Transcript Support and Locomotion

Support and Locomotion
Muscles
Muscles work by contracting:
getting smaller in size
Three types of muscles
–Skeletal (Striated, voluntary)
–Cardiac (Heart)
–Smooth (Involuntary)
Skeletal Muscle
Called striated because of how it
looks
Responsible for voluntary actions
Human body has over 700 different
skeletal muscles (this makes up
~35% to 45% of the total body
weight!)
SkM contracts by having two
proteins, actin and myosin, slide past
each other
Skeletal Muscle
The sarcomere is the
functional unit of muscle
contraction
Thin filaments consist of
two strands of actin and
one tropomyosin coiled
about each other
Thick filaments consist of
myosin molecules
Actin (thin filament) and
myosin (thick) slide past each
other
Myosin has little “feet” called
cross-bridges
Skeletal Muscle
At rest, tropomyosin blocks the
myosin binding sites on actin
Skeletal Muscle
When Ca2+ binds to the troponin
complex, a conformational change
results in the
movement of the
tropomyosintropinin
complex and
exposure of
actin’s myosin
binding sites
Skeletal Muscle
Using ATP, cross-bridges from
myosin “grab” binding sites on
actin and pull the filaments
closer
This action occurs over and
over until the muscle fiber is
completely contracted
Muscles are controlled by the
Nervous System
Action potentials run along a neuron
until they reach a synapse, where they
release neurotransmitters (ACh)
Once at the muscle cells, the action
potential releases Ca2+ from the
sarcoplasmic reticulum
The Ca ions allow the proteins on the
actin and myosin to bind, forming the
cross-bridges
Cardiac Muscles
Cardiac muscles are those that
power the heart
Very similar to SkM, except
CM is controlled by the SA
node, not a motor neuron
Smooth Muscles
SmM surround blood vessels
and most hollow organs:
uterus, bladders, GI tract
Most SmM contraction is slow
and sustained, sometimes
rhythmic (peristalsis)
Smooth Muscles
SmM contraction can be
initiated by stretching,
hormones, or the nervous
system
Most are involuntary, but some
can be controlled (urinary
bladder)
ATP
Large amounts of ATP are
required for muscle contraction
AND relaxation
–Breaks/reforms connections
between actin and myosin
–Powers pumps that return Ca2+
to the sarcoplasmic reticulum
Rigor mortis
Stiffening of muscles after death
Muscles run out of ATP after death
–Connection between actin and
myosin cannot be broken –
muscle remains contracted
–After ~72 hours, relaxation
occurs because of
decomposition
Skeletons
What do skeletons do?
–Provide the framework for
support of the body
Three basic types:
–Hydrostatic Skeleton
–Exoskeleton
–Endoskeleton
Hydrostatic Skeletons
– fluid pressure provides support
(Cnidarians, Annelids)
Exoskeleton
Encase the bodies of Arthropods
(insects, crustaceans, and
arachnids)
Made of proteins, chitin, or are
calcareous
Thin exoskeleton where the
animal needs to bend or move
Crustacea,
Molluska, and
Insecta
Endoskeleton
 Found in Echinoderms,
Chordates, and Sponges
 Serve several functions for
vertebrates:
1. Supports body and protects
internal organs
2. Used as muscle attachment
sites to allow locomotion
3. Produce blood parts (RBC’s,
WBC’s, and platelets
4. Serve as storage sites for
Calcium and Phosphorus
5. Some even aid in sensory
transduction (hammer, anvil,
and stirrup of the middle ear)
Cartilage
Consists of chondrocytes
embedded in a collagen/elastin
matrix
Located at ends of long bones
and between vertebrae
Functions as shock absorber
Bones
Compact bone provides
strength and rigidity as well as
attachment sites for muscles
Spongy bone is very porous;
site where blood cells are
produced (bone marrow)
How does the body move?
Muscles work in antagonistic
pairs
–One always
extends
(bends out)
while the
other always
flexes (bends in)
How does the body move?
A muscle attaching two bones
is attached to one fairly
immovable bone (origin) and
one that moves (insertion)
Tendons connect muscle to
bone
Ligaments connect bone to
bone
Joints are where two
bones meet
Three basic types of
joints:
–Fixed: Skull
–Hinge: Elbows and
knees
–Ball-and-Socket:
Shoulders and hips
Arthritis (joint inflammation)
Osteoarthritis (“wear-and-tear” arthritis)
– Cartilage covering the ends of bones
slowly wears away, causing stiffness
and soreness
Rheumatoid arthritis
– Autoimmune
disease in which
the body’s immune
system attacks the
synovial membranes