AP Lec muscles

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

ATPase

- an enzyme that hydrolyzes ATP

Aponeurosis

. can be described as a broad flat tendon connecting a muscle to bone or muscle to another muscle. It may sometimes be referred to as fascia.

Contraction cycle steps

1. ATP hydrolysis 2. Attachment of myosin to actin to form cross-bridges. 3. Power stroke 4. Detachment of myosin from actin.

Acetylcholine

A neurotransmitter that enables learning and memory and also triggers muscle contraction

Acetylcholinesterase

An enzyme that breaks down the neurotransmitter acetylcholine.

Detachment of myosin from actin

At the end of the power stroke, the cross-bridge remains firmly attached to actin until it binds another molecule of ATP. As ATP binds to the ATP-binding site on the myosin head, the myosin head detaches from actin.

Myoglobin

Binds oxygen molecules that diffuse into muscle fibers from interstitial fluid. It releases oxygen when it is needed by the mitochondria fro ATP production.

Ca2+

Calcium ions

Sarcomeres

Compartments within a muscle fiber containing thin and thick filaments. Goes from one Z disc to the next.

H zone

Contains thick but not thin filaments.

A band

Darker middle part of the sarcomere, which extends the entire length of the thick filaments.

Myosin binding site

Each actin molecule contains a _____ where a myosin head can attach.

Endomesyium and sarcolemma

Endomysium is a C.T. that wraps around sarcolemma

3 layers of C.T. that extend from the fascia to protect and strengthen skeletal muscle

Epimysium, Perimysium, and Endomysium

Sarcoplasmic reticulum

Fluid filled system of membranous sacs encircles each myofibril.

Troponin

Hold tropomyosin in place.

Tropomyosin

In relaxed muscle of thin filament, myosin is blocked from binding to actin because of these. They cover the myosin-binding sites on actin.

Dystrophin (seen in clinical)

Links thin filaments of the sarcomere to integral membrane proteins of the sarcolemma, which are attached in turn to proteins in the C.T. extracellular matrix that surrounds muscle fibers.

Actin

Main component of thin filament. Molecules join to form filaments that is twisted into a helix. On each actin molecule is a myosin-binding site, where a myosin head can attach.

Skeletal muscle

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

Epimysium

Outermost layer of dense, irregular C.T. encircling the entire muscle

Sarcolemma

Plasma membrane of a muscle cell

M line

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

Power stroke

The site of the cross-bridge where ADP is still bound opens. As a result, the cross-bridge rotates and releases the ADP.

Structural proteins

Titin, a-actitin

Regulatory proteins

Tropomyosin (thin) and troponin (thin)

Cross-bridges

When the myosin heads interact with thin filaments (actin) during a contraction.

Filaments

Smaller protein structures within myofibrils

Titin

Spans half a sarcomere. Connects a Z disc to the M line thereby helping to stabilize the position of the thick filament.

The sliding filament mechanism

With exposure of the myosin binding sites on actin (the thin filaments) - in the presence of Ca 2+ and ATP the thick and thin filaments "slide" on one another and the sarcomere is shortened

Fascia

a dense sheet or broad band of irregular C.T. that lines the body wall and limbs. Holds muscles with similar functions together. Allows free movement of muscles; carries nerves, blood vessels, and lymphatic vessels; and fills spaces between muscles.

Myofibrils

The contractile organelles of skeletal muscle.

Myofilaments

The contractile proteins, actin and myosin, of muscle cells

Attachment of myosin to actin to form cross-bridges

The energized myosin head attaches to the myosin-binding site on actin and releases the previously hydrolyzed phosphate group. When the myosin heads attach to actin during contraction, they are referred to as cross-bridges

ATP hydrolysis

The myosin head includes an ATP-binding site and an ATPase. This reaction reorients and energizes the myosin head. The products - ADP and a phosphate group - are still attached to the head

The sliding filament mechanism

a) during contraction, the thin filaments slide past the thick filaments so that actin and myosin filaments overlap.

ATP binding site

an active region on the myosin head that is also an enzyme that breaks ATP into ADP and Pi

Thin filament

composed mostly of the protein actin

Thick filament

composted mostly of the protein myosin

Transverse T tubules

extend through sarcoplasm form passageways through the muscle fiber

When calcium ions (Ca2+) binds to troponin

it undergoes a change in shape; This change moves tropomyosin away from myosin-binding sites on actin and muscle contraction begins as myosin binds to actin.

Perimysium

layer of dense, irregular C.T. but it surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles.

I band

lighter, less dense area that contains the rest of the think filaments.

Two contractile proteins in muscles

myosin (thick) and actin (thin)

Z discs

narrow, plate-shaped regions of dense protein material that separate one sarcomere from the next. (B in graph)

Endomysium

penetrates the interior of each fascicle and separates individual muscle fibers from one another.

Myosin heads

projects outward from the shaft in a spiraling fashion, each extending toward one of the six thin filaments that surround each thick filament. Contains an ATP-binding site and an ATPase.

Motor proteins

pull various cellular structures to achieve movement by converting the chemical energy in ATP to the mechanical energy of motion, that is, the production of force.

Delayed onset muscle sorenes

stiffness, tenderness, and swelling.

Myosin tail points toward

the M line in the center of the sarcomere.

Myosin

the main component of thick filaments and functions as a motor protein in all three types of muscle tissue.

Exercise-induced muscle damage

torn sarcolemmas in some muscle fibers, damaged myofibrils, and disrupted Z discs.

Zone of overlap

where thick and thin filaments overlap

Fascicle

Bundle of muscle fibers wrapped in perimysium.

Myofibrils are made of three proteins

1. Contractile proteins 2. Regulatory proteins 3. Structural proteins

Properties of Muscular tissue

1. Electrical excitability. 2. Contractibility. 3. Extensibility 4. Elasticity

Muscle fibers have 3 ways of producing ATP

1. From creatine phosphate 2. By anaerobic cellular respiration 3. by aerobic cellular respiration

Functions of muscular tissue

1. Producing body movements 2. Stabilizing body positions. 3. Storing and moving substances within the body. 4. Generating heat

Before the contraction cycle

Sarcoplasmic reticulum released Ca2+ into the sarcoplasm. There they bind to troponin. Troponin moves tropomyosin away from the myosin-binding sites on actin. The binding sites are free

Excitation-contraction coupling

Sequence of events that convert s action potentials in a muscle fiber to a contraction; Action potential travels across entire sarcolemma; occur during hidden (laten) period, between AP initiation and the beginning of mechanical activity (contraction); electrical signal does not act directly on myofilaments (it causes rise in intracellular calcium ion concentration that allows filaments to slide)

A-actinin

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