Muscles Flashcards
Cyclically binds with myosin cross-bridges during contraction
Actin
Possesses ATPase actvity
Myosin
Supplies energy to the myosin cross-bridge, moving it into “cocked” position
ATP
Transmits action potentials to the interior of the muscle fiber
T-tubule
Stores Ca2+ within the muscle fiber
Sarcoplasmic Reticulum
Binds to troponin, causing tropomyosin to shift out of its blocking position
Ca2+
Prevents myosin heads from binding to actin when the muscle fiber is at rest
tropomyosin
Required for detachment of the myosin heads from the actin filament
ATP
Almost all cells have ___.
intracellular machinery for movement
What are the contraction specialists of the body?
Muscle Cells
What are the 3 types of muscle cells?
Smooth
Skeletal
Cardiac
What is the basic function of muscle cells?
`Highly developed ability to contract, develop tension and do work
What does contraction of muscle allow?
- Purposeful movement of the body in relation to the environment
- Manipulation of external objects
- Propulsion of contents through hollow organs
- Empty the contents of organs to the environment
What is meant by contraction of muscle allows “purposeful movement of the body in relation to the environment”?
Skeletal muscle moves bone to allow movement
What is meant by contraction of muscle allows “manipulation of external objects”?
it allows you to peel fruit, move furniture, etc.
What is meant by contraction of muscle allows “propulsion of contents through hollow organs”?
contraction of smooth and cardiac muscle allows contents to move through the body
ex: blood pumping through heart (cardiac muscle), intestines (smooth muscle)
What is an example of “propulsion of contents through hollow organs” in cardiac muscle?
the heart pumping blood
What is an example of “propulsion of contents through hollow organs” in smooth muscle?
intestines
What is meant by contraction of muscle allows “empty the contents of organs to the environment”?
it allows our bodies to empty things like our bladder and uterus
contraction of smooth muscle allows us to empty our bladder
What comprises the largest group of tissues in the body?
muscle
How is muscle classified?
based on appearance (striated or unstriated)
based on function (voluntary (somatic) and involuntary (autonomic))
How is Skeletal Muscle classified?
striated (orderly)
voluntary (somatic)
How is Cardiac Muscle classified?
Striated (orderly)
Involuntary (Autonomic)
How is Smooth Muscle classified?
Unstriated (unorganized)
Involuntary (autonomic)
What does the afferent division of the PNS do?
it brings stimuli from outside world to the CNS and about the state of affairs in your body (all sensory info, if you’re in pain, your temp, digestion, etc.)
Awareness (shoutout Kaylea)
What is the efferent division of the PNS?
effect us and our environment
made up of Somatic Nervous System (gives us control over skeletal muscle)
and Autonomic Nervous System (consists of flight or flight (sympathetic) and rest and digest (parasympathetic))
What does the Somatic Nervous System do?
motor neurons that control skeletal muscles
What does the Autonomic Nervous System do?
Sympathetic and Parasympathetic nervous systems that control smooth and cardiac muscles and glands
What is the Peripheral Nervous System (PNS)?
PNS consists of fibers that bring information back and forth between the CNS and outside world
What are the levels of organization in skeletal muscle?
whole muscle = organ
muscle fiber = a cell
myofibril = intracellular structure
thick and thin filaments = myofilaments
myosin and actin = contractile proteins
What is a muscle fiber?
a very large, multinucleated muscle cell
made up of myofibrils
Why are muscle fibers multinucleated?
to maintain high protein production of such a large cell
What makes up the sarcomere?
myofilaments
How are tendons formed?
from muscle fibers that have alot of connective tissue
What are the thick filaments in a muscle cell?
myosin
What is myosin made up of?
two myosin subunits and a head (cross-bridge)
What do Light Chains do?
They enhance myosin-actin interactions
What are thin filaments in a muscle cell?
actin
How does actin form a chain?
it polymerizes
What is Globular (G) actin?
actin that is a free floating monomer and hasn’t formed a chain yet
What is tropomyosin?
A long regulatory protein that lays where myosin wants to bind on actin
What is troponin?
A regulatory protein that attaches to tropomyosin and helps it to stabilize and move allowing myosin to bind to actin
it has three subunits
What is the Sliding Filament Theory of Muscle Contraction?
Thick and thin filaments slide past each other to cause contraction
What does shortening do to banding in muscle cells?
It causes it to change
What is the A band?
all thick filament and any thin filament that overlaps it
What happens to the A band as the muscle contracts and relaxes?
it stays the same width because the thin filaments just slide by it
What is the I band?
