Chapter 10 - Muscular Tissue

Function of muscle tissue

-Create motion - muscles work with nerves, bones, and joints to produce body movements

-Stablize body positions and maintain posture

-Store substances within the body using sphincters

-Move substances by contractions

-Generate heat through thermogenesis

Function of skeletal muscle

Movement, heat, and posture

Apperance of skeletal muscle

Striated, multi-nucleated (eccentric), fibers parallel

Function of Cardiac muscle

pump blood continuously

Apperance of cardiac muscle

Striated, one central nucleus

Function of smooth muscle

Peristalsis, blood pressure, pupil size, erects hair

Apperance of smooth muscle

No striations, one central nucleus

Fascia

connective tissue that surround and protect muscular tissue

-holds muscles with similar functions together and carriers nerves and vessels that support the muscle cells

Epimysium

circles entire muscle

-rectural fibers

Perimysium

circles certain groups

-dense irregular

Endomysium

individual muscle fibers- outside plasma membrane

-dense irregular

Sacrocoplasm

chocked full of contractile proteins arranged in myofibrils

Sarcomere

An arrangment of thick and thin filaments sandwiched between two Z discs

Muscle contractions occurs in the ---------

Sarcomeres

Z discs

Narrow, plate-shaped regions of dense material that separate one sacromere from the next

A band

Dark, middle part of sacromere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments

I band

Lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z discs passes through center of each band

H zone

Narrow region in the center of each A band that contains thick filaments but no thin filaments

M line

Region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere

Step 1 of Sliding Filament Mechanism

ATP hydrolysis

Myosin heads hydrolyze ATP and become reoriented and energies

Step 2 of Sliding Filament Mechanism

Attachment

Myosin heads bind to actin, forming crossbridges

Step 3 of Sliding Filament Mechanism

Power stroke

Myosin crossbridges rotate toward center of the sacromere

When power stroke happens, ADP is released- cause release of energy

Step 4 of Sliding Filament Mechanism

Detachment

As myosin heads bind ATP, the crossbridge detach from actin

Happens at the end of power stroke, Thick and thin filaments are no longer connected

Rigor Mortis

After death... Release of calcium. No more atp. Crossbridges stay in place because no calcium will break down

acetylcholensterase

breaks down ACh after a short period of time

Acetylcholine ACh

Conscious though (to move a muscle) results in activation of a motor neruon, and release of this

Motor end plate

The plasma membrane on the 'far side' of the NML belongs to the muscle cell

Oxygen Debt or "Excess Post-Exercise Oxygen Consumption" (EPOC)

The amount of O2 repayment required after exercise in skeletal muscle to:

-Replenish ATP stores

-Replenish creatine phosphate and myoglobin stores

-Convert lactic acid back into pyruvate so it can be used in the Krebs cycle to replenish ATP

Motor unit is composed of

a motor neuron plus all the muscle cells it innervates

High precision-motor unit

Fewer muscle fibers per neuron

Laryngeal and extraocular muscles (2-20)

Low precision- motor unit

Many muscle fibers per neruon

Thigh muscles (2,000-3,000)

latent period

a brief delay. as the AP sweeps over the sarcolemma and Ca2+ ions are released from the SR

Slow oxidative fibers (SO)

Small, appear dark, are the least powerful type. They are very fatigue resistant

-Used for endurance like walking

Fast oxidative-glycolytic fibers (FOG)

intermediate in size, appear red-pink, and are moderately resistant to fatigue

-Used for most weightlifting activities

Fast glycolytic fibers (FG)

large, white, and powerful

-Suited to intense anaerobic activity of short duration

Isotonic contractions results in

movement

Concentric isotonic

a type of muscle contraction in which the muscle shorten while generating force

Eccentric isotonic

Contraction in which muscle tension is less than the resistance (the muscle lengthens)

Isometric contractions results in

no movement

-muscle force and resistance are equal

-supporting objects in a fixed position and posture