Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Bio II > Lecture 21- Musculoskeletal System > Flashcards

Lecture 21- Musculoskeletal System Flashcards

1
Q

Vertebrate Skeletal Muscle

A

Contractile tissue -> Movement

Motor Output -> Mechanical Force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the functions of vertebrate skeletal muscle?

A

Locomotion
Manipulation of environment
Blood circulation
Peristalsis/feeding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Skeletal Muscle

A

Sometimes called “striated muscle”
Moves skeleton
Attached to bones via tendons: Cords of connective tissue
Most abundant tissue in body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the most abundant tissue in the body?

A

Skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the function of tendons?

A

Cords of connective tissue. Attaches skeletal muscle to bones.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a muscle fiber?

A

Long, cylindrical cell. Multinucleate- many cells fused.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are T (transverse) tubules?

A

Infolding of plasma membrane, located within the muscle fiber.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the sarcoplasmic reticulum?

A

Specialized ER of muscle cells, located within the muscle fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are myofibrils?

A

Longitudinal fibers within cell. 2 types of filaments- thin filaments and thick filaments.
Myofibril is hundreds of sarcomeres end to end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the two types of myofibril filaments?

A

Thin filaments and thick filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What protein makes up thin filaments?

A

Actin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What protein makes up thick filaments?

A

Myosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Thick Filaments

A

~350 myosin molecules. Each myosin molecule has a head and a tail. The heads stick out, while the tails associate (intertwine) to form the thick filament.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Actin & Myosin

A

Present in many cells.
Best organized in muscle cells.
Filaments are arranged in a regular pattern, giving a striped or striated appearance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a sarcomere?

A

Basic contractile unit- overlapping thin and thick filaments.
Myofibril= hundreds of sarcomeres end to end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens during contraction in the sarcomere?

A

Thick and thin filaments slide past each other
-> Increases overlaps
-> Sarcomere gets shorter (muscle contracts)
The length of filaments remains constant, only the amount of overlap changes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

A(n) _________ is tough band of fibrous connective tissue that connects muscle to bone.

A

Tendon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

True or False: Muscle fibers (cells) are multinucleate.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Muscle fibers are composed of bundles of __________.

A

Myofibrils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the sarcoplasmic reticulum composed of?

A

Thin and thick filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Sliding filament model at rest

A

When a muscle is at rest, the myosin binding sites on the thin filaments are blocked by tropomyosin. This prevents the myosin heads on the thick filaments from attaching to the actin, essentially keeping the muscle relaxed.

22
Q

How is contraction coordinated?

A

A motor neuron transmits the message.
Motor unit: Motor neuron connected to ~150 muscle fibers
Each association= neuromuscular junction
All contract at once.

23
Q

How/what happens when a motor neuron sends a message?

A

The motor neuron sends an action potential-> Acetylcholine released.
Acetylcholine binds specific receptors-> PM depolarization in muscle fiber.
If the depolarization is strong enough, action potential in muscle fiber.

24
Q

Problem: Large Diameter. How is this fixed?

A

Axons narrow-> AP spreads easily- not so in muscle fibers

Solution: T tubules
AP travels along plasma membrane to T tubules, which help direct the signal to the sarcoplasmic reticulum. The sarcoplasmic reticulum releases Ca2+.

