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THREE TYPES OF MUSCLE
*Comprised of very long muscle cells
*Found in the muscles that move the skeleton
*Able to be controlled VOLUNTARIY*Display light & dark bands giving appearance of strips or STRIATIONS
Found only in the heart
Have some neutonal regulation that controls the beating of the heart(subconscious level)
Found in the walls of hollow visceral organs e.g:stomach & bladder
Can not be consciously regulated or controlled (involuntary)
Characteristics of Muscle Tissue
The ability to receive or respond to stimuli
The ability to shorten forcibly when adequately stimulated
The ability to be stretched or extended
The ability of a muscle fiber to recoil and resume its normal resting length after being stretched or contracted
Skeletal Muscle Functions
The movement of the skeleton
The ability to make minute changes in positon to maintain normal positioning
Muscle tissue and muscle connections surround joints and keep them in position
Muscles generate heat as they contract thereby maintaining normal body temp
Skeletal Muscle can be broken down into smaller and smaller functional units
Muscle - a bundle of muscle fascicles
Fascicle - A bundle of muscle fibers
Muscle fiber - the muscle cell
Muscle Cell- Contains Myosin and Actin
Connective Tissue Sheaths Endomysium
“within the muscle” A sheath of primarily reticular fibers that covers the muscle fiber
Connective Tissue Sheaths Perimysium
“around the muscle” A sheath of fibrous connective tissue that covers the muscle fascicle
Connective Tissue Sheaths Epimysium
“outside the muscle” - A sheath of dense irregular connective tissue that covers the whole muscle
Muscle Attachments The Origin
The place of attachment which provides little to no movement
Muscle Attachments The Insertion
The place of attachment which provides the most movement (moveable bone)
Muscle Attachments Direct or Fleshy attachments
The epimysium fuses to the periosteum of a bone or perichondrium of a cartilage
Muscle Attachments Indirect attachments
The connective tissue wrappings of the muscle extend beyond the muscle to form either a rope like tendon or a sheet like aponeurosis
Muscle Fiber Sarcolemma
Cell membrane of the muscle cell
Muscle Fiber Sarcoplasm
Cytoplasm of the muscle cell
Muscle Fiber Myoglobin
Red pigment that stores oxygen in the muscle
Muscle Fiber Myofibrils
Rod-like fibers that run parallel down the length of the muscle fiber. Hundreds to thousands of myofibrils can be found in one fiber and account for approximately 80% of the cellular volume
What are Myofibrils made of?
Primarily made up of thick filaments and thin filaments
What are thick filaments composed of?
Primarily composed of a protein called myosin
Globular heads on Myosin (thick) that can attach to actin.
What are thin filaments composed of?
Primarily composed of actin
A thin strand that wraps around Actin (thin) and blocks the actin binding sites
A three polypeptide complex that regulates the position of tropomyosin relative to the actin binding sites.
An elaborate smooth endoplasmic reticulum that’s primary function is to regulate intercellular levels of calcium
A long tube-like structure that are continuous with the sarcolemma
Runs in between two sarcoplasmic reticulums.
Action of the T Tubule:to initiate the release of calcium from the sarcoplasmic reticulum.
Shortening of the muscle fibers by the activation and movement of actin fibers over myosin fibers causing overlap (Sliding filament theory of contraction)
When does muscle contraction occurs?
when nerves excite the muscles by secreting a neurotransmitter called acetylcholine (ACH)
What do ACH causes?
Causes sarcolemma of the muscle fiber to produce an action potential which travels down the T tubule
KNOW THIS PARAGRAPH!
Neurons initiate the muscle contraction by secreting a chemical called Acetylcholine (ACH). This causes an action potential to occur on the surface of the Sarcolemma. The action potential then travels down the T-Tubule to activate the secretion of calcium from the Sarcoplasmic Reticulum. The calcium is then able to bind to Troponin which changes configuration. This change in configuration causes Tropomyosin to shift out of position allowing the globular head of Myosin to bind to the active site found on Actin.
Steps in Muscle Contraction
Cross Bridge formation
The Power stroke
Cross Bridge detachment
Cocking the myosin head
Cross bridge formation
This is when the Myosin head is attached to actin
The Power stroke
The changing of the myosin head configuration from a high energy position (straight) to low energy position (bent) causes movement of the actin fiber
Cross bridge detachment
This is when a new ATP molecule binds to the Myosin head causing the head to loose its grip on actin
Cocking the myosin head
Once ATP is bound it is quickly converted to ADP causing the myosin head to go back into its high energy position
Muscle Striations and Muscle Contractions A Band
Dark band where actin and myosin overlap
Muscle Striations and Muscle Contractions I Band
Light band where only actin can be found
Muscle Striations and Muscle Contractions H - Zone
the area where only myosin filaments can be found
Muscle Striations and Muscle Contractions Z - Line
The midline in the I band where actin filaments can connect to each other
Muscle Striations and Muscle Contractions M - Line
The mid-line in the H - Zone where Myosin fibers are anchored