Human Physiology Exam 3

striated

have dark and light bands under light microscope; cardiac and skeletal muscle

Unstriated

no banding, smooth muscle

Voluntary

skeletal muscle (somatic innervation)

Involuntary

cardiac and smooth (autonomic innervation)

Skeletal muscle

many muscle fibers lying parallel to one another, bundled together by connective tissue

Sacromeres

functional unit of the myofibril, found between two Z-lines,

What do sarcomeres consist of?

actin and myosin

A band

myosin (thick) filaments stacked along with parts of the actin (thin) filaments

H zone

myosin in center of A band devoid of actin

M line

extends vertically down the center of the A band; provides support

I band

has section of actin that doesn't project into A band

Myosin

two identical subunits shaped like a gold club, heads form cross bridges, tail ends are intertwined, orientated to center

Actin

spherical; joined into 2 twisted strands to form filament backbone, each molecule has binding site for myosin cross bridge

Tropmyosin

thread-like, covers the actin binding sites, preventing their association with myosin cross bridges

Troponin

has three polypeptide units for binding to tropomyosin, actin and Ca ions

What happens to the H zone and the I band during muscle contraction?

decrease

What happens to the A band during muscle contraction?

unaffected

What happens to the Z lines in muscle contraction?

come closer

What happens to the sarcomere and the muscles in muscle contraction

sarcomere shortens and so muscle shortens (contracts)

What fibers are slow oxidative?

type I

what fibers are fast oxidative?

type IIa

What fibers are fast-glycolytic?

type IIb

What contraction has muscle tension developed is less than its opposing load?

Isometric contraction

What contraction has muscles that cannot shorten and lift the object with that load

Isometric contraction

What contraction has no change in length, despite developing tension?

Isometric contraction

What contraction has muscle tension developed is greater than its opposing load?

Isotonic contraction

What contraction has muscles that usually shorten and lifts an object?

Isotonic contraction

What contraction has muscles that change length, but maintains a constant tension throughout the period of shortening?

Isotonic contraction

What contraction has two types of muscles?

Isotonic contraction?

What is concentric?

muscle shortens

What is eccentric?

muscle lengthens