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The Skeletomuscular System Bone- brief anatomy, bone formation, disorders Muscular system skeletal- structure, contract PowerPoint Presentation
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The Skeletomuscular System Bone- brief anatomy, bone formation, disorders Muscular system skeletal- structure, contraction, control smooth muscle cardiac muscle Innervation of muscle. Functions of bone (skeleton) Support and protection Blood cell formation

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slide1

The Skeletomuscular System

Bone- brief anatomy, bone formation, disorders

Muscular system

skeletal- structure, contraction, control

smooth muscle

cardiac muscle

Innervation of muscle

slide2

Functions of bone (skeleton)

Support and protection

Blood cell formation

Mineral storage (calcium especially)

Site for muscle attachmentbody movement

slide3

Bones classified by shape: long, short, flat,

irregular, round

Bone enclosed in periosteum, which is continuous

with tendons and ligaments

blood vessels in periosteum

Epiphysis- ends

spongy bone contains red marrow

compact bone, articular cartilage

Diaphysis- middle

compact bone

medullary cavity- contains yellow marrow (fat)

lined with endosteum (squamous epithelium)

slide4

Compact bone

osteocytes within lacunae

arranged in concentric circles called lamellae

This surrounds a central canal; complex is called

Haversian system

Canaliculi connect osteocytes to central canal and

to each other

slide6

Prenatal development

skeleton is mostly cartilaginous

Cartilage cells and then osteoblasts start to

deposit minerals

Cartilaginous disk (epiphyseal disk) remains

in epiphysis

Cells eventually stop dividing

slide7

Adults continually break down and build up bone

Osteoclasts remove damaged cells and release

calcium into blood

Osteoblasts remove calcium from blood and build

new matrix. They become trapped

osteocytes

slide8

Fracture repair

Hematoma- blood clot in space between edges

of break

Fibrocartilage callus- begins tissue repair

Bony callus- osteoblasts produce trabeculae

(structural supprt) of spongy bone and

replace fibrocartilage

Remodeling- osteoblasts build new compact bone,

osteoclasts build new medullary cavity

slide9

Axial skeleton

skull (cranium and facial bones)

hyoid bone (anchors tongue and muscles

associated with swallowing)

vertebral column (vertebrae and disks)

thoracic cage (ribs and sternum)

Appendicular skeleton

pectoral girdle (clavicles and scapulae)

upper limbs (arms)

pelvic girdle (coxal bones, sacrum, coccyx)

lower limbs (legs)

slide10

Joints

Immovable (synarthoses) bones sutured together

by connective tissue: skull

Slightly movable (amphiarthoses) connected by

fibrocartilage or hyaline cartilage:

vertebrae, rib/sternum joint, pubic

symphysis

Freely movable (diarthroses)- separated

ligaments- hold bones together

tendons- muscle to bone

lined by synovial membrane

slide11

Types of freely movable joints

Saddle: carpal and metacarpal bones of thumb

Ball and socket: shoulder and hip joints

Pivot- rotation only: proximal end of radius and ulna

Hinge- up and own movement in one plane:

knee and elbow

Gliding- sliding and twisting: wrist and ankle

Condyloid- movement in different planes but not

rotations: btw metacarpals and phalanges

slide12

Types of movement and examples (with muscles)

flexion- move lower leg toward upper

extension- straightening the leg

abduction- moving leg away from body

adduction- movong leg toward the body

rotation- around its axis

supination- rotation of arm to palm-up position

pronation- palm down

circumduction- swinging arms in circles

inversion- turning foot so sole is inward

eversion- sole is out

slide13

Elevation and depression- raising body part up

or down

Aging and bones

both bone and cartilage tend to deteriorate

cartilage: chondrocytes die, cartilage

becomes calcified

osteoporosis; bone is broken down faster

than it can be built

bones get weak and brittle; tend to fracture

easily

slide14

Skeleton and other systems

Skin makes vitamin D which enhances calcium

absorption

Skeleton stores calcium for muscle contraction,

nervous stimulation, blood clot formation

Red marrow- site of blood cell formation

Calcium levels regulated by

parathyroid hormone and calcitonin

kidneys (can help provide vitamin D)

digestive system (can release calcium

into blood)

slide17

Growth hormone regulates skeletal growth

stimulates cell division in epiphyseal disks

in long bones

Growth stops when epiphyseal disks are

converted to bone

When excess growth hormone is produced in

childhoodgigantism

In adulthood- acromegaly. Bones can’t grow

but soft tissue can

slide20

When muscle contracts, it shortens and causes

movement

Skeletal muscles attached to bones by tendons

Insertion- attachment to more movable bone

Origin- less movable

Refer to slide 13. Flexors and extensors act on

the same joint to produce opposite actions

slide23

Skeletal muscle structure

Connective tissue divides muscle tissue into

fascicles

muscle fibers (myofibers)

myofibrils

myofilaments (actin and myosin)

Each myofiber is formed from several myoblast

cells; myofiber cells have multiple nuclei

slide26

Muscles appear striated

A, I and Z bands appear to change position

relative to each other when muscle

contracts

Each muscle fiber is stimulated by a single

axon terminal from a somatic motor

neuron

Neuromuscular junction- neuron releases

acetylcholine at the motor end plate

in the sarcolemma

slide28

A single somatic motor neuron can produce

an axon with several terminal branches.

Each stimulates a different muscle fiber.

