Brainscape's Knowledge GenomeTM

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


See full index

Bio 107 > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Three main types of muscle and main function

A

1) Skeletal: attached to bones, responsible for movement
2) Cardiac: heart mass, contracts causing blood to pumped
3) Smooth: lines hollow organs, blood vessels, regulates their dimensions

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

Skeletal muscle

A

Voluntary

Striated

Long cylindrical cells

Multiple nuclei pushed to side

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

Cardiac Muscle

A

Involuntary

Striated

Connected via intercalated discs

Branched cells w/ 1-3 central nuclei

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

Smooth Muscle

A

Involuntary

NOT striated

Spindle shaped, one nucleus per cell

Lines internal organs

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

Motor unit

A

Motor neuron and all the muscle fibers it innervates

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

Skeletal muscle structure

A

Are attached to bone via tendons

Long (up to 35cm), Wide (0.1mm)

Cells are composed of fibrils (actin and myosin), containing contractile filaments

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

A-band

A

Both Actin and Myosin

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

I-band

A

Actin only

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

H zone

A

Myosin only

Filaments don’t overlap

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

Z-discs

A

Anchor thin filaments (actin)

Connect myofibrils to one another

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

T-tubules

A

Circle each sarcomere

At the end of each of the A bands and I bands meet

Allows AP to be carried deep within muscle cell

Extracellular fluid can go through T-tubule

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

Sarcoplasm reticulum (SR)

A

Calcium storage site

Terminal cisternae of SR lie close to T-tubule

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

Sarcolemma

A

Plasma membrane of muscle

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

Triad

A

T-tubule surrounded by terminal cisternae on either side

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

Titin

A

Anchors thick filament to Z-line

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

Thick filament

A

Myosin (globular head + tail)

Head is an ATPase (hydrolyses ATP)
that binds to actin

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

How is the myosin head arranged

A

Pointing away from M-line when stretched

Pointing in when relaxed

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

What Thin filaments structure, composed of

A

Double stranded helical actin chain

Troponin and tropomyosin are regulatory proteins
in skeletal and cardiac muscles

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

Tropomyosin

A

Thing strand

Can block myosin head from binding to actin

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

Troponin

A

Regularly arranged on tropomyosin

Calcium binding site
- changes shape when Ca2+ binds

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

Sliding filament theory

A

Thin filament pulled over thick filaments

Z-line pulled towards M-line

I band and H zone become narrower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

4 major steps of Cross bridge cycle

A

1) Cross bridge formation
2) Power stroke
3) Detachment
4) Energisation of myosin head

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Cross bridge formation

A

Myosin binds to actin binding site

Calcium binds to troponin, change shape, myosin-actin binding site exposed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Power Stroke

A

ADP released

Myosin head rotates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Importance of Calcium

A

Binds to troponin, the tropmyosin moves to expose the myosin binding sites on actin

Cross bridge cycle continues as long as calcium levels remain above threshold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Calcium regulation

A

Active Transport pumps move Ca2+ back into SR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Isotonic contraction of muscles

A

Shortening
SAME tension
Velocity variable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Isometric contraction of muscles

A

No shortening
Constant length
Different tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Length-tension relationship

  • what type of contraction does this occur?
  • definition/theory
A

Isometric contraction- when muscle doesn’t shorten but tension increases

Maximum active force (tension developed) of sarcomere is dependent on degree of actin/myosin overlap determining the number of cross-bridges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

@ optimal length what is actin and myosin like

A

Maximum number of cross-bridges formed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

@ reduced size of zone overlap what is actin and myosin like

A

Fewer cross-bridges formed and reduced tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

@ zero zone of overlap what is actin and myosin like

A

Zero tension due to no interactions between myosin and actin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Active tension when less tension than normal

A

sarcomere lengths less than 2.0um filaments collide and interfere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What um is maximal force developed of muscle (normal working range of muscle)

A

2.0-2.2 um

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Active tension when more tension than normal

A

Sarcomere length greater than2.2 active forces decline , less overlap, less cross bridges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Total tension equation

A

Sum of active tension and the passive tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Passive tension

A

Resistance from CT around muscle cells resist stretch

More you stretch more the collagen and muscle prevents your from stretching

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Total tension when stretching

A

The more you stretch, active force decreases, passive force decreases

Total can be more than 100%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Excitation-Contraction Coupling

A

AP enters T-tubules causing Ca2+ channels in SR to open

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What happens when AP travels down motor neuron?