The remaining portion of the thin filaments that do not project into the A band
What happens to the I band as the muscle contracts and relaxes?
It gets shorter as the muscle contracts because of thick and thin bands sliding
What is the Z line?
In the middle of the I band
where thin filaments attach
What is the H zone?
The lighter area in the middle of the A band, where thin filaments do not reach
thick filament with no thin filament overlapping
What is the M line?
The mid point of the Sarcomere
What is the sarcomere?
Z line to Z line
What does the M line do?
It keeps thick filaments in correct structural orientation
What is the Dark band?
The A band
What is the Light band?
the I band
What is the order of the bands from Z line working inward?
Z, I, A, H, M
Zee Intelligent Animal Has Muscle
Which of the following remains the same width during contraction?
A band
H zone
I band
A band
Which of the following describes a sarcomere?
A. 1 whole A band and ½ of each I band located on either side
B. 1 Z line to the next Z line
C. The functional unit of skeletal muscle
D. All of the above
All of the above
What occurs in the muscle during resting state?
Troponin and Tropomyosin are blocking the myosin binding site on actin
The myosin cross-bridge is held back
No attachment is possible between actin and myosin filaments
muscle is relaxed
What is Excitation-Contraction Coupling?
Excite the muscle when you want it to contract
During the resting state of a muscle, what is absent from the sarcoplasm?
Ca2+
What does the SERCA do?
It actively pumps Ca2+ into the SR
What are the steps in excitation of the muscle?
- membrane is depolarized
- when action potential reaches the nerve terminal, the depolarization opens voltage-gated calcium channels
- when calcium channels open, Ca2+ rushes in
- Influx of Ca2+ signals vesicles with ACh to fuse with active zones
- active zones release their content
- ACh diffuse across the neural muscular junction
- After diffusing across the neural muscular junction, ACh will bind to either:
- Acetylecholine binding site
- Acetylcholinesterase site
What happens during muscle excitation when the membrane action potential reaches the nerve terminal?
the depolarization opens voltage-gated calcium channels
What happens during muscle excitation when the voltage-gated calcium channels open?
Ca2+ rushes in
What does an influx of Ca2+ cause during muscle excitation?
influx of Ca2+ signals vesicles with ACh to fuse with active zones
During muscle excitation, what happens to active zones when ACh fuses with them?
they release their content and ACh diffuses across the neural muscular junction
During muscle excitation, what happens to ACh after it diffuses across the neural muscular junction?
it can either bind to the acetylcholine binding site or the acetylcholinesterase site
During Muscle excitation, what happens to ACh if it binds to the acetylcholine binding site?
It opens a cation channel allowing Na+ in and K+ out and causes depolarization (End Plate Potential (EPP)), which causes the muscle to contract
What kind of receptor is the acetylcholine binding site?
a nicotinic cholinergic receptor
What is the end plate potential (EPP)?
It is a depolarization event during muscle excitation that spreads along the muscle and causes an action potential, resulting in muscle contraction
During muscle excitation, what happens if ACh binds the acetylcholinesterase site?
The acetylcholinesterase site degrades ACh and ends the signal for muscle contraction
What is the sarcoplasmic reticulum (SR)?
modified ER, consisting of interconnecting tubules surrounding each myofibril like a mesh sleeve
a specialized membrane that takes AP from surface to center of cell
Where Calcium is stored
Where is calcium stored in the muscle?
Sarcoplasmic Reticulum
What is the T-Tubule?
it brings depolarization perpendicular to the surface of the muscle
a specialized membrane that take s AP from surface to the center of the cell
What does the spread of the action potential down T-tubules cause?
It activates Dihydropyridine receptors (DHPR)
What does a Dihydropyridine receptor (DHPR) do?
it is a voltage-gated calcium channel that prevents Ca2+ from coming in, functioning as a voltage sensor in skeletal muscle and triggering intracellular release of Ca2+ via the Ryanodine receptor (RyR)
shifts with voltage change
Where does the Dihydropyridine receptor (DHPR) function? What does it do?
In skeletal muscle as a voltage sensor to trigger release of Ca2+ from RyR
What does the Ryanodine receptor (RyR) do?
It allows Ca2+ to enter the cell when activated by the DHPR
What kind of channels are DHPRs and RYRs?
Ca2+ receptors
What is the steric block model of muscle contraction?
At rest, Tropomyosin and Troponin are preventing myosin from binding to actin
During exercise, an influx of intracellular Ca2+ binds to the C subunit on troponin.
This causes troponin to roll, moving tropomyosin in the process and uncovering actin’s binding site
This allows myosin to bind