Muscular system

Elasticity

Elasticity

Ability of the muscle to return to its original shape after being streched

Extensibility

Enables muscles to stretch or extend

Contractility

Allows muscles to shorten with force and pull on attachment point

Skeletal, Smooth, and Cardiac

Types of Muscle

Skeletal

Attached to bones or, for some facial muscles, to skin

Single, very long, cylindrical, multinucleate cells with very obvious striations

Cardiac

Walls of the heart

Branching chains of cells; uninucleate, striations; intercalated discs

Smooth

Mostly in walls of hollow visceral organs

Single, fusiform, uninucleate; no striations

Muscle fibers

Elongated smooth muscles are called______. It is responsible for the contraction and relaxation that allows us to move, maintain posture, and perform various bodily functions.

Sarcolemma

Plasma membrane that surrounds muscle fibers. It triggers muscle contraction through an electric signal called action potential.

Sarcoplasm

Provides energy for muscle contraction due to the presence of mitochondria and other organelles.

Myofibrils

They are responsible for the muscle contraction. It is an organized bundle of protein filaments.

myofilaments

The ability of muscle to shorten or contract depends on this

Skeletal muscle fibers

Packaged into organs called ______ that attach to the skeleton

Striated muscle

Its fibers have obvious stripes

Voluntary muscle

It is the only muscle type subject to conscious control

Endomysium

Each muscle fiber is enclosed in a delicate connective tissue sheath

Perimysium

Several sheathed muscle fibers are then wrapped by a coarser fibrous membrane

Fascicle

Perimysium form a bundle of fibers called

Epimysium

Many fascicles are bound together by an event tougher “overcoat” of connective tissue called _____

Tendon or Aponeurosis

The ends of epimysium that extend beyond the muscle blend either into strong ____ or a sheetlike _____

Sarcolemma

Many oval nuclei can be seen just beneath the plasma membrane

Sarcomeres

Find that the myofibrils are actually chains of tiny contractile. It also provides energy for muscle contraction due to the presence of mitochondria and other organelles.

Myofilaments and Thick filaments

Two types of threadlike protein

Thin filaments; Actin

____ composed of the contractile protein called _____

Sarcoplasmic reticulum

A specialized smooth endoplasmic reticulum. It also stores and release calcium ions, that are important in muscle contraction.

Tubules

Important in transmitting electrical impulses from the surface of muscle fiber. It ensures that the SR releases calcium ions during muscle contraction

Striations

Caused by the organization of actin and myosin filaments Actin and myosin slides over each other that causes shorteing or sacromeres that produces force.

Irritability/Responsiveness

Ability to receive and respond to stimulus

Contractility

Ability to forcibly shorten when adequately stimulated

Extensibility

Ability of muscle fibers to strech

Elasticity

Ability of muscles to recoil and resume their resting length after being stretched

Motor unit

Consists of one neuron and all the skeletal muscle fibers it stimulates

Axon

When a long, threadlike extension of the neuron

Axon terminals

Reaches the muscle, it branches into a number of ____

Neuromuscular junctions

Contain synaptic vesicles filled with a chemical referred to as a neurotransmitter

Acetylcholine

Specific neurotransmitter that stimulates skeletal muscle fibers

Synaptic cleft

The nerve endings and the muscle fiber membranes are very close, they never touch. The gap between them

Amyotrophic lateral sclerosis

Motor neurons degenerate over time, resulting in paralysis that gradually worsens.

Action potential

This movement of ions generates an electrical current

Graded responses

Different degrees of shortening, which generate different amounts of force.

Muscle twitches

Sometimes results from certain nervous system problems, this is not the way our muscles normally operate.

Unfused tetanus or Incomplete tetanus

When the muscle is stimulated so rapidly, no evidence of relaxation is seen and the contractions are completely smooth and sustained.

Direct phosphorylation of ADP by creatine phosphate

Found in muscle fibers but not other cell types.

Aerobic pathway

Rest and during light to moderate exercise, some 95 percent of the ATP used for muscle activity comes from aerobic respiration

Aerobic respiration

Occurs in the mitochondria and involves a series of metabolic pathways that use oxygen.

The initial steps of glucose breakdown occur via a pathway

The initial steps of glucose breakdown occur

Lactic acid

During the anaerobic glycolysis, the pyruvic acid generated during glycolysis is converted in to ______

Muscle fatigue

When we exercise our muscles strenuously for a long time

Isotonic contractions

The myofilaments are successful in their sliding movements, the muscle shortens, and movement occurs.

