limbs and back week 3 Flashcards Preview

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Flashcards in limbs and back week 3 Deck (107):
1

Describe the ATP pool in skeletal muscle

it is small and capable of supplying only for a very few contractions if not replenisehd

2

Why are ATP supplies only moderately depleted even as the muscle fatigues?

It is continually replenished

3

What is the function of creatine phosphate?

It is used to convert ADP to ATP and thus replenish the ATP store during muscle contraction.
Represents the immediate high-energy source for replacing the ATP supply in skeletal muscle, especially during intense exercise

4

What enzyme catalyses the reaction between ADP and creatine phosphate?

creatine phosphokinase

5

Where is CPK found?

Mostly in the sarcoplasm but some at the myosin heads too

6

How big is the creatine phosphate store?

Only 5 times to size of the ATP store and can't last over 1 minute

7

How is creatine phosphate replenished?

During recovery from fatigue by using the ATP synthesised by oxidative phosphorylation

8

Where do muscles get carbohydrates from?

Muscle cells contain glycogen stores which can be metabolised during muscle contraction to provide glucose for oxidative phosphorylation and glycolysis
Muscle cells can also take up glucose from the blood
ATP yields are dependent on an adequate oxygen supply

9

When are fatty acids important sources of energy for muscle?

During prolonged exercise

10

Where do muscles get fatty acids from?

Muscle cells contain fatty acids
they can uptake fatty acids from the blood
muscle cells can store triglycerides, which can be hydrolysed to produce fatty acids

11

How are fatty acids metabolised in muscle?

they are converted into acyl-carnitine in the cytosol then transported into the mitochondria
Then they are converted into acyl-CoA
Within the mitochondria acyl-CoA is then subjected to Beta oxidation and yields acetyl-CoA
This enters the citric acid cycle and ultimately produces ATP.

12

What is fatigue?

The inability to maintain power output of muscle, reversible by rest

13

What occurs as a result of fatigue?

reduced force, shortening and relaxation rate

14

Describe central fatigue

within the nervous system
loss of excitability of the motor cortex, possible reflex inputs from "metabo-receptors" in muscle
can include failure of transition in peripheral nerve and neuromuscular junctions (usually pathological)

15

Describe peripheral fatigue

within the muscle fibres
failure of excitation - contraction coupling, T-tubule action potential, SR activation, Ca2+ release

16

How can you determine the type of fatigue?

external stimulation - if direct muscle stimulation delivers smaller forces then fatigue is peripheral. If stimulation delivers "normal" forces, then fatigue is central

17

Describe excitation failure

most likely in short intensity exercise
High AP firing rates leads to accumulation of K+ ions in tubules
This would make the T-tubule unexcitable and impairs excitation contraction coupling
recovery from this type of fatigue would be rapid

18

When is central fatigue likely?

Probably likely in occupational work and recreational sport. sensation of fatigue may involve discomfort and lack of motivation.
probably not a factor in elite sport

19

When does peripheral fatigue occur?

fatigue is not due to decreased ATP
In fatigue concentrations of H+, Pi and ADP all increase
these changes impair calcium fluxes and impair force delivery at cross bridges

20

Why does the build up of ADP, Pi and H+ inhibit the function of ATP?

An increase in the right and side of the equation will shift the equilibrium to the left and hence slow the break down of ATP

21

What else do ADP, Pi and H+ all inhibit?

Ca2+ release and reuptake into the sarcoplasmic reticulum. This affects the force and speed of shortening and relaxation.
H+ also competes with Ca2+ for troponin binding

22

What is the main energy source for long duration exercise?

Carbohydrate and lipid metabolism

23

What is the main energy source for moderate duration exercise?

aerobic, fuel mix uses more carbohydrates

24

What is the main energy source for short duration exercise?

aerobic and anaerobic metabolism, carbohydrate dependent, inefficient glycolytic metabolism

25

Describe the processes of training

requires multiple repetitions of the exercise concerned
for strength - small numbers of high power contractions
for endurance - large numbers of low force contractions
in strength training type 2 fibres enlarge
in true endurance training (e.g. marathon) no demand for increased strength, type 1 fibres may enlarge but type 2 decrease. Usually there is a loss of fat.

26

Describe the neural phase of strength training

first 4-6 weeks
CNS response, increased recruitment of largest motor units and higher maximum firing rates

27

Describe the hypertrophy phase of strength training

large motor units grow
significant hormonal changes - after strenuous strength training, GH, local growth hormones and testosterone are all elevated for hours
connective tissues also strengthen
hypertrophy is slow
starts with the development of new filaments attached laterally to existing myofibrils
Later there is fibril splitting - the most enlarged fibrils split longitudinally - thus become more numerous

28

How can skeletal muscle fibres be classified?

