Muscle Types and Characteristics

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Questions and Answers

What is the primary characteristic of isometric contraction?

Muscle tension remains constant with no length change (correct)

Muscle lengthens while tension decreases

Muscle generates force as it lengthens

Muscle shortens while performing work

Which pathway is primarily responsible for regenerating ATP without oxygen?

Anaerobic pathway through glycolysis (correct)

Aerobic pathway in the mitochondria

Direct phosphorylation via creatine phosphate

Lactic acid conversion in the liver

What is produced as a byproduct in the anaerobic pathway during ATP regeneration?

Carbon dioxide

Creatine

Lactic acid (correct)

Glucose

Which muscle is responsible for raising the eyebrows?

Frontal belly of the occipitofrontalis Signup and view all the answers

Which type of muscle contraction is described as muscle shortening while doing work?

Concentric contraction Signup and view all the answers

What is the role of creatine kinase in ATP regeneration?

Breaks down creatine phosphate to regenerate ATP Signup and view all the answers

Which muscle is NOT primarily involved in facial expression?

Trapezius Signup and view all the answers

What key element binds with muscle fibers to initiate contraction?

Calcium Signup and view all the answers

Which muscle primarily acts as a prime mover for foot inversion?

Tibialis posterior Signup and view all the answers

What is the primary function of the triceps surae?

Plantar flex the ankle Signup and view all the answers

How does the fibularis brevis assist in foot movement?

It plantar flexes and everts the foot. Signup and view all the answers

Which muscle is responsible for flexing the great toe at all joints while also contributing to foot plantar flexion?

Flexor hallucis longus Signup and view all the answers

What is the role of the plantaris muscle in movement?

It assists in knee flexion and plantar flexes the foot. Signup and view all the answers

What shape do skeletal muscle fibers primarily have?

Cigar-shaped Signup and view all the answers

Which type of muscle is described as involuntary and lacking striations?

Smooth muscle Signup and view all the answers

What is the main role of myosin heads during muscle contraction?

To latch onto actin in the thin filaments Signup and view all the answers

What structure holds adjacent thick filaments together?

M-line Signup and view all the answers

Which muscle primarily elevates the mandible during jaw closure?

Masseter Signup and view all the answers

What mechanism explains muscle contraction according to basic physiology?

Sliding filament theory Signup and view all the answers

Which muscle is responsible for drawing the eyebrows inferiorly?

Orbicularis oculi Signup and view all the answers

What is the primary function of the buccinator muscle?

Compressing the cheek Signup and view all the answers

What is the primary function of cardiac muscle?

Pump blood throughout the body Signup and view all the answers

What type of muscle fibers are characterized by having multiple nuclei?

Skeletal muscle fibers Signup and view all the answers

Which muscle acts as an antagonist to the zygomaticus?

Depressor anguli oris Signup and view all the answers

Which muscle is involved in producing side-to-side grinding movements of the jaw?

Lateral pterygoid Signup and view all the answers

During muscle contraction, what happens to the thin filaments?

They slide past the thick filaments. Signup and view all the answers

Which muscle is primarily responsible for protruding the tongue?

Genioglossus Signup and view all the answers

How does the body ensure muscle fibers do not rip apart during forceful contractions?

Through the arrangement of fibers in bundles Signup and view all the answers

What is known as the region within a relaxed sarcomere that does not contain any thick filaments?

H zone Signup and view all the answers

Which muscle acts to elevate the hyoid bone during swallowing?

Digastric Signup and view all the answers

Which muscle pulls the lower lip down in a pouting expression?

Depressor labii inferioris Signup and view all the answers

What action does the occipital belly perform?

Fixes aponeurosis and pulls scalp posteriorly Signup and view all the answers

Which muscle helps in drawing the corners of the mouth laterally?

Risorius Signup and view all the answers

What is the primary function of the mylohyoid muscle during swallowing?

Elevates the hyoid bone and floor of mouth Signup and view all the answers

Which muscle is responsible for pulling the larynx and hyoid bone inferiorly?

Sternohyoid Signup and view all the answers

During swallowing, which term describes the movement that propels food to the esophagus?

Peristalsis Signup and view all the answers

How do the scalenes contribute to respiration?

They elevate the first two ribs. Signup and view all the answers

What action does the sternocleidomastoid muscle perform when contracting on both sides?