25
What happens during contraction?
Ca2+ binds troponin. Exposes myosin binding sites on actin.
26
Explain the Cyclical contraction in muscle fibers.
RESTING HIGH-ENERGY STATE: The muscle is at rest. Myosin heads on the thick filament are not bound to the thin filament because tropomyosin is covering the myosin-binding sites in actin of the thin filament. Myosin heads are in a high-energy state because they are bound to ADP. TROPOMYOSIN SHIFTS: A signal (AP-> acetylcholine) arrives from the nervous system, triggering the release of calcium stores from the sarcoplasmic reticulum (T tubules transmit signal) within the muscle fiber. Calcium binds to proteins on the thin filament, causing tropomyosin to move and expose the myosin-binding sites on the actin. CROSS-BRIDGE FORMATION (CONTRACTION): The exposed myosin-binding sites on the actin (thin filament) allow the myosin heads on the thick filament to bind to the actin, forming a cross-bridge. Each myosin head forms 5 crossbridges/second. ADP AND THE POWER-STROKE: The bound myosin head undergoes a conformational change, releasing ADP and inorganic phosphate from the bound ATP. This change in the myosin head is the power stoke. The power stroke pulls the thin filament toward the center of the sarcomere, causing the muscle fiber to shorten (contract). ATP REBINDING (LOW E STATE): After the power stroke. a new ATP molecule binds to the myosin head. The binding of ATP causes the myosin head to detach from the actin, breaking the cross-bridge. ATP HYDROLYSIS AND HIGH-ENERGY RETURN: The ATP bound to the myosin head is then hydrolyzed back into ADP and inorganic phosphate. This hydrolysis resets the myosin head back to its high-energy state (bound to ADP).
27
What causes the cross-bridge (contraction)?
The tropomyosin shifts after the Ca2+ binds to proteins on the thin filament, exposing the myosin-binding sites on the actin. The myosin heads on the thick filament can then bind to the actin on the think filament, causing the cross-bridge.
28
What causes the power-stroke?
The bound myosin head undergoes a conformational change, releasing ADP and inorganic phosphate from the bound ATP. This change in the myosin head is the power stroke. The power stroke pulls the thin filament toward the center of the sarcomere, causing the muscle fiber to shorten (contract).
29
What are the sources of E for contraction?
Energy for contraction comes from ATP. Immediate power: Each myosin head forms 5 crossbridges/second. There is only enough ATP for a few seconds of activity present. Short-term boost: Muscles store creatine phosphate- Transfers P to ADP-> ATP for contraction Worth ~15 seconds of ATP Long-term: Glycogen- 100s of glucose monomers. Can be broken down into ATP.
30
Cardiac Muscle
Walls of heart Striated Branched cells Unique functionality- contract simultaneously, independently. Intercalated discs
31
Smooth Muscle
Wall of digestive tract, bladder, uterus, blood vessels (involuntary) Not attached to bone not stiated No T tubules Not well developed SR Less efficient Slow contractions, slow relaxation
32
Muscle Summary
Contractile tissue Voluntary or involuntary Movement of organism Movement within organism
33
What are antagonistic muscle pairs?
Muscles that are the opposite of each other (contacting muscle vs. relaxing muscle)
34
3 Functions of Skeleton
1. Support body 2. Protect internal organs 3. Movement (Involves motor signals from NS, antagonistic muscle pairs)
35
What is a hydrostatic skeleton?
Fluid-filled cavity Closed Fluid under pressure Cnidarians, nematodes, annelids 2 Contractile Layers Longitudinal, circular- Antagonistic Peristalsis: Movement produced by rhythmic waves of contractions Front-> back Great for small or aquatic animals
36
What are the 2 types of hard skeletons required for larger, faster, more coordinated organisms?
Exoskeletons and endoskeletons
37
Exoskeleton
External Non-living- does not grow Arthropods- chitin- protection, movement Mollusks- CaCO3- protection
38
Endoskeleton
Internal Echinoderms, chordates Living- able to grow 2 types- cartilage, bone
39
What are the key differences between exoskeletons and endoskeletons?
Exoskeletons cannot grow while endoskeletons are living and grow. Exoskeletons are external while endoskeletons are internal.
40
What are transverse tubules (t-tubules)?
Extensions of the plasma membrane that connection action potentials to the sarcoplasmic reticulum
41
What happens to calcium ions after they are released by the sarcoplasmic reticulum?
Calcium ions binds to the thin filaments at troponin complexes which causes tropomyosin to unbind from the myosin binding sites (actin's active sites).
42
How does the sarcomere appear when muscle fibers are at rest?
Tropomyosin covers actin's active sites (myosin binding sites) and the Z lines are far apart.
43
What are intercalated discs and what is their function?
Specialized junctions in cardiac muscle that permit ions to move between cells and therefore allow action potentials to quickly pas to all cardiomyocytes.
44
How does the sarcoplasmic reticulum respond to an action potential?
Releases calcium ions
45
A(n)_________ is a chemical synapse between a motor neuron and a muscle fiber.
Neuromuscular junction
46
A(n)_________ is the repeating unit between two Z lines of striated muscle tissue.
Sarcomere
47
What is creatine phosphate?
Phosphorylated creatine molecule that serves as a reserve to convert into ATP for short-term energy during muscle contractions.
48
Which neurotransmitter do motor neurons release?
Acetylcholine (ACh)
49
Cardiac muscle consists of individual cardiomyocytes connected by ________ to work as a single functional organ or syncytium.
Intercalated discs
50
True or False: At rest, there are no thin filaments crossing the M line.
True

Bio II (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions