Muscle Tissue

Question 1

What’s the muscle cell hierarchy?

Answer 1

2 muscle cell types: striated and non striated

Striated: skeletal (myoglobin, voluntary direct never muscle communication) and cardiac (myoglobin, involunary, indirect nerve muscle communication)

Non striated: smooth muscle (no myoglobin, involuntary, no direct nerve-muscle communication

Question 2

Skeletal muscle structure

Answer 2

• point of origin and insertion (causes movement if across a joint)
• fibres present (striated muscle cells). Can be slow oxidative, fast oxidative glycolytic or fast glycolytic
• myofibrils in each fibre (actin and myosin)
• muscles with similar actions grouped into compartments surrounded by fascia

Question 3

Compare and contrast slow oxidative, fast oxidative glycolytic and fast glycolytic muscle fibres (7)

Answer 3

Slow oxidative; aerobic, lots of myoglobin, red, many mitochondria, many cytochromes, fatty acids and lots of ATP/CO2

Fast oxidative glycolytic; aerobic, lots of myoglobin, red/pink, many to intermediate mitochondria, many cytochromes, fatty acids and glycogen, initially lots of CO2 then lots of lactate

Fast glycolytic; anaerobic, little myoglobin, pale, few mitochondria, few cytpchromes, glycogen ,lots of lactate/little ATP

Question 4

What are the four compartments of the lower leg?

Answer 4

• anterior compartment
• lateral compartment
• superficial posterior compartment
• deep posterior compartment

Question 5

!!What’s compartment syndrome

Answer 5

• trauma in one compartment may cause internal bleeding, placing pressure onto blood vessels and nerves
• aggravated by passive stretch of muscle group leading to deep, poorly localised pain
• paresthesia (pins n needles)
• shiny, swollen skin with bruising
• compartment feels tense and firm
• prolonged capillary refill time
• a fasciotomy is used to cut skin and relive pressure

Question 6

!! What’s myasthenia gravis?

Answer 6

• autoimmune disease
• antibodies directed against Ach receptor (neuromuscular junction)
• symptoms appear if more than 30% of receptors blocked
• leads to muscle weakness

-ptosis
(Drooping of eyelid)

Question 7

Cardiac muscle structure

Answer 7

• caardiomyocytes
• centrally positioned nuclei
• intercalated disks (electrical and mechanical coupling with adjacent cells)
• BRANCHING.

Question 8

Structure of purkyne fibres

Answer 8

• abundant glycogen
• sparse myofibrils
• extensive gap junction sites (rapid transmission)

Question 9

Smooth muscle function

Answer 9

Slower, more sustained contraction and less ATP needed

May remain contracted hours or days

Responds to nerves, hormones, drugs or local concentrations of blood gasses.

Question 10

Structure of smooth muscle

Answer 10

• spindle shaped (fusiform)
• single central large nucleus
• forms sheets, bundles or layers
• many caveolae (small, cave-like invaginations)

Question 11

!!what’s muscle hypertrophy

Answer 11

Over stretching.

• new fibrils made to replace old
• new sarcomeres added in middle of existing ones
• new fibres made from mesenchymal cells
• may be present in some cardiac pathologies (eg enlarged ventricles)

Question 12

!!Whats muscle atrophy

Answer 12

• loss of protein, reduced fibre diameter, loss of muscle power
• may occur due to disuse, surgery and disease
• commonly occurs in those 30+, 50% muscle loss by 80, temp regulation

Question 13

!!What’s duchess Muscular dystrophy?

Answer 13

• most common muscular dystrophy
• inheritance via X-linked recessive pattern, mutation of dystrophin gene
• w/o dystrophin, excess calcium enters mitochondria in muscle with water causing them to burst. Muscle cells burst (rhabdomyolyis). Causes creatine kinase and myoglobin levels to inc in blood
• muscle cells replaced by adipose tissue

Question 14

!! Whats the botulism toxin and Botox??

Answer 14

• botulism toxin produced by clostridium botulinum
• prevents release of neurotransmitter
• stops skeletal muscle contracting (flaccid paralysis)
• clinically used to treat muscle pasms (eg cervical dystonia)
• cosmetically used to treat wrinkles

Question 15

!! Whats organophosphate poisoning

Answer 15

• used as pesticides
• Ach esterase inhibited, Ach activity at neuromuscular junction reduced
• effects somatic and automatic signalling

Question 16

(Toxidrome - lots of a toxin in the body)

What are the muscarinic symptoms and nicotinic symptoms of cholinergic toxidrome??

Answer 16

Muscarinic symptoms:
S-salivation
L-lacrimation
U-urination
D-defecation
G-GI cramping
E-emesis (vomiting)

Nicotinic Symptoms:
M- muscle cramps
T-tachycardia
W-weakness
T-twitching 
F-fasciculations