than usual?

It can cause premature ventricular contraction or other issues Signup and view all the answers

What is the backup role of Purkinje fibers in the heart's conduction system?

To serve as the last resort when other pacemakers fail Signup and view all the answers