HS 125 Test 3

Tendon Sheath

tubelike tunnel around tendon of muscle lined with synovial membrane

Movement

Skeletal muscle contractions produce movement of the body as a whole(locomotion) or movement of its parts.

Heat Production

Produce heat due to catabolism. The heat produced by one cell is inconsequential, but because skeletal muscle cells are both highly active and numerous, they produce the majority of the body heat. Skeletal muscle contractions therefore constitute one of the most important parts of the mechanism for maintaining homeostasis of temperature

Posture

The continued patrial contraction of many skeletal muscles make possible standing, sitting, and maintain a relatively stable position of the body while walking, running, or preforming other movements.

Lever Systems: Class I

Fulcrum(F) between the load(L) and force or pull(P). • Not abundant • Generally serve as levers of stability Example: head tipped backward on the atlas.

Lever Systems: Class II

• Load(L) between the fulcrum(F) and force or pull(P). Example: Opening mouth against resistance (depression of the mandible)

Lever Systems: Class III

Force or pull(P) between the fulcrum(F) and the load(L). • Permit rapid and extensive movement • Most common type in the body Example: Flexing forearm at the elbow

Muscle Fiber (Cell)

Made up of Myofibril(s), contains many nuclei, sarcoplasmic reticulum, covered by the sarcolemma

Myofibril

made up on thick and thin filaments

Fascicle

many muscle fibers

Endomysium

surrounds entire muscle fiber

Perimysium

surrounds a fascicle (bundle) of muscle fibers

Epimysium

Surrounds entire muscle organ

Deep Fascia

surrounds deeper organs including epimysium of muscle

Superficial fascia

under the skin (also called hyperdermis)

Fascia

external to muscles, bones, other organs

Tendon

bands or cords of fibrous connective tissue that attach a muscle to a bone or other structure

Ligament

band of white fibrous tissue connecting bones to other bones

Parallel

muscles can vary in length, but long straplike muscles with parallel fascicles are the most typical. Example: The sartorius muscle, the rectus abdominis muscles, which run the length of the anterior abdominal wall, have parallel muscle fascicles that are “interrupted” by transverse intersections.

Convergent

muscles have fascicles that radiate out from a small to a wider point of attachment, much like the blades in a fan. Example: Pectoralis major muscle

Pennate

muscles are said to be “featherlike” in appearance. • Three categories of these muscles have uniquely different types of fascicle attachments that in some ways resemble the feathers in an old-fashioned plume pen. • Unipennate muscles, such as the soleus, have fascicles that anchor to only one side of the connective tissue shaft. • Bipennate muscles, such as the rectus femoris in the thigh, have a type of double-feathered attachment of fascicles. • Multipennate muscles, such as the deltoid, the numerous interconnecting quill-like fascicles converge on a common point of attachment.

Fusiform

muscles have fascicles that may be close to parallel in the center, or “belly,” of the muscle but converge to a tendon at one or both ends. Example: brachioradialis

Spiral

muscles, such as the latissimus dorsi, have fibers that twist between their points of attachment.

Circular

muscles, sometimes called orbicular muscles and sphincters, often circle body tubes or openings. Example: Orbicularis oris around the mouth, external anal sphincter

Muscle Actions

Any muscle that preforms an action is a ‘mover’

Antagonists

muscles that when contracting, directly oppose prime movers (or agonists). They are relaxed while the prime mover is contracting to produce movement • Simultaneous contraction of a prime mover and its antagonist muscle results in rigidity and lack of motion. • Antagonists are important in providing precision and control during contraction of prime movers.

Agonist (Prime movers)

Muscle that directly performs a specific movement. The movement produced by a muscle of a prime mover is described as the ‘action’ or ‘function’ of that muscle.

Synergists

muscles that contract at the same time as the prime mover. They facilitate or complement prime mover actions so that the prime mover produces a more effective movement.

Fixator

muscles generally function as joint stabilizers. They frequently serve to maintain posture or balance during contraction of prime movers acting on joints in the arms and legs. • Because fixator muscles assist the prime mover in performing an action, they are a type of synergist.

Axial Muscles: Neck & Back

Sternocleidomastoid

Trapezius

Patissimus dorsi

Axial Muscles: Chest

Pectoralis major

Serratus anterior

Axial Muscles: Abdominal Wall & Pelvic Floor

External oblique

Levator ani

Coccygeus

Appendicular Muscles: Shoulder & Arm

Deltoid

Biceps brachii

Triceps brachii

Brachialis

Appendicular Muscles: Forearm

Brachioradialis

Pronator teres

Appendicular Muscles: Buttocks

Gluteus maximus

Gluteus minimums

Gluteus Medius

Tensor fasciae latae

Appendicular Muscles: Thigh Anterior thigh

Quadriceps femoris group

Rectus femoris

Vastus lateralis

Vastus medialis

Vastus intermedius

Appendicular Muscles: Medial thigh

Gracilis

Adductor group (brevis, longus, magnus)

Appendicular Muscles: Posterior thigh

Semimembranosus

Semitendinosus

Biceps femoris

Hamstring group

Appendicular Muscles: Leg, Anterior Leg & Posterior Leg

Tibialis anterior

Gastrocnemius

Soleus

Points of attachment

Origin and insertion points may be used to name a muscle. Example, the sternocleidomastoid has its origin on the sternum and clavicle and inserts on the mastoid process of the temporal bone

Origin

Point of attachment that does not move when the muscle contracts. The bone is the more stationary of the two bones at a joint when contraction occurs.

