Download Chapter 9: Muscles and Muscle Tissue

Chapter 9:
Muscles and
Muscle Tissue
Governor Arnold Schwarzenegger
2
Muscle Functions
•
•
•
•
Producing Movement
Maintaining Posture
Stabilizing Joints
Generating Heat
3
3 Types of Muscle
•Skeletal
Muscle
•Cardiac
Muscle
•Smooth
Muscle
4
Skeletal Muscle
•attaches to
bones
which form
levers
•used for
bodily
movement
5
Cardiac Muscle
•forms the
heart
•used to pump
blood
through
circulatory
system
6
Smooth Muscle
•lines gut and
blood vessels
•controls
diameter of
these tubes and
in gut helps to
propel the
digested food
7
Property
Skeletal
Muscle
Cardiac
Muscle
Smooth
Muscle
Striations?
Yes
Yes
No
Nuclei per Cell
Many
Single
Single
Cells
Connected by
Intercalated
Discs or Gap
Junctions?
No
Yes
Yes
8
Property
Skeletal
Muscle
Cardiac
Muscle
Smooth
Muscle
Relative Speed
of Contraction
Fast
Intermediate
Slow
Voluntary
Control?
Yes
No
No
Nerves
Beats
spontaneously
but modulated by
nerves
Nerves
Hormones
Stretch
Control of
Contraction
9
Muscle cells
• Large, long cells called FIBERS
• Contain two types of proteins-actin and myosin
• Excitable (irritable),
contractile, extensible, and
elastic
• Myo-, mys, or Sarco code for
muscle
10
Skeletal Muscle
Anatomy
•Rich blood supply to center
of muscle, branch to
capillaries sheathing cells
•Rich nerve supply,
branching into each
muscle, ending one branch
to each muscle fiber
11
Structure of
Skeletal Muscle
•Cigar shaped, multinucleate
cells
•Packed with myofilaments
made of actin and myosin
creating visible bands
(striations)
•Varied length, may be over a
foot long
12
Structure cont.
• Surrounded by dense, fibrous
Connective tissue (CT)
sheaths
• Endomysium around each
fiber
• Perimysium around bundles of
fibers (fascicles)
• Epimysium around all
13
fascicles
Figure 6.1 Connective tissue wrappings of skeletal muscle.
© 2000 The Benjamin/Cummings Publishing Company
14
Microscopic
structure
• Muscle fibers filled with
Sarcoplasm
–Glycogen and myoglobin
• Nuclei pushed to the edge of
sarcolemma by long protein
strands that run length of the
cell, myofibrils
• Composed of contractile units,
sarcomeres, made of
myofilaments
15
Figure 6.3 Anatomy of a skeletal
muscle cell (fiber). (a) A portion of
a muscle fiber. One myofibril has
been extended. (b) Enlarged view
of a myofibril showing its banding
pattern. (c) Enlarged view of one
sarcomere (contractile unit) of a
myofibril. (d) Structure of the thick
and thin myofilaments found in the
sarcomeres.
© 2000 The Benjamin/Cummings Publishing
Company
16
Myofilaments
• Two types--actin and myosin
-Filaments are clusters of
actin and myosin
• Actin forms thin filaments
• Myosin forms thick filaments
17
Sarcomere
structure
•Alternating dark and light
bands
•Lateral dark bands--A-band
•End in light I-bands, with Zline in center marking joint
with next sarcomere on each
side
18
19
20
Muscle Contraction
• Sarcomere - basic unit of
muscle contraction
• Skeletal and cardiac muscle
are striated
• The striations are caused by
alignment of bands: the most
prominent are the A and I
bands and the Z line
• The unit between 2 Z lines is
called the sarcomere
21
Muscle ContractionSarcomere
• In the A band the 2 proteins overlap
• The I band contains only the actin protein
• When muscle contracts the sarcomere
shortens and the Z lines move closer together
22
23
Muscle Contractionrelaxed state
• When Muscle Contracts Protein
Filaments Slide Together
• Thin filaments: actin, attached to Z
line, found in both A and I bands
• Thick filaments: myosin, found in A
band
• Relaxed state:
24
Muscle ContractionContracted state
• When muscle contracts the
actin filaments slide into the A
band, overlapping with myosin
25
Muscle ContractionContracted state
• Notice what happens when muscle contracts:
– a) the Z lines move closer together
– b) the I band becomes shorter
– c) the A band stays at the same length
• This is called the "sliding filament" model of
muscle contraction
26
Muscle ContractionCrossbridge
• The filaments slide together because
myosin attaches to actin and pulls on it
• myosin head(H) attaches to actin filament
(A), forming a crossbridge
• After the crossbridge is formed the myosin
head bends, pulling on the actin filaments
and causing them to slide:
27
Actin
Molecule
28
29