Module 17 - Muscle 2

Question 1

how long is an AP compared to a muscle contraction

Answer 1

AP = 2ms
muscle contrac = 20-100ms, and start is slightly delayed after AP
(due to Ca2+)

Question 2

result of differing APs at diff rates

Answer 2

single AP = twitch
intermediate rate = summation, unfused tetanus
high rates = fused tetanus (max stimulation

Question 3

what is hennemans size principle

Answer 3

bigger the motor neuron cell body
the more muscle fibres it innervates (hence the larger contraction force)

Question 4

3 types of skeletal muscle

Answer 4

slow-twitch oxidative
fast-twitch glycolytic
fast-twitch oxidative

Question 5

what type of myosin ATPase do the 3 types of skeletal muscle have

Answer 5

slow oxd = low
fast oxd = high
fast glyc = high

Question 6

mitochond content in ech skeletal muscl etype

Answer 6

slow oxd = high
fast oxd = high
fast glyc = low

Question 7

general stuff with each skeletal muscle type

Answer 7

slow oxd = vry good blood supply, fatigue resistant, for sustained contrac, doesnt use much ATP, small

fast oxd = kinda intermediate, still resist fatigue, uses some glycogen, uses up lots of ATP,

fast glyc = fatigue prone, uses glycolytic metabolism so lactate accumulation+acidosis

Question 8

duchenne muscular dystrophy

Answer 8

x-linked disorder
mutation in dystrophin gene
causes skeletal muscle to not be linked properly
excess Ca can enter the cells = muscle fibres die = replaced with fat or conn tissue
(25-30yrs life expec)

Question 9

what causes myostatin deficiency

Answer 9

myostatin usually regulates
null mutation means it’s not produced
causing excess muscle, low body fat

Question 10

what is the structure of cardiac muscle cells

Answer 10

branched syncytium, incompletely fused cells which are joined by intercalated discs, gap junctions allow electric flow

Question 11

diff between normal APs and cardiac APs

Answer 11

much longer (200ms)
plateaus after AP fires
due to Ca2+ going in, channels inactivate slower

Question 12

how does cardiac excitation contraction coupling differ from skeletal

Answer 12

still uses L type Ca channel
but not phsyically linked to RyR
= CALCIUM INDUCED Ca RELEASE
but other than that, same thing
(also, the Ca from outside also contributes)

Question 13

what is pacemaker potential

Answer 13

slow depol prodcued by SA node
aka funny current

Question 14

what is the only neuronal input in cardaic contraction

Answer 14

symp and parasymp can affect HR
and also the conc Ca2+ = force of contrac

Question 15

what is frank starling law

Answer 15

more blood more stretch of cardiac muscle
= more forceful contraction

Question 16

what metabolism does cardaic muscle use

Answer 16

oxididative metab
cuz needs to beat continuously

Question 17

diff in smooth muscle composition compared to the others

Answer 17

no striations
no t tubules
no troponin
small spipndle shaped

Question 18

are smooth muscle cells coupled together or act independant

Answer 18

both lol
coupled w/gap junction = unitary (similar to cardiac)
or independent =multiunit

Question 19

2 functions of smooth muscle

Answer 19

propel contents of the organ it surrounds
regulate flow e.g. in blood vessels

Question 20

what is smooth muscle controlled by

Answer 20

autonomic nervous system

Question 21

how is smooth muscle diff in terms of contraction

Answer 21

slowly and for longer
more energy efficient
diff excitation contraction coupling mechanisms
can contract over large range of tensions

Question 22

what are the 3 sources for Ca2+ in smooth muscle

Answer 22

1. L type channel = ca induced ca release (same as cardiac
2. low ca in SR signals store operated ca channel
3. IP3 receptor (ligand gated ca channel in SR)
   controled by phospholipase C and GPCR
   (this mech means it can contract WITHOUT action potential)

Question 23

if no troponin in smooth muscle, what carries the Ca

Answer 23

calmodulin

Question 24

what does calmodulin-calcium complex activate

Answer 24

myosin light chain kinase
which phosphorylates the regulatory light chain
and switches on ATPase activity

Question 25

what example of smooth muscle is myogenic

Answer 25

in gut
pacemaker like acitivty

Question 26

what controls the cross bridges in the 3 types of muscle

Answer 26

skeletal and cardiac = troponin and tropomysoin
smooth = mysoin light chain kinase