Muscle Contractions Flashcards
Cardiac Muscle
Striated
Involuntary
Skeletal Muscle
Striated
Voluntary
Smooth Muscle
Non-Striated
Involuntary
Skeletal Muscle Properties
- Extensibility
- Elasticity
- Excitability
- Conductibility
- Contractility
Skeletal Muscle Functions
- Produces movement
- Maintains posture
- Stabilizes joints
- Generates heat
- Additional functions
Major events of muscle contraction
- Nerve impulse reaches the end of a motoneuronà release of the neurotransmitter acetylcholine (ACh)
- ACh diffuses rapidly across the gap of the neuromuscular junction and binds to ACh receptors on the motor endplate of the muscle fiber
- Stimulation of ACh receptors initiates impulses that travels along the sarcolemma, through the T tubules, to the sacs of the SR.
- Ca2+ is released from the SR into the sarcoplasm, where it binds to troponin molecules in the thin myofilaments.
- Tropomyosin molecules in the thin myofilaments shift.
- Actin’s active sites are exposed.
- Energized myosin cross bridges of the thick myofilaments bind to actin and use their energy to pull the thin myofilaments toward the center of each sarcomere.
- This cycle repeats itself many times per second, as long as adenosine triphosphate (ATP) is available.
- As the filaments slide past the thick myofilaments, the entire muscle fiber shortens.
Sliding Filament Theory
- Distance between the two Z-disks shortens
- This arrangement and interactions between actin and myosin allows for the shortening of the sarcomeres which generates force!
Sensory Receptors: Classification
- By the type of stimulus they detect
- By their body location
- By their structural complexity
Type of Stimulus Detected by Receptors
- Mechanoreceptors
- Thermoreceptors
- Photoreceptors
- Chemoreceptors
- Nociceptors
Receptor Body Location
- Exteroceptors
- Interoceptors
- Proprioceptors
Receptor Structural Complexity
- Simple receptors
- Complex receptors
Motor Unit
Motor neuron and all the skeletal muscles it innervates.
Axon of motor neurons extend from the spinal chord to the muscle. There each axon divides into a number of axon terminals that form neuromuscular junctions with muscle fibers scattered throughout the muscle.
Most Important Characteristic of a Muscle
- Ability to develop tension (force) Tension can be: * Active * Passive - Exert a force on the bony lever
Active Tension
Tension developed by the contractile elements of the muscle.
- Initiated by cross-bridge formation and movement of the actin and myosin.
- Length of the muscle affects the ability of the muscle to create tension.
Passive Tension
Refers to the tension developed in the elastic component of the muscle.
- Does not contribute to movements in the middle of range of motion but contribute when muscle is lengthened.
- Added to the active tension when the muscle is lengthened.
- Become slack when the muscle is shortened.
