Muscle Structure Quiz

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Questions and Answers

What is the primary role of the sarcoplasmic reticulum in muscle fibres?

To serve as the primary energy source for muscles

To provide structural support to muscle fibres

To store calcium ions necessary for muscle contraction (correct)

To store proteins needed for muscle contraction

Which statement accurately describes the structure of muscle fibres?

Muscle fibres contain only one nucleus

Muscle fibres are aligned in a circular pattern

Muscle fibres are completely isolated from blood capillaries

Muscle fibres consist of parallelly arranged myofilaments (correct)

What distinguishes the I-band from the A-band in striated muscle myofibrils?

The I-band is made up of actin filaments, whereas the A-band contains myosin (correct)

The A-band is isotropic while the I-band is anisotropic

The I-band contains myosin while the A-band contains actin

The I-band appears darker than the A-band

What is the connective tissue layer that holds muscle bundles together called?

Fascia Signup and view all the answers

Why are muscle fibres referred to as a syncitium?

They contain many nuclei within a single cell structure Signup and view all the answers

What term is used to describe the first seven pairs of ribs?

True ribs Signup and view all the answers

Which pairs of ribs are classified as vertebrochondral ribs?

8th to 10th pairs Signup and view all the answers

What characteristic distinguishes floating ribs from other types of ribs?

They are not attached ventrally. Signup and view all the answers

How many bones make up each limb in the appendicular skeleton?

30 bones Signup and view all the answers

What type of cartilage connects the true ribs to the sternum?

Hyaline cartilage Signup and view all the answers

What is the role of the globular head in the myosin filament?

It functions as an active ATPase enzyme. Signup and view all the answers

Which part of the meromyosin structure is referred to as the 'heavy meromyosin' (HMM)?

The globular head of the meromyosin. Signup and view all the answers

How is muscle contraction initiated?

By a signal from the central nervous system via a motor neuron. Signup and view all the answers

What does the sliding filament theory explain?

How muscle fibers contract by sliding thin filaments over thick filaments. Signup and view all the answers

What is the significance of the neuromuscular junction?

It is the junction between a motor neuron and the muscle fiber. Signup and view all the answers

Which of the following bones is NOT part of the forelimb?

Tibia Signup and view all the answers

What forms the pelvic girdle?

A fusion of three bones: ilium, ischium, and pubis Signup and view all the answers

What articulates with the head of the humerus to form the shoulder joint?

Glenoid cavity Signup and view all the answers

Which of the following correctly describes the number of phalanges in the human hand?

14 Signup and view all the answers

Which statement accurately describes the clavicle?

It articulates with the acromion of the scapula. Signup and view all the answers

What type of joint does not allow any movement?

Fibrous joint Signup and view all the answers

Which joint type is characterized by a fluid-filled synovial cavity?

Synovial joint Signup and view all the answers

Which of the following joints allows for limited movement?

Cartilaginous joint Signup and view all the answers

What is the primary function of joints in the body?

To act as a fulcrum for movement Signup and view all the answers

Which of these is a type of synovial joint?

Hinge joint Signup and view all the answers

Study Notes

Skeletal Muscle Structure

Organized skeletal muscle contains muscle bundles, known as fascicles, held together by fascia, a collagenous connective tissue.
Each fascicle consists of numerous muscle fibers (muscle cells) surrounding a plasma membrane called the sarcolemma.
Muscle fibers contain multiple nuclei and are filled with sarcoplasm, which houses the endoplasmic reticulum, known as the sarcoplasmic reticulum, functioning as a calcium ion reservoir.
Myofibrils, abundant in muscle fibers, are composed of filaments that display light and dark bands; the light bands (I-band) are made of actin, while dark bands (A-band) consist of myosin.

Myosin and Actin Interaction

Myosin filaments are assembled from polymerized proteins called meromyosins, characterized by a globular head (heavy meromyosin) and a tail (light meromyosin).
The globular head serves as an ATPase enzyme with binding sites for ATP and actin.
Muscle contraction operates via the sliding filament theory, where thin filaments (actin) slide over thick filaments (myosin).
Contraction is initiated by signals from the central nervous system (CNS) through motor neurons at the neuromuscular junction.

Rib Structure and Function

Ribs are thin, flat bones attached posteriorly to the vertebral column and anteriorly to the sternum, featuring two articulation surfaces on their dorsal ends.
True ribs (first seven pairs) connect directly to the sternum via hyaline cartilage; false ribs (8th, 9th, 10th pairs) connect indirectly while floating ribs (11th and 12th pairs) lack anterior attachment.
The rib cage is formed by thoracic vertebrae, ribs, and sternum.

Appendicular Skeleton

Comprises the limbs and girdles, with each limb consisting of 30 bones.
Forelimb (hand) includes the humerus, radius, ulna, carpals (8), metacarpals (5), and phalanges (14).
Hind limb (legs) includes the femur (longest bone), tibia, fibula, tarsals (7), metatarsals (5), and phalanges (14).
Patella (knee cap) is a cup-shaped bone protecting the knee joint.

Girdles and Joint Function

Pectoral girdle consists of the clavicle and scapula, facilitating upper limb articulation with the axial skeleton.
Scapula is a triangular bone located between the second and seventh ribs, featuring the acromion for humeral articulation.
Pelvic girdle is made of two coxal bones formed by the fusion of ilium, ischium, and pubis, including the acetabulum for femur articulation.

Joints and Movement

Joints enable movement by serving as points of contact between bones or between bones and cartilages, acting as fulcrums for muscle-generated forces.
Joints are classified as fibrous (no movement, e.g., skull sutures), cartilaginous (limited movement, e.g., vertebrae), and synovial (considerable movement, e.g., knee).
Examples of synovial joints include ball-and-socket (shoulder), hinge (knee), pivot (between atlas and axis), gliding (carpals), and saddle (thumb).

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Description

Test your knowledge on the organization of skeletal muscles, including muscle bundles and fascicles. This quiz covers the key structural elements and their functions within the muscle system.