biol 3410 10/10

Announcements

  • Exam scores are being processed and expected to be entered by tomorrow.

  • Students encouraged to sign up for exam review to discuss missed items and study strategies.

Topic Introduction

  • New topic: Skeletal Muscle, focusing on muscle contraction.

  • Skeletal Muscle will be the primary focus for the next exam.

  • A resource on creatine supplements is available for students interested.

  • Lab will not meet next week; lab quizzes will remain open for an additional week.

Poll Everywhere Activity

Question 1: Identify Tissue

  • Most selected answer: Voluntary and Striated = Skeletal Muscle.

  • Characteristics of Skeletal Muscle:

    • Presence of striations.

    • Multiple nuclei per long fiber.

    • No intercalated discs.

Question 2: Identify Tissue Type

  • Correct answers: Cardiac Muscle, Involuntary, Striated.

  • Key distinguishing features:

    • Found only in the heart.

    • Presence of intercalated discs.

    • Branching cells observed.

Question 3: Identify Smooth Muscle

  • Correct answers: Involuntary, Non-striated.

  • Characteristics of Smooth Muscle:

    • Single nucleus per cell.

    • Fusiform shape (wide in the middle, tapered at the ends).

    • Arranged in sheets, responsible for organ function (e.g., movement in digestive system).

Case Study Introduction

  • Patient: 26-year-old gymnast, reports jaw fatigue while eating, difficulty spotting students during coaching.

  • Clinical Findings: Electromyographic studies indicate weakness during repeated muscle contraction and droopy eyelids.

Muscle Types and Their Functions

Types of Muscle Tissue

  • Skeletal Muscle: Movement of bones, voluntary control.

  • Cardiac Muscle: Involuntary, found in the heart, pumps blood.

  • Smooth Muscle: Involuntary, found in organs, controls movement of substances within the body.

Functions of Muscle Tissue

  • Supports skeletal structure, allows for movement of bones and substances (e.g., food, blood).

  • Important for posture and stabilizing joints.

  • Generates heat through contraction (shivering response).

  • Provides structural support to soft tissues.

Properties of Muscle Tissue

  • Excitability: Ability to respond to stimuli, crucial for muscle contraction.

  • Contractility: Muscle's ability to shorten forcibly; related to extensibility (ability to stretch).

  • Resting Length: Each muscle maintains a certain resting length for optimal function.

Histology and Anatomy of Skeletal Muscle

Organizational Structure

  • Muscle Organ: Composed of bundles of fascicles (muscle cell groups).

  • Muscle Fiber: Individual muscle cell.

  • Myofibrils: Bundles within each muscle fiber responsible for contraction.

Connective Tissue Layers

  • Epimysium: Surrounds entire muscle.

  • Perimysium: Surrounds fascicles; organizes muscle fibers.

  • Endomysium: Surrounds each muscle fiber; includes plasma membrane (sarcolemma).

  • Connective tissues help in attaching muscles to bones via tendons.

Sarcomere Structure

  • Sarcomere: Functional unit of muscle contraction, located between Z discs.

  • Key Structures:

    • A Band: Dark band where thick filaments (myosin) are located.

    • I Band: Light band where thin filaments (actin) are present.

    • H Zone: Light region within A band where only thick filaments are present.

    • M Line: Central line in the A band that anchors the thick filaments.

Contractile Proteins

  • Thick Filaments: Composed of myosin (dimer structure with tails and heads).

  • Thin Filaments: Composed of actin, along with regulatory proteins tropomyosin and troponin.

Sliding Filament Theory

  • Describes muscle contraction mechanism:

    • Interaction of actin (thin) and myosin (thick) filaments.

    • Myosin heads pull on actin filaments, leading to muscle shortening.

  • Essential for all voluntary and involuntary muscle movements.