Biology Chapter 6: Muscular System Flashcards

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Questions and Answers

During contraction, a skeletal muscle insertion moves toward the origin.

True

What is the attachment called for a muscle that moves an attached bone?

Antagonist

Origin

Agonist

Insertion (correct)

Which of the following is NOT one of the types of ordinary body movements?

Adduction

Dorsiflexion (correct)

Flexion

Hyperextension

What is flexion?

Decreases the angle of the joint, bringing two bones closer together. Signup and view all the answers

What is the opposite of flexion?

Extension Signup and view all the answers

What is rotation in terms of muscle movement?

Movement of a bone around its longitudinal axis. Signup and view all the answers

What does abduction refer to?

Movement of a limb away from the midline. Signup and view all the answers

What does adduction refer to?

Movement of a limb toward the midline. Signup and view all the answers

What is circumduction?

Combination of flexion, extension, abduction, and adduction. Signup and view all the answers

What is dorsiflexion?

Lifting the foot so that the superior surface approaches the shin Signup and view all the answers

Which muscle is responsible for pulling the corners of the mouth downward?

Platysma Signup and view all the answers

Which muscle is primarily used in blinking and squinting?

Orbicularis oculi Signup and view all the answers

What is a prime mover muscle?

Muscle with the major responsibility for a certain movement. Signup and view all the answers

What is the function of the fixator muscle?

Stabilizes the origin of a prime mover. Signup and view all the answers

What do we call the muscle that opposes or reverses a prime mover?

Antagonist Signup and view all the answers

What does adhesion mean in the context of muscle movements?

The process where a limb moves toward the midline. Signup and view all the answers

What is the muscular system responsible for?

Body movement Signup and view all the answers

What are the three basic muscle types of the body?

Skeletal, cardiac, smooth. Signup and view all the answers

What are two characteristics of muscles?

Skeletal and smooth muscle cells are elongated; contraction is due to the movement of microfilaments. Signup and view all the answers

The prefixes MYO and MYS refer to _ and SARCO refers to _ in muscle terminology.

muscle, flesh Signup and view all the answers

What is a key characteristic of skeletal muscle?

Striated and voluntary Signup and view all the answers

What are the connective tissue wrappings of skeletal muscle?

Endomysium, perimysium, epimysium, fascia. Signup and view all the answers

What type of attachments can skeletal muscles have?

Tendons and aponeuroses Signup and view all the answers

Where can skeletal muscles attach?

Bones, cartilages, and connective tissue coverings. Signup and view all the answers

Which statement about smooth muscle is correct?

It is involuntary and lacks striations. Signup and view all the answers

What characterizes cardiac muscle?

Involuntary with intercalated discs Signup and view all the answers

What are four functions of skeletal muscle?

Produce movement, maintain posture, stabilize joints, generate heat. Signup and view all the answers

What is the sarcolemma?

Specialized plasma membrane of muscle cells. Signup and view all the answers

What does the sliding filament theory describe?

Activation by nerve causes myosin heads to attach to thin filaments and pull them toward the sarcomere center. Signup and view all the answers

What are graded responses?

Different degrees of muscle shortening Signup and view all the answers

What causes muscle fatigue?

Oxygen debt and accumulated lactic acid. Signup and view all the answers

What are the two types of muscle contractions?

Isometric and isotonic Signup and view all the answers

What is muscle tone?

The continuous partial contraction of a muscle. Signup and view all the answers

How does exercise affect muscles?

Increases muscle size, strength, and endurance. Signup and view all the answers

List the 5 golden rules of skeletal muscle activity.

<ol> <li>Muscles cross at least one joint. 2. Bulk lies proximal to the joint. 3. At least 2 attachments: origin and insertion. 4. Muscles can only pull; never push.</li> </ol> Signup and view all the answers

Study Notes

Muscular System Overview

Muscles are essential for all types of bodily movement.
There are three basic muscle types: skeletal, cardiac, and smooth.

Muscle Characteristics

Skeletal and smooth muscle cells are elongated and known as muscle fibers.
Muscle contraction results from the movement of microfilaments.

Muscle Terminology

"MYO" and "MYS" prefixes relate to muscles.
The prefix "SARCO" refers to flesh.

Skeletal Muscle Features

Most skeletal muscles attach to bones via tendons.
Skeletal muscle cells are multinucleate and striated, exhibiting visible banding.
Skeletal muscles are under voluntary control.

