Chapter 9 Flashcards
Where are the myosin filaments anchored
the M line
What is a triad made out of?
sarcoplasmic reticulum, t tube, sarcoplasmic retitculum
What are the characteristics of myofilaments?
made up of actin (thin) myosin (thick)
laidown parallel to one another, slide past
one single bundle/unit of myofilaments, a sarcomere can produce a contraction
muscle is made up of
muscle bundles
surrounded by epimysium
muscle bundles are made up of
muscle fibers
surrounded by Perimysium
muscle fibers (muscle cell) are made up of
muscle fibrils
surrounded by Endomysium
muscle fibrils are made up of
sarcomeres
sarcomeres are made up of
muscle filaments
muscle filaments are made up of
proteins
what are the general functions of muscle?
movement/stability of somatopleure movement of splanchopleure heat production coelomic pressurization heart beat structural intergrity of blood vessels, control dilation communicatio
chain of anatomy of a muscle
muscle-muscle bundle-muscle fiber(muscle cell)-myofibrils-sarcomere-muscle filament- protein
what is the plasma membrane of the cell called?
sarcolemma
what are myofibrils and what are their characteristics?
myofibrils, grouped with one another within a cell
- working units of a muscle cell
- gives it the striated look
- made up of sarcomeres that are laid end to end, made up of myofilaments
describe coelomic pressurization, a function of the muscle
for ventilazation
-it increases volume in the ribs, space to breathe
each myofibril within a muscle cell is surrounded by a network of
tubes and sacs
what is a sarcoplasmic reticulum
network = specialized membrane-bound organelle called
what do tubes and sacs do?
these tubes & sacs transmit the continuation of the nerve impulse to the muscle cell.
smallest functional unit of a muscle
sarcomere
what filament twist together?
actin
thick filaments
group of myosin proteins
has heads and tails, heads bundeled together
middle of a sarcomere
M line
what do tubes and sacs do for a muscle cell?
each one of the myofibrils is surrounded by a network tubes and sacs
going to transmit an action potential thats been generated on the outside of the cell on the sarcomlemma, and its going to carry that action potential down into the cell, into the interior
actin filaments are anchored on?
z line, dont connect the same on the other side of the sarcomere
T (transverse) tubules run which way?
transvere, to the sarcolemma, surface into the cell
T tubules are associated with what
the Z line
what’s special about the sarcoplasmic reticulum? near T Tubules
calcium ions inside of it This is stored in enlarged sections, known as terminal cisternae, bracketing T-tubules
**not a sight of calicum storage
what are terminal cisternae?
bracketing T-tubules, contains Ca 2+ .calcium ions inside of it This is stored in enlarged sections
steps of an action potential in a muscle cell
- transverse tubules run into right angles from the sarcolemma
- sarcoplasmic reticulium deep into the muscle cell then it connects to the sarcoplasmic reticulium
- it does this because when you depolarize the sarcolemma, a neurotransmitter has been release from a neuron and its going to bind to receptors onto the muscle cell
- if it’s a big enough stimulus it will depolairize that region and will create an action potential that will be propigated along the sarcolemma,
- when that action potential reaches the T Tubules opening into the sarcolemma, then the T tubules will carry that action potential down through the T tubules
neuromuscular junction
The portion where the neuron is communicating with the muscle cell
where you’re actually going to send the neurotransmiters from the neuron into the muscle cell
motor unit
many muscle fibers (muscles cells) may be innervated by one motor neuron
actual spot spot of communication is called the
motor endplate
acetylcholine
As with typical neuron, Ca2+ floods into the terminal end of neuron at NM-junction, releasing a neurotransmitter
-released by calcium
how acetylcholine causes an action potential
- acet. crosses the gap and then bind to receptors on the muscle cell, open up chemically gated ion channels which is the stimulus
- if enough neurotransmitter has been released, causehuge graded potentional, then causes volated gate on the sarcolemma to reach threshold membrane potential for that volatge gate channel
- when it does reachaction potential,will be propigated along the sarcolemma, it will deporlize that section of the motor end plate will create an action potential on the sarcolemma
- the action potential travels along the sarcolemma until it reaches the T Tubules and then its carried down into the cell to reach sarcoplasmic reticulum, releases calcium into the cell
- action potential allows cell to release calcium goes into the myofibril because sarcoplasmic reticulum surrounds it
action potential
action potential along the sarcolemma, t tubules, until it reaches the sarcoplasmic reticulum
sarcoplasmic ret.
