A&P Chapter 10

slow oxidative fibers functional characteristics

•capacity for generating ATP is high and done by aerobic respiration •rate of ATP hydrolysis by myosin ATPase is slow •slow contraction velocity •high fatigue resistance •lowest amount of creatine kinase •low glycogen stores •first in recruitment •fibers are abundant in postural muscle such as those of neck •primary functions of fiber is to maintain posture and aerobic endurance activities

fast oxidative glycolytic fibers functional characteristics

•capacity for generating ATP is intermediate and done by both aerobic respiration and anaerobic glycolysis •fast rate of ATP hydrolysis by myosin ATPase •fast contraction velocity •intermediate muscle resistance •intermediate amount of creatine kinase •intermediate glycogen stores •second in order of recruitment •location where fibers are abundant is lower limb muscles •primary functions of fiber is walking, sprinting

fast glycolytic fibers

•capacity for generating ATP is low and done by anaerobic glycolysis •fast rate of ATP hydrolysis by myosin ATPase •fast contraction velocity •low fatigue resistance •highest amount of creatine kinase •high glycogen stores •third in order of recruitment •location where fibers are abundant is extra ocular muscles •primary functions of fiber is rapid, intense movements of short duration

slow oxidative fibers structural characteristics

•large amount of myoglobin content •many mitochondria •many capillaries •red color

Fast oxidative-glycolytic fibers structural characteristics

•large amount of myoglobin content •many mitochondria •many capillaries •red-pink color

regeneration of muscle tissue

•mature skeletal muscle fibers cannot undergo mitosis •skeletal muscle fibers cannot divide and have limited powers of regeneration; cardiac muscle fibers can regenerate under limited circumstances; and smooth muscle fibers have the best capacity for division and regeneration

skeletal muscle

•microscopic appearance and features: long cylindrical fiber with many peripherally located nuclei; unbranched; striated •location: most commonly attached by tendons to bones •fiber diameter: very large (10-100) •connective tissue components: endomysium, perimysium, and epimysium •fiber length: very large (100 um-30cm=12 inches) •contractile proteins organized into sarcomeres: yes •sarcoplasmic reticulum: abundant •transverse tubules present: yes, aligned with each A-I band junction •junctions between fibers: none •auto

fast glycolytic fibers structural characteristics

•small amount of myoglobin content •few mitochondria •few capillaries •white (pale) color

H zone

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

Filaments (myofilaments)

Contractile proteins within myofibrils that are of two types: thick filaments composed of myosin and thin filaments composed of actin, tropomyosin, and troponin; sliding of thin filaments past thick filaments produces muscle shortening.

I band

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

muscle fiber (cell)

Long cylindrical cell covered by endomysium and sarcolemma; contains sarcoplasm, myofibrils, many peripherally located nuclei, mitochondria, transverse tubules, sarcoplasmic reticulum, and terminal cisterns. The fiber has a striated appearance.

functions of muscular tissue

Producing body movements, stabilizing body positions, storing and moving substances within the body, and generating heat.

Tropomyosin

Regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from binding to actin.

On the basis of their structure and function, skeletal muscle fibers are classified as

Slow oxidative (SO) fibers Fast oxidative-glycolytic (FOG) fibers Fast glycolytic (FG) fibers

Most skeletal muscles contain ________.

a mixture of all three fiber types. their proportions vary within the typical action of the muscle

troponin

a regulatory protein that is a component of the thin filament. When calcium ions (Ca2+) bind to troponin, it undergoes a change in shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin

Actin

contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction

excitation-contraction coupling

This concept connects the events of a muscle action potential with the sliding filament mechanism

Myosin

contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules of thin filament during muscle contraction

Myofibril

Threadlike contractile elements within sarcoplasm of muscle fiber that extend entire length of fiber; composed of filaments.

Muscle proteins

contractile, regulatory, structural

A band

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

Properties of Muscular Tissue

electrical excitability, contractility, extensibility, elasticity

what fiber does a shot putter most heavily rely on?

fast glycolytic fibers

what fiber does a soccer player most heavily rely on?

fast oxidative glycolytic fibers?

cardiac muscle

location: heart function: pump blood appearance: one nucleus/ striated/ intercalated discs control: involuntary

skeletal muscle

location: skeletal function: move bones appearance: multi-nucleated/ striated control: voluntary

Visceral (SMOOTH) muscle

location: various organs (GI tract) functions: various functions (peristalsis) appearance: one nucleus/ NO striations control: involuntary

contractile proteins

myosin and actin

Z disc

narrow, plate-shaped regions of dense material that separate one sarcomere from the next

muscle contraction

occurs because cross-bridges attach to and "walk" along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the center of a sarcomere. As the thin filaments slide inward, the Z disc come closer together, and the sarcomere shortens

skeletal muscle

organ made up of fascicles that contain muscle fibers (cells), blood vessels, and nerves: wrapped in epimysium

M line

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

Contraction and relaxation of skeletal muscle fibers

section ⬇️

with few exceptions, muscles develop from mesoderm

skeletal muscles of the head and limbs develop from general mesoderm. other skeletal muscles develop from the mesoderm of somites

3 types of muscle tissue

skeletal, cardiac, smooth

what fiber type does a marathoner most heavily rely on?

slow oxidative fibers?

contraction cycle

the repeating sequence of events that causes the filaments to slide 1. Myosin ATPase hydrolyzes ATP and becomes energized 2. the myosin head attaches to actin, forming a cross-bridge 3. the cross-bridge generates force as it rotates toward the center of the sarcomere (power stroke) 4. binding of ATP to the myosin head detached it from actin. the myosin head again hydrolyzes the ATP, returns to it's original position, and binds to a new site on actin as the cycle continues

structural proteins

titin, nebulin, alpha-actin, myomesin, dystrophin

Why do you continue to breathe heavily for a period of time after stopping exercise?

to "pay back" your oxygen debt The extra oxygen goes toward: 1. replenishing CP stores 2. converting lactate into pyruvate 3. reloading O2 onto myoglobin

regulatory proteins

troponin and tropomyosin

Muscles constitute about ____ our body weight

40-50%

Actinin

Structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules.

Titin

Structural protein that connects Z disc to M line of sarcomere, thereby helping to stabilize thick filament position; can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils.

Myomesin

Structural protein that forms M line of sarcomere; binds to titin molecules and connects adjacent thick filaments to one another.

Dystrophin

Structural protein that links thin filaments of sarcomere to integral membrane proteins in sarcolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers; thought to help reinforce sarcolemma and help transmit tension generated by sarcomeres to tendons.

Nebulin

Structural protein that wraps around entire length of each thin filament; helps anchor thin filaments to Z discs and regulates length of thin filaments during development.

The NMJ

The events at the NMJ produce a muscle action potential: •voltage-gated calcium channels in a neurons synaptic end bulb open, resulting in an influx of calcium. this causes exocytosis of a neurotransmitter into the synaptic cleft • NT binds to ligand-gated Na+ channels on the motor endplate, which causes an influx of Na+ into the muscle • this depolarizer the muscle and results in Ca2+ release from the sarcoplasmic reticulum •NT (neurotransmitter) gets broken down by acetylcholinesterase

length-tension relationship

The force of a muscle contraction depends on the length of the sarcomeres prior to the contraction

Motion results from

alternating contraction (shortening) and relaxation of muscles

Fascicle

bundle of muscle fibers wrapped in perimysium