Module 7 - Muscles pt. 1 Flashcards
(20 cards)
What is skeletal muscle tissue? What is it’s appearance? Where is located? How is the control? What is the function?
- long cells
- attached to bones
- voluntary control
- movement; stabilize body position, heat production
What is cardiac muscle tissue? What is it’s appearance? Where is located? How is the control? What is the function?
- branched cells
- heart wall
- involuntary
- movement of blood
What is smooth muscle tissue? What is it’s appearance? Where is located? How is the control? What is the function?
- spindle shaped
- viscera and blood vessel walls
- involuntary
- regulation of organ volume; transport of organ contents
How is skeletal muscle organized?
- each muscle is composed of 100’s and 1000’s of muscle cells (called muscle fibre)
- 3 connective tissue layers protect and organize muscle fibres (epimysium, perimysium, endomysium)
- the three connective tissue layers extend beyond the muscle tissue to form the tendon
- tendons attach muscle to bone
What is the sarcoplasmic reticulum? What does it contain more of than the cytoplasm? How does it connect to the cell membrane (sarcolemma)? What is its key importance?
- the SR is an extensive network of membranes that cover the myofibrils
- contains a higher concentration of Ca+ ions than in the cytoplasm
- connects to muscle cell membrane (sarcolemma) by transverse tubules or T-tubules
- key importance switching muscle contraction on and off
What are myofibrils? What are they formed by?
myofibrils fill individual muscle cells
formed by protein myofilaments
1. thin (actin) filaments
2.thick (myosin) filaments
What are thick filaments composed of? What happens during muscle contraction? What does the binding form?
- composed of the protein myosin
- myosin heads bind to thin filaments during muscle contraction
- binding forms a ‘cross-bridge’
What are thin filaments composed of? Which one blocks what?
- composed of the proteins actin, tropomyosin and troponin
- tropomyosin blocks myosin binding sites in the resting state
What is the sarcomere?
- thick and thin filaments are organized into sarcomeres (=basic functional unit of striated muscle)
- sarcomeres line up along the length of the muscle fibre
What is the sliding filament mechanism?
- during muscle contraction, myosin heads bind to thin filaments
- myosin heads pull thin filaments toward the sarcomere centre
- the amount of overlap increases
- the sarcomeres (and thus the muscle) shortens
- the myofilaments themselves are not changing in length –> they are simply overlapping more causing muscle shortening
- this process requires calcium ions (Ca2+) and energy from ATP
What is the motor unit?
- motor neurons transmit nerve impulses (action potentials) to muscle cells to cause contraction
- a single motor neuron stimulates a number of muscle fibres (=motor unit)
- the number of motor units activated at one time determines the strength of muscle contraction
What is the neuromuscular junction? What does it contain?
- synaptic end bulb (motor neuron axon terminal)
- synaptic cleft
- motor end plate (region of sarcolemma in contact with the synaptic bulb)
What is muscle cell excitation?
the excitation of muscle fibres causing it to contract follows the phases:
- the release of neurotransmitter from the motor neuron (acetylcholine)
- the activation of acetylcholine receptors on the muscle cell
- the generation of a muscle action potential
- the breakdown of acetylcholine
What is muscle contration?
with the excitation of the muscle fibre (action potential generation):
- the sarcoplasmic reticulum (SR) releases stored calcium into the sarcoplasm
- calcium binds to troponin on actin filaments to reveal myosin binding sites
- myosin heads bind to actin (=cross-bridge formation) and swivel (=power stroke) which shortens the sarcomere
- cross-bridges separate and calcium is actively reabsorbed into the SR –> relaxation
Why is calcium important?
-calcium combines with troponin –> changes the orientation of tropomyosin in order to expose the binding sites for myosin on the thin filament
Why is ATP important?
- energy from the breakdown of ATP (bound to myosin heads) is used to swivel myosin heads (powerstroke)
- following the powerstroke, ATP MUST REBIND to myosin in order for myosin to detach, allowing the muscle to relax
What are the principles of muscle function?
- muscles attach to bones ACROSS THE JOINT at which movement occurs
- skeletal muscles produce movements by exerting force s on tendons which in turn pull bones or other structures (i.e skin)
- when a muscle contracts, it shortens and draws a movable bone toward a stationary one
What is muscle attachment?
the ORIGIN is the point of attachment on the stationary bone
-the INSERTION is the point of attachment on a movable bone
Most movements are coordinated by several muscles acting together: which 3?
- prime movers - principle muscle causing movement
- synergist - assists the prime mover (contracts in the same direction)
- antagonist - opposes the action of the prime mover (contracts in the opposite direction)
What are 7 facts about smooth muscle?
- spindle shaped cells
- no striations
- single nucleus
- found in the walls of hollow organs and blood vessels
- involuntary
- myofilaments are irregularly arranged
- contract by sliding filaments
