Introduction to the Muscular System
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Which of the following statements about smooth muscle is true?

  • Smooth muscle is exclusively found in the heart.
  • Smooth muscle fibers are larger than those in skeletal muscle.
  • Smooth muscle contracts under conscious control.
  • Smooth muscle features a single, centrally located nucleus. (correct)

What is a key feature distinguishing cardiac muscle from smooth muscle?

  • Cardiac muscle operates only during voluntary movements.
  • Cardiac muscle is under conscious control.
  • Cardiac muscle has striated fibers joined by intercalated disks. (correct)
  • Cardiac muscle fibers are not fatigue resistant.

Which statement accurately describes the contraction characteristics of smooth muscle?

  • Smooth muscle contractions vary significantly with conscious effort.
  • Smooth muscle contractions are only found in the digestive organs.
  • Smooth muscle contractions are slow and uniform. (correct)
  • Smooth muscle contractions are quick and forceful.

Where in the body can you find smooth muscle?

<p>In the walls of airways and the stomach. (B)</p> Signup and view all the answers

Which of the following best describes the type of muscle found in the myocardium?

<p>Cardiac muscle, which is involuntary and fatigue resistant. (C)</p> Signup and view all the answers

What is the primary function of skeletal muscle tissue?

<p>Facilitating locomotion (B)</p> Signup and view all the answers

Which property of muscle allows it to return to its original shape after being stretched?

<p>Elasticity (B)</p> Signup and view all the answers

What type of muscle tissue is responsible for involuntary movements in the body's organs?

<p>Smooth muscle (B)</p> Signup and view all the answers

What characteristic is unique to cardiac muscle tissue compared to skeletal and smooth muscle?

<p>Presence of intercalated discs (B)</p> Signup and view all the answers

Which muscle property is primarily related to the ability to respond to stimuli?

<p>Excitability (D)</p> Signup and view all the answers

Which muscle is not primarily composed of skeletal muscle tissue?

<p>Smooth muscle of the intestines (D)</p> Signup and view all the answers

What function does skeletal muscle NOT directly perform?

<p>Regulating circulatory flow (A)</p> Signup and view all the answers

Which pair of characteristics is true for skeletal muscle fibers?

<p>Cylindrical and striated (A)</p> Signup and view all the answers

What is the role of ATP in muscle contraction?

<p>It is necessary for the detachment of myosin from actin. (B)</p> Signup and view all the answers

How do muscles primarily generate ATP during prolonged exercise?

<p>Primarily through aerobic respiration. (C)</p> Signup and view all the answers

What factor is NOT associated with muscle fatigue?

<p>Increased myosin actin binding. (A)</p> Signup and view all the answers

Which of the following conditions is classified as a muscle disorder?

<p>Muscular dystrophy. (A)</p> Signup and view all the answers

What process leads to the production of lactic acid during muscle activity?

<p>Anaerobic glycolysis. (D)</p> Signup and view all the answers

What role do troponin and tropomyosin play in skeletal muscle contraction?

<p>They regulate the interaction between actin and myosin filaments. (B)</p> Signup and view all the answers

Which property distinguishes fast-twitch muscle fibers from slow-twitch muscle fibers?

<p>Fast-twitch fibers contract rapidly but fatigue quickly. (C)</p> Signup and view all the answers

What is the primary structure found in skeletal muscle fibers that is essential for contraction?

<p>Sarcomeres containing actin and myosin. (C)</p> Signup and view all the answers

What characterizes the contraction of smooth muscle compared to skeletal muscle?

<p>Smooth muscle contractions are slower and more sustained. (C)</p> Signup and view all the answers

How do cardiac muscle cells ensure a coordinated contraction of the heart?

<p>By interconnected cells via intercalated discs. (B)</p> Signup and view all the answers

Which feature is NOT associated with smooth muscle cells?

<p>They have striations visible under a microscope. (B)</p> Signup and view all the answers

What primary mechanism underlies the contraction of muscle fibers according to the sliding filament theory?

<p>The overlapping of actin and myosin filaments. (C)</p> Signup and view all the answers

Which statement correctly reflects the energy metabolism of skeletal muscle fibers?

<p>Slow-twitch fibers use aerobic pathways and resist fatigue. (B)</p> Signup and view all the answers

Flashcards

Smooth Muscle Location

Found in the walls of airways, eyes, stomach, intestines, and blood vessels.

Smooth Muscle Function

Involuntary muscle that moves food, empties liquid, and controls blood vessel width.

Cardiac Muscle Location

Only found in the heart wall (myocardium).

Cardiac Muscle Function

Responsible for heart pumping action controlled by the cardiac conduction system.

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Cardiac Muscle Properties

Striated, branched fibers with intercalated disks, involuntary, and fatigue resistant.

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Muscular System Function

The muscular system moves bones, food, blood, and fluids; maintains posture, facilitates respiration, communication, and organ/vessel constriction, creates body heat (thermogenesis), and controls the heartbeat.

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Skeletal Muscle

A type of muscle tissue attached to bones by tendons. It's responsible for locomotion, facial expressions, and posture. It's striated, voluntary, and long, cylindrical, multinucleated cells.

