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Flashcards in Muscle Deck (37):
1

Classes of joints

Fibrous - bones linked by fibrous connective tissue e.g. sutures
Cartilaginous - linked by hyaline/fibrocartilage
Synovial - enclosed by fluid filled synovial capsule

2

Types of synovial joint

Plane e.g. intervertebral
Saddle e.g. CMC pollicis
Hinge e.g. elbow
Pivot e.g. proximal radioulnar
Ball and socket e.g. hip
Ellipsoid e.g. MCP/radiocarpal

3

Isotonic contraction

muscle shortens/lengthens but tension stays the same

4

Isometric contraction

muscle length stays constant but tension may change

5

Types of movement produced by motor system

reflexive
rhythmic
voluntary

6

Skeletal muscle made up of

fascicles (bundle)
muscle cell/fibres
myofibrils
myofilaments

7

Fascial coverings of skeletal muscle

epimysium covers whole muscle
perimysium covers fascicles
endomysium covers individual muscle cells

8

Muscle cell types

I - slow, aerobic and rich in myoglobin
IIa - fast twitch, oxidative and glycolytic
IIx - fast twitch, glycolytic

IIb found in animals but not in humans

9

Detecting stretch and detecting tension

Stretch by muscle spindles (intramural fibres within)
Golgi tendon organs for tension

10

Myasthenia gravis

autoantibodies to AChR, blocks or destroys
Treated with AChesterase

11

Muscular dystrophy

mutation in dystrophin (binds actin filament to sarcolemma) gene

12

Satellite Cells action

stem cells attached to skeletal muscle which replicates in response to muscle damage, on stays as precursor and other helps to repair

13

Sarcomere features

Dark A band - single length of thick (myosin) filament
I bands - zone of thin (actin) filaments without thick
H zone - thick filament area not superimposed by thin
M line - disk in middle, cross connecting elements of cytoskeleton
Z line - end of sarcomere where actin is anchored

14

Contractile proteins

Myosin - forms thick filaments
Actin - forms thin filaments
Tropomyosin and troponin - regulatory
Titin - biggest known muscle protein, spans half the length of sarcomere, provides elasticity and stabilises myosin

15

Actin forms

G-actin - globular
F-actin - thin filaments, polymerised G-actin subunits

16

Angel of death mushroom toxin

Phalloidin, locks F-actin fibres together causing paralysis

17

Tropomyosin

Blocks S1 binding to actin when Ca++ is low

18

Troponin types and functions

C - binds Ca++ at two sites to change troponin I and T
I - binds actin
T - binds tropomyosin and controls positioning of tropomyosin on actin filament to decide whether myosin binding site is open or not

19

Troponin in MI

Released into the blood in event of MI so free troponin can be an indicator that it's occurred

20

Muscle contraction steps

ATP hydrolysed in S1 causing S1 head to 'cock' (recovery stroke)
Pi released from myosin causing it to bind to actin
ADP released causing power stroke
New ATP binds to release actin from myosin

21

Smooth muscle organisation

loose bundles of thick and thin filaments

22

Smooth muscle control of contraction since there's no troponin

Caldesmon forms complex with tropomyosin when Ca is low to restrict myosin binding to actin
Caldesmon can be phosphorylated to prevent binding to actin
Myosin regulatory chain can be phosphorylated to prevent it blocking myosin binding, occurs in presence of Ca-calmodulin
Can be regulated by hormones

23

Roles of Ca in muscle (4)

Trigger striated muscle contraction
Triggers smooth muscle contraction
Helps initiate glycogenolysis in striated muscle
Ensures sarcolemma sealing to prevent ion leakage and depolarisation in striated

24

Neural factors affecting muscle function

Descending drive
Motor neuron recruitment/coding

25

Biomedical factors affecting muscle function

X sectional SA
Muscle fibre type
Elastic properties
Muscle architecture
Length-tension
Load velocity
Contraction time

26

Factors affecting muscle function

Temperature
Fatigue
Increased elasticity means stronger forces can be generated

27

Muscle strength definition

maximum force/tension output, measured by 1RM

28

Muscle torque

size of muscle force x distance away from centre of rotation (joint)

29

Greatest power developed at what rate of maximum contraction speed

1/3 of maximum

30

Neural factors affecting muscle strength

Activation of motor units (frequency and number)
Involvement of afferent/efferents
Synchronisation

31

Sarcopenia effects

Decreased neural activation
Fibre atrophy
Muscle architecture (pennation angle)
Loss of elasticity
Loss of MHC II
Agonist/antagonist coactivation

32

Fuel sources

Muscle/liver glycogen
Plasma glucose
Muscle/adipose TAG
Plasma lipoproteins
Ketone bodies (in prolonged fasting/very long exercise)

33

ATP production methods

Adenylate kinase (ADPx2=ATP+AMP)
Creatine kinase (first 5 secs before glycolysis starts)
Glycolysis
FA oxidation (slow)
TCA and ETC

34

Phosphorylase kinase activation in liver and muscle

In muscle adrenaline stimulates PKA, contraction increases cytosol Ca
In liver Glucagon stimulates PKA and Ca release to cytosol

35

Upregulation of glycolysis enzymes

Hexokinase by use of glucose-6-p
Phosphofructokinase-1 by [AMP] inc by adenylate kinase
Pyruvate kinase by [AMP]

36

Anaerobic exercise effects on body

Type II fibre size increases, more glycogen storage

37

Aerobic exercise effects

Higher glycogen synthase activity
Higher fatty acid transporter expression
AMPK activity increases so more fats can be oxidised
Size and number of mitochondria increases