Neuroscience Lecture 15: Skeletal Muscle Anatomy

What is the largest organ in the body?

Skeletal muscle

How many muscles make up skeletal tissue?

600

What are the four critical roles of skeletal muscle besides movement?

1. Glucose control

2. Temperature

3. Homeostasis

4. Endocrine

What interaction does skeletal muscle attach to bones with?

Tendons/cartilage

What is the respiratory function of skeletal muscle?

Mechanical ventilation

Is skeletal muscle excitable?

Yes

What shape of skeletal muscle surrounds openings?

Circular

What shape of skeletal muscle have origins wider than insertion points and has maximum force production?

Convergent

What shape of skeletal muscle are long muscles with good endurance?

Parallel

What is another term for parallel skeletal muscle?

Strap muscle

What shape of skeletal muscle have a large number of muscle fibers and tire easily?

Pennate

What shape of skeletal muscle have same direction diagonal insertions?

Unipennate

What shape of skeletal muscle have opposite diagonal insertions

Bipennate

What shape of skeletal muscle are spindle-shaped and have a muscle belly wider than the origin or insertion (sometimes considered parallel)?

Fusiform

What is the external sheath that surrounds the entire muscle?

Epimysium

What is the external sheath that surrounds the fascicles?

Perimysium

What is the external sheath that surround individual muscle fibers?

Endomysium

Where do somatic motor neurons originate?

Ventral horn of spinal cord

Which neurons convey impulses for muscular contraction?

Somatic motor neurons

Where do somatic motor neurons synapse at?

Neuromuscular junction

What two resources do blood vessels provide for muscle contraction?

1. Nutrients

2. Oxygen

What is each muscle fiber perfused by?

Capillaries

What are the two histological features of skeletal muscle?

1. Multinucleated

2. Cross-striations

What are the two types of skeletal muscle classifications?

1. Slow-twitch (1)

2. Fast-twitch (2A, X, B)

What is the plasma membrane unique to muscle cells?

Sarcolemma

What is the extension of sarcolemma that helps signals reach deep in the cell?

T-tubule

What is the calcium storage organelle unique to muscle cells?

Sarcoplasmic reticulum

What is the component of muscle fibers that contain sarcomeres?

Myofibril

Which organelle of muscle cells help propagate action potentials?

T-tubule

What is the junction formed by the t-tubule and sarcoplasmic reticulum components?

Triad junction

Which part of muscle cells is where contraction takes place?

Sarcomeres

What is the thick filament found in sarcomeres?

Myosin

What is the thin filament found in sarcomeres?

Actin

What is the line that makes up one end of the sarcomere?

Z-disc

What is the line that bisects the sarcomere?

M-line

What does myosin attached to the M-line form?

A-band

What does actin attached to the Z-disc form?

I-band

What component of contraction is performed by myosin?

Power stroke

What do the globular actin monomers polymerize to form?

Filamentous actin

What are the two actin-binding proteins that allow actin-myosin interaction to be regulated by Ca2+?

1. Troponin

2. Tropomyosin

How many thin filaments surround each myosin thick filament?

6

What is the junction of motor neuron axon terminal and sarcolemma of muscle fiber?

Neuromuscular junction

What is released in the neuromuscular junction that depolarizes the sarcolemma of the innervated muscle fiber to generate an action potential

Acetylcholine

What is the specialized region of sarcolemma proximal to the nerve terminal?

Motor end plate

What does acetylcholine binding cause an increase in the permeability of?

Ligand-gated Na channels

When occurs when the threshold is reached with depolarization of the postsynaptic membrane by Na channels?

Action potential forms