Muscular System Test Review

Supination

"Turning backward" supination occurs when the forearm rotates laterally so that the palm faces anteriorly, and the radius and ulna are parallel.

Pronation

"Turning forward" pronation occurs when the forearm rotates media leave so that the palm faces posteriorly. Pronation brings the radius across the owner so that the two bones form an X shape.

A Band

(aka dark bands) The area of the sarcomere that contains only myosin. (On the image, it is the section of only dark lines in the center under the H Zone)

I Band

(aka light bands) The area of the sarcomere that only contains the the actin filaments. (On the image, it is the are with no dark lines)

What is aerobic respiration?

95% of ATP used for muscle activity comes from aerobic respiration. It occurs in the mitochondria and involves a series of metabolic pathways that use oxygen. They are collectively called oxidative phosphorylation. Glucose is broken down completely to carbon dioxide and water, and some energy released from broken bonds are captured in ATP bonds. It provides a good ATP harvest, but it is fairly slow.

Actin

A contractile protein that is part of the thin filaments in muscle fibers

Abduction

Abduction is moving a limb away from the midline, or median plane, of the body. Like moving your arm away from the trunk of your body. The terminology also applies to the Fanning movement of the fingers or toes when they are spread apart.

Myosin cross bridges attached to what during a muscle contraction?

Actin filaments

Adduction

Adduction is the opposite of abduction. It is the movement of a limb toward the body midline. Like moving your arm closer to the trunk of your body.

Know the organized order of muscles (largest to smallest)

Epimysium, perimysium (surrounds the fascicles), fascicles, Endomysium (surrounds the muscle fiber), muscle fiber, myofibril, myofilament

Eversion

Eversion is also a special movement of the foot. To evert the foot, turn the soul laterally. (Kind of like bending your ankle inward)

Extension

Extension is the opposite of flexion. It is a movement that increases the angle between two bones or parts of the body. If extension is greater than 180°, it is hyperextension.

Flexion

Flexion is the opposite of extension. Flexion is a movement, generally in the sagittal plane, that decreases the angle of the joint and brings two bones closer together. Flexion is typical of hinge joints (bending the knee or elbow), but it is also common at ball-and-socket joints (for example, bending forward at the hip).

Fusiform muscle

Fusiform muscles are a spindle shaped muscle with an expanded belly midsection, such as the biceps brachii muscle of the arm.

Convergent muscle

In a convergent muscle, the fascicles convergent toward a single insertion tendon. Such a muscle is triangular or fan shaped, such as the pectoralis major

Parallel muscle

In a parallel arrangement, the links of the fascicles run parallel to the long axis of the muscle. These muscles are strap-like. Like the sartorius.

Inversion

Inversion is a special movement of the foot. To invert the foot, turn the sole medially. (Like rolling your ankle)

The functions of calcium in skeletal muscle contractions

Myosin heads cannot cross bridges and allow a muscle to contract without calcium. The attachment of the myosin cross bridges to actin requires calcium ions. The calcium ions trigger the binding of myosin to actin initiating filament sliding.

Naming muscles: location of the muscle's origin and insertion

Occasionally, muscles are named for their attachment sites. For example, the sternocleidomastoid muscle has its origin on the sternum (sterno) and clavicle (cleido) and inserts on the mastoid process of the temporal bone.

What is a motor unit?

One motor neuron may stimulate a few muscle cells or hundreds of them, depending on the particular muscle and the work it does. One neuron and all the skeletal muscle cells it stimulates is referred to as a motor unit.

Myosin

One of the principal contractile proteins found in muscle, myosin heads are what bond with actin filaments to help a muscle contract. They also contain ATPase enzymes, which split ATP to generate power for muscle contraction.

Rotation

Rotation is movement of a bone around it's longitudinal axis. Rotation is a common movement of ball-and-socket joints and describes the movement of the atlas around the dens of the axis (as in shaking your head no).

Where are the calcium ions stored in skeletal muscle?

Sarcoplasmic reticulum

Bipennate muscles

Short fascicles attach obliquely to opposite sides of a central tendon.

Multipennate muscles

Short fascicles attach obliquely to several different sides of a central tendon.

