Hesi A2 Muscles

How are muscles organized?

Muscles are organized as Muscle, Fascicle, Muscle fiber (cell), Myofibril, Myofilament (Actin/Myosin)

What tissue layers make up a fascicle?

Epimysium, Perimysium, Endomysium

What are the three muscle types?

• Skeletal: Striated, voluntary, attached to bones.

• Smooth: Non-striated, involuntary, found in organs/vessels.

• Cardiac: Striated, involuntary, found only in the heart.

What is the basic functional unit of muscle contraction?

The sarcomere is the basic functional unit of muscle contraction.

What is the Sliding Filament Theory?

Muscle contraction occurs when thick (myosin) and thin (actin) filaments slide past each other, shortening the sarcomere.

What are key chemicals required for muscle activation?

Calcium (Ca2) is stored in the sarcoplasmic reticulum and binds to troponin, while ATP is required for cross-bridge formation.

How are muscles connected to bones?

Tendons connect muscle to bone; Ligaments connect bone to bone.

What are the key muscles in the head?

Temporalis (closes jaw)

Masseter (closes jaw)

Orbicularis oculi (blinks)

Key muscle in the neck

Sternocleidomastoid (rotates head)

Key muscles in the torso?

Pectoralis major (chest)

Latissimus dorsi (back)

Rectus abdominis (abs)

Diaphragm (breathing)

Key muscles in the upper extremities?

Deltoid (shoulder)

Biceps brachii (flexes forearm)

Triceps brachii (extends forearm)

Key muscles in the lower extremities?

Quadriceps (thigh)

Hamstrings (back of thigh)

Gastrocnemius (calf)

What does Flexor mean?

• Flexor: Reduces angle of a joint.

What does extensor mean?

• Extensor: Increases angle of a joint.

What does abductor mean?

• Abductor: Moves limb away from midline.

What does adductor mean?

• Adductor: Moves limb toward midline

What are synergists and antagonists in muscle movement?

Synergists assist in performing the same set of joint motion, while antagonists oppose that motion, providing balance and control.

What is the neuromuscular junction?

The neuromuscular junction is the area where a motor neuron communicates with a muscle fiber, allowing for muscle contraction.

What are some common muscle-related disorders?

• Strains: Overstretching or tearing of muscles or tendons.

• Sprains: Overstretching or tearing of ligaments.

• Muscular dystrophies: Genetic disorders leading to muscle weakness and degeneration.

Which nerves innervate specific muscles?

Different muscles are innervated by specific spinal nerves; for example, the phrenic nerve innervates the diaphragm, while the radial nerve innervates muscles in the posterior arm.

How do muscles work with the skeletal system to create movement?

Muscles contract to pull on bones, creating motion at joints; this action is coordinated to produce smooth and controlled movements.