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Muscle structure and function Flashcards

1
Q

What are the three types of muscle?

A

Skeletal, smooth and cardia

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2
Q

Characteristics of skeletal muscle

A

Voluntary and striated , attached to bones

Long, cylindrical, multinucleate

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3
Q

Characteristics of cardiac muscle

A

Striated and found in walls of heart

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4
Q

Characteristics of smooth muscle

A

Involuntary/visceral found in walls of hollow organs

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5
Q

What are the three main functions of muscle?

A

Movement, support and heat production

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6
Q

Characteristics of spinal nerves

A

Part of somatic nervous system
31 pairs of spinal nerves
Sensory (afferent) and motor (efferent)

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7
Q

What is a myotome?

A

Group of muscles innervated by a single spinal nerve

Skeletal muscles innervated by spinal nerves derived from the same segmental level of the spinal cord as the somite

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8
Q

How does the musculoskeletal system develop?

A

Paraxial mesoderm form segmented blocks called epithelial somites
Under notochord influence, each somite block reorganises into 3 groups of progenitor tissue cells:
Dermatome, myotome and sclerotome

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9
Q

What are epithelial somites?

A

Blocks of neural tube located on either side of the neural tube in the developing embryo

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10
Q

How do dermatomes assist the development of the musculoskeletal system?

A

Give rise to connective tissue and dermis of skin

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11
Q

How do myotomes assist in the development of the musculoskeletal system?

A

Develop skeletal muscle (dorsal and ventrolateral muscles of body wall)

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12
Q

How do sclerotomes assist in the development of the musculoskeletal system?

A

Give rise to vertebrae and rib cage

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13
Q

Where is most smooth muscle derived from?

A

Lateral plate mesoderm and neural crest (gut develops from splanchic mesoderm)

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14
Q

Where is most cardiac muscle derived from?

A

Splanchnic (visceral) layer of lateral plate mesoderm surrounding developing heart tissue

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15
Q

Where is most skeletal muscle derived from?

A

Each myotome, receiving its nerve supply from the spinal nerves derived from the same segmental level of the spinal cord as the somite

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16
Q

Diameter and length of skeletal muscle fibres

A

10-100 micrometres, length is up to 35 cm

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17
Q

What is a motor unit?

A

A group of muscle fibres with one single motor neurone supplying them

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18
Q

What are the specialised stretch receptors in skeletal muscle?

A

Neuromuscular spindle

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19
Q

How many motor neurone innervate a muscle fibre?

A

One, but a neurone could connect to many muscle fibres

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20
Q

How many muscle fibres are in motor unit 2?

A

3

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21
Q

How many muscle fibres are in motor unit 1?

A

2

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22
Q

Size variation in motor units

A

From 2-3 in larynx to 2000-3000 in gastrocnemius muscle

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23
Q

What do tendons do?

A

Attach muscle to bone

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24
Q

What happens to tendons when they approach muscle?

