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Principles of pharmacology and physiology > Skeletal muscle > Flashcards

Skeletal muscle Flashcards

1
Q

Definition of terminal cistenae

A

Areas of sarcoplasmic reticulum of muscle cells surrounding T tubules, store Ca, release it when action potentials down T tubules

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2
Q

Types of muscle

A

Skeletal
Cardiac
Smooth

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3
Q

Properties of skeletal muscle

A

Large fibres, multinucleate cells

Striated

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4
Q

Properties of cardiac muscle

A

Small fibres, uninucleate
Striated
Joined in series by intercalated discs

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5
Q

Properties of smooth muscle

A

Small fibres

No striations

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6
Q

Describe the sarcoplasmic reticulum and T system

A

Arranged as repeating networks around myofibrils
Terminal cisterna, surround T tubules, store Ca2+ from ryanodine receptors and release when membrane depolarized
When membrane depolarized, voltage sensor proteins activated
T tubules and adjacent cistern form triad

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7
Q

Function of nebulin

A

Acts as a template for actin filaments

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8
Q

Function of titin

A

Extends from Z to M

During relaxation, generates passive tension through extension when sarcomere stretched

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9
Q

Functional stages of sarcomere, resting stage

A

Some interdigitation between actin and myosin

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10
Q

Functional stages of sarcomere, contracted stage

A

Increased interdigitation

Concentric contraction

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11
Q

Functional stages of sarcomere, stretched stage

A

No interdigitation
H and I bands are wide
A band always remains
Eccentric contraction

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12
Q

Innervation, initiation of contraction

A

Each muscle fibre needs to be innervated, electrically separated
Acetylcholine released from motor end plate, bind to voltage gated Na+ channels
Na+ channels open, Na+ enters cell
Depolarization spreads over membrane via T tubules

Voltage dependent Ca channels in T tubules open => Ryanodine receptors on SERCA open
Ca2+ released into sarcoplasm, binds to troponin complex, tropomyosin changes, myosin head can teach contract

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13
Q

Contraction cycle,

Detachment of myosin from actin

A

ATP binds to myosin => link between myosin and actin weakens => crossbridge detaches

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14
Q

Contraction cycle, recovery stroke

A

ATP => ADP and Pi
Myosin head moves backwards and binds to actin
Crossbridge forms

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15
Q

Contraction cycle, power stroke

A

Pi is released => initiates the power stroke
Actin is pulled towards the M line
ADP leftover is released

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16
Q

Effects of force generation in the contraction cycle

A

Increases binding affinity

Myosin head generates force, straighten up, forces thin filament=power stroke, sarcomere shortens

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17
Q

Comparison of action potential to the twitch

A

Action potential is considerably shorter than twitch time

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18
Q

Effects of summation of Ca2+

A

Frequency of twitch occurs at faster rate than Ca2+ can be removed
If Ca2+ not removed, muscle cannot relax fully between twitches
Increase in Ca2+, exposes more myosin binging sites on actin, increases cross bridges, increases tension

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19
Q

What happens when muscles relax

A

Ca2+ removed into sarcoplasmic reticulum by ATPase
Ca2+ conc decreases, released from troponin, tropomyosin to recover
Crossbridges release and muscle relaxes

20
Q

Function of T1 oxidative fibres

A

Sustained cont

Posture

21
Q

Function of T2A glycolytic/oxidative fibres

A

Phasic movements

Walking

22
Q

Function of T2B glycolytic fibres

A

Phasic movements

Jumping, quick

23
Q

Speed of development of max tension in T1 oxidative fibres

A

Slowest

24
Q

Speed of development of max tension in T2A oxidative/glycolytic fibres

A

Medium

25
Q

Speed of development of max tension in T2B glycolytic fibres

A

Fast

26
Q

Myosin ATP activity in T1

A

Slow

27
Q

Myosin ATP activity in T2A oxidative/glycolytic fibres

A

Fast

28
Q

Myosin ATP activity in T2B glycolytic fibres

A

Fast

29
Q

Diameter of fibres in T1 oxidative fibres

A

Small

30
Q

Diameter of fibres in T2A oxidative/glycolytic fibres

A

Medium

31
Q

Diameter of fibres in T2B glycolytic fibres

A

Large

32
Q

Metabolism of T1 oxidative fibres

A

Oxidative aerobic

33
Q

Metabolism of T2A fibres

A

Glycolytic, can become more oxidative with training

34
Q

Metabolism of T2B fibres

A

Glycolytic, anaerobic

35
Q

Capillary density of T1 oxidative fibres

A

High

36
Q

Capillary density of T2A oxidative/glycolytic fibres

A

Medium

37
Q

Capillary density of T2B glycolytic fibres

A

Low

38
Q

Mitochondrial content of T1 oxidative fibres

A

High

39
Q

Mitochondrial content of T2A oxidative/glycolytic fibres

A

Moderate

40
Q

Mitochondrial content of T2B glycolytic fibres

A

Low

41
Q

Endurance of T1 oxidative fibres

A

Fatigue resistant

42
Q

Endurance of T2A oxidative/glycolytic fibres

A

Fatigue resistant

43
Q

Endurance of T2B glycolytic fibres

A

Fully fatigued

44
Q

Proportion between force and time between types

A

T1, characterised by endurance, little force

T2, characterised by great fore for short periods of time

45
Q

Length tension relationships in sarcomeres

A

Tension related to no of cross bridges formed between thick and thin filaments
In elongated fibres, v few cross bridges, v little power
As sarcomere shortens, more cross bridges form, force increases until cross bridges reach z disc, no new binding sites, tension decreases

Principles of pharmacology and physiology (25 decks)

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