EXAM 3 Chapter 9 The Muscular System 1: Skeletal Muscle Tissue and Muscle Organization単語カード | Quizlet

skeletal muscle

attaches to skeleton

has single, long & cylindrical striated cells

the only multinucleate type of muscle

controlled voluntarily

cardiac muscle

occurs in the heart wall

has branching chains of striated cells

one nucleus per cell; some binucleate

intercalated discs contains several types of cell jun.

cardiac cells are electrially coupled by gap junctions

controlled involuntarily

smooth muscle

occurs in walls of hollow organs

single, fusiform nonstriated cells

uninucleate (one cell)

controlled involuntarily

1. excitability

2. contractility

3. extensibility

4. elasticity

What are the 4 specialized properties the three types of muscles share?

excitability

ability of muscles to respond to nerve signals or stimuli

causes electrical impulses to travel along the muscle cells' plasma membrane

contractility

ability to generate a strong pulling force while muscle cells shorten (contract)

elasticity

ability of a muscle, after being stretched (or contraction), to recoil passively to its original (or resting) length

extensibility

the ability to continue to contract over a range of resting lengths

1. movement

2. maintain posture and body position

3. supports soft tissue

4. regulates entrance and exit of materials

5. heat generation

6. joint stabilization

What are the functions of skeletal muscles?

epimysium

What surrounds skeletal muscles?

bundles of muscle fascicles

What is skeletal muscle comprised of?

bundles of muscle fibers

What are muscle fascicles comprised of?

perimysium

What surrounds muscle fascicles?

muscle fiber (myofiber or muscle cell)

a highly elongated cell (in skeletal or smooth but NOT in cardiac muscle) holds together many myofibrils

endomysium

What surrounds muscle fibers/myofiber/muscle cells?

sarcolemma

plasma membrane of a muscle fiber (muscle cell)

comprised of abundant myofibrils

sarcoplasm

cytoplasm of muscle fiber (muscle cell(

contains numerous myofibrils

myofibril

a cylindrical structure, as long as entire muscle fiber (muscle cell)

consists of sarcomeres

surrounded by sarcoplasmic reticulum

myofibrils because they can shorten

What structure is responsible for contraction of the skeletal muscle fiber and why?

because a myofibril is attached to the sarcolemma at each end of the cell

Why does myofibrils contraction lead to shortening of the entire cell?

sarcoplasmic reticulum (SR)

an internal membrane complex similar to the smooth endoplasmic reticulum of other cells

STORES calcium ions

sarcoplasmic reticulum (SR)

What structure in skeletal muscle is closely associated with the transverse (T) tubules?

sarcoplasmic reticulum (SR)

What structure in skeletal muscle plays an important role in controlling the contraction of individual myofibrils via the release of calcium ions?

- STORES calcium ions

transverse (T) tubules

deep invaginations of the sarcolemma (into the sarcoplasm) which allow electrical impulses (that stimulate the membrane to contract) to quickly travel to the interior of the cell

terminal cisternae

expanded chambers on either side of a transverse tubule where the tubule of the SR has enlarged and fused

triad

the combination of a pair of terminal cisternae plus a transverse tubule

sarcomere

myofibrils consists of sarcomeres, which are repeating units of myofilaments; the smallest functional unit of muscle fiber

myofilaments

What is the smallest functional until of muscle fiber?

myofilaments

the sarcoplasm of muscle contains protein filaments, which generate contractile force

- fills up most of the sarcoplasm of each muscle fiber

- organized in the repeating units called sarcomeres

myofilaments

What determines the striation pattern in skeletal muscle fibers?

actin and myosin

What are the 2 primary types of myofilaments in muscle cells?

actin filaments

protein filaments found in THIN filaments

myosin filaments

protein filaments found in THINK filaments

parallel to the long axis of the cell

sarcomeres arranged side to side (dark and light band appearance)

How are myofibrils arranged in a muscle cell/fiber?

M line

a group of proteins, which link the thick filaments that lie in the center of the sarcomere

Z lines

open meshwork of interconnecting proteins called ACTININS, which occur where thin filaments from adjacent sarcomeres join

actin filaments (thin) attach to the Z lines and extend towards the M line

Where do thin filaments (actin) attach and extend towards?

