ANPH111: The Muscular System

Comprehensive vocabulary flashcards covering anatomical terminology, tissue types, histology, sliding filament physiology, membrane excitability, and muscular anatomy from ANPH111.

Acetylcholine

Chemical messenger released from the end of a motor neuron.

Actin

Thin myofilament protein that resembles two strands of pearls.

Aerobic respiration

Process that breaks down fatty acids for energy when oxygen is present.

Anaerobic respiration

Process that breaks down glucose for energy when oxygen is not plentiful.

Antagonist

Muscles that oppose the action of a prime mover.

Aponeurosis

Flat, broad tendon that attaches a muscle to another muscle or to bone.

ATP (Adenosine triphosphate)

Energy currency used in cells to perform various functions, including muscle contraction, and released as $ATP \rightarrow ADP + P$.

Atrophy

Decrease in the size of a muscle.

Belly

The thick midsection of the muscle.

Complete tetanus

Condition in which impulses arrive so fast the muscle cannot relax between stimuli and twitches merge into one prolonged contraction.

Creatine phosphate

Compound stored in muscle that is used for short bursts of high-energy activity.

Endomysium

Delicate connective tissue covering each individual muscle fiber.

Epimysium

Connective tissue covering that surrounds the entire skeletal muscle as a whole and binds all muscle fibers together.

Fascia

Connective tissue surrounding the muscle.

Fascicles

Bundles of muscle fibers.

Hypertrophy

Enlargement of a muscle.

Incomplete tetanus

Condition of rapid muscle contraction with only partial relaxation.

Insertion

The end of a muscle that attaches to the more mobile bone.

Isometric contraction

Contraction in which the tension within a muscle increases while its length remains the same.

Isotonic contraction

Contraction in which the muscle changes length to move a load.

Motor unit

A motor neuron and all the muscle fibers it stimulates.

Muscle fiber

An elongated skeletal muscle cell.

Muscle tone

Continuous state of partial muscle contraction that allows for the maintenance of posture.

Myofibrils

Long, thread-like protein bundles that fill the sarcoplasm of a muscle fiber.

Myofilaments

Fine protein fibers that make up a myofibril, such as actin and myosin.

Myosin

Thick myofilament protein that resembles golf clubs.

Neuromuscular junction

Connection or synapse where a motor neuron and a muscle fiber meet.

Origin

The end of a muscle that attaches to the more stationary (non-movable) bone.

Perimysium

Sheath of connective tissue encasing each muscle fasciculus (bundle of muscle fibers).

Prime mover

The main muscle triggering a specific movement.

Sarcomere

The contractile unit of the myofibrils of a muscle, containing actin and myosin.

Sarcoplasm

The cytoplasm of a muscle fiber cell.

Synaptic cleft

Narrow space between the presynaptic terminal of a motor nerve and the postsynaptic membrane of the muscle fiber.

Synergists

Muscles that assist in the movement of a bone by working together.

Tendon

Strong, fibrous cord through which a muscle attaches to a bone.

Transverse (T) tubules

Tubules that extend across the sarcoplasm and wrap around sarcomeres at the A band, allowing electrical impulses to travel deep into the cell.

Treppe

Phenomenon in which each successive twitch contracts more forcefully than the previous one.

Twitch

A single, brief cycle of rapid contraction and relaxation of a muscle.

Skeletal muscle

Voluntary, striated muscle tissue composed of long, multi-nucleated cells with peripheral nuclei that makes up to $40\%$ of body weight.

Smooth muscle

Involuntary, non-striated muscle composed of small cells with a single nucleus capable of stretching, found in the walls of blood vessels and internal organs.

Cardiac muscle

Involuntary, striated muscle tissue composed of cylindrical, intermediate-sized cells connected by intercalated discs.

Intercalated discs

Specialized cell junctions between cardiac muscle cells containing gap junctions that help coordinate contractions.

Contractility

Ability of a muscle to shorten with force.

Excitability

Capacity of muscle tissue to respond to a stimulus.

Extensibility

Ability of muscle to be stretched to its normal resting length and beyond to a limited degree.

Elasticity

Ability of a muscle to recoil to its original resting length after being stretched.

Sarcolemma

The cell membrane of a muscle fiber that contains the T-tubules.

Sarcoplasmic reticulum

Type of smooth endoplasmic reticulum (SER) surrounding myosin that stores and releases $Ca^{2+}$.