Isometric contractions

Contractions in which the muscles do not shorten

Aerobic exercise

This exercise results in stronger, more flexible muscles with greater resistance to fatigue

Origin

Attached to the immovable or less movable bone

Insertion

Attached to the movable bone

Flexion

A movement, generally in the sagittal plane, that decreases the angle of the joint and brings two bones closer together

Extension

The opposite of the flexion, so it is a movement that increases the angle, or distance, between two bones or parts of the body.

Rotation

Movement of a bone around its longitudinal axis

Abduction

Moving a limb away from the midline, or median plane, of the body

Adduction

The opposite of abduction, so it is the movement of a limb toward the body midline.

Circumduction

A combination of flexion, extension, and abduction, and adduction commonly seen in ball-and-socket joints, such as the shoulder.

Dorsiflexion

up and down movement of the foot and ankle. Pointing your toe toward your head is _____

Plantarflexion

Pointing your toe away from your head

Supination

Occurs when the forearm rotates laterally so that the palm faces anteriorly (or up) and the radius and ulna are parallel, as in anatomical position

Pronation

Occurs when the forearm rotates medially so that the palm faces posteriorly

Opposition

The saddle joint between metacarpal 1 and the carpals allows opposition of the thumb. This is an action in which you move your thumb to touch the tips of the other fingers on the same hand

Prime mover

Muscles that have the major responsibility for causing a particular movement

Antagonists

Muscles that oppose or reverse a movement

Synergists

Help prime movers by producing the same movement or by reducing undesirable movements

Fixators

Specialized synergists. Hold a bone still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone

Frontalis

Covers the frontal bone, and runs from the cranial aponeurosis to the skin of the eyebrows, where it inserts.

Rectus (straight)

Fibers run parallel to that imaginary line

Oblique (at a slant)

Muscle fibers run ___ to the imaginary line

Circular, Convergent, Parallel, and Pennate

Arrangement of Fascicles

Circular

Generally known as Sphincters

Arranged in concentric rings

Found in external body openings

Convergent

Fascicles ___ toward a single insertion tendon

Triangular and fan-shaped

Parallel

The length of the fascicles run parallel to the long axis of the muscles

most skeletal muscles are in this shape

Pennate

A pattern where short fascicles attach obliquely to a central tendon

It produces more tension or force but smaller range of motion

Uni, Bi, and Multipennate

Types of pennate

Unipennate

Fibers on one side of the tendon

Multipennate

Tendon branches within muscle

Bipennate

Fibers on both sides of tendon

Orbicularis oculi

The fibers of ____ run in circles around the eyes. It allows us to close the eyes, squint, blink, and wink.

Orbicularis oris

Often called the “kissing” muscle, it closes the mouth and protrudes the lips

Buccinator

Runs horizontally across the cheek and inserts into orbicularis oris.

Zygomaticus

Extends from the corner of the mouth to the cheekbone. It is often referred to as the “smiling” muscle because it raised the corners of the mouth.

Masseter

Runs from the zygomatic process of the temporal bone to the mandible, the masseter covers the angle of the lower jaw. This muscle closes the jaw by elevating the mandible

Temporalis

A fan-shaped muscle overlying the temporal bone. It inserts into the mandible and acts as a synergist of the masseter in closing the jaw

Platysma

A single sheetlike muscle that covers the anterolateral neck. Originates from the connective tissue covering of the chest muscles and inserts into the area around the mouth.

Sternocleidomastoid

Two-headed muscles, one found on each side of the neck

Pectoralis major

A large fan-shaped muscle covering the upper part of the chest. Its origin is from the sternum, shoulder girdle, and the first six ribs.

Intercostal muscles

Deep muscles found between the ribs. This is important in breathing because they help to raise the rib cage when you inhale.

Rectus Abdominis

The most superficial muscles of the abdomen. They run from the pubis to the rib cage, enclosed in an aponeunrosis.

External oblique

Paired superficial muscles that make up the lateral walls of the abdomen.

Internal oblique

Paired muscles deep to the external obliques. Their fibers run at right angles to those of the external obliques.

Transversus abdominis

The deepest muscle of the abdominal wall. It arises from the lower ribs and iliac crest and inserts into the pubis.

Trapezius

Most superficial muscles of the posterior neck and upper trunk.

Latissimus dorsi

Two large, flat muscles that covers the lower back.

Erector spinae

The prime mover of back extension.

Quadratus Lumborum

Form part of the posterior abdominal wall. Acting separately, each muscle of the pair flexes the spine laterally.

Deltoid

Form the rounded shape of your shoulders.

Biceps brachii

The most familiar muscle of the arm because it bulges when you flex your elbow.