Zone of Overlap

area where the thin filaments pass between the thick filaments

thin and thick overlap

A band (anisotropic band)

the area containing THICK filaments, including the:

- M line

- H line

- Zone of overlap

appears as a dark band

H band

area contains THICK filaments ONLY

I band (isotropic band)

the area containing THIN filaments only

appears as a light band

Z lines move closer together

I and H bands shorten

What happens to the Z lines during contraction?

What happens to the I and H bands during contraction as well?

Tropomyosin

protein molecules that form a long chain, which overs the active sites, preventing actin-myosin interaction

Troponin

protein molecules that hold the tropomyosin strand in place

- changes position to move the tropomyosin molecules, exposing the active site, prior to a muscle contraction

- act as the regulator molecule of a muscle contraction

Cross-bridges because they connect the thick and thin filaments during a muscle contraction

What are myosin heads also known as and why?

spindle-shaped cylinders

triangles

sheets

What are the various shapes of skeletal muscle?

whole muscle (organ)

muscle fascicles

muscle fibers (cells)

myofibrils

sarcomere

myofilament (actin and myosin)

What are the levels of organization in skeletal muscle? (gross to microscopic)

epimysium

dense irregular connective tissue sheath wrapped around a whole muscle

perimysium

fibrous connective tissue sheath wrapped around a fascicle

endomysium

thin reticular fiber connective tissue sheath wrapped around each muscle fiber

origin

immovable (or less movable) attachment from which a muscle extends

insertion

more movable attachment of a muscle

tendons, aponeuroses, or direct (fleshy) attachment

Skeletal muscles attach to bones through what?

muscle contraction

exerting a pull, or tension, and shortening the muscle fibers in length

muscle fibers are stretched to near-optimal length before stimulation of contraction occurs

Explain near-optimal length in muscles.

Calcium ions

The presence of what is needed to TRIGGER for a contraction?

ATP

The presence of what is REQUIRED for the contraction to occur?

Sliding Filament Theory

theory or mechanism that explains the physical changes that occur between the thin and thick filaments during muscle contraction

H band and I band get smaller

Zone of overlap gets larger

Z lines move closer

A band remains constant throughout contaction

What happens in the Sliding Filament Theory of muscle contraction?

bind to active sides on thin filaments causing sliding to occur

What do the myosin heads of thick filaments do during the Sliding Filament Theory

Cross-bridge binding

the myosin heads pivots toward the M line, pulling the thin filaments toward the center of the sarcomere

detaches and returns to its original position

What happens to the cross bridge after it pivots towards the M line?

binds, pivot, detach, and return

What is the cycle in which the myosin heads follow in the Sliding Filament Theory?

Z lines move towards the M line when the think filaments pull on the thin filaments

How does the sarcomere shorten?

1. an impulse from the sarcolemma signals the sarcoplasmic reticulum to release Ca2+

2. Ca2+ initiates the sliding of the myofilaments

(muscle contraction)

What happens when a nerve cell stimulates a muscle fiber?

neuromuscular synapse

a specific synapse between a motor neuron and a muscle cell

synaptic terminal

the expanded tip of the motor neuron's axon, at the neuromuscular synapse

synaptic vesciles

small secretory vesicles (filled with acetylcholine) in the cytoplasm of the synaptic terminal

neurotransmitter

a chemical released by a neuron to communicate with another cell

Acetylcholine

a neurotransmitter that signals the muscle cell to contract; released at axon terminal

synaptic cleft

a narrow space that separates the synaptic terminal from the motor end plate of the skeletal muscle fiber

Acetylcholinesterase

an enzyme that breaks down ACh molecules and is released by the basal lamina of the cell into the synaptic cleft

1. electrical impulse arrive at synaptic terminal

2. ACh is released and binds to receptor sites on motor end plate

3. action potential (AP) is generated

4. AP travels all over the surface of the sarcolemma and into each T tubule

5. APs continue to be generated until AChE removes the bound ACh.

(ACh is immediately broken down by AChE after it signals a single contraction)

