Muscle Tissue Types and Structures

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Questions and Answers

What type of muscle contraction occurs when the length of the muscle changes while the tension remains constant?

Eccentric contraction

Isotonic contraction (correct)

Isometric contraction

Concentric contraction

Which muscle is considered the agonist during forearm extension?

Biceps brachii

Deltoid

Pectoralis major

Triceps brachii (correct)

What is the role of an antagonist muscle?

To produce the same movement as the agonist

To assist the agonist

To oppose the action of the agonist (correct)

To stabilize joints

Which connective tissue surrounds an entire muscle?

Epimysium Signup and view all the answers

Where is the insertion point of the muscle that has its origin in the thoracic vertebrae and extends to the humerus?

Humerus Signup and view all the answers

Which of the following actions is performed by the superior fibers of a muscle that originates from the occipital bone?

Elevation of the scapula Signup and view all the answers

What action does the pectoralis major muscle primarily perform?

Medial rotation of the arm Signup and view all the answers

Which feature distinguishes the origin from the insertion of a muscle?

Insertion is typically less stable Signup and view all the answers

What is the primary action of the triceps brachii?

Extend the forearm Signup and view all the answers

What is the origin of the long head of the triceps brachii?

Scapula Signup and view all the answers

Which muscle shares the same insertion point as the iliacus?

Psoas major Signup and view all the answers

Which head of the quadriceps femoris is responsible for flexing the thigh?

Rectus femoris Signup and view all the answers

What action does the biceps brachii perform as a prime mover?

Flexion of the forearm Signup and view all the answers

Which muscle primarily extends the leg at the knee?

Rectus femoris Signup and view all the answers

Which muscle originates from the os coxae and is involved in thigh flexion?

Psoas major Signup and view all the answers

What is the common insertion point for all heads of the quadriceps femoris?

Patella and tibia Signup and view all the answers

What is the main function of smooth muscle tissue?

To move substances along internal passageways Signup and view all the answers

Which connective tissue layer surrounds individual muscle fibers?

Endomysium Signup and view all the answers

How are skeletal muscle fibers characterized?

Multinucleate and striated Signup and view all the answers

What defines the sliding filament theory?

Myosin heads of thick filaments slide thin filaments along Signup and view all the answers

Which statement about skeletal muscles is correct?

They allow for body movement and posture maintenance Signup and view all the answers

What roles do tendons serve in the muscular system?

Attach muscles to bone or skin Signup and view all the answers

Which component is mainly involved in muscle contraction?

Myofilaments Signup and view all the answers

What does muscle tone refer to?

The constant tension in a resting muscle Signup and view all the answers

Which type of muscle tissue is responsible for the involuntary propulsion of blood?

Cardiac muscle Signup and view all the answers

What defines the function of myofibrils within muscle fibers?

They facilitate muscle contraction through interaction of thick and thin filaments Signup and view all the answers

Study Notes

Muscle Tissue

There are three types of muscle tissue: smooth, cardiac, and skeletal
Smooth and cardiac muscle tissue are found in other organ systems
Skeletal muscles form the muscular system

Smooth Muscle

Found in hollow organs
Responsible for movement of substances along internal passageways
Description: Elongated, single nucleus, arranged in a sheet-like structure, no striations

Cardiac Muscle

Found in the walls of the heart
Responsible for pumping blood
Description: Branching cells separated by intercalated discs, striated, single nucleus

Skeletal Muscle

Attached to bones, cartilage, and skin
Responsible for voluntary movement
Description: Long, cylindrical, multinucleate, striated

### Skeletal Muscle: Structure

Muscle fibers are organized into bundles called fascicles
Muscle fibers contain myofibrils
Myofibrils are composed of myofilaments

Connective Tissue Coverings

There are three layers of connective tissue that surround muscles: endomysium, perimysium, and epimysium
Endomysium: Surrounds each muscle fiber
Perimysium: Surrounds fascicles
Epimysium: Surrounds the entire muscle

