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Flashcards in Muscles Deck (61):
1

Functions of Muscular System

produce movement
maintain posture
generate heat
stabilize joints

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Three Types of Muscle Tissue

Skeletal/Voluntary/Striated
Smooth/Involuntary/Non-striated
Cardiac

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muscles attached to the skeletal system and constitutes approx. 40% of body weight

Skeletal Muscle

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arranged in 2 layers, one running circularly and the other longitudinally

Smooth Muscle

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found only in the heart

Cardiac

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Chemical Composition of Muscle Tissues

70% water
20% protein
5% carbohydrate, lipid, inorganic salts

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Connective Tissue Sheathes Which Surround the Skeletal Muscles

Epimysium
Perimysium
Endomysium

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tougher coat of connective tissue that bound many fascicle

Epimysium (fascia)

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coarser fibrous membrane that covers bundle of fibers called fascicles

Perimysium

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bundle of muscle fibers

fascicle

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a delicate loose connective tissue that surrounds each muscle fiber

Endomysium

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- cytoplasm of each muscle cell
- contains numerous myofibrils

Sarcoplasm

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- a threadlike structure that extends from one end of the muscle fiber to the other
- consists of myofilaments (proteins) myosin and actin

Myofibrils

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- comprises the larger thick filaments that are made mostly of bundled molecules of the protein myosin
- resemble like minute golf clubs
- extends the entire length of a dark A band and the mid parts of the filaments are smooth but their ends are studded with small projections

Myosin filaments

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- part that attaches to exposed sites on the actin and - ----- known as cross bridge when they link the thick and thin filaments together during contraction

myosin heads

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myosin heads when they link the thick and thin filaments together during contraction

cross bridge

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comprises the tin filaments/myofilaments which resemble 2 minute strands of pearls twisted together
anchored to the Z disc (disc-like membrane)

Actin filaments

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calcium-binding sites attached at specific intervals along actin filaments

Troponin

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- expose attachment sites on the actin myofilaments when calcium binds to troponin
- cover attachment sites when calcium is not bound to troponin

Tropomyosin

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- highly ordered arrangement of myosin and actin
- basic structural and functional unit of a skeletal muscle
- contractile unit of muscle
- extends from on Z-disc to another Z-dic

Sarcomere

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- darker, central region of the sarcomere
- extends the length of myosin filaments

A band

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- a network of protein fibers for the attachment of actin
- attachment point of actin

Z line

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- a light band which consist only of actin
- spans each Z disk and ends at the myosin filaments

I band

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- light zone which contains only of myosin
- disappears during contraction

H zone

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- dark, straining band at the center of the sarcomere where myosin is anchored
- attachment point of myosin

M line

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cell membrane of the muscle fiber

Sarcolemma

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- tube-like invagination located along the surface of sarcolemma
- arranged at regular intervals along the muscle fiber and wrap around sarcomeres where the myosin and actin filaments overlap
- connect the sarcolemma to the sarcoplasmic reticulum

Transverse/T-tubules

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nerve cells along which action potentials travel to skeletal muscle fibers

Motor Neuron

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consist of a single motor neuron and all the skeletal muscle fiber it innervates

Motor Unit

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- junction between a branch of an axon and a muscle - - --- fiber function is to release Ach in response to an action potential at the neuromuscular junction

Neuromuscular Junction or Synapse

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axon terminal

Presynaptic terminal

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- space between the presynaptic terminal and the muscle fiber membrane
- Na is abundant

Synaptic Cleft

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muscle membrane fiber

Postsynaptic Membrane

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small vesicles in the presynaptic terminal which contain acetylcholine

Synaptic Vesicles

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- a molecule released by the presynaptic nerve cell that stimulates or inhibit a post synaptic cell
- neurotransmitter

acetylcholine

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enzyme that breaks down acetylcholine

Acetylcholinesterase

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- the sliding of actin myofilaments past myosin ------------ - myofilaments during contraction

Sliding Filament Model

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Types of Muscle Contraction

Isotonic
Isometric

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- myofilaments are successful in their sliding movements
- muscle shortens and movement occurs

Isotonic

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- contraction in which muscles do not shorten; no net movement
- myofilaments are trying to slide but muscle is pitted against some immovable object

Isometric

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Physiologic Properties of Muscle

Excitability
Contractility
Tonus
Extensibility
Elasticity

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the capacity of the skeletal muscle to respond to stimulus

Excitability

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the ability of skeletal muscle to shorten with force

Contractility

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the ability of the skeletal muscle to sustain partial contraction in response to stretch receptors

Tonus

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skeletal muscle can be stretch

Extensibility

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the ability of the skeletal muscle to recoil to their original resting length after they have been stretched

Elasticity

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Types of Muscles

Prime mover/ Agonist
Antagonist
Synergists
Fixators

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- muscle that has major responsibility for causing a particular movement
- produces flexion

Agonist/Prime Mover

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- muscles that oppose or reverse a movement
- for muscles with opposing action

Antagonist

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- muscles that help prime movers by producing the same movement or by reducing undesirable movements
- group of muscles working together to produce a movement

Synergists

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- specialized synergist that hold a bone still or stabilize the origin of a prime mover
- postural muscles that stabilize the vertebral column, muscles that anchor the scapula to the thorax

Fixators

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- the head
- fixed
- attached to the immovable or less immovable bone

Origin

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- end of the muscle attached to the movable bone
- when muscles contract, itmoves toward the origin
- mobile

insertion

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longest muscle in the body

Sartorius

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nuclei in skeletal muscle

sarcolemma

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- smooth endoplasmic reticulum
- has a high concentration of calcium ions

Sarcoplasmic Reticulum

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provides the final go signal for contractions

Calcium`=

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long, threadlike extension of a neuron

nerve fiber or axon

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Potassium diffuses from this

sarcolemma

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products of breakdown of acetylcholine

acetic acid
choline (goes back to axon terminal)

61

acetylcholine receptors are present in these folds

sarcolemma