Motor unit- a motor neuron and the muscle

fibers it innervates

slide30

How muscles contract

A bands- thick filaments- myosin

I bands- thin filaments- actin

“Edges” of A band are darker because thin and

thick filaments overlap there

H bands- center of A band; lighter because

thin filaments do NOT extend there

Z bands (disks) define boundaries of the functional

unit, or sarcomere

slide31

Sliding filament theory of contraction

A bands do not decrease in length;

I bands do

Thin filaments slide past thick filaments

How?

Cross bridges extending from myosin to actin

slide34

Detachment of a cross bridge from actin at

end of a power stroke requires a new

ATP to bind to myosin ATPase.

Rigor mortis at death: no ATP is available

ADP remains bound to cross bridges (and thus

actin to myosin)

Muscles remain stiff until they begin to

decompose

slide35

Regulation of contraction

Actin filament associates with troponin and

tropomyosin

Tropomyosin blocks the attachment sites in actin

for the cross bridges when muscle is realxed

To move tropomyosin, troponin interacts with

calcium

slide37

When Ca 2+ binds

troponin, the complex

shifts. The cross

bridges can now bind

to actin. Contraction

can continue as long

as calcium is bound

to troponin.

slide38

How is calcium level in cells regulated?

Calcium is stored in sarcoplasmic reticulum

Released from terminal cisternae by stimulus

from motor neuron

Transverse tubules are continuous with plasma

membrane (sarcolemma). Help conduct

action potentials into the muscle fiber.

slide40

Relaxation of muscle

sarcoplasmic reticulum actively

accumulates calcium

process involves hydrolysis of ATP

(Note: muscle activity requires a lot of ATP)

slide41

Movement of skeletal muscles

Twitch-rapid contraction and relaxation of fibers

Muscle can twitch is response to a single pulse

stronger the shock, stronger the twitch

graded contraction of whole muscle-

depends on number of fibers contracting

Summation of twitches- if rapid enough produces

tetanus

Isometric- muscle exerts tension without

shortening

Isotonic- shortening does occur

slide42

Series-elastic component

Tendons have elasticity

Elastic recoil helps muscles return to resting

length

Length-tension

muscle is at optimum length for contraction

when it is at resting length

slide43

Energy requirements of skeletal muscles

At rest, most energy obtained from fatty acids

Exercise: glycogen and glucose also used

ATP is used for: movement of cross bridges

pumping of calcium into sarcoplasmic

reticulum

(i.e., for contraction AND relaxation)

slide44

Capacity for aerobic exercise

Maximal oxygen uptake (VO2 max)

varies by age, size and sex

Lactate threshold- percentage of maximal oxygen

uptake at which significant increase in lactate

is seen (usually 50-70%; higher in athletes)

Light exercise: most energy derived from fatty acids

At lactate threshold: fatty acids and glucose equally

Heavy exercise: over 60% glucose

slide45

Oxygen debt- oxygen stores in hemoglobin,

myoglobin depleted

How is oxygen debt “repaid”?

Phosphocreatine helps produce more ATP

A lot more phosphocreatine than ATP in

muscle cells

slide47

Not all muscles have the same contraction speed

Slow-twitch- red fibers; lots of myoglobin and

blood supply

Fast-twitch- fewer capillaries and less myoglobin

(white fibers)- anaerobic activity

Intermediate fibers- fast twitch but with high

oxidative capacity. Resistant to fatigue

slide48

A given motor neuron stimulates one type of

fiber.

Muscles used routinely are mostly smaller

with slow-twitch fibers

Fatigue

accumulation of K+ reduces action

potential

accumulation of lactic acid lowers pH

increased H+ concentration may

interfere with other processes?

slide49

Effect of endurance training on muscles

Increased ability to obtain energy from fatty

acids (spare glycogen)

Increased myoglobin, mitochondria

Lactate threshold is raised

Does NOT increase size of muscle (anaerobic

training does)

e.g., weightlifting- increases thickness of myofibrils

and helps build new ones

slide50

Alpha and gamma motoneurons can be

stimulated simultaneously by upper

motor neurons

Gamma motoneurons help maintain muscle tone

Reflexes- unconscious reaction to muscle stretch

(by contraction)

monosynaptic- one synapse within CNS

Golgi tendon organs- disynaptic reflex

monitor tension in tendon

Reciprocal innervation- agonist is stimulated,

antagonist is inhibited

slide51

Upper motor neurons act on descending motor

tract

Alpha motoneuronsextrafusal fibers

bigger and more numerous than intrafusal

myofibrils all along length

this causes muscle contraction

Gamma motoneurons intrafusal fibers

tightens spindles

enhances sensitivity of spindles

slide52

Upper motoneurons usually stimulate both

simultaneously (coactivation)

Alpha motoneurons promote muscle contracting

Gamma motoneurons help maintain muscle tone

Reflexes are produced as an unconscious

response to particular stimuli

Can be simple or complex

Golgi tendon organs monitor tension

summary
Summary
  • Skeletomuscular system provides support for the body
  • Bones provide structure; also important for calcium homeostasis and production of blood cells
  • Skeletal muscles are attached to bones by tendons
  • Muscles are innervated by motor units
slide54

Summary, continued

Functional unit of muscle cell is myofibril

“Sliding filament” mechanism requires ATP

and calcium

calcium influx regulated by nervous system

aerobic and anaerobic respiration supply

ATP for muscle contraction

regulated by different types of muscle

fibers

physical training affects the aspects

of these fibers