Three types of muscles- Cardiac, Muscle, and Skeletal

Skeletal muscle takes 40% of body weight, voluntary

Smooth muscle - Involuntary, widely distributed, mostly organs

Cardiac muscles and smooth muscles are autorhytmic

Functions of muscles - Contractility (contraction), Excitability (response to electrical stimulus), Extensibility (Stretch beyond normal length), Elasticity (return to resting length)

Skeletal Muscle - Type of muscle that contains multiple nuclie, and is very long and cylindrical

Cardiac Muscle- Type of muscle that contains a single nucleus, is cylindrical and branched

Smooth Muscle- Type of muscle that contains a single nucleus and is spindle-shaped

epimysium - covers the whole muscle

perimysium- divides muscles into bundles of muscle fibers called fascicles

endomysium - pathways for vessels and nerves

Motor neuron - from the brain and spine, extend via nerves

Myoblasts - cells that create muscle

Functions of muscles - Movement, Maintainance, Respiration, Production of Heat, Contractions in the heart, Constriction of organs and vessels, and Communication

Sarcomere- highly ordered units of myosin and actin myofilaments seperated by Z-lines, smallest portion of the muscle that can contract, structural and functional units of skeletal muscle

Myofibrils - Sarcomeres joining end-to-end

Titin gives the muscle ability to stretch and recoil, and is the largest protein in the human body

Ca2+ release is the “switch” for muscle contraction

Motor-end plate- Sarcolemma

Myosin Myofilaments - head (binds to actin and are ATPase enzymes), body (bends and straightens)

Hypertrophy

The increase in the size of muscle cells, leading to greater muscle mass. NOT INCREASE IN NUMBER

Electrical Component

Refers to the electrical signals that stimulate muscle contraction and growth.

Mechanical Component

Involves the physical forces and tension applied to muscles during resistance training that promote hypertrophy.

Definitions of Neuromuscular System Terms

• Sacrolemma: The plasma membrane surrounding a muscle fiber.

• Transverse Tubules: Extensions of the sarcolemma that penetrate into the muscle fiber.

• Myofibrils: Long, thread-like structures within muscle fibers that contain the contractile proteins.

• Myofilaments: The filaments of myofibrils, composed of actin and myosin.

• Sarcomeres: The basic contractile units of muscle fibers.

• L-band: The light band in a sarcomere, primarily composed of actin.

• A-band: The dark band in a sarcomere, containing both actin and myosin.

• M-lines: The middle line of a sarcomere that anchors myosin filaments.

• H-zone: The lighter region in the A-band where only myosin is present.

• Z-disk: The boundary structure of a sarcomere that anchors actin filaments.

• Titin: A large protein that helps stabilize myosin filaments in the sarcomere.

• G Actin: Globular actin, the monomeric form of actin.

• F Actin: Filamentous actin, a polymer of G actin that forms thin filaments.

• Synaptic cleft: The gap between the axon terminal and the muscle fiber at a neuromuscular junction.

• Motor-end plate: The specialized region of the muscle fiber membrane at the neuromuscular junction.

• Acetylcholine: A neurotransmitter that transmits signals from motor neurons to muscle fibers.

• Acetylcholinesterase: An enzyme that breaks down acetylcholine in the synaptic cleft.

• Tropomyosin: A protein that blocks the binding sites on actin filaments in a relaxed muscle.

• Troponin: A protein complex that regulates muscle contraction by binding calcium ions.

• Myosin molecule: The thick filament protein that interacts with actin to produce muscle contraction.

• Action potential: A rapid electrical signal that travels along the muscle fiber membrane.

• Axon Terminals: The endings of motor neurons that release neurotransmitters.

• Tendons / Aponeuroses: Connective tissues that attach

Muscle naming

1. Location - pectoralis (Chest), gluteus (buttocks), brachial(arm)

2. Size - maximus (large), minimus (small), longus (long), brevis (short)

3. Shape - deltoid (triangle), quadratus (rectangular), teres (round)

4. Orientation of fascicles - rectus (straight)

5. Origin - branchioradialis, origin in the arm (brachium), ends inserts into the radius

6. Number of heads - Biceps (two heads), Triceps (three heads)

7. Function - Abductors and adductors