Flexes the neck Signup and view all the answers

Which muscles are primarily responsible for neck extension and hyperextension?

Splenius Signup and view all the answers

What is the role of the thyrohyoid muscle?

Depresses the hyoid bone or elevates the larynx Signup and view all the answers

What characterizes the erector spinae muscles?

They are responsible for back extension Signup and view all the answers

Study Notes

Muscle Types

Three main muscle types: skeletal, smooth, and cardiac.
Skeletal and smooth muscles are elongated, indicating structural similarities.
Myofilaments are essential for muscle contraction and include myosin and actin.
Terminology includes "myo" and "mys" (muscle) and "sarco" (flesh).

Skeletal Muscle

Characterized by a cigar shape and multinucleated cells.
Largest muscle fibers can reach lengths of 30 cm, exhibiting striations.
Predominantly voluntary, often activated by reflexes.
Muscle fibers are delicate and fragile but arranged in bundles for strength.

Smooth Muscle

Involuntary muscle with no striations, found in walls of hollow organs (e.g., stomach).
Has a spindle shape and single nucleus.
Arranged in layers (circular and longitudinal) to facilitate organ movement through peristalsis.

Cardiac Muscle

Found only in the heart; striated but involuntary.
Responsible for pumping blood to various body tissues.
Comprises intercalated discs connecting branching cells that allow coordinated contractions.
Contains pacemaker cells to regulate heart rate.

Muscle Structure

Skeletal muscles are enveloped in connective tissues (endomysium, perimysium, epimysium) that provide durability.
Myofibrils made from sarcomeres house myofilaments responsible for contraction.
Thick filaments (myosin) contain ATPase enzymes necessary for muscle contraction.
Thin filaments (actin) bind to myosin heads during contractions.
The I band contains only thin filaments, whereas the A band contains thick filaments and overlaps with thin ones.

Contraction Mechanism

The sliding filament theory explains muscle contraction through the sliding action of thin filaments relative to thick ones.
Muscle contractions involve myosin heads attaching to actin binding sites, generating tension.
Types of contractions: concentric (muscle shortens), eccentric (muscle lengthens), and isometric (muscle tension without change in length).

ATP Regeneration Pathways

Direct phosphorylation of ADP by creatine phosphate via creatine kinase provides rapid ATP production.
Anaerobic pathway uses glycolysis to convert glucose into lactic acid, generating less ATP.
Aerobic pathway occurs in mitochondria for extensive ATP production (up to 35 ATP).

Muscle Functions

M-line connects adjacent thick filaments.
Calcium ions play a critical role in initiating contractions by signaling muscle fibers.
Specialized muscle contractions help maintain posture and enable movement.

Facial Muscles

Epicranius: Raises eyebrows and pulls scalp forward/backward.
Zygomaticus: Major and minor versions help in smiling.
Buccinator: Compresses cheeks during chewing and whistling.
Platysma: Tenses neck skin and depresses lower lip.

Muscles of Mastication

Masseter: Primary muscle for jaw closure and elevating mandible.
Temporalis: Closes jaw and maintains position of the mandible.
Pterygoid Muscles: Help in side-to-side grinding movements and jaw protrusion.

Suprahyoid Muscles

Aid in swallowing and position of the hyoid bone.
Includes Digastric, Stylohyoid, Mylohyoid, and Geniohyoid.

Infrahyoid Muscles

Assist in depressing the hyoid bone during swallowing and speech.
Includes Sternohyoid, Sternothyroid, Omohyoid, and Thyrohyoid.

Neck and Trunk Muscles

Sternocleidomastoid: Flexes and rotates the head; vital for head movements.
Erector Spinae: Major back extensor, critical for posture and trunk stability.

Muscles of the Posterior Compartment (Leg)

Triceps Surae: Comprises gastrocnemius and soleus; key for plantar flexion.
Popliteus: Unlocks the knee joint at the beginning of flexion.
Tibialis Posterior: Important for foot inversion and supporting the medial arch.

Intrinsic Muscles of the Foot

Facilitate toe movement and provide support to the foot's arch.

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Description

Explore the three main types of muscle: skeletal, smooth, and cardiac. Understand their similarities, differences, and the unique features of skeletal muscles. This quiz will help you reinforce your knowledge of muscle anatomy and physiology.