What are the steps during Neural Stimulation of a Muscle?

motor unit

consists of one motor neuron and all the skeletal muscle fibers it innervates (controls)

- contains different numbers of muscle fibers distributed widely within a muscle

simultaneously

All muscle fibers in a motor unit contract _________.

level of control of the movement

The size of a motor unit indicates what?

muscle twitch

a single, momentary contraction, which is a response to a single stimulus

contain different numbers of muscle fibers distributed widely within a muscle

all or non principle

a characteristic in which each muscle fiber either contacts completely or does not contract at all

how many motor units are activated

The amount of force, exerted by the muscle as a whole, depends on what?

recruitment

the smooth but steady increase in muscular tension produced by increasing the number of motor units that is activated

muscle tone

resting tension in a skeletal muscle

muscle spindles

specialized muscle cells that are monitored by sensory nerves, which control the muscle tone in the surrounding muscle tissue

muscle hypertrophy

enlargement of skeletal muscles that undergo excessive repeated stimulation that produces near-maximal tension

muscle atrophy

reduction in skeletal muscle size, tone, and power as a result of inadequate stimulation to maintain resting muscle tone in the affected area

slow oxidative fibers (red fibers / type I fibers)

thin fibers that are red because of their abundant myoglobin (oxygen-binding pigment in sarcoplasm)

obtain energy from AEROBIC metabolic reactions

abundant mitochondria and rich capillary supply

contract slowly; extremely resistant to fatigue as long as enough oxygen is present

deliver prolonged contractions

best for maintaining postures

intermediate (fast oxidative) fibers / type II fibers

contract quickly

oxygen dependent and have a high myoglobin content

abundant mitochondria and rich capillary supply

fatigue resistant but less so than Type I

best for long-term production of fairly strong contractions, such as required in locomotion of lower limbs

fast glycolytic fibers (white fibers/ type IIx fibers)

pale fibers because they contain little myoglobin

twice the diameter of Type I fibers

contain more myofilaments

generate much more power

depend on ANAEROBIC pathways to make ATP

few mitochondria and capillaries present

contract rapidly; fatigue quickly

best for short bursts of power (lifting heavy; upper limbs)

fascicle

bundle of muscle fibers

parallel muscle

the long axes of the fascicles are parallel to the long axis of the muscles, and the muscle extends from origin to insertion

has a central body, or belly

ex: biceps brachii muscle

convergent muscle

the origin is broad, and the fascicles converge toward the tendon of insertion, its common attachment site

fibers may pull on a tendon, tendinous sheet, or a slender band of collagen fibers known as a raphe

ex: pectoralis major muscle

circular muscle (sphincter)

the fascicles are arranged in concentric rings around an opening or recess

when muscle contracts, the diameter of the opening decreases (close-tighten)

ex: orbicularis oris muscle

pennate muscle (penna, feather)

the fascicles are short and attach at an oblique angle to a tendon that runs through the body (the whole length) of the muscle

unipennate muscle

the fascicles insert into one side of the tendon

ex: extensor digitorum longus muscle of the anterior leg

bipennate muscle

the fascicles insert into both sides of the tendon

ex: rectus femoris muscle of the thigh

multipennate muscle

the fascicles insert into a tendon that branches within the muscle

looks like many feathers situated side by side, whose quills are all inserted into one tendon

ex: deltoid muscle

agonist (prime mover)

a muscle whose contraction bears the main responsibility for a PARTICULAR MOVEMENT

ex: biceps brachii for forearm flexion at the elbow

antagonist

group(s) of muscles whose actions oppose that of the corresponding agonist

ex: tricepts brachii, during forearm flexion, are stretched and maybe slightly relaxed, and stablizes the flexion movement; BUT THEY ALSO ACT AS AGONISTS for extension of the forearm

synergist

aid the agonists, either by adding a little extra force to the same movement or by reducing undesirable extra movements that the agonist may produce; they stabilize joints, as fixators

externus or superficialis

muscles visible at the body surface

internus or profundus

muscles lying beneath the body surface