Similarities and differences between skeletal, smooth, and cardiac muscles

Skeletal muscles are striated and involuntary, they contract Rapidly with great force but tire easily and must rest after short periods. Smooth muscles do not have striations and are involuntary, they are spindle-shaped and mononucleic. Cardiac muscles are only found in the heart, they are striated and involuntary, the cardiac fibers are arranged in spiral or figure 8 bundles.

Naming muscles: location of the muscle

Some muscles are named for the bone which they are associated. For example, the temporalis and frontalis muscles overlie the temporal and frontal bones of the skull, respectively.

Naming Muscles: Direction of the muscle fibers

Some muscles are named in reference to some imaginary line, usually the midline of the body or the long axis of a limb bones. When a muscle's name includes the term rectus (straight), it's lines run parallel to that imaginary line. The term oblique tells you that the muscle fibers run obliquely (at a slant) to the imaginary line. Examples include the rectus femoris and the external oblique muscles.

Naming muscles: shape of the muscle

Some muscles have a distinctive shape that helps to identify them. For example, the deltoid muscle is roughly triangular (deltoid means triangular).

Naming muscles: relative size of muscle

Such terms as maximus (largest), minimus (smallest), and longus (long), are often used in the names of muscles. For example, the gluteus maximus is the largest muscle of the gluteus muscle group.

The function of the muscular system

The essential function of a muscle is contraction

unipennate muscles

The fascicles insert only into one side of a central tendon

What is the synaptic cleft?

The gap between The nerve endings and the muscle cells' membranes

What is anaerobic glycolysis?

The initial steps of glucose breakdown occur via a pathway called glycosis. During glycosis, (which occurs in the cytosol), glucose is broken down to pyruvic acid, and small amounts of energy are captured in ATP bonds. The pyruvic acid then enters the oxygen requiring aerobic pathways that occur within the mitochondria to make more ATP. However, when movement becomes intense, the sluggish aerobic mechanisms cannot keep up. And so pyruvic acid is transformed into lactic acid.

What is the major function of the sarcoplasmic reticulum in skeletal muscle contraction?

The main role of this elaborate system is to store calcium and to release it on demand when the muscle fiber is stimulated to contract.

H-Zone

The middle of a sarcomere, where there is a gap between actin filaments, but still contains overlapping myosin in the center. (On the image, it is the spot above where there are only dark lines in the center)

Circular muscle

The pattern of a muscle is circular when the fascicles are arranged in concentric rings. Circular muscles are typically found surrounding external body openings which they close by contracting. Examples include the orbicularis Orbis.

What causes the mechanical force of contraction in muscle contraction?

The sliding of thick and thin myofilaments

What is the neuromuscular junction?

When a long, threadlike extension of the neuron, called the axon, reaches the muscle, it branches into a number of axon terminals, each of which forms junctions with the sarcolemma of a different muscle cell. These are neuromuscular junctions.

What is the purpose of acetylcholine In a muscle contraction

When a nerve impulse reaches the axon terminals, a chemical referred to as a neurotransmitter is released. The specific neurotransmitter that stimulates skeletal muscle cells is acetylcholine

What is an isometric muscle contraction?

When contractions in the muscles do not shorten. Myosin myofilaments are "spinning their wheels", but the tension of the muscle keeps increasing. They try to slide, but the muscle is pitted against some immovable object.

The sliding filament theory

When muscle fibers are activated by the nervous system, the myosin heads attach to binding sites on the thin filament, and the sliding begins. Each cross bridge attaches and detaches several times during a contraction, generating tension that helps to pull the thin filaments toward the center of the sarcomere.

Naming muscles: action of the muscle

When muscles are named for their actions, terms such as flexor, extensor, and adductor appear in their names. For example the adductor muscles of the thigh all bring about its adduction, and the extensor muscles of the wrist all extend the wrist.

What is an isotonic contraction?

When the myofilaments are successful in their sliding movements, the muscle shortens, and a movement occurs. For example, bending your knees, arms, and smiling.

Naming muscles: number of origins

When the term biceps, triceps, or quadriceps forms part of a muscle name, one can assume that the muscle has two, three, or four origins, respectively. For example, the biceps muscle of the arm has two heads, or origins, and the triceps muscle has three.