skeletal muscle

Question 1

what are myofibrils made of

Answer 1

myofilaments made of actin and myosin

Question 2

what is a unit of muscle

Answer 2

myofibril

Question 3

what is a unit of a myofibril

Answer 3

sarcomere

Question 4

how to actin molecules make up an actin filament

Answer 4

all join to a nebulin rod

Question 5

what do myosin filaments sit between

Answer 5

Z discs and M line

Question 6

where is calcium stored

Answer 6

sarcoplasmic reticulum

Question 7

how does an action potential cause a release of Ca

Answer 7

acetyl choline binds to the receptors of the neuromuscular junction.
this causes an influx of Na which depolarises the cell (T tubules).
Voltage gated Ca2+ channels open

Question 8

explain the sliding filament model

Answer 8

Ca2+ binds to troponin, leading to a conformational change so tropomysosin moves to expose the actin binding site
myosin head binds to actin and forms a cross bridge
myosin head rotates, pulling actin past myosin
ATP is Hyrolysed from myosin as ADP + Pi causing the mysoin head to bend and do a power stroke
myosin returns to original position

Question 9

How is rigor mortis caused

Answer 9

no ATP, so ATP dependent pumps stop working so Ca2+ cause actin myosin cross bridges
and then the bridges cannot be broken

Question 10

describe hypocalcemia in dogs

Answer 10

involuntary contraction as low calcium levels will lead to a spontaneous action potential (due to high natural amount of ACH)

Question 11

describe hypocalcemia in ruminants

Answer 11

have naturally low ACH levels, so low calcium will prevent an action potential, so no muscle contraction

Question 12

how is creatine phosphate produced

Answer 12

ATP + Creatine
Catalysed by creatine Kinase