Troponin

Protein complex on actin that provides an attachment site for $Ca^{2+}$.

Tropomyosin

Filament lying along the grooves of actin that covers or exposes attachment sites for myosin.

Z disk

Protein fibers that form the boundary of the sarcomere and provide the attachment site for actin.

H zone

Center region of a sarcomere that contains only thick myosin filaments.

I band

Light band of the sarcomere that contains only thin actin filaments.

A band

Dark band of the sarcomere where actin and myosin overlap; does not change length during contraction.

M line

Protein structure in the center of the H zone where myosin filaments are anchored.

Resting Membrane Potential

State where voltage-gated $Na^+$ channels are closed and $K^+$ diffuses out through leak channels, making the inside of the membrane negatively charged relative to the outside.

Depolarization

Phase in which voltage-gated $Na^+$ channels open and $Na^+$ diffuses into the cell, making the inside of the membrane positively charged relative to the outside.

Repolarization

Phase where voltage-gated $Na^+$ channels close and additional voltage-gated $K^+$ channels open, restoring the negative charge inside the cell.

Sliding filament model

Mechanism of contraction where actin and myosin filaments slide past each other, shortening sarcomeres, H zones, and I bands without shortening individual myofilaments.

Acetylcholinesterase

Enzyme released into the synaptic cleft that breaks down acetylcholine to stop muscle contraction.

Rigor mortis

Postmortem muscle stiffness that occurs when a person dies and no ATP is available to release cross-bridges between actin and myosin.

Threshold

The weakest electrical stimulus needed to produce a contractile response in a muscle.

All or None Law

Principle stating that a muscle fiber either contracts fully or does not contract at all (no in-between).

Slow Twitch Fibers

Dark meat muscle fibers that contract and fatigue slowly, utilize aerobic respiration, and are rich in myoglobin for long-distance endurance.

Fast Twitch Fibers

White meat muscle fibers that contract and fatigue quickly, utilize anaerobic respiration and glycogen, and are suited for sprinters.

Myoglobin

Iron-containing protein that imparts a dark/red color to slow-twitch fibers and helps $O_2$ bind within muscle tissue.

Occipitofrontalis

Forehead muscle responsible for raising the eyebrows.

Orbicularis oculi

Circular muscle around the eye that allows blinking.

Orbicularis oris

Circular muscle surrounding the mouth known as the 'kissing muscle'.

Zygomaticus

Cheek muscle known as the 'smiling muscle'.

Masseter

Primary chewing (mastication) muscle of the head.

Intrinsic tongue muscles

Muscles originating and inserting entirely inside the tongue that function to change its shape.

Extrinsic tongue muscles

Muscles originating on bones around the oral cavity or soft palate and inserting onto the tongue to move it.

Suprahyoid muscles

Muscles originating from the base of the skull and mandible that insert onto the hyoid bone to elevate or stabilize it.

Infrahyoid muscles

Muscles originating from the sternum and larynx that insert onto the hyoid bone to depress or stabilize it.

Pharyngeal constrictors

Muscles (superior, middle, inferior) originating on the larynx and hyoid that insert onto the pharynx to constrict it during swallowing.

Diaphragm

The main muscle of respiration that moves during quiet breathing to allow air into the lungs.

External intercostals

Thoracic muscles located between the ribs that elevate the ribs during inspiration.

Internal intercostals

Thoracic muscles located between the ribs that depress the ribs during forced expiration.

Rectus abdominis

Center muscle of the anterior abdominal wall that compresses the abdomen.

Deltoid

Triangular shoulder muscle that acts as the primary abductor of the upper limbs.

Biceps brachii

Anterior arm muscle referred to as the 'flexing muscle' that flexes both the elbow and the shoulder.

Triceps brachii

Three-headed posterior arm muscle that functions to extend the elbow.

Iliopsoas

Muscle of the hip and thigh region that flexes the hip.

Gluteus maximus

Buttocks muscle that functions to extend the hip and abduct the thigh.

Quadriceps femoris

Group of four anterior thigh muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) that extend the knee.

Hamstrings

Posterior thigh muscle group (biceps femoris, semimembranosus, semitendinosus) that flexes the knee, rotates the leg, and extends the hip.

Tibialis anterior

Muscle on the front of the lower leg that inverts the foot.

Gastrocnemius

Calf muscle that acts to flex the foot and leg.

Soleus

Deep lower leg muscle attaching to the ankle that flexes the foot.