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Muscle Properties

Muscles exhibit four key properties: excitability (respond to stimuli), contractility (ability to shorten), extensibility (ability to stretch), and elasticity (ability to return to original shape).

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Muscle Tissue Types

There are three main types of muscle tissue in the body: skeletal, smooth, and cardiac.

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Muscle Attachment

Skeletal muscles attach to bones via tendons, which are tough connective tissues.

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Muscle Function: Locomotion

The muscular system's ability to cause movement of the body.

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Muscle Function Composition

Muscles are composed of muscle cells (fibers), connective tissue, blood vessels, and nerves.

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Muscle Naming

Muscles have names based on their location, origin and insertion points, number of origins, function, size, shape, or fascicle orientation.

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Muscle contraction

The process where muscle fibers shorten, driven by myosin pulling actin filaments.

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ATP in muscle

The energy currency for muscle contraction; needed to release the cross-bridged myosin from actin.

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Muscle fatigue

Inability of a muscle to sustain force or contract efficiently.

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Muscle energy sources

Muscles use different energy sources (ATP, phosphagens, glycolysis, respiration) depending on the activity.

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Muscle disorders

A diverse range of conditions affecting muscle function, from genetic mutations to cramping.

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Muscle Fiber Types

Skeletal, smooth, and cardiac muscles, each with unique structures and functions.

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Skeletal Muscle Structure

Long, cylindrical, multinucleated cells with myofibrils, sarcomeres, actin, and myosin.

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Smooth Muscle Function

Involuntary movements in internal organs, maintaining pressure.

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Cardiac Muscle Feature

Specialised heart muscle with branched cells and intercalated discs.

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Sliding Filament Theory

Actin and myosin filaments slide past each other causing muscle contraction.

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Muscle Contraction Trigger

Nervous system stimulation, neurotransmitters, and the neuromuscular junction.

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Involuntary Muscle Characteristics

Smooth and Cardiac muscles: controlled automatically.

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Muscle Contraction Speed

Skeletal muscle fibers are fast or slow depending on energy usage—twitch types and fatigue.

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Study Notes

Introduction to the Muscular System

  • Muscles make up about 1/3 of the body's weight.
  • Blood vessels and nerves control muscle function.
  • The muscular system produces body heat and moves: bones (skeletal system), food (digestive system), blood (circulatory system), and fluids (excretory system).

Functions of the Muscular System

  • Body movement (locomotion)
  • Maintaining posture
  • Respiration (diaphragm and intercostal muscles)
  • Communication (verbal and facial)
  • Constriction of organs and vessels
  • Heartbeat
  • Production of body heat (thermogenesis)

Properties of Muscle

  • Excitability
  • Contractility
  • Extensibility
  • Elasticity

Types of Muscle Tissue

  • Skeletal muscle
  • Smooth muscle
  • Cardiac muscle

Skeletal Muscle

  • Attaches to bone by tendons (connective tissue).
  • The Achilles tendon is the largest tendon in the body.
  • Makes up about 40% of body weight.
  • Responsible for movement, facial expressions, posture, and respiration.
  • Composed of muscle fibers (cells), connective tissue, blood vessels, and nerves.
  • Muscle fibers are long, cylindrical, and multinucleated.
  • Muscle fibers range from 1mm to 4cm in length.
  • Develops from myoblasts.
  • Skeletal muscles are striated (striped).
  • Nuclei are peripherally located.
  • Mostly voluntary.

Smooth Muscle

  • Found in walls of internal organs (airways, eyes, stomach, blood vessels, and bladder).
  • Involuntary (automatic).
  • Moves food through digestive tract, empties bladder, controls blood vessel width.
  • Non-striated (no stripes).
  • Smaller and spindle-shaped cells.
  • Single nucleus.
  • Contractions are slow and uniform (consistent).

Cardiac Muscle

  • Found only in the heart.
  • Involuntary.
  • Responsible for heart pumping.
  • Striated (striped).
  • Branching cells.
  • Single nucleus.
  • Fatigue-resistant.
  • Fibers are joined by intercalated discs.
  • Controlled by the autonomic nervous system (ANS) and hormones.

Muscle Nomenclature

  • Muscle names are often descriptive.
  • Named by location (pectoralis muscles), origin and insertion (brachioradialis), number of origins (biceps), function (flexor digitorum), size (vastus), shape (deltoid), or fascicle orientation (rectus).

Muscle Shapes

  • Parallel/Fusiform: Fibers run parallel for long contractions and endurance.
  • Convergent: Fibers converge to maximize force at insertion.
  • Pennate: Many fibers per unit for strength but tire quickly (Unipennate, Bipennate, Multipennate).
  • Circular: Fibers surround an opening, forming sphincters (examples: orbicularis oris and oculi).

Muscle Tissue Summary

  • Table summarizing skeletal, smooth, and cardiac muscle locations, functions, striations, nucleus characteristics, control, and contractions (Provided in a separate table)

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Muscular System PDF

Description

This quiz covers the fundamentals of the muscular system, including its structure, functions, and types of muscle tissue. Explore how muscles contribute to movement, posture, respiration, and body heat production. Dive into the properties of muscle and the significance of skeletal muscle in the body.

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