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

a

b

  • Action potential travels down axon of
    alpha motor neuron
  • Acetylcholine is release
  • Action potential is generated across the
    sarcolemma
  • Muscle fiber contracts

c

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.

d

e

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.

f

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

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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

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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