A

Axon terminal voltage gated channels open Ca2+ enters axon terminal

Vesicles containing Ach fuse with terminal membrane, releasing Ach into neuromuscular junction (synaptic cleft)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

How are Ach receptors on activated on post-synaptic neuron?

A

Ach binds to ligand (Ach) gated channels causing them to open ;predominantly Na+, enters, K+ leaves muscle cell making it less negative (end plate potential) aka depolarisation of Post-SN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

How is muscle AP triggered

A

Sufficient ligand channels are open and causes threshold to be reached

Voltage gated Na+ channels open and AP triggered

AP travels along sarcolemma into T-tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Excitation contraction coupling

- Ca2+ released

A

AP conducted down T-tubule causing coming into close contact with SR

Voltage-gated Ca2+ channels open in SR

Ca2+ released into cytosol/sarcoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Ca2+ binds to

A

2 Ca2+ binds troponin, causing conformational change

When Ca2+ concentrations reach critical threshold myosin binding sites on actin exposed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

When does muscle contraction end

A

Ends when Ca2+ levels fall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

How is calcium levels reduced

A

Pumped back into SR by Ca2+ ATP-ase pumps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is the result of actin on Ca2+ leaving

A

Troponin moves back covering myosin binding site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Creatine Phosphate

A

Can act as an ATP “store”

Creatine phosphate + ADP = creatine + ATP

Anaerobic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Anaerobic glycolysis properties

A

Good for short intense exercise: Fast but inefficient

Build up of lactate and H+ max. 120s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What does acidification of cell inhibit

A

phosphofructokinase (PFK)

51
Q

Aerobic metabolism

A

Efficient, slower

Requires Oxygen, therefore good blood supply

Max 300W

52
Q

What substances break down to form products of cellular respiration

A

Fatty acids, amino acids, pyruvic acid, oxygen from haemoglobin, myoglobin in muscle fibers

53
Q

Myoglobin

A

High affinity for O2, and stores it

54
Q

Two ways to increase muscle tension

A

Increase frequency of stimultion (e.g. AP’s)

Recruiting additional motor units

55
Q

Temporal Summation

A

Additional AP’s initiated before Ca2- levels return to resting

Causes calcium levels to remain high and continuing force development

56
Q

Tetanus

A

Muscle contraction sustained, by high frequency of AP’s

57
Q

Type 1

A 
Slow oxidative
Moderate SR pumping capacity
Small Diameter
High mitochondria/myoglobin/blood supply
Moderate glycolytic capacity
Aerobic

Darker due to more mitochondria

58
Q

Type 1 muscle fiber properties

A

Slow twitch
Units with neurons innervating slow aerobic cells

Maintain posture, walking, low intensity exercise

POSTRUAL

59
Q

Type 2B

A

Fast twitch
Fast ATPase Rate- High SR pumping
Larger diameter, not relying on blood supply as much
Low mitochondria/myoglobin/blood supply

High glycolytic capacity

Anaerobic glycolysi

60
Q

Glycolytic capacity

A

Measure of maximum capacity of glycolysis to generate ATP

61
Q

which type of muscle fiber is recruited first

A

Type 1

62
Q

Regulation of force dependent on

A

Number of AP’s coming down motor unit

The number of motor units recruited

63
Q

Hypertrophy

A

Increase/growth in muscle size

64
Q

Atrophy

A

Reduction in activity- loss of innervation

65
Q

Relationship between motor unit and tension

A

As more units recruited, tension increases, as fast twitch fibres starting to be recruited

66
Q

Atrial cells structure

A

100um long 10um wide

No t-tubules
Contract relatively weak

Allows co-ordinated contraction of all myocytes

67
Q

How are atrial cells joined and what is the purpose of this?