Connective Tissue Wrappings

Connective tissue surrounds and bundles skeletal muscle cells:
- Endomysium: surrounds individual muscle fibers.
- Perimysium: wraps around a fascicle (bundle) of fibers.
- Epimysium: covers the entire muscle.
- Fascia: outside of the epimysium.

Types of Skeletal Muscle Attachments

Epimysium merges into tendons (cord-like) or aponeuroses (sheet-like) for attachment.
Tendons are primarily made of collagen fibers and traverse joints.
Aponeuroses attach muscles indirectly to bones, cartilages, or other tissues.

Smooth Muscle Characteristics

Lacks striations and features spindle-shaped cells with a single nucleus.
Involuntary and primarily located in the walls of hollow organs.
Arranged in two layers, contracting alternately to change organ size and shape.

Cardiac Muscle Characteristics

Striated, single-nucleus cells that branch and are interconnected at intercalated discs.
Found exclusively in the heart and is involuntary.
Cushioned by endomysium and arranged in spiral bundles.

Functions of Skeletal Muscle

Responsible for movement, posture maintenance, joint stabilization, and heat generation.

Microscopic Anatomy of Skeletal Muscle

Sarcolemma: specialized plasma membrane of muscle cells.
Myofibrils: long organelles housed within muscle cells.
Sarcoplasmic reticulum: smooth endoplasmic reticulum that stores and releases calcium.
Sarcomere: contractile unit of muscle fibers with distinct light (I band) and dark (A band) regions.

Myofilament Arrangement

Thick filaments are composed of myosin; thin filaments consist of actin.
Myosin heads form cross bridges with actin during contraction.
H zone: area where actin filaments do not overlap with myosin at rest.

Muscle Cell Stimulation and Contraction

Excitability allows muscle cells to respond to stimuli.
Contractility refers to the muscle's ability to shorten upon stimulation.
Extensibility and elasticity permit stretching and recoil of muscle fibers.

Nerve Stimulation and Action Potential

Motor neurons stimulate skeletal muscles to contract.
A motor unit comprises one motor neuron and the skeletal muscle fibers it activates.
Neuromuscular junctions facilitate communication between nerve impulses and muscle cells.

Muscle Contraction Mechanism

Acetylcholine (ACh) is the key neurotransmitter that binds to sarcolemma receptors, initiating muscle contraction.
Sodium ions enter the cell, generating an action potential that triggers contraction.

Sliding Filament Theory

Myosin heads attach to actin and pull them towards the sarcomere's center, resulting in muscle shortening.

Graded Responses in Muscle Contraction

Muscle contractions can vary depending on the frequency of stimulation and the number of stimulated fibers.
Graded responses include twitch (brief), tetanus (sustained), unfused (incomplete), and fused (complete) tetanus.

Muscle Strength and Energy

Muscle force correlates to the number of fibers stimulated.
Muscles use stored ATP for initial contraction; glucose breakdown produces more ATP through various pathways.

Energy Pathways

Direct phosphorylation of ADP by creatine phosphate resynthesizes ATP quickly (lasting ~15 seconds).
Aerobic respiration through glucose metabolism generates ATP efficiently when oxygen is available.
Anaerobic glycolysis can produce ATP rapidly without oxygen but leads to lactic acid and muscle fatigue.

Muscle Fatigue and Oxygen Debt

Fatigued muscles cannot contract despite stimuli; oxygen debt must be repaid to remove lactic acid.
Low ATP levels and increased acidity contribute to reduced muscle contraction efficiency.

Types of Muscle Contractions

Isotonic contractions allow movement as myofilaments slide past each other.
Isometric contractions increase muscle tension without shortening or movement.

Muscle Tone

Muscle tone is maintained through partial contraction of some fibers even at rest, providing stability.

Effects of Exercise on Muscles

Regular exercise enhances muscle size, strength, and endurance.
Aerobic exercise promotes flexibility, more effective metabolism, and improves organ efficiency.
Resistance exercise increases muscle size due to hypertrophy of individual muscle cells.

Golden Rules of Skeletal Muscle Activity

Most skeletal muscles cross at least one joint.
The bulk of skeletal muscle lies proximal to the joint crossed.
Skeletal muscles have at least two attachments: origin and insertion.
Muscles can only pull, never push.### Muscle Contraction
During contraction, skeletal muscle insertion moves toward the origin.