Myofilaments

Composed of thick and thin filaments
Thick filaments: Comprised of myosin molecules with heads and tails; myosin heads bind to thin filaments
Thin filaments: Mainly two strands of filamentous actin (F-actin) twisted around each other; contain myosin binding sites
Sarcomere: the functional unit of thick and thin filaments

Neuromuscular Junction

One motor neuron controls each muscle fiber
Nerve impulses travel from the nervous system to the muscle

Sliding Filament Theory

Myosin heads of thick filaments slide along thin filaments
This shortens the sarcomere, not the filaments themselves

Muscle Attachments

Tendons: Merge connective tissues at muscle ending and attach bones, skin, or other muscles
Aponeurosis: Thin, flattened connective tissue attachment
Muscles generally cross joints
Insertion: Bone which moves the most
Origin: Bone which moves the least

Muscle Function

Muscle tone: Constant tension in resting muscle; motor units are stimulated randomly
Isometric contraction: Length remains constant; tension changes
Isotonic contraction: Tension remains constant; length changes

Muscle Groups

Agonist: Produces movement; also known as the "prime mover"
Antagonist: Opposes the action of the agonist
Synergist: Assists the agonist in performing its action; includes stabilizing fixators

Specific Muscles

Trapezius:
- Origin: Occipital bone, C7, and thoracic vertebrae
- Insertion: Scapula and clavicle
- Action: Elevates, retracts, or depresses the scapula depending on fiber contraction
Pectoralis Major:
- Origin: Clavicle, sternum, and cartilage of ribs
- Insertion: Humerus
- Action: Adducts arm, medially rotates, and aids in flexion and pull ribs upwards
Latissimus Dorsi:
- Origin: Thoracic, lumbar vertebrae, and illium
- Insertion: Humerus
- Action: Extends, adducts, and medially rotates arm
Deltoid:
- Origin: Clavicle and scapula
- Insertion: Humerus
- Action: Abducts arm (prime mover), flexes and extends arm depending on fiber contraction
Biceps Brachii:
- Origin: Two heads on the scapula
- Insertion: Radius
- Action: Flexes forearm (prime mover) and supinates forearm
Triceps Brachii:
- Origin: Long head on scapula, lateral and medial heads on humerus
- Insertion: Ulna
- Action: Extends forearm (prime mover); stabilizes shoulder joint

Hip Flexors

Iliacus:
- Origin: Os coxae (ilium) and sacrum
- Insertion: Femur
- Action: Flexes thigh (prime mover)
Psoas Major:
- Origin: Lumbar vertebrae and T12
- Insertion: Femur
- Action: Flexes thigh (prime mover)
- Other actions: Flexes vertebral column laterally, maintains posture
Gluteus Maximus:
- Origin: Os coxae (ilium), sacrum, coccyx
- Insertion: Femur
- Action: Extends thigh (prime mover)
- Other actions: Abducts and laterally rotates thigh
Biceps Femoris:
- Origin: Long head: os coxae (ischium); Short head: femur
- Insertion: Fibula and tibia
- Action: Flexes leg at the knee (prime mover)

Knee Extensors

Quadriceps femoris:
- Origin:
  - Rectus femoris: os coxae (ilium)
  - Vastus lateralis: femur
  - Vastus medialis: femur
  - Vastus intermedius: femur
- Insertion: Patella and tibia
- Action:
  - All heads: Extends leg at knee (prime mover)
  - Rectus femoris only: Flexes thigh

Walking Muscles

Muscles work together to produce opposing movements, allowing for walking forward
Hip Flexors: Initiate forward movement of the leg
Knee Extensors: Push off and extend the leg back
Hip Extensors: Keep the thigh extended
Knee Flexors: Prepare the leg for the next step

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Description

Explore the three types of muscle tissue: smooth, cardiac, and skeletal. This quiz will cover their characteristics, structures, and functions within the human muscular system. Test your knowledge on the unique roles and structures of each muscle type.