Human AP I (Lecture): Exam 3, Muscular

What is the sarcoplasmic reticulum?

A storage and release site for calcium ions in muscle cells.

What is the sliding filament theory?

The process of sarcomere shortening caused by the sliding of thin and thick filaments past each other.

What is excitation-contraction coupling?

The sequence of processes that links the action potential to muscle contraction.

What happens when a skeletal muscle fiber contracts?

The H bands and I bands get smaller, the zones of overlap get larger, and the Z lines get closer together, while the width of the A band remains constant.

What are myosin molecules?

Myosin molecules are thick filaments in muscle fibers that interact with actin to produce contraction.

What is a Z line?

A structure in muscle fibers where thin filaments are anchored.

What does each thin filament consist of?

Each thin filament consists of two protein strands coiled helically around each other.

What is a neuromuscular junction?

The synapse or junction where a motor neuron communicates with a skeletal muscle fiber.

What connects during muscle contraction?

Thin filaments and thick filaments become connected by myosin cross-bridges.

What is the epimysium?

The dense layer of connective tissue that surrounds an entire skeletal muscle.

How do muscle fibers differ from typical cells?

Muscle fibers have many nuclei and are larger than typical cells.

What is incomplete tetanus?

A condition where muscle tension increases gradually to a steady maximum tension due to repeated stimulation without complete relaxation.

What is a motor unit?

A single motor neuron together with all the muscle fibers it innervates.

Why is oxygen needed during the recovery period?

Additional oxygen is required to restore energy reserves consumed during exercise.

What is complete tetanus?

A state of muscle contraction where there is no relaxation between stimuli, resulting in a sustained contraction.

What causes a contraction similar to graph (b)?

The muscle must be stimulated again before it has relaxed from the previous stimulation.

Can a skeletal muscle contract without shortening?

Yes, during isometric contraction, muscle tension can increase without shortening.

How do slow fibers compare to fast fibers?

Slow fibers take longer to reach peak tension and appear dark red due to higher myoglobin content.

What is a circular muscle?

A muscle that controls the diameter of an opening.

What is a Grade II muscle strain?

A partial tear with swelling and limited movement.

What are microtears?

Microtears are small injuries to muscle fibers that can heal without causing inflammation.

What are the most common lever systems in the body?

The most common lever systems in the body are those that have the applied force between the fulcrum and the load, known as second-class levers.

What is a synergist?

A synergist is a muscle that assists the muscle that is primarily responsible for a given action.

What occurs during an isotonic contraction?

In an isotonic contraction, muscle tension exceeds the load, allowing the muscle to lift the load.

What is the insertion of a muscle?

The insertion of a muscle is the end that is attached to the point that moves when the muscle contracts.

What is the relationship between a muscle that abducts and one that adducts?

A muscle that abducts the humerus and a muscle that adducts it are antagonists to each other.

What regions do axial muscles stabilize and position?

Axial muscles stabilize and position the head, neck, and trunk.

What are three sources of stored energy utilized by muscle fibers?

The three sources are ATP, creatine phosphate, and glycogen.

Which muscles are included in the rotator cuff?

The rotator cuff includes the supraspinatus, infraspinatus, subscapularis, and teres minor, but not the rhomboid.

How do the biceps brachii and triceps brachii compare in action?

The biceps brachii flexes the forearm at the elbow, while the triceps brachii extends it.

What is the mechanism of tetanus toxin?

Tetanus toxin blocks inhibitory neurotransmitters in the spinal cord, causing continuous muscle contraction.

What is true about the quadriceps femoris muscle group?

The quadriceps femoris extends the leg at the knee and includes the rectus femoris.

What are the extrinsic eye muscles?

The extrinsic eye muscles include the inferior rectus, medial rectus, superior rectus, lateral rectus, inferior oblique, and superior oblique.

What causes the 'six-pack' appearance in abdominal muscles?

The 'six-pack' appearance is due to the structure of the rectus abdominis muscle.

What is the main difference between tendinitis and tendinosis?

Tendinitis is characterized by acute inflammation, while tendinosis involves chronic degeneration without inflammation.

What is correct about the gluteal muscles?

The gluteus medius and gluteus minimus are primarily responsible for hip abduction.

What causes muscle weakness in Myasthenia Gravis?

In Myasthenia Gravis, muscle weakness occurs because antibodies block ACh receptors on the muscle membrane.

What situation most likely leads to disuse atrophy?

Long-term bed rest or limb immobilization is likely to lead to disuse atrophy.

What are the labeled structures of a thick filament?

In a thick filament, A = Myosin Tail, B = Titin, C = Free Head.

What percentage of energy do mitochondria supply at peak muscle exertion?

At peak levels of muscle exertion, mitochondria can supply only about one-third of the energy required by the muscle.