Chapter 9: Muscle Tissue and Contraction

These flashcards cover key terms and definitions related to muscle tissue, contraction mechanisms, and specific muscle functions from the provided lecture notes.

Skeletal muscle

Long, cylindrical fibers; multiple nuclei; voluntary control; striated.

Cardiac muscle

Branched fibers; single nucleus; involuntary control; striated; intercalated discs.

Smooth muscle

Spindle-shaped fibers; single nucleus; involuntary control; non-striated.

Fascia

Connective tissue covering groups of muscles.

Tendon

Cordlike connective tissue attaching muscle to bone.

Aponeurosis

Broad sheet-like tendon.

Epimysium

Connective tissue around the entire muscle.

Perimysium

Connective tissue surrounding fascicles (bundles of fibers).

Endomysium

Connective tissue surrounding individual muscle fibers.

Triad

T-tubule + 2 terminal cisternae of sarcoplasmic reticulum (SR).

Motor end plate

Region of sarcolemma at the neuromuscular junction (NMJ).

Sarcomere

Structural unit of a muscle fiber; contractile unit.

Z-line

Anchors thin filaments; boundary of sarcomere.

A band

Entire length of thick filaments; includes overlap.

I band

Thin filaments only; light area.

H zone

Thick filaments only; center of A band.

M line

Center of thick filaments.

Neuromuscular junction (NMJ)

Motor neuron terminal, synaptic cleft, and motor end plate.

Acetylcholine (ACh)

Neurotransmitter that stimulates muscle contraction.

Sliding filament model

Mechanism of muscle contraction involving myosin and actin interaction.

Excitation-contraction coupling

Process by which action potentials trigger muscle contraction.

ATP

Molecule that powers muscle contraction and energy processes.

Creatine phosphate

Storage molecule that quickly regenerates ATP from ADP.

Acetylcholinesterase

Enzyme that breaks down ACh in the synaptic cleft.

Oxygen debt

Amount of oxygen required after exercise to restore energy levels.

Lactic acid threshold

Point during exercise when muscles switch to anaerobic metabolism.

Motor unit

Motor neuron and all muscle fibers it innervates.

Recruitment

Increasing number of motor units activated for a stronger contraction.

Red fibers (slow-twitch)

Type I muscle fibers characterized by high myoglobin and fatigue resistance.

White fibers (fast-twitch)

Type II muscle fibers characterized by low myoglobin and quick fatigue.

Twitch

Single contraction from one stimulus.

Threshold stimulus

Minimum stimulus required to cause a muscle contraction.

Latent period

Delay between stimulus and muscle contraction.

Isotonic contraction

Muscle changes length while maintaining constant tension.

Isometric contraction

Muscle tension increases but length remains unchanged.

Calmodulin

Binding protein in smooth muscle that binds Ca²⁺.

Intercalated discs

Connect cardiac muscle cells; contain gap junctions.

Syncytium

Mass of cells functioning as a unit due to electrical connectivity.

Agonist

Prime mover muscle responsible for a specific movement.

Antagonist

Muscle that opposes the action of the agonist.

Synergist

Muscle that assists the agonist during a movement.

Buccinator

Muscle that compresses cheeks. Cheek.

Sternocleidomastoid

Muscle that flexes/rotates the head. Side of the neck

Temporalis

Muscle that elevates the mandible. Temple.

Pectoralis major

Muscle involved in adduction and flexion of the arm. Chest.

Latissimus dorsi

Muscle that extends and adducts the arm. Lower back

Masseter

Muscle that elevates the jaw, primarily responsible for chewing. Closes the mouth.

Erector Spinae 

along spinal column, extends vertebral column. 

Rotator cuff

supraspinatus, infraspinatus, teres minor, subscapularis. A group of muscles and their associated tendons that stabilize the shoulder joint and allow for arm rotation.

abdominal muscles

A group of muscles located in the front of the abdomen, including the rectus abdominis, obliques, and transversus abdominis, responsible for trunk movement and stability.

linea alba

A fibrous structure that runs down the midline of the abdomen, providing support and serving as an attachment point for abdominal muscles.

quadriceps

A group of four muscles located in the front of the thigh, responsible for extending the knee and stabilizing the leg during movement. rectus femoris, vastus lateralis, vastus medialis, vastus intermedius.

trapezius

A large, triangular muscle located in the upper back, responsible for moving, rotating, and stabilizing the scapula and extending the neck.

coracobrachialis

A muscle located in the upper arm that assists in flexing and adducting the arm at the shoulder joint. Medial Arm.

Neurotransmitters & smooth muscle contraction

Chemicals released by nerve cells that transmit signals to smooth muscle, triggering contraction and relaxation.

Acetylcholine vs Norepinephrine

Acetylcholine is a neurotransmitter that stimulates muscle contraction in both skeletal and smooth muscle, while norepinephrine primarily affects smooth muscle by causing contraction in vascular and some visceral smooth muscle.