bio 004 lecture exam 3 Muscle Tissue and Microanatomy Overview

how does skeletal muscle produce movement?

by exerting force on tendons; pull on bones or other structures; most muscles will cross one joint and attach to the articulating bones of the joint

Muscle Belly

Fleshy portion of the muscle.

muscle attachments

consists of: origin, insertion and action

Origin

Attachment of muscle tendon to stationary bone.

Insertion

Attachment of muscle tendon to movable bone.

action

the main movements that occur with muscle contraction

lever systems

to produce movement, bones act as levers; consists of 2 different forces

Effort

Force exerted by muscle contraction.

Load/Resistance

Force opposing movement, like body weight.

mechanical advantage/disadvantage

determined by the distance of the load from fulcrum

Mechanical Advantage

smaller distance from fulcrum require less effort needed to move heavier load.

Mechanical Disadvantage

More effort needed for farther load.

classification of levers

consists of 3 classes:
first class, second class and third class

First Class Lever

Fulcrum between effort and load.

Second Class Lever

Load between fulcrum and effort.

Third Class Lever

Effort between fulcrum and load.

coordination among muscles

muscles do not work in isolation; movements are often the result of several muscles acting as a group

Agonist

Muscle that contracts to cause action.

Antagonist

Muscle that stretches in response to agonist.

Synergists

Muscles aiding prime mover's action.

Fixators

Muscles stabilizing the origin of prime mover.

Compartment

Group of muscles with common function. (ex: upper extremities flexors and extensors)

Static Stretching

Sustained stretching held for 30 seconds.

Range of Motion (ROM)

Normal movement extent of joints.

characteristics used to name muscles

Direction, size, shape, action, number of origins, location, and origin and insertion.

Rectus (direction)

Muscle fibers parallel to midline.

transverse (direction)

perpendicular to midline

oblique (direction)

diagonal to midline

Maximus; minimus (size)

Largest muscle in a group; smallest muscle in group

longus; brevis (size)

longest in muscle group; shortest in muscle group

latissimus; longissimus (size)

widest in muscle group; longest in muscle group

magnus (size)

largest in muscle group

major; minor (size)

larger in muscle group

vastus (size)

large in muscle group

Deltoid (shape)

Triangular-shaped muscle.

trapezius (shape)

trapezoid

serratus (shape)

saw-toothed shape

rhomboid (shape)

diamond shaped

orbicularis (shape)

circular

piriformis (shape)

pear-shaped

gracilis (shape)

slender

Flexor (action)

Muscle decreasing joint angle.

extensor (shape)

increase joint angle

Abductor (shape)

bone moves away from midline

adductor (shape)

bone moves toward midline

levator (shape)

elevates

depressor (shape)

lowers

pronator (shape)

turns palm posteriorly

supinator (shape)

turns palm anteriorly

sphincter (shape)

decreases the size of an opening

Biceps (origins)

Muscle with two origins.

tricep (origins)

muscle with three origins

quadriceps (origins)

muscle with four origins

sternocleidomastoid

originates on the sternum and clavicle & inserts on the mastoid process of the temporal bone

3 types of muscle tissue

skeletal, cardiac, smooth

Skeletal Muscle Tissue

Striated and voluntary muscle covering skeleton; enable humans to move and perform daily activities

Cardiac Muscle Tissue

Striated, involuntary muscle in heart walls; to pump blood throughout the body's circulatory system

Smooth Muscle Tissue

Involuntary and non striated; 4.Rich blood supply; require huge amounts of energy/continuous amounts of oxygen; generate large amounts of metabolic wastes

characteristics of muscle tissue

excitability, contractility, extensibility, elasticity

Excitability

Ability to respond to stimulation.

Contractility

Ability to shorten forcibly when stimulated.

Extensibility

Ability to stretch beyond resting length.

Elasticity

Ability to return to resting length.

Functions of Muscle Tissue

Movement, posture maintenance, stabilization of joints and production of body heat

production of movement

when muscles contract they contribute to gross and fine movement

maintenance of posture and body position

constant muscle activity provides tension that allows us to hold a body position, such as sitting upright, standing, holding your head still.

Stabilization of joints

Pull on bones to facilitate movement.

Generation of heat

Muscle contraction produces heat, regulating body temperature.

nerve and blood supply to muscles

Rich blood supply; require huge amounts of energy/continuous amounts of oxygen; generate large amounts of metabolic wastes

Muscle capillaries

Long, winding vessels adapting to muscle length changes.

Connective Tissue Sheaths

Layers wrapping individual muscle fibers for support.

functions of CT sheaths

Support and reinforcement (prevent bulging muscle from bursting during strong contractions); Provide routes for the entry and exit of blood vessels and nerve fibers; Continuous with tendons; transmit pulling force to the bone that is to be moved

Epimysium

outside the muscle; Dense irregular CT surrounding the entire muscle; Can blend with the deep fascia between neighboring muscles or the superficial fascia deep to the skin

Perimysium

CT surrounding each fascicle of muscle fibers.

Fascicles

Bundles of muscle fibers within a muscle.

Endomysium

within the muscle; CT sheath surrounding individual muscle fibers.

Muscle attachments

Connections between muscles and bones or cartilage.

Direct attachments

Epimysium fuses to bone or cartilage.

Indirect attachments

Tendons or aponeurosis anchor muscle to skeletal elements.

Skeletal muscle fibers

Long, cylindrical cells with multiple nuclei.

Sarcoplasm

Cytoplasm of a muscle cell, rich in glycogen.

Myoglobin

Oxygen-storing red pigment in muscle cells.

Myofibrils

Rod-like structures within muscle fibers for contraction.

Striations

Dark and light bands along myofibrils.

striations of sarcomere

Dark bands (A bands); Lighter region among the dark bands (H zone); H Zone is bisected by a dark line (M line); Z line or Z disc: Middle interruption of the I bands

Sarcomere

Definition: smallest contractile unit; a functional unit of skeletal muscle
Location: area of a myofibril that goes between 2 Z discs.

Myofilaments

Actin and myosin which are responsible for motility and shape change for every cell in the body.

Thick filaments

contain myosin (red); centrally located; extend the entire length of the A band; connected at the M line

Thin filaments

Actin filaments extending across I band; partway to the A band; anchored by alpha-actinin (Z-disc)

Elastic filament

Desmin connecting myofibrils, providing elasticity: extend from the Z disc; connect each myofibril to the next

Myosin

Thick filament with heavy and light chains; Globular heads: during contraction, they link the thick and thin filaments together to form cross-bridges and swivel around their
point of attachment acting as motors to generate force.

Actin

thin filaments; kidney shaped polypeptide units activate sites to which myosin heads attach during contraction

regulatory proteins in thin filaments

consists of tropomyosin and troponin

Tropomyosin

Protein blocking myosin binding sites on actin.

Troponin

Complex regulating muscle contraction via calcium binding.

proteins that help form myofibril

titin, dystrophin, nebulin, myomesin and C proteins

titin

holds thick filaments in place; helps muscle spring back into shape after stretching.

dystrophin

links the thin filaments to the integral proteins of the sarcolemma

Nebulin, myomesin, C proteins:

bind filaments/sarcomeres together; maintain alignment.

Sarcoplasmic Reticulum

regulating calcium ions; stores and releases calcium on demand when muscle fibers are stimulated