As fast twitch (2a/2b) or slow twitch (1)

29

How can the different types of muscle fibres be distinguished from one another?

the activities of oxidative and glycolytic pathways.

30

Describe fast twitch fibres

the activity of the glycolytic enzymes is high and the activity of the oxidative enzymes is low. -
very few mitochondria
more extensive sarcoplasmic reticulum than slow twitch
fatigue quickly

31

Describe slow twitch fibres

meet metabolic demands by oxidative phosphorylation
fatigue more slowly

32

What is special about 2a fibres?

They contain both high glycolytic and oxidative capacity - rare in humans

33

What is spacial summation?

Since fast-twitch muscle fibres are more difficult to excite slow twitch muscle fibre motor units are recruited first.
As more force is required, fast fibres are recruited

34

What are the advantages of spacial summation?

The first muscle fibres recruited have high resistance to fatigue
the small size of the slow-twitch muscle units allows fine motor control

35

What are the three bones of the elbow joint?

The humerus, ulna and radius

36

What are the two articulations of the elbow joint?

Humeri-ulnar = between the trochlea of the humerus and the trochlear notch of the ulna
Humero-radial = between the capitulum and upper surface of the radial head

37

What limits movement at the elbow joint?

fossas

38

Describe movement at the elbow joint

Flexion and extension - hinge joint, very stable, not likely to dislocate

39

How can hyperextension occur?

If the olecranon fossa forms a foreman instead, the olecranon of the ulna can pass right through

40

Describe the proximal radioulnar joint

also contained within the elbow joint capsule
the articulation between the head of the radius and the radial notch of the ulna
annular ligament wraps around the head of the radius and maintains stability of the radius
allows rotation during pronation and supination of the forearm.
Primary supination muscle is the biceps

41

What are the 3 flexors of the elbow joint?

Brachialis (primary flexor)
Brachioradialis (accesorry) only when forearm is mid-pronated
Biceps bracchi - only if palm is upwards

42

What is the extensor muscle of the elbow joint?

triceps brachii (long head, lateral head, medial head)

43

What forms the compartments of the forearm?

The interosseous membrane

44

What is the function of the interosseous membrane?

Stabilises the radius and ulna

45

What muscles are contained within the superficial and intermediate layers the anterior compartment of the forearm?

flexor carpi ulnaris
palmaris longus
flexor carpi radialis
pronator teres

46

What is the nerve supply to the superficial and intermediate layers of the anterior compartment of the forearm?

all musculocutaneous nerve except flexor carpi ulnaris which is supplied by the ulnar nerve

47

What muscles are contained in the deep layer of the anterior compartment of the forearm?

flexor digitorum profundus
flexor policis longus
pronator quadratus

48

What is the nerve supply to the deep layer of the anterior compartment of the forearm?

Musculocutaneous expect half of flexor digitorum profundus is supplied by the ulnar nerve - the part that flexes the ring and little fingers

49

Which muscles are contained within the superficial layer of the posterior compartment of the forearm?

brachioradialis
extensor carpi radialis longus
extensor carpi radialis brevis
aconeus
extensor digitorum
extensor digiti minimi
extensor carpi lunaris
extensor retinaculum

50

What is the nerve supply of the superficial layer of the posterior compartment of the forearm?

Radial nerve

51

Which muscles are contained within the deep layer of the posterior compartment of the forearm?

Abductor policis longus
extensor policis brevis
extensor indicis
extensor policis longus

52

What is the nerve supply to the deep layer of the posterior compartment of the forearm?

radial nerve

53

What is epicondylitis?

Tennis / golfer's elbow
caused by resisting / limiting wrist movement
pain radiates along affected muscles

54

What side is tennis elbow?

lateral

55

What side is golfer's elbow?

medial

56

how is epicondylitis treated?

rest or injection of corticosteroids if pain is severe

57

What is the cubital fossa?

A triangular shaped depression anterior to the elbow

58

What is the lateral boundary of the cubital fossa?

brachioradialis

59

What is the medial border of the cubital fossa?

pronator teres

60

What is the superior border of the cubital fossa?

imaginary line between the medial and lateral epicondyles

61

What is the floor of the cubital fossa?

brachialis

62

What is the roof of the cubital fossa?

deep fascia reinforced by bicipital aponeurosis

63

What is contained in the cubital fossa?

tendon of biceps
brachial artery
median nerve
radial nerve (underneath brachioradialis)

64

Why is the cubital fossa an important site for venipuncture?

deep fascia protects the underlying brachial artery and median nerve
safe place to take blood sample

65

Describe the blood supply to the forearm

the brachial artery bifurcates in the cubital fossa into the radial and ulnar arteries.