Muscle Attachments

Muscles attach to at least two points, including an immoveable bone (origin) and a moveable bone (insertion).

Types of Ordinary Body Movements

Flexion: Decreases the angle of the joint, bringing bones closer.
Extension: Increases the angle between bones; hyperextension occurs beyond 180 degrees.
Rotation: Movement around a bone's longitudinal axis, common in ball-and-socket joints.
Abduction: Moving a limb away from the midline.
Adduction: Moving a limb toward the midline.
Circumduction: A circular motion combining flexion, extension, abduction, and adduction.

Special Movements

Dorsiflexion: Lifting foot so toes approach the shin.
Plantar Flexion: Pointing toes downward (depressing the foot).
Inversion: Turning the sole of the foot medially.
Eversion: Turning the sole of the foot laterally.
Supination: Forearm rotation laterally, making radius and ulna parallel (palm faces anteriorly).
Pronation: Forearm rotation medially, bringing the radius across the ulna (palm faces posteriorly).
Opposition: Moving the thumb to touch other fingers.

Types of Muscles

Prime Mover (Agonist): Major muscle responsible for a movement.
Antagonist: Muscle opposing a prime mover; stretched and relaxed when the agonist acts.
Synergist: Helper muscle that aids prime movers and prevents unwanted movements.
Fixator: Stabilizes the origin of a prime mover.

Naming Skeletal Muscles

Based on direction of fibers (e.g., "rectus" for straight).
Relative size (e.g., "maximus" for largest).
Location (e.g., "temporalis" for temporal bone).
Number of origins (e.g., "triceps" for three heads).
Origin and insertion locations (e.g., "sterno" for sternum).
Muscle shape (e.g., "deltoid" for triangular).
Action (e.g., "flexor" for flexing a bone).

Fascicle Arrangements

Circular: Concentric rings, like sphincters (e.g., orbicularis).
Convergent: Fascicles converge toward a single tendon (e.g., pectoralis major).
Parallel: Length runs parallel to the muscle (straplike muscles).
Fusiform: Spindle-shaped with an expanded belly (e.g., biceps brachii).
Pennate: Fascicles attach obliquely to a central tendon, can be unipennate, bipennate, or multipennate.

Head and Neck Muscles

Facial Muscles: Frontalis, orbicularis oculi, orbicularis oris, buccinator, zygomaticus.
Chewing Muscles: Masseter, temporalis.
Neck Muscles: Platysma, sternocleidomastoid.

Specific Muscles and Their Functions

Frontalis: Raises eyebrows.
Orbicularis Oculi: Closes eyes, squints, blinks.
Orbicularis Oris: Closes mouth, protrudes lips.
Masseter: Closes jaw, elevates mandible.
Buccinator: Flattens cheek, assists in chewing.
Sternocleidomastoid: Flexes neck, rotates head.

Muscles of the Trunk, Shoulder, and Arm

Anterior Muscles: Pectoralis major, intercostals (external and internal).
Abdominal Muscles: Rectus abdominis, external and internal obliques, transversus abdominis.
Posterior Muscles: Trapezius, latissimus dorsi, erector spinae, quadratus lumborum, deltoid.

Muscles of the Upper Limb

Biceps Brachii: Supinates forearm, flexes elbow.
Triceps Brachii: Extends elbow (antagonist to biceps).
Flexor and Extensor Muscles: Flexor carpi radialis, ulnaris, extensor carpi radialis, and digitorum.

Muscles of the Lower Limb

Gluteus Maximus: Hip extension.
Gluteus Medius: Hip abduction.
Iliopsoas: Hip flexion; stabilizes upper body.
Quadriceps Group: Extend knee; some also flex hip.
Hamstring Muscles: Flex knee, extend hip.
Gastrocnemius and Soleus: Plantar flex foot.

Fun Facts

Zygomaticus: Used to grin.
Buccinator: Important for playing saxophone.
Orbicularis Oculi: Involved in blinking and squinting.
Platysma: Contributes to expressions like the "sad clown."

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Description

Explore the muscular system through this set of flashcards covering key concepts such as the types of muscles and their characteristics. This quiz is designed to reinforce your understanding of muscle function and structure in the human body.