A

Joined by gap junctions, allows electric activity to spread from one cell to next

68
Q

Ventricular cells structure

A

100um long 30um wide

Branched

Have well developed T-tubular system which carries excitation into interior of cell

69
Q

How are ventricular cells joined and what is the purpose of this?

A

By numerous gap junctions forming ‘sheets’ that wrap around ventricles

70
Q

What is the purpose of desmosomes in relation to contraction

A

Prevent cells from separating during contraction

71
Q

Intercalated disc function in relation to contraction

A

co-ordinated contraction of all myocytes

unlike skeletal muscle where fibres are recruited via motor neurons

72
Q

Myogenic muscle

A

Initiates contractions without nervous input

73
Q

How is AP generated in cardiac muscle

A

Sino-atrial node located in right atria

74
Q

Where does this AP spread

A

Spreads throughout atria then Purkinje Fibres to the ventricles

75
Q

How long is cardiac AP

- length relative to skeletal and nerve

A

> 100ms long

AP much longer than nerve and skeletal due to presence of ionic currents that hold the cell depolarised for a period comparable to that of a twitch

76
Q

Why is there a plateau in tension development

A

Due to large Ca2+ current, slow to open slow to close, L-type channel, K+ moves out barely in little amounts

77
Q

Can cardiac muscle tetani

A

No highly unlikely, due to absolute refractory period (long AP)

78
Q

Three major stages in cardiac muscle AP

A

0- rapid depolarisation fast voltage gates Na+ channel

2- plateau due to slow voltage gated Ca2+ channel (L-type Ca2+ channel)

3- Repolarisation due to closing of Ca2+ and opening of K+ channels

79
Q

Excitation coupling cardiac muscle

A

Depolarisation wave opens L-type Ca2+ channels in T-tubule

Ca2+ influx balanced by Na+/Ca2+ exchanger

80
Q

What happens after Ca2+ enters Cytoplasm

A

Calcium induced calcium release
or RyRa

Ca2+ binds to RyRa opening channel allows Ca2+ to leave SR

81
Q

What happens after Ca2+ released from RyRa

A

Ca2+ intracellular conc. allows Ca2+ to bind to troponin

82
Q

What is special about troponin for cardiac muscle excitation?

A

Only ONE calcium specific site (skeletal muscle has TWO)

83
Q

How is Ca2+ transported out of cell

A

Ca2+ ATPase into SR

sarcolemmal Na+/Ca2+ exchange
(3Na in, 1 Ca out)

mitochondria

sarcolemma Ca- ATPase

84
Q

How is AP graded in skeletal muscle?

A

Recruiting more muscles

85
Q

How is AP graded in cardiac muscle

A

Changing Ca2+ conc.

86
Q

How is Heart rate (HR) set, and how is it modified

A

set by pacemaker in SAN

Rate modified by autonomic nerves releasing neurotransmitters

87
Q

How is Stroke volume increased

A

Increased HR
Increased stretch of ventricles (length)
Certain neurotransmitters

88
Q

Pacemaker potential

A

Slow depolarisation due to If channel ‘funny’ (mostly Na+ driven), SPONTANEOUSLY

89
Q

Vagus nerve

Parasympathetic

A

Decreases heart rate

RELEASES ACh

90
Q

What is special about ACh in innervation in cardiac muscle?

A

It is INHIBITORY, slows down HR

91
Q

Sympathetic cardiac nerves

A

Can innervate both pacemakers, and ventricular myocytes

Affect heart rate AND stroke volume

Releases noradrenaline

92
Q

How does ACh slow down heart rate

A

by hyperpolarising RMP, so takes longer to reach threshold

Decreases rate of spontaneous depolarisation

93
Q

How does Noradrenaline increase heart rate

A

Increases rate of spontaneous depolarisation = increasing heart rate

94
Q

“Automaticity”

Increasing HR increases… because…

A

Contractile force (Stroke volume)

Less time available for Ca2+ to be pumped out of cell = more Ca2+ in cell, increase CICR by SR = stronger contraction