66

Where do the radial and ulnar arteries lie?

lateral to the tendons of the flexor carpi ulnas and flexor carpi radialis

67

Why is the ulnar artery more difficult to palpate?

Mostly covered by the flexor carpi ulnaris

68

what is gastrulation?

a process of cell division and migration resulting in the formation of 3 germ layers

69

What are the three germ layers called?

ectoderm, mesoderm, endoderm

70

What does ectoderm form?

epidermis of skin and its derivatives
epithelial lining of mouth and anus
cornea and lens of eyes
nervous system
sensory receptors in the epidermis
adrenal medulla
tooth enamel
epithelium of pineal and pituitary glands

71

What does mesoderm form?

notochord
skeletal system
muscular system
muscular layer of stomach lining
excretory system
circulatory and lymphatic systems
reproductive systems
lining of body cavity
adrenal cortex

72

What does endoderm form?

epithelial lining of digestive tract
epithelial lining of respiratory system
lining of urethra, urinary bladder and reproductive system
liver
pancreas
thymus
thyroid and parathyroid glands

73

When does mesoderm differentiate?

days 17-21

74

what does mesoderm differentiate into?

paraxial
intermediate
lateral plate

75

what does paraxial mesoderm form?

cells moving bilaterally and cranially
forms somites

76

what does intermediate mesoderm form?

genitourinary systems

77

what does lateral plate mesoderm form

somatic and splanchnic layers

78

where does skeletal muscle originate from?

paraxial mesoderm

79

where does smooth muscle originate from?

visceral layer of the lateral plate mesoderm

80

where does cardiac muscle originate from?

visceral later of the lateral plate mesoderm

81

what type of mesoderm gives rise to somites?

paraxial

82

what stimulates the start of somitogenisis?

NOTCH accumulation on the pre-somatic mesoderm
signal for somite formatoin
once somite is formed NOTCH decreases

83

What is a somite?

a block of mesoderm which gives rise to skeletal muscle

84

what do somites split into?

sclerotome and dermatomyotome

85

What does sclerotome form?

the vertebrae and ribs

86

what does dermatomyotome split into?

dermatome and myotome

87

what does dermatome form?

dermis of the back

88

what does myotome form?

muscles

89

What are myoblasts?

myotome cells - committed muscle cell precursors

90

What are the transcription factors involve in skeletal muscle formation?

MYOD and MYF5

91

Which molecules regulate somite differentiation?

WNT proteins (activating)
BMP (inhibitory)
sonic hedgehog
noggin

92

describe smooth muscle

orientates from splanchnic mesoderm
serum response factor (SFR) is responsible for smooth muscle cell differentiation
SFR unregulated by kinase phosphorylation pathways
Myocardin / myocardin-related transcription factors enhance SFR activity

93

Describe skeletal muscle

myoblasts fuse to form long multinucleate fibres
striated , contain many mitochondria
under control of genes sets including MYOD, Mfy5 and myogenic
tendons are derived from the sclerotome under the control of the transcription factor sceraxis

94

Describe cardiac muscle

splanchnic mesoderm surrounding developing heart tube
striated - different from skeletal
myoblasts adhere to each other via intercalated disks
MYOD not involved in early cardiac muscle development
TInnman - homeobox gene responsible for specification of cardiac muscle

95

what do sensory neurons do?

relay information centrally to the spinal cord

96

What do motor neurons do?

responsible for causing muscle contraction - ventral horn of the spinal cord

97

What are peripheral nerves?

The axons of motor and sensory neurons

98

Describe the spinal cord in terms of innervation

caudal part of the CNS
continuous with the brain stem
organised segmentally - 8 cervial, 12 thoracic, 5 lumbar and 1 coxygeal
each segment gives rise to a pair of spinal nerves

99

What nerves form the cervical plexus?

C1-C5

100

What nerves from the brachial plexus?

C5-T1

101

What nerves from the lumbosacral plexus?

T12-S5

102

Describe the difference between myelinated and unmyelinated nerves/

myelinated - large diameter, fast conduction, touch, vibration, motor output
non-myelinated - small diameter, slow conduction, pain, hot, cold

103

What is a myotome?

each muscle is supplied by a particular level / segment of the spinal cord and its corresponding spinal nerve

104

What is a dermatome?

An area of skin innervated by a particular level / segment of the spinal cord

105

What is the ASIA scale used for?

to determine the level and extent of spinal cord injury

106

What is proprioception?

sensations arising from the deep field as a result of the actions of the organism

107

What factors contribute to proprioceptive sensations?

passive displacement of the joints (and skin)
movement sense (awareness of joint movement)
Position sense (awareness of static joint position)