releases calcium into myofibril
z-line
endplate of each sarcomere is called a, thinner actin attaches to these endplates
myosin is
laid down between the actin, parallel to actin
I Band
portion of the actin that doesn’t overlap with myosin shows up as lighter looking,
A Band
where myosin exists, overlap and no overlap, beginning of myosin to the end, darker bc thick
H Band
no overlap, nothing but myosin
zone of overlap
is the portion of the a-band outside of the h-band in which the thick and thin filaments overlap.
triad
t-tubules and the adjacent terminal cisternae from sarc retic. form a structure
triads are located
at the zones of overlap of the sarcomere
relating back to action potential, terminal cisternae, t tubules, to sarc. retic where calcium releaes
troponin does what?
prevents complete attachment of myosin heads touching actin, blocjs active site
sliding filament model facts pt. 1
MYOSIN has a tail and a head.
The tail is bound together with other myosin tails to form a thick filament
The head is sticking out and facing the thin filaments
When a myosin head rocks back toward the M-line, it attaches to the ACTIN filament, forming a CROSS-BRIDGE.
cross-bridge
When a myosin head rocks back toward the M-line, it attaches to the ACTIN filament , head will rock towards the tail
tropomyosin
Troponin is laced around the actin in a spiral-like manner by a structural protein, holds it
Troponin-Tropomyosin complex
blocks the complete attachment of myosin and thus the formation of a cross bridge
what happens when a cross bridge is formed?
natural tendendy of the myosin is to rock backwards towards the M line , but troponin is blocking
what is the natural state of filaments?
the myosin heads want to rock back on themselves, forming cross-bridges and causing the filaments to slide past one another.
when the cross bridge takes place, myosin?
brings/ grabs actin towards the M line, the contraction is the actin sliding over closer, takes actin from both sides, shortens sarcomere and brings z-line closer together
what is basically a contraction?
bringing the z-line closer, bringing the M line closer
action potential
sarcolemma->down t Tubules-> triad (terminal cist)-> releases calcium to zone of overlap where filaments are sliding past each other
what happens when the Ca2+ floods in and the Ca2+ ions bind to the troponin?
changes the shape of the troponin-tropomyosin complex enough to move it out of the way enough to allow the cross bridges to form and the myosin heads to rock backwards
-works like a rope, relax the braid, fibers move away from each other
a contraction happens when specifically
when myosin causes actin to slide past each other, shortening the sarcomere, and thus the muscle of which it is a part , happens every single zone of overlap
when heads form cross bridges towards m line= contraction
what happens at the end of the process when calcium is moved away?
is pumped back to the sarcoplasmic reticulum, the troponin-tropomyosin complex can again form a barrier.
what takes energy in a muscle cell and what does not?
does not:cross bridges, myosin heads to rock towards m line
takes energy: to reset them so they can do it again, consume ATP to reset myosin heads
what happens when you die to your muscles?
no ATP is available, you can’t move (rigor mortis)
-sacroplasmic reticulum will release calcium as it breaks down, which will move troponin out of the way which will make you contract but not reset the myosin, rigor mortis, takes awhile to break down sarc. reticulum can’t reset, eventually lose rigor mortis, break down cross bridges so your muscles are relaxed again
what happens when you flood calcium into your myofibrils?
cause active sites to remain open until they are cleared out , once calcium back to sarcomplasmic reticlum active sites are blocked, ATP relax myosin heads, muscle will relax
what does the length-tension relationship depend on?
