chapter 12 muscles pt 1

Muscle Functions

movement and generating force to push

generates heat to keep body warm

Where do skeletal muscles attach?

bones of skeleton

What are cardiac muscles functions?

moves blood through circulatory system

Where are smooth muscles located?

inside organs and blood vessels

function of smooth muscle

propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control

what muscles are striated and multi nuclei?

skeletal muscles

what muscles are striated and single nuclei?

cardiac muscles

what muscles are not striated and single nuclei?

smooth muscles

what muscles originate in the autonomic system?

smooth and cardiac

what muscles only work when activated by motor neurons?

skeletal muskles

which muscles are involantary?

smooth and cardiac

which muscles neurons start in the brain?

skeletal muscles

what muscles make up the most in the body?

skeletal muscles

What connects muscle to bone?

tendons made of collagen fibers

origin of a muscle

end of muscle attached to bone that does not move during contraction

Insertion

attachment to movable bone

flexor

muscle that brings bones together

extensor

muscle that pushes bones away from each other

Do muscles pull or push?

pull

antagonist muscle

muscles cannot push so 1 muscle when activated causes other muscles to relax

satellite cells

Stem cells aiding muscle repair and growth.

fasicles

bundles of muscle fibers

Sarcolemma

plasma membrane of a muscle fiber

sarcoplasmic reticulum

A specialized endoplasmic reticulum in muscle cells that stores calcium ions.

what are muscle fibers made of?

myofibrils

terminal sisternae

enlarged portion of the sarcoplasmic reticulum; part of triad

T-Tubes

part of SR that come down and meet up with terminal cysternae to open up ryanadine channels; bring AP down to SR

where does action potential start in muscle cells

t-tubes

Myofibrils

Microscopic protein filaments that make up muscle cells.

What are thick filaments made of?

myosin

2 light chains of myosin

makes neck of myosin stiff and regulates muscle contraction

where are the head and tail of myosin located

headsticks out on the ends of the fiber

tails are in the middle of the fiber

thin filaments

actin

Myosin Crossbridge

Head of the myosin molecule that contains ATP binding sites and attaches to actin during muscle contraction

Sarcomere

Repeating units of light and dark bands

Z disk

protein fibers that form attachment site for f- actin

I band

light band thin filament only

orientation of z disc to I bands

z disc runs through each i band on both sides

A BAND

has both thick and thin filaments

what is the darkest region of sarcomere

a band

specifically, where in the A band is the darkest region

where thick and thin filaments overlap

H zone

The region at the center of an A band of a sarcomere that is made up of myosin only

m line

middle of sarcomere

where do thick filaments attach to on a sarcomere

m line

what part of myosin attaches to m line

tails

what is Titin

A series elastic component protein responsible for allowing the sarcomere to stretch and recoil

where does titin extend from

Z disk to M line

function of titin

holds the thick filaments in place, thus maintaining the organization of the A band, and helps the muscle cell spring back into shape after stretching.

Nebulin

Holds F-actin strands together

where is nebulin located in

inside of thin filaments and attaches from z disc

function of nebulin

Stabilizes the I band

it binds to actin filaments along their entire length.

How would muscle striations look different during contraction then in the relaxed state?

The light part would shorten, but the dark part would stay the same.

During contraction, the thin filaments slide inward, so the I band shortens.

The length of the thick filaments does not change, so the A band remains constant in length.

sliding filament theory

actin filaments slide toward each other during muscle contraction, while the myosin filaments are still

i band during contraction

shortens

A band during contraction

stays the same

H zone during contraction

shortens

Overlap of myosin and actin

during contraction

increases

myosin cross bridges

attach to thin filament and force thin filament toward center of sarcomere

what causes force for contraction in muscles

movement of myosin cross bridge

at rest what prevents myosin from fully binding to actin

tropomyosin

what type of interaction is myosin and actin when there is tropomyosin

weak interactions

when active what causes the tropomyosin to move away from actin

Ca2+ binding to troponin

power stroke

action of myosin pulling actin inward (toward the M line)

1. Rigor State

Myosin tightly bound to actin without ATP.

No ATP is attached.

2. ATP Binding to Myosin

Myosin detaches from the actin filament.

ATP hydrolysis

Myosin turns ATP → ADP + Pi.

Myosin shifts into a cocked position, storing potential energy.

Myosin now weakly binds to a new position on actin.

cocked position

High-energy state of myosin head before power stroke.

Ca2+ binds to troponin

power stroke

tropomyosin is pulled away so that myosin binding sites on actin are uncovered.

strong binding

what happens at end of contraction cycle

myosin releases adp and goes back to weak contraction