Musculoskeletal system Flashcards
Support structure that provides rigidity to the body, surfaces for muscle attachment, and protection
-Hydrostatic
-muscular hydrostat
-exoskeleton
-endoskeleton
Hydrostatic skeletons
-muscular force developed by contracting against fluids
ex)how earthworms (annelids) move, tube feet in echinoderms(sea stars)
Muscular hydrostat
-movement achieved via muscle action (no bones, cartilage, or fluid for support): complex muscle arrangments required.
ex) trunks, tongues
Exoskeletons
-surrounds the body as a rigid, hard case
-interior surfaces are sites of muscle attachment
-animals must molt periodically to grow
-area/mass ratio does not support large body size
Endoskeletons
-internal skeletons to which muscles attach
-made of cartilage and bone both of which are living tissues
-an efficient framework for muscle attachment; continuous growth possible
Ball and socket
type of joint
-rotates in two planes
-eg) hip, large range of motion but requires stabilization
Hinge
joint type
-move one plane
eg)knee, limited range of motion but stronger and more stable
Gliding
joint type
-surface slides
-lateral veterbral joins
-eg)spine, allows flexibility while maintaining alignment
Combination
join type
-multiple join types
eg)mammal jaw, important for chewing
Limb movement
-muscles exert forces on joints, thereby moving limbs
-because muscles can only contract, muscle arrangement is typically antagonistic(one pulls one way, the other pulls the other.
Skeletal muscle(voluntary)
-long, multinucleate, striated cells(vertical lines)
-fast-acting, cerebral control
-attached to skeletal elements (by tendons to bones)
Smooth muscles(involuntary)
-long, unstriated(no vertical lines),uninucleate cells
-slow acting; autonomic control
-walls of blood vessels, alimentary canal, ect.
Cardiac muscle
-uninucleate, striated cells
-fast acting; autonomic control
-restricted to the heart
-cells function as a single unit(myocardium)
Levels of muscle
Bone, tendon, muscles with fascicles (which many muscle fibers, which are made of myofibrils, which are made of myofilaments
Myofilaments
Actin-thin filaments(lighter part)
myosin-thick filaments(darker)
Striated cells
Striations are the result of the uniform arrangement of myofilaments
-thin filaments are anchored by dense structures called z-lines
-a myofibril unit called a sarcomere, extends between two successive z-lines
When does muscle contraction occur
When myofilaments slide past one another, drawing the Z line toward the center of the sarcomere
note that myofilaments do not contract whereas myofibrils do
Steps of muscle contraction
1)ADP and P1 attached to myosin head,
2)allows myosin heads to bind to actin,
3)causing the actin head to deform, pulling the actin filament toward the center of the sarcomere. ADP and p1 are released.
4)Binding of new ATP molecule to muslin head to detach the link
5)Cleavge of ATP into ADP+P1 returns head to original shape
MYosin is a motor protein that can convert chemical energy(ATP) into mechanical energy
Nerves timulate muscle contractons
Skeletal muscles are under cerebral control,
1)when a motor neuron delivers an electrochemical impulse to a muscle
2)the neurotransmitter acetylcholine is released across synapses. This stimulate muscle to produce an electrochemical impulse
3)impulse is carried into muscle fibers via T tubules
4)impulse stimulates sarcoplasmic reticulum to released Ca++
Actin
When muscles are relaxed that means the myosins head cant bind to actin because of
-tropomyosin-blocks myosin heads from binding to actin
-for a muscle to contract, tropomyosin must move out of the way. This is controlled by troponin, a regular protein complex
-When nerves signal muscles to contract, Ca++ is released from the sarcoplasmic reticulum. Ca++ binds to troponin, which alters the configuration of the troponin-tropomyosin complex and allows the myosin head to bind with actin.
Tropomyosin, troponin
tropomyosin
tropomyosin-blocks myosin heads from binding to actin
troponin
for a muscle to contract, tropomyosin must move out of the way. This is controlled by troponin, a regular protein complex
What is needed to break the cross-bridge between actin and myosin?
ATP
The size of a muscle response depends on
1) motor unit- a motor neuron plus all the muscle fibers contracted by the axonal branches of the motor neuron
2)The number of motor units recruited- precise contractions require smaller motor units than large forceful contractions
-most muscles contain motor units in a variety sizes which are selectively activated by the nervous system
