11.1 - 11.3

alpha-actinin

- found in the Z disc - binds to actin molecules of the thin filament and to titin

Myosin

-A contractile protein present in muscle fibers that aids in contraction and makes up the majority of muscle fiber -functions as a motor protein

H zone

-thick filaments only -In the center of A bands

I band

-thin filaments only -located at the end of A bands -Z disc pass through the center -Isotropic

Most plentiful proteins in skeletal muscles

1. actin 2. myosin 3. Titin

Which molecules has a ATP-binding site? 1) Tropomyosin 2) troponin 3) myosin 4) actin

3) myosin

What is the neurotransmitter released at the neuromuscular junction?

ACh

Myosin heads have binding sites for _____.

ATP and actin

Which types of muscles have Transverse Tubules

Cardiac and skeletal

3 proteins myofibrils are built from

Contractile protein Regulatory protein Structural protein

4 Special muscle properties

Electrical Excitability Contractility Extensibility Elasticity

Does ACh have a excitatory or inhibitory effect on neuromuscular transmission?

Excitatory

True or false ? Myosin are known as thick filaments

False

True or false? Tropomyosin is known as thin filaments

False

True or false? To initiate muscle contraction Ca2+ binds to tropomyosin

False. Binds to troponin

True or False ? Muscle fibers continue to undergo division once fusion of myoblast has occurred

False. Once fusion has occurred, the muscle fibers loses its ability to undergo cell division

What are actin molecules known as ?

G actin for globular porteins

The storage form of glucose that is present in muscles cells is known as ?

Glycogen

During an iotonic muscle contraction what happens to the Hzone ?

It get shorter

True or false ? A thick filament contains about 300 myosin molecules

True

What stimulates a muscle fiber in order for it to contract ?

a somatic motor neuron

Sarcomere

a structural unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band.

Extensibility

ability of muscle to stretch without being damaged

Electrical Excitability

ability to respond to certain stimuli by producing action potentials

Main component of the thin filament

actin

2 types of contractile proteins

actin and myosin

What does a thin filament contain ?

actin, troponin, tropomyosin

Where are sarcomeres found in which types of muscle?

cardiac and skeletal

Traid

formed by T tubules & 2 terminal cisternae

contractile proteins

generate force during contraction

regulatory proteins

help switch the contraction process on and off

Nebulin

helps maintain alignment of the thin filaments in the sarcomere

Sarcolmma

is the plasma membrane of a muscle fiber

Dystrophin

links the thin filaments to the integral proteins of the sarcolemma

satellite cells

myoblasts that persist in mature skeletal muscle

What happens during the power stroke of the contraction cycle?

myosin head pivots from 90 degrees angle to 45 degree angle

The synapse between a somatic motor neuron and a skeletal muscle fiber is known as .....

neuromuscular junction (NMJ)

troponin

regulatory protein that binds to actin, tropomyosin, and calcium

Filaments

smaller fibers located with in the myofibrils

M line

supporting proteins that hold the thick filaments together in the H zone

What happens at the onset of contraction ?

the sarcoplasmic reticulum release calcium ions into the sarcoplasm

2 types of filaments in the myofibril:

thick and thin (used for contraction)

structural proteins

titin, myomesin, nebulin, dystrophin

Regulatory proteins 2 types

tropomyosin and troponin

F actin

A fibrous protein made of a long chain of G actin molecules twisted into a helix; main protein of the thin myofilament

Tropomyosin

-A protein of muscle that forms a complex with troponin regulating the interaction of actin and myosin in muscular contraction -each tropomyosin molecule only covers 7 G actin molecules

contraction cycle steps

-ATP hydrolysis -Attachment of myosin to actin -Power stroke -Detachment of myosin from actin

Glycogen

-a large polysaccaride consisting of thousands of glucose molecules covalently linked together -serves as a storage form of glucose, can be used for ATP synthesis

Sarcoplasm

-cytoplasm of a muscle fiber -surrounded by the sarcolemma -have mitochondria inside which produce large amounts of ATP for muscle contraction

A bands

-dark bands from the presence of thick filaments -At the end of this band thick and thin filaments over lap -Anisotropic

Myomesin

-found in the M line -binds to titin and thick filaments to connect them together at the M line

titin (gigantic)

-helps stabilize the position of the thick filament -accounts for much of the extensibility & elasticity of myofibrils -Spans half a sarcomere, from Z disc to M line

Z disc

-separates one sarcomere from the next -Narrow, plate-shaped regions of dense protein material

Myoglobin

-stores oxygen until it is needed by the mitochondria to generate ATP -a red colored oxygen binding protein that is found only in a muscle

Transverse tubules (T-tubules)

-tiny invaginations or tunnel in from the plasma membrane -filled with extracellular fluid

NMJ 3 components

1) synaptic end bulb of a terminal branch of the somatic motor neuron 2) synaptic cleft 3) motor end plate

sliding filament mechanism

The explanation of how thick and thin filaments slide relative to one another during striated muscle contraction to decrease sarcomere length

Actin

Thin filament of protein found in muscles

Contractility

ability of muscle to contract forcefully when adequately stimulated generating movement & tension

Elasticity

ability of muscle to return to its original length & shape after contraction or extension

NMJ (neuromuscular junction) consists of

axon terminals, synaptic cleft, and junction folds

myoblast

embryonic cell that develops into a cell of muscle fiber

Myofibrils

extend through the sarcoplasm that contractile elements of the skeletal muscle fibers

2 main phases of the skeletal muscle action potential

1) depolarizing phase 2) repolarizing pahse