Download Skeletal muscle tissue

The Muscular System
Chapter 10
There are four characteristics associated
with muscle tissue:
 Excitability
- Tissue can receive & respond to stimulation
 Contractility
- Tissue can shorten & thicken
 Extensibility
- Tissue can lengthen
 Elasticity
- After contracting or lengthening, tissue
always wants to return to its resting state
The characteristics of muscle tissue enable it to
perform some important functions, including:
 Movement – both voluntary & involuntary
 Maintaining posture
 Supporting soft tissues within body cavities
 Guarding entrances & exits of the body
 Maintaining body temperature
Types of muscle tissue:
• Skeletal
• Cardiac
• Smooth (Visceral)
Types of muscle tissue:
Skeletal muscle tissue
• Associated with & attached to the skeleton
• Under our conscious (voluntary) control
• Microscopically the tissue appears striated
• Cells are long, cylindrical & multinucleate
Cardiac muscle tissue
• Makes up myocardium of heart
• Unconsciously (involuntarily) controlled
• Microscopically appears striated
• Cells are short, branching & have a single nucleus
• Cells connect to each other at intercalated discs
Smooth (visceral) muscle tissue
• Makes up walls of organs & blood vessels
• Tissue is non-striated & involuntary
• Cells are short, spindle-shaped & have a single
nucleus
• Tissue is extremely extensible, while still retaining
ability to contract
Anatomy of skeletal muscles
epimysium
tendon
perimysium
Muscle
Fascicle
Surrounded by
perimysium
Skeletal
muscle
Surrounded by
epimysium
endomysium
Skeletal
muscle
fiber (cell)
Surrounded by
endomysium
Microanatomy of a Muscle Fiber (cell)
Microanatomy of a Muscle Fiber (Cell)
transverse
(T) tubules
sarcoplasmic
reticulum
terminal
cisternae
sarcolemma
myoglobin
mitochondria
thick myofilament
thin
myofilament
myofibril
nuclei
triad
Muscle fiber
sarcomere
Z-line
myofibril
Thin filaments
Thick filaments
Thin myofilament
Myosin molecule of
thick myofilament
Thin Myofilament
Z-line
(Z-disc)
(myosin binding site)
Thick myofilament
M-line
(has ATP
& actin
binding
site)
 Play IP sliding filament theory p.5-14 for overview of thin & thick filaments
Sarcomere
A band
Z line
Z line
H zone
I band
Thin
myofilaments
Zone of
overlap
Thick
myofilaments
M line
Zone of
overlap
Sliding Filament Theory
• Myosin heads attach to actin molecules (at binding (active) site)
• Myosin “pulls” on actin, causing thin myofilaments to slide across
thick myofilaments, towards the center of the sarcomere
• Sarcomere shortens, I bands get smaller, H zone gets smaller, &
zone of overlap increases
• As sarcomeres shorten, myofibril shortens. As myofibrils
shorten, so does muscle fiber
• Once a muscle fiber begins to contract, it will contract
maximally
• This is known as the “all or none” principle
Anatomy of the Muscular System
•Origin
Muscle attachment that remains
fixed
•Insertion
Muscle attachment that moves
•Action
What joint movement a muscle
produces
i.e. flexion, extension, abduction,
etc.
• For muscles to create a movement,
they can only pull, not push
• Muscles in the body rarely work alone,
& are usually arranged in functional
groups surrounding a joint
• A muscle that contracts to create the
desired action is known as an agonist or
prime mover
• A muscle that helps the agonist is a
synergist
• A muscle that opposes the action of the
agonist, therefore undoing the desired
action is an antagonist
Skeletal muscle movements at joints
Flexion/extension
Abduction/adduction
Rotation – left/right; internal(medial)/external(lateral)
pronation/supination
Elevation/depression
Protraction/retraction
Dorsiflexion/plantarflexion
Inversion/eversion
An Overview
of the Major
Skeletal
Muscles

Figure 7-11(a)
An Overview
of the Major
Skeletal
Muscles

Figure 7-11(b)