Musculoskeletal system

-Hydrostatic -muscular hydrostat -exoskeleton -endoskeleton

-muscular force developed by contracting against fluids ex)how earthworms (annelids) move, tube feet in echinoderms(sea stars)

-movement achieved via muscle action (no bones, cartilage, or fluid for support): complex muscle arrangments required. ex) trunks, tongues

-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

-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

type of joint -rotates in two planes -eg) hip, large range of motion but requires stabilization

joint type -move one plane eg)knee, limited range of motion but stronger and more stable

joint type -surface slides -lateral veterbral joins -eg)spine, allows flexibility while maintaining alignment

join type -multiple join types eg)mammal jaw, important for chewing

-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.

-long, multinucleate, striated cells(vertical lines) -fast-acting, cerebral control -attached to skeletal elements (by tendons to bones)

-long, unstriated(no vertical lines),uninucleate cells -slow acting; autonomic control -walls of blood vessels, alimentary canal, ect.

-uninucleate, striated cells -fast acting; autonomic control -restricted to the heart -cells function as a single unit(myocardium)

Bone, tendon, muscles with fascicles (which many muscle fibers, which are made of myofibrils, which are made of myofilaments

Actin-thin filaments(lighter part) myosin-thick filaments(darker)

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 myofilaments slide past one another, drawing the Z line toward the center of the sarcomere note that myofilaments do not contract whereas myofibrils do

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

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++

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-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

ATP

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