Muscle Tissue

Question 1

What is myalgia?

Answer 1

Muscle pain

Question 2

What is Myasthenia?

Answer 2

Weakness of the muscle

Question 3

What is Myocardium?

Answer 3

Muscular component of the heart

Question 4

What is Myopathy?

Answer 4

Any disease of the muscles

Question 5

What is Myoclonus?

Answer 5

A sudden spasm of the muscles

Question 6

What is the sarcolemma?

Answer 6

The outer membrane of a muscle cell

Question 7

What is the sarcoplasm?

Answer 7

The cytoplasm of the muscle cell

Question 8

What is a sarcosome?

Answer 8

The mitachondria

Question 9

What is the sarcomere?

Answer 9

The contraction unit in striated muscle

Question 10

What is the sarcoplasmic reticulum?

Answer 10

The smooth endoplasmic reticulum of a muscle cell

Question 11

What is the epimysium?

Answer 11

The dense connective tissue that surrounds the entire muscle tissue

Question 12

What is the perimysium?

Answer 12

Connective tissue that surrounds a muscle fasicle

Question 13

What is the endomysium

Answer 13

Connective tissue that surrounds individual muscle fibres

Question 14

What is a muscle fibre?

Answer 14

A striated muscle cell, each cell contains numerous myofibrils

Question 15

In myofibrils what are the thick and thin filaments?

Answer 15

Thin filaments = actin

Thick filaments = myosin

Question 16

What is the structure of skeletal muscle fibres

Answer 16

• Have peripheral nuclei
• Bordered by endomysium that contain cappillaries and venules
• Striations of alternating dark A bands and light I bands with a thin Z band in the middle of each I band

Question 17

What are t-tubules?

Answer 17

At each AI junction one transverse tubule extends down from sarcolemma

Question 18

What is the sliding filament theory?

Answer 18

1) Myosin cross bridge attaches to the actin myofilament
2) Working stroke- the mysoin head pivots and bends as it pulls on the actin filament, sliding towards the M line. ADP and inorganic phosphate are released
3) As new ATP attaches to the myosin headgroup the cross bridge detatches (myosin head group in low energy configuration)
4) As ATP is split into ADP and Pi cocking of the myosin head occurs

Question 19

What is the structure of myosin?

Answer 19

• An individual myosin molecule has a rod like structure from which it has two heads
• Each thick filament consists of many myosin molecules whose heads protrude ay opposite ends of the filaments

Question 20

What two components make up an actin molecule?

Answer 20

Two protein components:

• F-actin fibres
• G-actin globules

Question 21

What three components make up the thin filaments?

Answer 21

• Actin
• Tropomyosin
• Troponin

Question 22

What is the M line?

Answer 22

Where the myosin molecules lack myosin heads

Question 23

What is the role of calcium ions in the contraction mechanism?

Answer 23

• As calcium binds to TnC of troponin a conformational chage moves tropomyosin away from actin’s binding sites
• This allows myosin heads to bind actin, and contraction can begin
• The tropomyosin sits in the cleft of the G-actin ‘spheres’

Question 24

What are the names and functions of the troponins involved?

Answer 24

TnT = binds to troponin
TnC = binds to calcium
TnI = Inhibitor

Question 25

In 7 stages, explain innervation/contraction coupling

Answer 25

1) ACh released by motor neurone binds to receptors on motor end plate
2) Action potential generated in response to binding of ACh and subsequent end plate potential is propagated across the surface membrane and down t-tubules
3) Action potential triggers calcium release from sarcoplasmic reticulum
4) Calcium binds to TnC on actin filaments; conformational change leads to actin binding to myosin head groups
5) Powered by ATP, cross bridge cycling occurs
6) Calcium ions actively taken up by sarcoplasmic reticulum when there is no longer local action potential
7) With calcium no longer bound tropomyosin blocks actin binding sites

Question 26

What is Duchene muscular dystrophy?

Answer 26

• Most common muscular dystrophy
• Inherited through X-linked recessive pattern
• Mutations of the dystrophin gene
• Absence of dystrophin allows:
• Excess calcium to enter the muscle cell
• Calcium taken up by the mitachondria
• Water taken with it
• Mitachondria burst
• Muscle cells burst (rhabdomyolysis)
• Creatine kinase and myoglobin levels high in the blood

Question 27

What are the signs and symptoms of duchene muscular dystrophy?

Answer 27

• Sway back

- Poor balance

Question 28

What markers are used for cardiac ischaemia?

Answer 28

Troponin I and T

Question 29

What is botox and how is it used?

Answer 29

• Botulism toxin produced by Clostridium botulinum
• Blocks neurotransmitter release at the motor end plate
• Causes non-contractile state of skeletal muscle (flacid paralysis)
• Clinically used to treat muscle spasms (eg. cervical dystonia)
• Used cosmetically to treat wrinkles

Question 30

What is organophosphate poisoning?

Answer 30

• Organophosphates are used as pesticides

- Inhibits normal functioning of ACh esterases so ACh activity is potentiated at the neuromuscular junction

Question 31

What are the signs and symptoms of organophosphate poisoning?

Answer 31

Muscarinic Symptoms (SLUDGE)
 S = salivation
 L = Lacrimation
 U = urination
 D = defecation
 G = GI cramping
 E = Emesis

Nicotinic Symptoms (MTWTF)
 M = muscle cramps 
 T = tacchycardia
 W = weakness
 T = Twitching
 F = Fasciculations

Question 32

What is malignant hypothermia?

Answer 32

• Severe reaction to anaesthetics (succinylcholine)
• Autosomal recessive inheritance pattern- RyR1 gene
• Affects males more than females
• Causes massive contractile fasciculation
• -> muscle rigidity caused by increased calcium release leading to excessive heat and metabolic acidosis
• Leads to increased muscle breakdown and hyperkaleamia