LO 7 Flashcards
Movement is caused by the ability of the muscle cells, called fibers, to _________
Shorten and contract - all muscle cells specialize in contraction (shortening)
Muscle cells shortened by converting ______ into _______
- Chemical energy obtained from food
- Mechanical energy
What are the three types of muscle tissue that exist in the body?
- Skeletal
- Cardiac
- Smooth
Describe skeletal muscle
- Also called striated or voluntary muscle
- Represents 40% - 50% of body weight
- Attached to bones
- Microscopic striations
- Voluntary contractions
- Multi-nucleated cell/fiber (arranged around periphery of cell)
Describe cardiac muscle
- Composes the bulk of the heart
- Cells branch frequently and are joined to each other by unique dark bands called intercalated discs - discs enable interconnected nature of cardiac muscle cells, allowing heart to contract efficiently as a unit
- Involuntary control
- Many nuclei that are centrally located
Describe smooth muscle
- Also called non striated, involuntary, or visceral muscle
- Appears smooth under the microscope
- Found in walls of hollow, visceral structures - e.g.digestive tract, blood vessels, and uterus
- Involuntary control
- Long, narrow spindle shaped cells
- Single, centrally located nucleus
Describe the structure and attachment of skeletal muscle
- Composed mainly of striated / skeletal muscle cells ‘fibers’ and connective tissue
- They extend from one bone across a movable joint to another bone
- One bone is typically more stationary than the other in any given moment of movement
______ is the attachment point of the muscle to the bone that remains relatively fixed when movement at the joint occurs
Origin
______ is the point of attachment to the bone that moves when a muscle contracts
Insertion
The main part of skeletal muscle is called the ______
Body
Describe tendons
- Attach muscle to bones
- Strong, dense chords of fibrous connective tissue
- Some enclosed in synovial lined tubes called tendon sheaths
- Lubricated by synovial fluid
What are bursae?
- Small, synovial-lined sacs containing a small amount of synovial fluid
- Located between tendons and underlying bone
- Decrease friction at the joint
Describe the microscopic structure of skeletal muscle
- Each tissue consists of specialized contractile cells called fibers
- Each fiber contains two kinds of very fine, thread like structures - thick myofilaments made of myosin, thin myofilaments made of actin
Thick myofilaments are made of ______
Myosin
Thin myofilaments are made of ______
Actin
What is the basic, functional, contractile unit of skeletal muscle?
Sarcomere
Describe sarcomeres
- Basic functional unit of skeletal muscle
- Contains numerous actin and myosin myofilaments - the arrangement gives the appearance of dark and light stripes under a microscope
- They are separated by dark bands called z lines or discs
Explain the sliding filament model
- During contraction, thick and thin myofilaments (myosin and actin) attach to one another by forming ‘cross bridges’
- Cross bridges act as levers to pull the myofilaments past each other
- As muscle contracts, myofilaments slide past each other
- Contraction requires calcium (for crossbridge formation) and ATP (for energy)
What are the three primary functions of skeletal muscle?
- Movement
- Posture / muscle tone
- Heat production
Describe how skeletal muscles produce movement
- Muscles produce movement by ‘pulling’ on bones
- As a muscle contracts, it pulls the insertion bone closer to the origin bone
- Movement occurs at the joint between the origin and the insertion
- Groups of muscles usually contract / relax in a coordinated way to produce a single, smooth, coordinated movement - muscles contained in the group include the prime mover, synergist, and antagonist
This muscles contraction is mainly responsible for producing movement
Prime mover (e.g. if the biceps are prime movers the brachialis act as synergist and the triceps act as antagonists)
This muscles contraction helps the prime mover produce a movement
Synergist (e.g. the brachialis is a synergist for the biceps)
This muscles actions oppose the action of the prime mover in a movement (e.g.produces a movement opposite to the prime mover and synergist)
Antagonist (e.g. the triceps are antagonists for the biceps)
Describe skeletal muscles role in posture
- Maintaining posture is made possible thanks to a specialized contraction called a tonic contraction
- Only a few muscles fibers shortened/contract at one time - the muscle as a whole doesn’t shorten and contract
- For purposes of posture, movement is not produced
- The muscles do hold in position, maintaining muscle tone, which is referred to as posture
- Good posture balances the distribution of weight and counteracts gravity - reduces strain on muscles, tendons, ligaments, Bones and keeps our head from flopping forward
- Poor posture causes fatigue and may lead to deformity