Depends on the orientation of the myofilaments
Depends on the number of cross-bridges formed
what happens when you shorten?
can disrupt the 3-D orientation of the filaments, leading to less cross-bridges , myosin heads cannot make as much contract by over shortening, too short not going to generate maximum force
what happens in terms of lengthning?
can reduce the zone of overlap, leading to less cross-bridges ,reducing the amount of tension and force
middle ground is when
you can generate the most force and tension, when overlaps are not to short or long
Cardiocytes
essentially the same as striated, skeletal muscle
uninucleated w/ branching muscle cells
short, broad T-tubules lacking triads and located at the Z-lines rather than zone of overlap
no triads, ttubules on z line
big differences of cardiac muscle tissue
- sarcoplasmic reticulum lacks terminal cisternae, no triad and contacts the sarcolemma,
- sarcolemma is permeable to extracellular calcium, can come outside and can go into the cell itself not having to be released from sarc. retic unlike skeletal
intercalated disc in cardiac muscle tissue
- sarcolemmas of adjacent discs are interdigitating and connected by gap junctions
- important bc gap junctions signal to cell allow to pass cell from one cell don’t need neuron, can coordinate cardiocytes
- signal can travel directly from cell to cell, essentially causing the muscle to act like a single cell (coordinated). , contract smooth wave from one wave to another,
whats important in cardiac muscle
external to myofilament, myofibirils, t tubules are different, no terminal cisternae, sarcoriticulum can reach and touch sarcolemma
cardiocytes (automaticity or (autorhythmicity)
rhythm of it is automatic, dont need to send a signal
due to prepotential (pacemaker potential)
-
prepotential (pacemaker potential)
- specialized cardiac muscle cells that contain very little myofibrils. —–these are called the Conducting System or Nodal System (like nerves)
- this includes the sinoatrial node, atrioventricular node and the conducting cells.
The cells of the sinoatrial and atrioventricular nodes are
“leaky” and allow sodium to slowly enter the cell, don’t keep sodium out at a constant rate, once it has repolarized these cells of the nodes will allow sodium to leak, when sodium enters the cell The membrane potential gradually rises toward threshold and spontaneously generates a depolarization, the nervous system is not required to generate action potentials, only to regulate them. Even if no neural signal, reach thereshold by itself, cause contration of heart, why heart does not require nervous system to set heart rate
nervous singnals in terms of cardiac muscle
Nervous signals, modify this heart rate to speed or slow
doesn’t require those signals to beat or have a set heart rate
nervous signals, only purpose to regulate and modify those things
where is smooth muscle located?
located in the walls forming sphincters for the digestive and urinary systems 0f the viscera and blood vessels as well as and within the eyes inside actually globe of eye , NOT in heart
characteristics of smooth muscle
- the fibers are long and slender, tapering like a football. This is called fusiform, spindle shaped
- lacks T-tubules and lack sarcoplasmic reticulum is in the form of a loose network, not in triads or anything like that, spread out in the cell
- respond to ANS, still have actin and myosin, they are spread out in a fishnet stocking arrangment rather than sarcomeres arrangment and overlapping
thick filaments in smooth muscle
thick filaments are scattered throughout the sarcoplasm and have more myosin heads per filament
dense bodies in smooth muscle
thin filaments are attached to Dense Bodies, which are scattered throughout the sarcoplasm and attached to the sarcolemma
- Thin filament, dense bodies, where X’s cross over
- That’s where actin is attached
- dense bodies-connect one cell to another, X shape, contract X’s together
filaments in smooth muscle
- when the filaments slide past each other, the cell shortens by twisting like a corkscrew, does not show striations
- dense bodies connect one cell to another transmitting force from cell to cell, coordinating contraction
unlike striated muscle, smooth muscle
combines to calmodulin(unlike troponin), which activates Myosin Light Chain Kinase
Myosin Light Chain Kinase, (smooth muscle)
The kinase allows cross bridges to form, thus initiating contraction.
Plasticity in smooth muscle
unlike striated muscle, smooth muscle can stretch and adapt to the new length. This is a result of the arrangement of the myofilaments. This allows smooth muscle to retain function even when stretched, as in the walls of the digestive tract.
- no length muscle tension curve
- when muscles stretch out, they still work will because of plasticity
