Ch. 11 Myofibers

Skeletal muscle cells characteristics

= myofibers

contract under voluntary control

• same as striated muscle cells

• arranged in sarcomeres

• attached to bones via tendon

• produce movement

Muscle cells can only contract with

force

• become shorter or thicker

Sarcolemma

plasma membrane of a myofiber

Endomysium

connective tissue that surrounds individual myofiber

Nucleus

houses DNA that codes for protein filaments

Thick filament

myosin

Thin filament

actin

Z - disk

dense region that separates one sarcomere from another

Sarcomere

functional unit within a myofiber, filaments between z-disk

synapse

union between axon terminal and myofiber

axon

long thin projection from a neuron that delivers a neurotransmitter

A

sarcolemma

B

endomysium

C

nucleus of muscle cell

D

thick and thin filaments

E

myelinated axon

F

synaptic knob of axon terminal

G

mitochondria

H

myosin (thick) filaments

I

actin (thin) filaments

J

z-disk

K

sarcomere

A

synapse

B

axon

A

synapse

B

axon

what is this

myofiber

Myofibers

elongated, multinucleated muscle cells that make up skeletal muscle tissue

Origin

where a muscle group attaches to bone thats not involved in major movement during contraction

Insertion

attachment of the muscle group to the bone that is moved during contraction

action

describes what type of movement is generated by the contracting muscle

flexion

bending the elbow

extension

straightening the elbow

abduction

raising arms laterally

adduction

dropping arms to side

medial rotation

toes toward midline (rotation of hip)

lateral rotation

toes away from midline (rotation of hip)

elevation

shoulder shrugs up

depression

dropping shoulder down

pronation

palms down

supination

palms up

dorsiflexion

lifting of toes

dropping of heel

plantarflexion

pointing of toes

eversion

sole of foot away from midline

inversion

sole of foot towards midline

sarcolemma function

plasma membrane of a myofiber

endomysium function

connective tissue that surrounds individual myofibers

nucleus of muscle cell function

houses DNA

codes for protein filaments

myelinated axon function

transmission of action potential travels

synaptic knob of axon terminal function

release neurotransmitter, acetylcholine

• depolarizes muscle cell

• produce contraction

mitochondria function

powerhouse of cell

• produce ATP

myosin function

use ATP energy to

• change shape = produce power stroke of contraction

actin function

have binding sites for myosin

z disk function

dense region

• separates one sarcomere from another

sarcomere function

functional unit in myofiber

• made of filaments between z disk

• generate mechanical force/ movement