Brainscape's Knowledge GenomeTM

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


See full index

health & disease > L25 - skeletal muscle > Flashcards

L25 - skeletal muscle Flashcards

1
Q

what is skeletal muscle?

A
  • voluntary, conscious
  • attached to bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

key characteristics of skeletal muscle

A
  • made of fibres
  • involved in posture and movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are tendons?

A

bundles of collagen fibres that attach muscle to bone

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

what is skeletal muscle made of?

A

bundles of multinucleate muscle cells

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

what is a muscle fibre?

A

single muscle cell

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

what is a myofibril?

A

each muscle cell formed from bundles of actin and myosin filaments which are organised into myofibrils

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

describe arrangement of actin filaments around a myosin filament

A

6 actin around 1 myosin

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

what is the sarcoplasmic reticulum?

A
  • like endoplasmic reticulum
  • acts as a Ca2+ store
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

structure of skeletal muscle

A

striated pattern

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

Z-DISC

A
  • borders of sarcomeres
  • smallest functional units
  • core made of actin
  • alpha actions bind and cross like the ends of F-actin from sarcomeres at z line
  • alpha actinin-2 in all muscle fibres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the thin filament made up of?

A

actin, tropomyosin, troponin

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

M-Band

A

myomesin

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

what is the thick filament made up of?

A

myosin and titin

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

A band

A
  • dark band
  • myosin
  • centre of sarcomere
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

I band

A
  • lighter band
  • only contains thin filaments
  • actin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

M line/disc

A

proteins that link central regions of the thick filaments

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

H zone

A

light area at end of thin filaments

18
Q

describe thick filaments

A
  • 15nm in diameter
  • lots of motor protein myosin
  • myosin. made of heavy and light chains
19
Q

describe myosin

A
  • tail made of 2 chains
  • globular hear which projects at an angle
  • half of the heads orientated to left, other to right
  • creates area in middle called M-region
20
Q

describe thin filaments

A
  • made of filamentous F-actin strands
  • which are made of a string of globular G-actin subunits
  • contain tropomyosin: blocks active sites
  • filaments attached at z disc
21
Q

describe tropomyosin

A
  • blocks active sites
  • bound by calcium binding protein troponin
22
Q

what is the interaction between actin and myosin filaments regulated by?

A

troponins

23
Q

troponin I

A

inhibitory

24
Q

troponin C

A

calcium binding

25
Q

troponin T

A

tropomyosin binding

26
Q

sliding filament theory

A
  1. contraction causes force
  2. myofilaments stay same length but it causes more overlap
27
Q

what does an increase in calcium initiate?

A

contraction

28
Q

cross bridge cycling 3 stages

A
  1. resting muscle
  2. activation of contraction
  3. terminating cross bridge
29
Q

describe stage one of cross bridge cycling: resting muscle

A
  • myosin molecule bound to ADP + Pi
  • tropomyosin covers myosin binding sites on acting filaments so they can’t bind
30
Q

describe stage 2 of cross bridge cycling: activation of contraction

A
  • muscle stimulated
  • calcium levels in cytosol increase
  • calcium binds to troponin
  • so uncovers myosin binding sites on actin
  • myosin molecule + ADP binds to actin
  • cross bridge formation causes release of ADP and Pi and movement of the cross bridge
31
Q

describe stage 3 of cross bridge cycling: terminating cross bridge

A
  • ATP binds to myosin
  • breaks actin-myosin cross bridge
  • ATP converted to ADP and Pi
  • so myosin returns to energised position
32
Q

how are skeletal muscle contractions neurogenic?

A
  • contractions need synaptic input from motor neurones
  • a single motor neurone can innervate muscle fibres so they all contract at same time
33
Q

describe the neuromuscular junction

A
  • axon terminal and the motor endplate = NMJ
    myelin sheath that surrounds the motor neurone ends near the surface of the muscle fibre
34
Q

what do the axon terminals in the NMJ contain?

A

vesicles with ACh

35
Q

motor end plate of NMJ

A

area of muscle fibre directly under the axon terminal

36
Q

describe how NMJ works

A
  1. A.P at motor neurone depolarised axon terminal
  2. so voltage dependent calcium channels open
  3. causes release of ACh vesicles through synapse
  4. ACh diffuses to motor end plate
  5. activates NICOTINIC ACh receptors (ionotropic receptors)
  6. motor end plates is depol
  7. this is end plate potential
37
Q

fast twich fibres in skeletal muscle

A
  • glycolytic
  • explosive power
38
Q

slow twich fibres in skeletal muscle

A
  • aerobic
  • fatigue resistant
39
Q

what is the speed of contraction determined by?

A

the myosin heavy chain isoform expressed by the fibre

40
Q

is there a gene for speed?

A
  • alpha actinin 3 is expressed in a subset of fast twitch muscles
  • genetic variant encoding premature stop codon results in truncated form of this actinin
  • absence of variant correlates with athletic performance
41
Q

myopathies (genetic skeletal muscle diseases)

A
  • present at birth
  • develops at infancy
  • non progressive
  • non degenrative
  • defect in actin
42
Q

dystrophies

A
  • birth or later
  • progessive
  • degenerative
  • defects in memb / proteins

health & disease (19 decks)

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