Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Organ Systems > skeletal muscle > Flashcards

skeletal muscle Flashcards

0
Q

explain cardiac muscle features

A

• Striated: generate force
• Contracts rhythmically
• Innervated by ANS
strong quick continuous involuntary

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

Explain skeletal muscle features

A

• Striated: generate force
• Contracts only when stimulated
• Innervated by somatic motor neurons
strong quick discontinuous, voluntary contraction

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

Explain smooth muscle features

A

• Non-striated: for pressure loads and maintain organ dimensions
• Contracts continuously
• Innervated by ANS
weak slow involuntary contraction

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

Explain Gross features of skeletal muscle

A
  • Epimysium surrounds whole muscle
  • Perimysium surrounds muscle fascicles
  • Endomysium surrounds a muscle fiber
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

explain the many features of a muscle fiber

A

a single cell with multiple nuclei, organelles and contractile structures.
– Several myoblasts fuse to form a single muscle fiber
– Satellite cells are stem-like (repair) cells that survive into adulthood.
• Sarcolemma is the cell membrane around a single muscle fiber
• T-tubules are infoldings of sarcolemma
•sarcoplasmic reticulum stores and releases Ca++

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

Sarcoplamic reticulum (SR) consists of two regions

A
  1. Sarcotubules store Ca++ bound to calsequestrin.

2. Terminal cisternae contact T-tubules

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

what is a Triad ?

A

Triad is where action potentials trigger release of Ca++ from terminal SR

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

what are myofibrils?

A

• A myofibril is a chain of fused sarcomeres that runs the length of the muscle

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

what is a sarcomere?

A

Part of the cytoskeleton containing thick (myosin) and thin (actin) myofilaments
• Joined to each other by Z-lines
• Surrounded by SR

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

describe the sarcomere cytoskeleton

A

it provides stability for contractile elements

• Z-lines connects sarcomeres and their alignment makes muscle “Striated”.

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

these 2 proteins form a flexible filamentous network that surrounds the myofibrils.
• account for 15% of the total protein in the myofibril.

A

Titin (aka connectin) and nebulin

-titin is an elastic component in muscle which can stretch under tension

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

what 3 components make up the thin filaments known as myofilaments.

A

• Actin: globular proteins (G actin) polymerized into doubled strands (F actin)
• Tropomyosin: cover myosin binding sites
• Troponin: a regulatory protein bound to
tropomyosin; activated by Ca++

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

what role do the thick filaments known as myosin play.

A

– Tails form thick portion of myofibril

– Head and neck form cross bridges that bind to actin.

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

describe why skeletal (and cardiac) muscle is striated

A
  • Striations are due to regularity of sarcomere structure within muscle fibers
  • Z lines align with each other
  • Z lines form the edges of sarcomeres, with I and A bands indicating different sectors of myofibrils
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are motor neurons?

A
  • cell bodies in ventral horn project axons out through ventral root to muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the neuromuscular junction?

A

-synapse formed by motor neuron on skeletal muscle

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

Describe structure and functions of neuromuscular junction

A
  • motor neuron axons branch and synapse onto muscle end-plate
  • junctional folds on muscle cell lined with Ach receptors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why do motor neurons release ACh onto neuromuscular junctions?

A
  • ACh increases permeability of Na/K channel, creating EPP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the function of EPP (End-plate potential)?

A
  • Large depolarization (like EPSP, but greater)

- EPP is sufficient amplitude to exceed threshold for AP (one axonal AP can initiate muscle AP)

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

Muscle action potential

A

EPP’s depolarize neighboring voltage-gated Na channels that generate muscle action potentials.

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

Describe first step in muscle excitation

A

Begins with Ca release from SR:

  • AP spreads along T-tuble
  • AP current activates DHP receptors
  • when activated, DHP does not permit Ca flux into cell.
  • It does conduct voltage to the RyR
  • Ryanodine receptor (RyR) releases Ca from SR terminal cisternae.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe contraction during AP of muscle excitation

A
  • Ca released from terminal cisternae of SR

- Ca binds to troponin to initiate contraction

22
Q

Describe relaxation after AP

A
  • Ca sequestered into longitudinal sarcotubules of SR via Ca-ATP-ase.
  • Ca then translocated back to terminal cisternae for subsequent release.
23
Q

What are the two primary cofactors that facilitate contraction?

