Functions of the Muscular System

These flashcards cover the major concepts, functions, and properties of the muscular system as discussed in the lecture notes.

What are the major functions of the muscular system?

1. Movement of the body 2. Maintenance of posture 3. Respiration 4. Production of body heat 5. Communication 6. Constriction of organs and vessels 7. Contraction of the heart.

What type of muscle tissue is primarily responsible for voluntary movements?

Skeletal muscle.

Where is cardiac muscle located?

In the heart.

What type of muscle is responsible for moving food through the digestive tract?

Smooth muscle.

The ability of muscle to shorten forcefully or contract.

contractility

What does excitability refer to in muscle tissue?

The capacity of muscle to respond to a stimulus.

The ability of a muscle to be stretched beyond its normal resting length and still be able to contract.

extensibility

What is elasticity in muscle tissue?

The ability of muscle to recoil to its original resting length after being stretched.

What surrounds each skeletal muscle?

Connective tissue layers including epimysium, perimysium, and endomysium.

What is the sarcolemma?

The cell membrane of muscle fibers.

Bundles of protein filaments in muscle fibers that are responsible for contraction.

myofibrils

The theory that explains how myofilaments interact to produce muscle contraction by sliding past each other.

sliding filament model

What neurotransmitter is released at the neuromuscular junction to stimulate muscle contraction?

Acetylcholine (ACh).

The structural and functional unit of a muscle fiber, composed of actin and myosin myofilaments.

sarcomere

What happens to the H zone during muscle contraction?

disappears as actin and myosin myofilaments slide past each other.

What are the two major types of protein myofilaments in muscle fibers?

Actin (thin filaments) and myosin (thick filaments).

It serves as a specialized endoplasmic reticulum that stores and releases calcium ions to initiate contraction.

sarcoplasmic reticulum

tubular invaginations of the sarcolemma that allow action potentials to reach the interior of the muscle fiber.

T-Tubules

They are regulatory proteins on actin that prevent myosin binding in a relaxed state; they move to expose binding sites when Ca2+Ca2+ binds to troponin

role of troponin and tropomyosin play in muscle contraction

What constitutes a motor unit?

A single motor neuron and all the muscle fibers it innervates.

What is the all-or-none principle?

muscle fiber contracts to its max potential or not at all for a given stimulus.

Muscle Length changes while tension remains constant

Isotonic Contraction

The constant state of partial contraction in relaxed muscles that helps maintain posture and stability.

muscle tone

A reduced capacity to work despite stimulation, often caused by ATP depletion, calcium imbalances, or lactic acid buildup.

muscle fatigue

Fibers that contract slowly, exhibit high endurance, and rely primarily on aerobic respiration.

slow-twitch (Type II) muscle fibers

Fibers that contract quickly and powerfully but fatigue rapidly, relying more on anaerobic metabolism.

fast-twitch (Type II) muscle fibers?

How is energy stored in muscles for rapid regeneration of ATP?

Energy is stored as ATP and creatine phosphate, which can rapidly regenerate ATP from ADP.

What are the origin and insertion of a muscle?

The origin is the stationary attachment point; the insertion is the attachment point on the bone that moves during contraction.

the muscle that produces the movement

agonist

the extra oxygen required after exercise to restore resting metabolic conditions, such as recharging ATP and creatine phosphate.

oxygen debt

Protein structures that mark the boundaries of a sarcomere and anchor the thin actin filaments.

Z-disks

The dark-colored region that contains the full length of the thick myosin filaments.

A-band in a sarcomere

Part of a sarcomere that contains only thin actin filaments and lies on either side of the z-lines

I-band in a sarcomere

An oxygen-binding protein in muscle fibers that provides a reserve of oxygen for aerobic respiration.

myoglobin

Enlargement of muscle fibers from use.

Hypertrophy

An enzyme that breaks down acetylcholine in the synaptic cleft to prevent continuous muscle stimulation.

role of acetylcholinesterase

The pivot of the myosin head that pulls the actin filament toward the center of the sarcomere.

power stroke

The structure formed when a myosin head binds to an exposed active site on an actin filament.

cross-bridge

What are T-tubules in simple terms

tiny tubes in muscle cells that carry the electrical signal inside so the muscle can contract

Wasting away of muscle from disuse.

Atrophy

the segment between two Z lines and is the functional unit of muscle contraction.

Sarcomere

physically covers the myosin-binding sites on actin. it prevents contraction when the muscle is relaxed

tropomyosin

respond to calcium and control the position of tropomyosin

troponin

the central region of a sarcomere where there is myosin only, with no actin overlap.

h zone

what is fast twitch fibers used for?

sprinting, jumping, lifting something heavy

the muscle’s calcium storage tank, its a network of tubes inside muscle cell. main job is to store and release calcium

Sarcoplasmic Reticulum (SR)

a protein inside muscle cells that stores oxygen.

Myoglobin