After Midterm Flashcards
What are the three types of muscles?
skeletal muscles, cardiac muscles, smooth muscles
What is the major differences in the types of muscles?
how their cells are organized and how contraction is initiated
Which muscles are striated?
skeletal and cardiac
Which muscles are unstriated?
smooth muscles
Which muscles are voluntary?
skeletal muscles
which muscles are involuntary?
cardiac and smooth
How do you tell apart striated and unstriated muscles?
striated muscles have alternating light and dark bands
When are muscles categorized as voluntary?
if they are innervated by the motor division of the peripheral nervous system.
when are muscles categorized as involuntary?
if they are innervated by the autonomic division of the peripheral nervous system
what do smooth muscles include?
- the muscles that line your blood vessels
- your respiratory tract
- the lining of your digestive system
- form a muscle layer around many organs in your body.
what are muscles anchored by?
tendons
What are muscles made up of?
multinucleated cells that are called muscle fibers
What do muscle fibers originate from?
many embryonic muscle cells which are called myoblasts, fusing together to form multinucleated myotubes.
What are muscle fibers made of?
Muscle fibers are made of parallel subunits that are called myofibrils
what do the parallel arrangement of fibers and myofibrils allow for?
allows the fibers to generate force along a common axis
where are actin thin filaments anchored?
the z-disks
where are the myosin thin filaments anchored?
to the m-line
What are this filaments composed of?
- 2 strands of actin that form a helix
- tropomyosin
- troponin complex
what happens at myosin binding sites?
thick filaments bind to thin filaments
what does the tropomyosin filament do at rest?
hide the myosin binding site
what do g-actin form?
long double-stranded polymers that twist together to form the helix.
How are myosin molecules connected?
by the tails
what does the head region of the myosin thick filament contain?
both an actin binding site and a site for binding ATP cross bridges
What are thick filaments composed of?
hundreds of identical myosin proteins
what is the number of cross bridges produced proportional to?
the total tension produced by a muscle fiber
what is a cross bridge?
physical interaction between the myosin head and the actin filament
what happens to sarcomeres during muscle contraction?
they shorten
why do muscle filaments shorten during contraction?
the thin filaments actively slide along the thick filaments towards the midline
Do the lengths of the thick and thin filaments change during contraction?
no, the extent of overlap changes.
what is the h-zone?
the distance between one dark band and the next dark band
what is the binding of myosin a result of?
the hydrolysis of ATP
what are the three steps of the cross bridge cycle?
- the binding
- the power stroke
- the release
what is responsible for the release of the myosin head from the actin thin filaments?
the binding of a new molecule of ATP
What happens when intracellular calcium in the muscle is low?
he filamentous protein tropomyosin blocks the myosin binding site on actin
What happens when the cellular concentration of calcium becomes elevated?
calcium binds to troponin
what happens when calcium binds to troponin?
Binding of calcium to troponin drags tropomyosin filament off the myosin binding sites allowing the myosin head to form a cross bridge with the actin thin filaments
what three proteins make up the troponin complex?
TNT, TNC, TNI
What does TNT do?
directly interacts with tropomyosin
what does TNC do?
contains the binding site for calcium
what does TNI do?
the protein which keeps tropomyosin in its resting position where it covers all the binding sites for myosin
what happens when your muscle cells run out of ATP?
rigamortis
What causes cramps?
An imbalance in either ATP or calcium handling between the cytoplasm and the sarcoplasmic reticulum
when do muscle fibers contract?
when a postsynaptic end plate potential at the neuromuscular junction causes a propagated action potential in the fiber sarcolemma
how does an action potential in the muscle fiber change the free concentration of calcium in the cytosol of the muscle fiber?
t tubules will conduct action potentials into the cell interior causing calcium release from the sarcoplasmic reticulum that surrounds the myofibrils
what is the source for regulatory calcium in skeletal muscles?
The calcium that comes from the storage compartment from the sarcoplasmic reticulum
what are the 4 molecules that contribute to the control of free calcium in the cytosol of muscle cells?
- dhpr receptor
- ryr
- calcium pumps
- calsequestrin
what are calcium pumps involved with?
continuously sequestering calcium from the cytoplasm of the muscle fiber
what does calsequestrin do?
sequesters calcium from inside the sarcoplasmic reticulum.
what is a twitch?
the relative amount of tension produced by a single AP
What is the amount of tension produced during a single twitch proportional to?
the concentration of calcium in the cytoplasm
How do you increase the size and strength of a contraction?
a series of APs to depolarize the muscle fiber
what is temporal summation?
the addition of tension due to rapid stimulation
what is a motor unit?
All of the muscle fibers that are innervated by a single motor neuron
How can neurons increase the amount of tension?
- increasing action potential frequency (temporal summation)
- recruiting more motor units
True or false:
all myosin head ATPase can hydrolyze ATP at the same speed to form cross bridges at the same speed.
false
what is the force generated by a given sarcomere proportional to?
the number of cross bridges that are formed
how can sarcomeres generate different amounts of force?
they need to produce more cross bridges
True or false:
The higher the load the more difficult it becomes for the myosin heads to slide the thin filaments towards the middle the sarcomere and to shorten those sarcomeres.
true
what is an isometric contraction?
a contraction of the muscle without movement of the skeletal elements
what is force proportional to?
the cross sectional area of a muscle.
what is the rate at which a muscle can work dependent on?
It’s rate of ATP production.
True or false: ATP is needed for both muscle contraction and muscle relation
true
Why is ATP required for relaxation?
you need to pump the calcium that was released from the sarcoplasmic reticulum from the cytosol back into the storage compartment in the sarcoplasmic reticulum.
what is creatine phosphate?
a high energy molecule that can be stored in the muscle
when is calcium an effective signal?
when it’s lifespan is extremely short
what is responsible for the myosin head extending and binding?
ATP being hydrolyzed to ATP
what is responsible for the power stroke and the sliding of filaments?
Release of the high energy phosphate
what is responsible for the myosin head detaching from the actin filaments?
attachment of a new ATP molecule to the myosin head
