A&P1 CH 10 Muscles

myo, mys, sacro are all prefixes for what

muscle

what are the 3 types of muscle

skeletal, cardiac, smooth

what types of muscle cells are elongated and referred to as muscle fibers

skeletal and smooth

four main characteristics of muscle

excitability

contractility

extensibility

elasticity

define excitability within muscles

responsiveness; ability to receive and respond to stimuli

define contractility

ability to shorten forcibly when stimulated

define extensibility within muscles

ability to be stretched

define elasticity within muscles

ability to recoil to resting length

in which muscle tissue are striations present

skeletal and cardiac

the muscle function body movement is what

locomotion

muscles can stabilize body ___ and maintain ___

position and posture

muscle store by using what

sphincters 

muscles move substances by doing what

pumping blood, blood flow, digestion, propelling gametes

muscles generate heat as they contract, this is known as

thermogenesis

one entire muscle is considered an

organ made up of different tissues

what are the different tissues in a muscle organ

skeletal, nerve and blood supply, connective tissue sheaths, and attachments

each muscle receives what 3 things

nerve, artery, and veins

skeletal muscle has nerves supplying every fiber to do what

control activity

contracting muscle fibers require a lot of oxygen and nutrients which requires them to have

a dedicated blood supply

what do CT sheaths do

support cells and reinforce whole muscle

what is an epimysium

dense irregular CT surrounding entire muscle that blends with fascia

what is the outermost covering of a muscle

fascia

what are fascicles

groups/bundles of muscle fibers

what is a perimysium

dense irregular CT surrounding fascicles

what does the perimysium do

separates bundles of muscle

what is a endomysium

fine reticular fibers surrounding each muscle cell

biggest thing being covered

muscle

smallest thing being covered

thin and thick filaments

what are the types of attachment

insertion and origin

define insertion

attachment to moveable bone

define origin

attachment to immovable/less moveable bone

attachments can be

direct or indirect

define direct attachment

fleshy; epimysium fused to periosteum (bone) or perichondrium (cartilage)

in a direct attachment, epimysium can be fused to ___(bone) or ____(cartilage)

periosteum or perichondrium

define indirect attachment

connective tissue wrappings extend beyond muscle  as ropelike tendon or sheetlike aponeurosis

what are skeletal muscles

long, cylindrical, multinucleate cells (forms from fusion of myoblasts)

unfused myoblasts become _____

myosatellite cells

what do myosatellite cells do

growth and repair of muscles

what is a sacrolemma

muscle fiber plasma membrane

a sacrolemma is modified to respond to what

nervous system

what is a sacroplasm

muscle fiber cytoplasm

a sacroplasm is used for

nourishment and some communication

what do glycosomes store

glycogen

muscle cells readily use glycogen for

energy

what does myoglobin store

O2

myoglobin is used to make ___ using O2

ATP

what are some modified organelles in muscle

myofibrils, sarcoplasmic reticulum, T tubules

what are myofibrils

densely packed, rodlike elements

how many myofibrils can one muscle fiber contain

1000s (~80% of muscle cell volume)

sarcoplasmic reticulum stores

calcium

what do T tubules do

transport

myofibril features 

striations, sarcomeres, and myofilaments

a thick myofilament contains what

myosin

a thin myofilament contains what

actin

what is a sarcomere

smallest contractile unit (functional unit) of muscle fiber

individual sarcomeres align end to end along ___; similar to boxcars of a train

myofibril

what are striations

stripes formed from repeating series of dark and light bands along length of each myofibril

what is a myofilament

orderly arrangement of actin (thin) and myosin( thick) myofilaments within sarcomere

what is a Z disc

narrow, plate-shaped region of dense material that separates one sacromere from the next (zig-zagged)

what is an A band

dark, middle part of sacromere that extends entire length of thick filament and includes those parts of thin filaments that overlap thick filaments

what is an I band

lighter, less dense area of sacromere that contains remainder of thin filaments but no thick filaments. A Z disc passes through center of each I band

what is the H zone

narrow region in center of each A band that contains thick filaments but no thin filaments

what is the M line

region in center of H zone that contains proteins that hold thick filaments together at center of sacromere

what are the contractile muscle proteins

myosin and actin

what is myosin

contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads

where do the two myosin heads bind

to myosin-binding sites on actin molecules of thin filament during muscle contraction

what is actin

contractile protein that is the main component of thin filaments, each molecule has a myosin binding site

what happens during muscle contraction between filaments

heads link thick and thin filaments together, forming cross bridges

what are the regulatory muscle proteins

tropomyosin and troponin

what is tropomyosin

regulatory protein that is a component of thin filament, w/ covers on binding sites

what does tropomyosin do when skeletal muscle fibers are relaxed

covers myosin-binding sites on actin molecules, preventing myosin from binding to actin

what is troponin

regulatory protein that is a component of thin filament, w/ calcium

what does troponin do when calcium binds to it

changes shape which moves tropomyosin away from myosin-binding sites on actin molecules, exposing binding sites on actin

structural proteins

titin and dystrophin

what is titin

structural protein that connects Z disc to M line of sacromere, thereby helping to stabilize thick filament position, can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils 

what is dystrophin

structural protein that links thin filaments of sacromere to integral membrane proteins in sacrolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers; thought to help reinforce sacrolemma and help transmit tension generated by sacromeres to tendons

what is the sacroplasmic reticulum (SR)

network of smooth endoplasmic reticulum tubules surrounding each myofibril

what does the sacroplasmic reticulum do

stores and releases Ca2+

how are transverse (T) tubules formed

by protrusion of sacrolemma into cell interior

what do the T tubules do

increase muscle fiber’s surface area and allow electrical nerve transmissions to reach interior of cell

tubule proteins act as

voltage sensors that change shape in response to an electrical current

what happens when an electrical impulse passes by

T tubule proteins change shape, causing SR proteins to change shape, causing a release of Ca2+ into cytoplasm

first part of a muscle contraction

neuromuscular junction

second part of muscle contraction

muscle fiber excitation

third part of muscle contraction

excitation-contraction coupling

fourth part of muscle contraction

cross bridge cycle

parts of the neuromuscular junction

a motor neuron fires an axon potential (AP) down its axon

the motor neuron’s axon terminal releases acetylcholine (ACh) into the synaptic cleft

ACh binds receptors on the junctional folds of the sacrolemma

ACh binding causes a local depolarization called an end plate potential (EPP)

parts of the muscle fiber excitation

the local depolarization (EPP) triggers an AP in the adjacent sacrolemma

parts of the excitation contraction coupling

AP in sarcolemma travels down T tubules

sarcoplasmic reticulum releases Ca2+

Ca2+ binds to troponin, which shifts tropomyosin to uncover the myosin-binding sites on actin. myosin heads bind actin

parts of the cross bridge cycle 

contraction occurs via cross bridge cycling

whose decision is it to move

activated by brain

what does the brain do when it decides to move

signal sent down spinal cord to motor neurons that activate muscle fibers

neurons and muscle cells are ___, meaning that they are capable of action potentials (APs)

excitable cells

action potentials are also

electrical impulses

at the neuromuscular junction, muscles are stimulated by what

somatic motor neurons

each axon divides into many what as it enters the muscle

branches

what is formed when axon branches end on muscle fiber

neuromuscular junction (NMJ)

neuromuscular junction (NMJ) is also called

motor end plate

axon terminal and muscle fiber meet at synapse causing a 

functional junction between neuron and muscle cell

within the NMJ, neuron axon terminals contains what

synaptic vesicles filled with neurotransmitter