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.