Download Skeletal System

Skeletal System
Without the structure and support
given by a skeletal system,
organisms would NEVER be able
to grow larger than bacteria, if
they would be able to grow at all!
Hydro, Exo, and Endo
There are 3 different types of skeletons
1. Exoskeleton: Hard, hollow structures
that envelope that body (such as in
Arthropods)
2. Hydrostatic skeleton: Uses the
pressure of internal body fluids to support
the body (such as in Cnidarians)
3. Endoskeletons: Hard internal
structures (such as in us)
Exoskeleton
Hydrostatic Skeleton
Endoskeleton
The Endoskeleton
• Because of the nature and direction of this class
(and because you SHOULD have discussed
Hydrostatic and Exoskeletons in great deal in
other classes ) we will focus on the
Endoskeleton.
• (if you have any questions about the hydrostatic
and exoskeleton, make sure to ask)
• If not for the support of our skeletons, and the
fact that they give attachment sites for our
muscles, humans would not stand a chance
Cartilage and Bone
• The endoskeleton is composed of
connective tissues called bone and
cartilage.
• Cartilage is made up of cells scattered in
a gelatinous matrix of polysaccharides and
protein fibers.
• Bone is made up of cells in a hard extracellular matrix of calcium carbonate
(CaCO3) and protein fibers
Cartilage
Bone
JOINTS
• Bones meet in areas called Articulations
(Joints)
• They are unique in that they articulate in
ways that allow limbs to swivel, hinge, or
pivot
• The articulation occurs in a way to allow
muscles to alter the normal structure of
bone and allow motion
Tendons
• Many bones have muscles (usually
skeletal muscle) that are attached directly
to them.
• These muscles are attached at areas
called by Tendons
• Tendons are bands of tough, fibrous,
connective tissue.
• Tendons can be damaged, pulled, torn,
and bruised (which can be incredibly
painful)
Tendon
Muscle Movement
• In the case of a limb, muscles allow for most of
the entire bone function.
• Muscles can exert force ONLY by contracting,
so pairs of muscles must work together to allow
a bone to move back and forth.
• This paring of muscles is called an Antagonistic
Muscle Group.
– The muscle that swings a limb towards another is
called a Flexor
– The muscle that straightens them out is called an
Extensor
Antagonistic Muscle Group
Types of Muscle
• There are 3 types of muscle (well kind of 2
and a half)
– Skeletal Muscle
– Smooth Muscle
– Cardiac Muscle
• Often times the scientific community will
include Cardiac Muscle within Smooth Muscle,
we will consider it seperately
Types of Muscle
• Skeletal Muscle:
– Always is attached to bone
– Primary function is to move the skeleton
– Secondary function aids fluid and blood
movement within the body
– Is multinucleated
– Is unbranched
– Activity is voluntary
• Signals from the motor neuron are required
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Types of Muscle
• Cardiac Muscle:
– Located only in the heart
– Function is to pump blood
– Will have 1 or 2 nuclei
– Branched: Intercalated discs form direct
cytoplasmic connections end to end
– Activity is “non-voluntary,” meaning that
signals from motor neurons are NOT required
Cardiac Muscle
Cardiac Muscle
Types of Muscles
• Smooth Muscle:
– Located in the intestines, arteries, etc
– Its MAIN Functions are to move food and help
regulate blood pressure
– Single nucleus
– Unbranched
– Activity is “non-voluntary,” meaning that
signals from motor neurons are NOT required
Smooth Muscle
Smooth Muscle
Smooth Muscle
Types of Muscles
Contraction in Skeletal
Muscles
• So why are skeletal muscles striped (Striated)?
Contraction in Skeletal Muscles
• These striations are called sarcomeres.
• The sarcomeres alternate between light
and dark units, giving the striped
appearance.
• Muscle contraction is actually „Sarcomere
Contraction‟
• As the individual sarcomeres contract, the
muscle itself contracts
Sarcomere
Sarcomere
Sarcomere
Sliding Filament Model
• So the question became, “How do sarcomeres
contract?”
• The theory we currently use is called the sliding
filament model.
• This model uses the striated appearance of the
skeletal muscle to describe two different types of
filaments within the muscle
– Thick filament (Made of long strands of protein called
Myosin)
– Thin filament (Made of a globular protein called
Actin)
Sliding Filament Model
• As the sarcomeres contract, the thin (Actin)
filament slides over the thick (Myosin) filament
• This movement allows for a simple contraction of
the skeletal muscle
• This happens in the presence of ATP
• Actin and Myosin connect at various points
during the sliding process
• ATP is catalyzed into ADP and a phosphate ion
by the Myosin molecule, and the myosin
molecule will briefly release the actin molecules
and slightly change shape.
• Then the myosin will reattach to the actin further
down the strand, ultimately causing contraction
Sliding Filament Model
Sliding Filament Model
The Power Stroke
• This change in protein structure of the
Myosin thick filament is common in the
presence of ATP (ATP alters the shape of
a lot of proteins)
• However, because this change moves the
entire filament, it is called the power
stroke
Rigor Mortis
• Myosin and Actin fibers normal state is
„locked together,‟
• This is the reason that shortly after an
animal that has skeletal muscle dies, it
enters a stiff state called rigor mortis
• Without an active supply of ATP, the
myosin and actin fibers interlock and will
not release until they begin to break down
Rigor Mortis
Relaxation
• So how do they relax?
• Aside from Thin actin filaments and Thick
myosin filaments, skeletal muscles also
contain Tropomyosin and Troponin.
• Tropomyosin and Troponin work together
to block myosin binding sites on actin.
• When the myosin-actin interaction can not
occur, the filaments no longer contract
– This is usually neurologically controlled
Relaxation