muscular and neuromuscular systems
The nervous system
Motor units
The central nervous system (CNS)
The peripheral nervous system
The brain
The spinal cord.
The sensory division
The motor division
The motor unit is the functional unit of the
nervous system.
All the muscle fibers of a motor unit contract together when they are stimulated by the motor neuron.
Neuromuscular System
Activation of Muscles
- Action potential travels down axon of
alpha motor neuron - Acetylcholine is release
- Action potential is generated across the
sarcolemma - Muscle fiber contracts
All of muscle fibers in the motor unit contract and develop force at the same time. ✅
Proprioception
Muscle spindle
are proprioceptors that consist of several modified muscle fibers enclosed in a sheath of connective tissue
Golgi tendon organs (GTOs)
Proprioceptors located in tendons near the myotendinous junction
When an extremely heavy load is placed on the muscle, discharge of the GTO occurs.
Musculoskeletal System
Muscles do not act directly to exert
force they function by pulling against bones that rotate about joints and transmit force to the environment.
Muscles can only pull, not push; forces can be manifested as either pulling or pushing forces against external objects.
Muscular System
Macrostructure microstructure
Each Skeletal muscle is an organ that contains muscle tissue, connective tissue, nerves, and blood vessels.
Fibrous connective tissue, or epimysium, cover the body’s more than 430 skeletal muscles.
connective tissues
Epimysium
Perimysium
Endomysium
:
Myosin and Actin
The arrangement of myosin and actin filaments gives skeletal muscle its striated appearance.
The discharge of an action potential from a motor nerve signals the release of calcium from the sarcoplasmic reticulum into the myofibril, causing tension development in muscle
Actin filaments at each end of sarcomere slide inward on myosin filaments, pulling Z-line toward the center of the sarcomere and thus shortening the muscle fiber
contraction Phases
Resting Phase
Excitation-contraction coupling phase
Contraction phase
Recharge phase
Relaxation phase
No action potential / No calcium release
action potential travel down to motor neuron / calcium released
Crossbridge, produced ATP
ATP releases Myosin head