Insertion

Point of attachment that moves when the muscles contracts. The insertion bone moves along a ‘line of force’ toward the origin bone when the muscle shortens.

Sarcoplasm

cytoplasm

Sarcoplasmic reticulum

networks of tubules that temporarily store calcium ions. The membrane of the SR continually pumps the calcium ions from the Sarcoplasm and stores the ions within its sacs

Myofilaments

Make up the myofibrils, there are two types, thick filaments and thin filaments. They are made up of four proteins myosin, actin, tropomyosin, and troponin.

T-tubules

Structure unique to muscle cells, system of transverse tubules extending across the sarcoplasm at a right angle to the long axis of the cell. Function is to allow electrical signals or impulses travelling along the sarcolemma to move deeper into the cell

Triad

allows electrical signals traveling along a T tubule to stimulate the membranes of adjacent sacs of the SR

Myofibrils

cytoskeleton of the muscle fiber, very fine cytoskeleton filaments that extend lengthwise along the skeletal muscle fiber and almost fill the sarcoplasm. Consist of a line up of many sarcomeres

Sarcomere

Segment of the myofibril between two successive Z disks (Z lines). Sarcomere functions as a contractile unit.

A-bands

wide dark stripes cross striations alternate with the lighter stripes formed by I-bands. Runs the entire length t of the thick filaments (aka. Anisotropic band)

Dystrophin

protein that holds the actin filaments to the sarcolemma

Globular actin (G -actin)

strung together like beads to form two fibrous stands (f-actin) that twist around each other to form the bulk of the thin filament.

Elastic filament

composed of a protein called titin (connectin) anchor the thick filaments to the z-disks. Thought to give the myofibrils and muscle fibers their characteristic elasticity.

H-band

middle region of the thick filaments where they do not overlap the thin filaments

M-line

holds together and stabilize the thick filaments they from the middle line in the thick filaments.

Z-Disk

dense plate or disk to which the thin filaments directly anchor, uses as a landmark separating one sarcomere from the next

I-bands

Segment that include the z-disk and the ends of the thin filaments where they do not overlap the thick filaments (aka. Isotropic band)

Characteristics of Muscle Tissue

• Excitability or irritability

–ability to be stimulated

•Contractility – muscle cells can contract or shorten, allows muscle tissue to pull on bones and produce body movement. Sometimes muscle fibers work by resisting a load without becoming shorter, this is still considered contracting.

• Extensibility – ability to extend or stretch, allows muscle to return to their resting length after contracted. Muscles can still extend while exerting force.

• Elasticity – the ability to ‘bounce back’ or recoil to its resting shape. Storing energy then releasing energy to make muscle activity faster, stronger, and more efficient.

Major Events of Muscle Contraction & Relaxation: Excitation and Contraction

1. A nerve impulse reaches the end of a motor neuron and triggers release of the neurotransmitter acetylcholine (Ach).

2. Ach diffuses rapidly across the gap of the neuromuscular junction and binds to Ach receptors on the motor endplate of the muscle fiber.

3. Stimulation of Ach receptors initiates an impulse that travels along the sarcolemma, through the T tubules, to the sacs of the sarcoplasmic reticulum (SR).

4. Ca++ is released from the SR into the sarcoplasm, where it binds to troponin molecules in the thin myofilaments.

5. Tropomyosin molecules in the thin myofilaments shift and thereby expose actin's active sites.

6. Energized myosin cross bridges of the thick myofilaments bind to actin and use their energy to pull the thin myofilaments toward the center of each sarcomere. This cycle repeats itself many times per second, as long as adenosine triphosphate is available.

7. As the filaments slide past the thick myofilaments, the entire muscle fiber shortens.

Major Events of Muscle Contraction & Relaxation: Relaxation

1. After the impulse is over, the SR begins actively pumping Ca++ back into its sacs.

2. As Ca++ is stripped from troponin molecules in the thin myofilaments, tropomyosin returns to its position and blocks actin's active sites.

3. Myosin cross bridges are prevented from binding to actin and thus can no longer sustain the contraction.

4. Because the thick and thin myofilaments are no longer connected, the muscle fiber may return to its longer, resting length

Neuromuscular junction (NMJ)

a chemical synapse formed by the contact between a motor neuron and a muscle fiber. It is here that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction. Point of contact between nerve endings and muscle fibers.

Motor Neuron

nerve cell that transmits nerve impulses from the brain and spinal cord to muscles and glandular epithelial tissues

Motor endplate

point at which motor neurons connect to the sarcolemma to form the NMJ.

ACh receptor sites

Where ACH can bind to stimulate contraction located in the sarcolemma between the synaptic clefts.

synaptic cleft

the space between neurons at a nerve synapse across which a nerve impulse is transmitted by a neurotransmitter

Synaptic vesicles

vesicles contain neurotransmitters that diffuse to the synaptic cleft and bind to ion channels on the postsynaptic membrane. These steps allow adjacent neurons to communicate and initiate an action potential.

Acetylcholine (ACh)

type of neurotransmitter used by motor neurons at the NMJ to stimulate muscle contraction at or in some autonomic synapses (in ganglionic synapses, parasympathetic effectors, and some sympathetic effectors).