BL. Muscles. session 7

Question 1

Which structural feature of muscle tissue is unique to smooth muscle cells?

Answer 1

during contraction, the actin (thin) and myosin (thick) filaments assemble on dense bodies.

Question 2

which line does not shorten when sarcomere contracts

Answer 2

A line

Question 3

which muscle type doesn’t contain t- tubules?

Answer 3

SMOOTH muscle

Question 4

where are the myosin binding sites?

Answer 4

on G actin

Question 5

which muscles contain gap junctions? role?

Answer 5

Smooth and cardiac

provide initial Ca2+ ion ‘spark’.
allowing efflux of more Ca2+ ions from the sarco/endoplasmic reticulum in smooth muscle cells

provide pathway for conduction around cardiomyocytes

Question 6

Which protein does not move during the cross-bridge formation process?

Answer 6

actin
(only moves AFTER cross link formation)

activated head of myosin moves towards myosin binding site on actin and attach itself

Question 7

How is skeletal muscle generated during fetal development?

Answer 7

from myotubes during fetal development and arise from myoblast stem cells.

Question 8

what is the skeletal repair mechanism for muscle rips?

Answer 8

Differentiation of muscle satellite cells into myofibrils and myofibres to replace damaged muscle (hyperplasia follows muscle injury)

Question 9

when is troponin I and C released following a MI?

Answer 9

released over the next 7 days

Question 10

when is creatine kinase released following a MI?

Answer 10

occur over a much shorter period than troponin C and I.

-2-3 days compared to 7.

Question 11

mutation of which protein causes Duchenne muscular dystrophy?
which type of inheritance?

Answer 11

Dystrophin
X linked recessive

protein does not insert into sarcolemma like it should.

Question 12

which structure of the NMJ is missing in patients with myasthenia gravis?

Answer 12

• endplate invaginations missing

- less mitochondria

Question 13

when are slow twitch fibres used?

Answer 13

long distance running

Question 14

compare slow vs fast twitch fibres

Answer 14

Slow

• smaller diameter
• darker colour due to myoglobin
• fatigue resistant

Fast

• larger diameter
• paler colour
• easily fatigued

Question 15

what are the two types of fast twitch fibres. compare them.

Answer 15

Type 2A

• fast oxidative glycolytic
• rich blood supply;y
• aerobic
• high myoglobin
• many mitochondria (less than T1) *
• many cytochromes *
• assist T1 and T2B activities

Type 2B

• fast glycolytic
• poor blood supply
• anaerobic
• low myoglobin
• few mitochondria *
• few cytochromes *
• strength/ jumping/ sprinting

Question 16

which muscle doesn’t contain myoglobin?

Answer 16

smooth

Question 17

contrast the different molecules produced by slow vs fast twitch fibres

Answer 17

type 1- lots of ATP/ CO2
type 2A- lots of CO2 then lots of lactate
type 2B- lots of lactate/ little ATP

Question 18

how does cardiac muscle repair?

Answer 18

can’t - incapable of regeneration

fibroblasts lay down scar tissue instead

Question 19

how does smooth muscle repair

Answer 19

retain mitotic activity and can form new smooth muscle cells

Question 20

describe conduction pathway of heart

Answer 20

SA node
spreads across atria
AV node
spreads down septum via Bundle of His
Right and Left bundle branches
arrives at apex
Purkinje fibres