Section 1, Chapter 9 Muscular System
-
Upload
michael-walls -
Category
Documents
-
view
217 -
download
2
description
Transcript of Section 1, Chapter 9 Muscular System
Chapter 9, Section 1
Muscular System
Muscle is derived from Musculus, for “Mouse”
Imagine a mouse running beneath the skin.
Functions of Muscles:
1. Body movement
2. Maintain posture
3. Produces heat
4. Propel substances
through body
5. Heartbeat
Types of muscles:
1. Smooth muscle
2. Cardiac muscle
3. Skeletal muscle
Imagine a mouse running beneath the skin.
Smooth Muscle Fibers
Characteristics of smooth muscles
• Involuntary control
• Tapered cells with a single, central nucleus
• Lack striations
• Visceral Smooth Muscle
• Form sheets of muscle
• Cells are connected by gap junctions
• Multi-unit Smooth Muscle
• unorganized cells that
contract as individual cells • Cells are connected by gap junctions
• Muscle fibers contract as a group
• Rhythmic contractions
• Within walls of most hollow organs
(viscera)
contract as individual cells
•Located within the iris of eye
and the walls of blood vessels
Cardiac Muscle
•Located only in the heart•Located only in the heart
•Striated cells
•Intercalated discs
• Muscle fibers branch
•Muscle fibers contract
as a unit
• Self-exciting and rhythmic
Skeletal Muscle
• Usually attached to bone
• Voluntary control
• Striated (light & dark bands)
• Muscle fibers form bundles
• Several peripheral nuclei
Coverings of Skeletal Muscle
Fascia
• Dense connective tissue surrounding
skeletal muscles
Tendons
• Dense connective tissue that
attaches muscle to bones
• Continuation of muscle facia and • Continuation of muscle facia and
bone periosteum
Aponeurosis
• Broad sheet of connective tissue
attaching muscles to bone, or to
other muscles.
Coverings of Skeletal Muscle
Epimysium
• Connective tissue closely
surrounding a muscle
• Lies deep to fascia
PerimysiumPerimysium
• Surrounds organized bundles of
muscle fibers, called fascicles
Endomysium
• Connective tissue that surrounds
individual muscle fibers (cells)
Figure 9.3 Scanning electron micrograph of a
fascicle surrounded by its perimysium. Muscle
fibers within the fascicle are surrounded by
endomysium.
Organization of Skeletal Muscle
Fascicle
• Organized bundle of muscle fibers
Muscle Fiber
• Single muscle cell
• Collection of myofibrils
MyofibrilsMyofibrils
• Collection of myofilaments
Myofilaments
• Actin filament
• Myosin filament
Figure 9.2
Skeletal muscle
organization
Sarcolemma
• Cell membrane of muscle fibers
Sarcoplasm
• Cytoplasm of muscle fibers
Sarcoplasmic Reticulum
• Modified Endoplasmic Reticulum
Skeletal Muscle Fibers
• Modified Endoplasmic Reticulum
• Store large deposits of Calicium
sarcolemma
Figure 9.2 c. A single muscle fiber
composed of several myofibrils. A
sarcolemma (membrane) surrounds the
cell, and an extensive sarcoplasmic
reticulum runs along the cell.
Skeletal Muscle Fibers
(Transverse)T-tubules:
• invaginations of sarcolemma,
extending into the sarcoplasm.
Cisternae:
• Enlarged region of sarcoplasmic
reticulum, adjacent to t-tubules
Openings into t-tubules
reticulum, adjacent to t-tubules
Triad
• T-tubule + adjacent cisternae
Myofibrils
Myofibrils
• Actin – thin filaments
• Myosin – thick filaments
Striations
Figure 9.4 Organization of actin and myosin filaments
Striations
• appear from the
organization of actin and
myosin
Sarcomere
Sarcomere
• Functional unit of
skeletal muscle
•Area between
adjacent Z-lines
•During contraction
Z-lines approach together
and sarcomeres shorten
• I Bands (light): actin filaments
• Z Line = attaches to actin
filaments (center of I bands)
• A Band (dark) : Myosin
filaments and overlapping actin
filaments
Striation Pattern of Skeletal Muscle
Figure 9.5 thin and thick filaments in a
sarcomere.
• Thick myofilaments
• Myosin proteins
• Cross-bridges (heads) on myosin
• Cross-bridge attaches to actin
during contraction
• Thin myofilaments
• Actin proteins
• Associated with troponin
and tropomyosin proteins
MyofilamentsMyofilaments
Cross-BridgesCross-Bridges• Myosin cross-bridges are extended when muscles are at rest “cocked”
position.
•During a contraction, cross-bridges bind to actin and “spring” forward. (Power Stroke)
• Cross-bridges pull on actin as they spring forward.
• ATP is required to “recock” the cross-bridges. (Recovery stroke)
Myosin cross-bridge
In the “cocked” position
Myosin cross-bridge
In the “sprung” position
Actin binding site
Power stroke