Skeletal and Muscular Systems

Powerpoint #2Unit 8 – Chapters 36

Working together to create movement

Skeletal System

Structures:

Bones

Cartilage

Ligaments

Functions

Supports body

Protects internal organs

Allows for movement

Stores mineral reserves

Provides a site for blood cell formation

• How many bones in a human Skeleton?• 206

• How many in babies?• ~ 300

• Axial Skeleton: spine, ribcage, skull

• Appendicular: arms, legs, pelvic girdle, shoulders

• What are bones?• A solid network of living cells and

protein fibers that are surrounded by deposits of calcium salts

Bones: 3 Parts Spongy bone

•Not soft or spongy• Very strong• Structure resembles the supporting structure of bridges. • Strong but lightweight

Compact bone:

• Very dense (no spaces like spongy bone)• Outer portion of bone• Contains Haversian canal for veins and arteries to run through

Haversian Canals

Bone Marrow:•Soft tissue•Found in bone cavities•Yellow Marrow: fat cells•Red marrow: •makes red blood cells, platelets and most white blood cells• ~1/2 red marrow turns into

yellow in adults• If severe blood loss, some

yellow can turn back to red

Development of bone:• Cartilage: Tough, elastic, connective

tissue• Found in: ears, between bones,

larynx, and other various places.

Development of Bone• http://www.youtube.com/watch?v=78RBpWSOl08

• Ossification: cartilage replaced by bone

• Osteoblasts:cells that build bone

• Osteoclasts:cells that break down bone• Growth Plates (epiphyseal plates): found in most

long bones (leg and arm bones) cartilage continues to grow here until completely replaced by bone during adolescence=stop growing

Types of Joints -Ball and socket

Types of Joints- Hinge

Types of Joints- Saddle

Types of Joints

• Pivot

Structure of Joints

Anterior Cruciate Ligament

Fractures

Structure of Joints• Bursa: small fluid-filled sac• provides a cushion between bones

and tendons and/or muscles around a joint.

Bursitis

Arthritis

Arthritis

Rheumatoid arthritis Osteoarthritis

Compare Osteoarthritis and normal knee

Total Knee Replacement

Total Knee Replacements

Total Knee Replacement

Osteoporosis

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Types of Muscle

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The human body is comprised of ~640-850 muscles (sources varying regarding what is defined as different parts of a single muscle or as several muscles)

makes up 30-35% (in women) and 42-47% (in men) of body mass.

Three types of muscle:

Skeletal muscle

Smooth muscle

Cardiac muscle

A. Skeletal (Striated) Musclemoves various parts of the skeletonvoluntary controlRepeated activation of a skeletal muscle

can lead to fatigueCan have many nuclei Striated (striped appearance)

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Skeletal Muscles work in PAIRSBending or straightening of elbow

requires the coordinated interplay of the biceps and triceps muscles

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B. Smooth Muscle

Located in the blood vessels, the

respiratory tract, the iris of the eye,

the gastro-intestinal tract

contractions are slow and uniform

Is fatigue resistant

Activation is involuntary

Has one nucleus

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C. Cardiac Muscle

Functions to provide the contractile activity of the

heart

Activation is involuntary (like smooth muscle)

Can have 2 nuclei, usually has 1

Is very fatigue resistant

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myofibril muscle fiber muscle fiber bundle

Components of skeletal muscle

Muscle Fibers: Cylinder-shaped cells that make up skeletal muscle

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Made of myofibrils which is made up of a number of

myofilaments Two types of protein myofilaments:

- Actin: thin filament

- Myosin: thick filament

Divided into functional units called sarcomeres,

seperated by region called Z lines.

Group of fibers activated via same nerve: motor unit

High microscope magnification of sarcomeres

within a myofibril

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Muscle Contraction

Muscle Contraction Steps

1. Myosin head attaches to binding site on actin forming a cross bridge

1. After the cross bridge is formed the myosin head bends, called a power stroke, pulling on the actin filaments and causing them to slide.

1. Myosin attached to actin until another ATP binds causing it to release (explains rigor mortis)

1. Muscle contraction is a little like climbing a rope. The cross bridge cycle is: grab -> pull -> release, repeated over and over

Control of Muscle Contraction (animation)

1. Muscle cells are "shocked” by nerve impulses from motor neurons.

2. Neurotransmitters (acetylcholine) are released by neuron, stimulating muscle fiber to release Ca2+

3. When a muscle is relaxed, tropomyosin blocks cross-bridges.

4. When Ca2+ high enough, it binds to troponin, displacing tropomyosin, exposing myosin binding sites on actin.

5. Myosin can now form crossbridge

Control of Muscle Contraction (Neuromuscular junction)

Tendons

Connect Muscle to Bone

Tendon Ruptures

Terminology

Sprain: when a ligament is stretched too much

Strain: when a muscle or tendon is stretched too much