Basics of Muscular System

1. Movement-skeletal & smooth muscle aid in movement or bones and fluids

2. Posture maintance-skeletal muscles contract to maintain the body in a sitting or standing position

3. joint stabilization-tendons that cross over joints stabilize joint as the muscle tone (constant low level contraction) places tension on the tendon

4. heat generation-muscular contractions generate heat influencing body temperature

1. able to contract - when long cells shorten with a pulling force created that contracts the muscle; may cause movement or stabilization

2. able to extend - at the end of a contraction the muscle may return to its original length by relaxing or extended with the aid of an opposing muscle

3. able to become excitable - muscle cells respond to nerve impulses by contraction

4. elasticity - muscles may be stretched beyond its normal size and recoil back to its normal size

skeletal muscle, cardiac muscle, and smooth muscle

• - multinucleated
• - striated
• - voluntary muscle that attaches to bones and causes skeletan to move

• - binucleated
• - branched
• - striated involuntary muscle that makes up the wall of the heart

non-striated involuntary muscle that assists in the movement of internal viscera

- has capacity to stretch widely and contract powerfully

the outer-most layer that is a sheath of dense connective tissue that externally surrounds the entire muscle

bundles within the muscle that is surrounded by a sheath of fibrous connective tissue called perimysium

a sheath of fibrous connective tissue with fascicles in it

a sheath of reticular fibers that surrounds the bundles within the fascicles

epimysium, perimysium, and endomysium

• - help to organize a muscle
• - extend out of the muscle area to join ligaments
• - help to transfer the contracting force of the fiber over to the bone so the joint is moved

• nerves supply the excitability signals
• blood vessels bring in nutrients & remove waste

origin - side of a muscle that attaches to a bone that does not move when the muscle contracts

insertion - the joint it crosses wioll move when the muscle contracts.

Note: insertion moves toward its origin

lie on the sides of the cell right below the sarcolema (cells membrane)

cells membrane (same as plasma membrane, but the term is sarcolema for muscles)

basic contraction unit formed by the arrangement of thin myofibrils called actin and a thick myofibril called myosin

made up of sarcomeres and contain both actin and myosin

actin is thin and myosin is thick

protein strands that make up myofibrils

where the sarcomere boundary is at. distance between a z line is the sarcomere. Actin extends from the z line to the middle of the sarcomere. In the middle of the sarcomere and in between actin strands lies myosin strands.

the myosin length, including the area where actin and myosin overlap, is the A-band

is where only myosin is present

the region where only actin is present

the m-line is down the middle of the sarcomere

• 1. Muscle fibers (muscle cell)
• 2. Myofibrils
• 3. Myofilaments

the visible stripes result from the arrangement of myofibrils in the sarcoplasm

explains how a muscle contraction happens

by the release of calcium from the terminal cisternae once a nerve impulse is received

calcium ions bind to troponin on actin where the troponin-tropomyosin complex moves exposing the myosin binding sites.

provides power for myosin to move by "energizing" the molecule and changing its conformation (cocked position)

attaches to the actin filament (cross bridge) and in a swivel action pulls the actin filament (power stroke).

binds the myosin head causing it to release actin and return to a ckocked position.

the myosin binds multiple times pulling towards the center further and further down the actin strand. Ad the filaments slide past each other, the overall size shortens.

the released calcium is re-absorbed by the terminal cisternae

Z lines come closer to each other

I and H bands become smaller

A band and M line remain the same

after a contraction, the muscle can be stretched to its original position by the action of an opposing muscle

molecules in sarcomeres that resist overstretching and attach to myosin

smooth ER of muscle cells (muscle fibers) that run longituninal around myofibrils. It stores cacium which are released for contraction and reabsorbed

a continuation of a sarcolemma is a triad

high in myoglobin content and in mitochondria & is vascularized. Requires good oxygen and is not easily fatigued. these fibers do not generate a lot of power

low myoglobin content and in mitochondria larger in diameter. greater capability to produce power.

intermediate in all aspects between red and white

myocardium is the muscle of the heart wall and contracts to pump blood.

by cell junctions called intercalated discs and have a branching pattern. Each cell has one-two nuclei in the center with sarcomeres as which makes the tissue looks striated.

• -blood vessel walls
• -respiratory tract
• -digestive tubes
• -urinary organs
• -reproductive organs
• -the eye

• Note: these layers have fibers running perpendicular to each other. As they alternate contractions they shorten and constrict the organ
• 1. longitudinal layer (parallel to the axis)
• 2. circular layer (perpendicular)

• - no striations and no sarcomeres
• - calcium ions signal contraction & forces are not high
• - can contract for a long time before fatiguing

disorder in which muscle is destroyed and replaced with connective tissue (diagnosed during childhood)

muscle degeneration from pelvis to cranium, predominantly in men usually living to 20 years old.. It is related to the lack of production of a protein that influence cell structure

chronic pain syndrome of lower back or neck muscles that affects 2% of people, mostly omen, treated with antidepressants, exercise, and pain relievers. Not truly a muscle disorder

• cardiac muscle - week 3 of development
• skeletal muscle - week 7 of development

skeletal - once formed (does have limited regerated capacity in case of injury though)

cardiac - by age 9

smooth - divides as needed & has great regenerative ability

called sarcopenia that is reversible with exercise

muscle tissue is replaced with connective tissue as one ages