A

Calcium (permission) and ATP (motivation)

24
Q

What is the function of Ca in muscle contraction permission?

A
  • Ca is released from SR and binds to troponin.

- Troponin alters tropomyosin to expose actin’s binding site for myosin.

25
Q

What is the function of ATP in muscle contraction motivation?

A
  • ATP binds to myosin head and hydrolyzes to ADP and P

- ADP + P enables myosin head to bind to actin

26
Q

What are the 4 stages of the sliding filament mechanism of contraction?

A
  1. Crossbridge attachment
  2. Working stroke
  3. Detachment
  4. ATP hydrolysis
27
Q

What conditions are required for actin to bind to myosin?

A

The myosin head needs to face up to ATP

28
Q

What event triggers bending of the myosin head?

A

Working stroke

29
Q

What conditions are necessary for muscle to relax?

A

As ATP attaches to the myosin head, the cross bridge detaches. Detachment is necessary for relaxation.

30
Q

What does myosin type II head do?

A
  • In skeletal muscle, myosin type II heads bind individually and do not step one after the other.
  • second head interacts with active head to orient and stabilize structure
31
Q

What causes myosin head to restore its initial position?

A

As ATP is split in ADP and P, cocking of the myosin head occurs.

32
Q

Sarcomere contraction

A

The net effect of myofibril contraction is the approach of two actin molecules toward center, shortening sarcomere.

33
Q

What happens during continued contraction?

A
  • The two actin ends approach each other actually to the point of overlapping.
  • Contraction can occur as long as there is some overlap between actin and myosin.
34
Q

Length-tension relationship

A

Total muscle tension is the sum of active and passive tensions

35
Q

Passive tension in length-tension relationship

A

Resistance of CT in muscle tissue (elastic titin fibers)

36
Q

Active tension (isomeric) in length-tension relationship

A

Active tension is proportional to number of cross bridges, maximal level L0. Stretching muscle to L0 improves contractility.

37
Q

Why does stretching muscle to L0 improve contractility?

A
  • Optimal overlap between actin and myosin
  • Tension on actin-myosin increases Ca binding forming more cross bridges. Beyond the optimal length, Ca binding diminishes.
  • When the muscle is very contracted and actins overlap, stretching it will readjust the myofibrils to a more optimal overlap for maximal contraction force.
38
Q

Velocity-tension relationship

A
  • The velocity of isotonic muscle contraction decreases with increased loads.
  • Increased loads slows the rate of cross bridge cycling
39
Q

Is appreciable power produced at no load in velocity-tension relationship?

A

No, at no load, velocity is maximal and no appreciable power is produced.

40
Q

Is power generated at excess load in velocity-tension relationship?

A

No, at excess load, muscle cannot contract, generating no power.

41
Q

Where is power maximal in velocity-tension relationship?

A

Power is maximal between two extremes of load

42
Q

Motor unit

A

Group of muscle fibers innervated by branches of single motor neuron

43
Q

What are small motor units in muscles used for?

A

Adapted for fine and precise motor control

44
Q

What are large motor units used for?

A

Adapted for greater force

45
Q

Twitch

A

Twitch is a movement of a single motor unit caused by a single action potential
- can be summed to generate tetanus

46
Q

What determines duration of twitch?

A

Level of myoplasmic Ca

47
Q

Spasm (cramp)

A

sudden involuntary contraction generated by continuous CNS activity or muscle dysfunction

48
Q

Wave (twitch) summation

A

Increasing frequency of motor neuron AP’s causes twitches to run together, diminishing the time for Ca sequestration and subsequent relaxation.

49
Q

Pathological Tetanus (lockjaw)

A

Summation of twitches without relaxation produced by neurotoxin produced by anaerobic bacterium.

50
Q

Energetics of Muscle

A

ATP is used to convert chemical energy into mechanical energy.

51
Q

What are the three metabolic sources for ATP?

A

1) Direct phosphorylation via creatine (quickest)
2) Anaerobic glycolysis - requires glucose
3) Aerobic oxidative phosphorylation of fatty acids - requires O2

52
Q

Where is myoglobin found?

A

In slower contracting oxidative types of muscles.

  • It has higher affinity for O2 and serves as O2 reservoir in skeletal and cardiac muscle
  • With lower O2 levels, it releases O2 for ATP in mitochondria
53
Q

on a long enough timeline the survival rate for everyone drops to ?

A

zero

Organ Systems (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions