Unit D4: Muscular system Flashcards
myosin:
- thicker than actin
- myofilament
- protein
- composed of myosin molecules(proteins)
- myosin molecule = 2 polypeptide chains wrapped around each other
- end of the chain has a distinctive globular region(the head)
- heads protrude at regular intervals out of muscle
location of the skeletal muscle:
attached to the skeleton
appearance of the cardiac muscle:
branched, striated cells
- intercalated discs
tropomyosin:
- protein that wraps around the actin and blocks the active sites
- stops myosin heads from binding to actin
sliding filament model:
- a muscle contracts as a result of its thin actin filaments sliding over its thick myosin filaments
- myosin and actin work together during a muscle contraction
why can muscles pull but cannot push?
Muscles shorten when they contract, so they can only pull, not push
botulism:
-toxins attack your nerves which results in weakness and paralysis of your muscles
- a potentially fatal muscular paralysis caused by a toxin produced by the bacterium Clostridium botulinum
- the toxin prevents the release of a muscle-stimulating compound released by muscle-related cells of the nervous system thus leading to paralysis
how do the myosin and actin act together in the sliding filament model?
- the myosin head grabs into the actin filaments(flexes), pulling them z-lines closer together
- this flex of the myosin filament shortens the myosin muscle fibre
- actin filament slides past the myosin filament in the direction of the flex
- ATP allows the myosin to detach from the actin and rest
what are the three types of muscle?
cardiac, smooth(visceral), skeletal(striated)
Energy for muscles:
- ATP provides the energy for muscles to work
- little ATP can be stored in muscles
- SO muscles need MORE ATP
- when ATP supply is low and O2 levels are low, lactic acid begins to accumulate, causing muscle pain!
- 3 additional source of ATP: creatine phosphate, fermentation, aerobic cellular respiration
abundance of mitochondria in the cardiac muscle:
the MOST numerous
- the most mitochondria
- needs the most energy
- most ATP
when a muscle is relaxed what do the myosin heads do?
they are raised and ready but unable to bind to actin because of tropomyosin blocking the active site
when are calcium ions diffused by facilitated diffusion?
INTO the sarcoplasm from the sarcoplasmic reticulum
cardiac muscle cells:
- striated, tubular, branched
- one nucleus per cell
- contracts involuntary
- found in the walls of the heart
- can tell by the vertical lines separated striations(intercalated disc)
blood vessels in skeletal bundles of muscle fibres:
supply oxygen and nutrients, remove cellular wastes
what causes the release of myosin from the actin active site?
the bind of ATP
myofilaments:
protein structures responsible for muscle contraction
- two types: myosin and actin
control of smooth muscle:
involuntary
myofibrils:
contractile unit in skeletal muscle
- 1 muscle fibre has hundreds of thousands of myofibrils
skeletal muscle in the body:
- each muscle in the body lies along the length of a bone
- a tendon(heavy band of tissue) attaches each end of a muscle to a different bone
- blood vessels and nerves run between bundles of muscle fibres
Muscular dystrophy:
a collective term for several hereditary conditions in which skeletal muscles degenerate, lose strength and are gradually replaced by fatty and fibrous tissue that impedes blood circulation
- this in turn accelerates muscle degeneration in a fatal spiral of positive feedback
- the decrease in size and wasting of muscle tissue
all of the steps of muscle contraction with the sliding filament model:
- Calcium ions(Ca2+) diffuse from the sarcoplasmic reticulum to sarcoplasm through facilitated diffusion
- Calcium ions bind to troponin
- Troponin-tropomyosin complex shifts to expose active site
- Myosin head binds to actin active site and flexes, pulling z-lines closer to the center
- ATP attaches to myosin, myosin then detaches from actin, ATP hydrolyzes(ATP to ADH) which causes myosin head to return to cocked position
- Calcium ions detach from troponin, troponin-tropomyosin complex shifts back over the active site
- Calcium actively transported out from the sarcoplasm back to the sarcoplasmic reticulum
energy production of skeletal muscle:
aerobic and anaerobic
parallel bundles in skeletal muscle:
- each whole skeletal muscle is composed of parallel bundles
- each bundle is composed of parallel units called fibres
- blood vessels and nerves run between them
location of the smooth muscle:
blood vessels, organs
location of caridac muscle:
forms the heart
actin:
- type of myofilament
- a protein
- composed mainly of globular(circular) actin proteins
- also contain some other proteins
- thin
skeletal muscle cells:
- striated and tubular(not branched)
- many nuclei
- contract voluntarily
- usually attached to the bones of the skeleton
action of cardiac muscle:
rhythmic (beat of heart)
skeletal muscle funtion:
- muscles work by shortening when they contract and lengthen when they relax
- produces body movement and support
- maintains body temperature
- skeletal muscles present in antagonistic pairs
–> one muscle of the pair contracts to move the body part, the other controls the returm of the body part back to the original position
sarcoplasm:
inside of skeletal muscle tissue
- inside myofil membrane
what is a muscle?
-a muscle is a contractile tissue found in animals, that acts by contracting
- muscles only pull (contracts and relaxes)
- 3 types
sliding filament model contraction:
- the heads of two ends of myosin filament are orientated in opposite directions(opposite sides)
- when heads attach to actin, they bend towards the center of the myosin
- left and right sides are pulled towards to center and
- both of the Z-lines move towards the center and contraction occurs(muscles sink)
energy production of cardiac muscle:
aerobic respiration
(O2)
- not capable of anaerobic
energy production of smooth muscle:
aerobic respiration
(O2)
- not capable of anaerobic
nerves in skeletal bundles of muscle fibres:
trigger and control muscle contractions
cardiac muscles:
- found only in the heart
- contracts and relaxes automatically
troponin:
protein that binds to tropomyosin that binds to calcium ions which causes the troponin-tropomyosin complex to shift away from the active sites for the myosin heads on the actin
control of cardiac muscle:
involuntary
appearance of skeletal muscle:
long fibres with striations
skeletal muscle fibres:
- parallel units in the bundles
- each fibre is a functional single-cell
- up to 20 cm long
appearance of smooth muscle:
long, cigar-shaped cells
abundance of mitochondria in smooth muscle:
least numerous
- not a lot of mitochondria
- least amount of ATP
skeletal muscles:
- attached to bones by tendons
- under voluntary control
sarcoplasmic reticulum:
- outside of myofil membrane and skeletal muscle tissue
- high concentration of Calcium ions
when are calcium ions actively transported?
OUT of the sarcoplasm and back to the sarcoplasmic reticulum
action of the smooth muscle:
slow and sustained
muscle cramps:
- painful muscle spasms triggered by strenuous exercise, extreme cold, dehydration, salt imbalance, low blood glucose, or reduced blood flow
action of the skeletal muscle:
fast(twitches)
abundance of mitochondria in skeletal muscle:
numerous
skeletal muscle structure largest to smallest(hierarchy):
muscle –> muscle-fibre buncle –> muscle fibre –> myofibrils(contractile unit) –> myofilaments
sarcomere:
the basic contractile unit of muscle fiber
- includes actin and myosin
- the repeating functional units in muscle cells
tetanus:
- occurs when the stimuli are coming so quickly that there is no relaxation phase
- a constant state of muscle contraction
tendon:
heavy band of tissue that attaches each end of a muscle to a different bone
smooth muscle:
- found in the lining of many organs
ex. stomach(churning), esophagus(peristalsis), blood vessels(arteries)
control of skeletal muscle:
voluntary
smooth muscle cells:
- non-striated
- one nucleus per cell
- contract involuntarily
- found in the walls of internal organs
- lots of nuclei(small boundary)