A

They turn into epimysium, which surrounds the muscle

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25
What are muscle fascicles made up of?
Bundles of cells called muscle fibres
26
What is the endomysium?
The connective tissue layer surrounding muscle fibres
27
What are the nuclei like in muscle fibres?
Located peripherally under the endomysium | Multinucleated - many myoblasts fuse together to form a single cell
28
Which nerve innervated muscle fibres?
Motor neuron
29
Which blood vessel supplies muscle fibres?
Arteriole
30
Why can muscle fibres contract?
Full of proteins - myofibrils made of filamentous proteins (myosin and actin)
31
Why are myofibrils striated?
Overlapping layers of protein fibres
32
What is the sarcolemma?
Muscle fibre cell membrane
33
What are T-tubules?
Pits in the sarcolemma which connect the outer environment to the nucleus Conducts electrical impulse to nucleus
34
Which organelle does the SR closely resemble?
It's a modified version of the smooth ER
35
Muscles in the anterior/flexor compartment of the arm
Coracobrachialis Biceps Brachii Brachialis
36
Muscle in the posterior/extensor compartment of the arm
Triceps
37
Muscles in the posterior/extensor compartment of the forearm
Brachioradialis, extensor carpi radialis longus, superficial and deep layer muscles
38
What are the 6 symptoms of compartment syndrome beginning with P?
``` Pain Palpably tense compartment Pain with passive stretch Paraesthesia Paralysis Pulselesness/pallor ```
39
What are the three types of biomechanics levers?
First/second/third
40
Equation for torque
Torque = effort x distance
41
What is a first order lever?
Fulcrum is in middle Load is pushing down and on left Effort is pushing down on right
42
What is a second order lever?
Fulcrum is pushing down on right, load is pushing down in middle, effort is pushing up on right
43
What is a third order lever?
Load is pushing down on left Effort is pushing up in middle Fulcrum is pushing down on right
44
Rhyme for remembering levers
1,2,3 | F,L,E (in middle)
45
3 examples of agonists vs antagonists
Flexors vs extensors Abductors vs adductors Pronator vs supinator
46
How does the arrangement of fascicles impact the lever?
Greater number of muscle fibres = greater power | Longer and more parallel arrangement = more muscle shortening
47
What are the 7 types of fascicle arrangement?
``` Circular Convergent Parallel Unipennate Multipennate Fusiform Bipennate ```
48
What is synergistic actions?
Synergistic muscles contract to prevent unwanted movement or aid the muscle of the agonist
49
Why does winged scapula occur?
Paralysis of the serratus anterior muscle due to damage of long thoracic nerve
50
What are the three phrases used to describe the direction of a muscle?
Rectus Transverse Oblique
51
What direction is a rectus muscle facing?
Straight/parallel to midline
52
What direction is a transverse muscle facing?
Perpendicular to midline
53
What direction is an oblique muscle facing?
Diagonal to midline
54
What are the four phrases used to describe the size of a muscle?
Maximus/minimus Longus Major/minor Brevis
55
Which 7 factors should you consider when naming muscle?
``` Direction Size Shape Action Number of origins Location Origin and insertion ```
56
How many heads does a bicep/tricep/quadricep muscle have?
2/3/4
57
What is neuromuscular disease?
Disease/damage of somatic motor neurone, neuromuscular junctions or muscle fibres
58
What is myasthenia Gravis?
Autoimmune damage to NMJ - causes muscle weakness and fatigue
59
What is myopathy?
Disease/disorder of skeletal muscle tissue
60
What is Duchenne's/Becker's muscular dystrophy?
x-linked inherited skeletal; muscle fibre degenerative disease - causes muscle weakness and wasting mainly in boys
61
How does Duchenne's/Becker's muscular dystrophy develop?
Dystrophin gene mutates - loses structural link between sarcolemma and sarcomere Dystrophin binds to actin and Marco-glyco complex Sarco-glyco complex has links to basal lamina - provides tensile strength Muscles contract and pull apart
62
What is Gower's sign?
Struggling to get up from floor
63
Difference between Duchenne and Becker's muscular dystrophy?
Duchenne's is complete break between sarcolemma and collagen in basement membrane Becker's = partial expression of dystrophin (normally shorter) Duchenne victims tend to die younger because diaphragm stops working
64
What is muscular hypertrophy?
Skeletal muscle growth after birth occur through enlargement of existing muscle cells - a process called hypertrophy. This is influenced by hormones and exercise
65
What is sarcopenia?
Reduction in muscle mass due to ageing - influenced by reduced hormonal signalling, reduced nervous stimulation, muscle disuse, protein synthesis and diet
66
What is creatine phosphate?
An amino acid bound to a phosphate group | Donates phosphate to ATP via creatine kinase
67
What is creatine kinase?
Enzyme that stimulates creatine phosphate to donate phosphate to ATP
68
What are kinases?
Enzymes that can phosphorylate
69
Is the process of phosphorylation reversible?
Yes
70
Which enzyme functions in mitochondrion to add phosphate group to phosphocreatine?
mtCK (mitochondrial creatine kinase)
71
What happens to phosphate in the cytosol of the mitochondria to stimulate contraction?
Muscle isoform of creatine kinase uses phosphocreatine to donate phosphate group to ATP Myosin heads use phosphate ATP used by myosin heads and can be used by SERCA pump to push calcium into SR
72
Characteristics of cardiomyocytes
Single cells, 1 or 2 nuclei located centrally, have darker regions that are intercalated disks (separate cells)
73
Which molecules form a diad?
T tubules and SR
74
What do gap junctions do?
Allow sarcoplasm to be shared between cardiomyocytes
75
What does MLCK stand for?
Myosin Light Chain Kinase
76
What does Tm stand for?
Tropomyosin
77
Characteristics of smooth muscle
Single cells with one centrally located nucleus and sheaths of basal lamina No troponin complexes Have smooth muscle myosin to turn into actin-binding structure when it has light chain of myosin phosphorylate
78
Which enzyme phosphorylates the light chain of smooth muscle?
MLCK
79
What is MLCK activated by?
Calcium
80
How does calcium activate MLCK?
When calcium enters smooth muscle it binds to calmodulin and activates calmodulin kinases to phosphorylate MLCK
81
What is a tendon?
A thick band of dense connective tissue that attaches muscle to bone
82
What is aponeurosis?
Broad sheet of dense connective tissue that attaches muscles to bone
83
What is the muscle attachment site origin?
Attachment site of muscle tendon/aponeurosis to less moveable or stationary bone
84
What is the muscle attachment site insertion?
Attachment site of muscle tendon/aponeurosis to more moveable bone
85
What is muscle group action?
A coordinated contraction of a group of muscles to bring about movement of body parts - several skeletal muscles often act as a group to effect movement of body parts

Musculoskeletal system (24 decks)

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