95
Q

Passive tension in heart

A

Lot of collagen, more stretch more total tension = more stroke volume

96
Q

How Noradrenaline acts

A

INCREASES Ca2+ release

Increases frequency of discharge of SAN thus frequency of AP

binds to B receptors and via second messengers acts on
L-type channel (more Ca2+ entering cell)

Ca2+ ATPase in SR
so more Ca2+ ready to be released when next AP comes

97
Q

Sympathetic Nervous System

A

Fight of flight response

98
Q

Parasympathetic Nervous System

A

Rest and digest

99
Q

Increase in Inotropy

A

Strengthening of muscle contraction

100
Q

Basic structure of smooth muscle

A

Spindle shape
100-400um long 5um wide
Central nucleus

No sarcomeres
Poor developed SR
No troponin
No t-tubules 
Few mitochondria
No striation
101
Q

Dense bodies

A

Act as z-lines to anchor actin to sarcolemma

Intermediate filaments attached

102
Q

Single unit (visceral) smooth muscle

WAVE like contractions

A

Sheets of electrically coupled cells act in unison

e.g. hollow organs
Spontaneously active

103
Q

Where is single-unit SM located

A

Blood vessels, hollow organs (digestive, respiratory, urinary, reproductive) RRUD

104
Q

Multiunit SM

A

Independent cells contract to its own innervation

E.g. iris, vas deferens, piloerectors (hairs)

105
Q

Why can smooth muscle contract further than skeletal and cardiac

A

Less organised, actin filaments don’t overlap as much and interfere

but slower

106
Q

Initiation of contraction in smooth muscle

A

Due to voltage-gated Ca channels for cross bridge cycle

Increase in intracellular Ca, enter mostly through cell membrane channels

107
Q

Contraction of smooth muscle can occur 3 three ways

A

Neural (iris)
Hormonal (uterus)
Spontaneous (gut) (myogenic)

108
Q

What is the source of Ca in SM

A

Extracellular and SR via IP3

109
Q

Ways which SM is regulated

A

Voltage, hormones, neurotransmitters, specific ions

110
Q

How is Ca released from SR in SM

A

By ligand-gated second messenger pathways (IP3) and by RyR

111
Q

What is activated when Ca2+ increase in SM

- what does it activate in turn

A

Calmodulin (binds 4 Ca2+ ions)

Activates myosin light chain kinase (MLCK)
which upregulates contraction

112
Q

How is MLCK activated

A

regulation in SM is MYOSIN (not actin) based

Regulatory protein turned on by phosphate, then allowing myosin to hydrolyse ATP

113
Q

When does contraction end in SM

A

when myosin light chain phosphatase (MLCP) removes phosphate group on myosin light chain

114
Q

Why is SM contraction slower

A

Enzyme regulated (NOT calcium regulated)

Slow but efficient

115
Q

What favours relaxation in SM

A

Increased MLCP

Decrease intracellular Ca2+

116
Q

What favours contraction in SM

A

Increased MLCK activity (Ca2+ regulated)

117
Q

How can SM contraction be graded

A

Difference in modulation of MLCK and MLCP

118
Q

What can modulate SM contraction

A 
Stretch
Neurotransmitters
Hormones
Environment
Histamine
Adenosine
Prostacyclin
Nitric oxide (NO)
119
Q

Nitric Oxide (NO) function in modulating

A

Inhibits cGMP-dependent mechanism which contract proteins

120
Q

What innervates SM what do they do

A

Autonomic nerve fibres branch, “diffuse junction”

121
Q

What are the subunits of Autonomic nerve fibres and what do they contain

A

Varcosities (in terminal axon) release neurotransmitters into synaptic cleft

122
Q

What happens when you stretch smooth muscle

A

Initially contract, effectively resisting the stretch

(e. g. blood vessels trying to maintain blood flow constant)
- Stretch activated calcium channels

Over time slowly relaxes, adapting to change in length (e.g. gut)
- via Ca dependent K+ channels, hyperpolarising membrane potential

123
Q

Stress relaxation

A

Your constant deformation (e.g. stomach) can be steady but your stress relaxation can decrease therefore you can eat more

Bio 107 (4 decks)

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