Skeletal muscles

Question 1

what allows movement to occur ?

Answer 1

the skeletal muscles that are controlled by motor nerves

Question 2

voluntary or involuntary and what are they controlled by ?

Answer 2

voluntary and somatic nervous system

Question 3

why does a muscle action potential occur ?

Answer 3

due to a rise in Ca2+ ions and a contraction occurs

Question 4

what is the length of each cell ?`

Answer 4

runs the length of the muscle so can be over 30cm long

Question 5

do the cells have one nuclei or more ?

Answer 5

multiple

Question 6

the muscle fibres are striated , what does this mean ?

Answer 6

they are striped due to the arrangement of contractile filaments myosin ( thick) and actin ( thin).

Question 7

is smooth muscle striated ?

Answer 7

nope

Question 8

the muscle fibres contain troppomysoin and troponin , what do these do ?

Answer 8

play important roles in regulating contraction.

Question 9

what does the term contraction mean ?

Answer 9

to the turning on of the force-generating sites— the cross bridges—in a muscle fibre.

Question 10

what neurotransmitter does the synaptic vesicle contain ?

Answer 10

acetylcholine

Question 11

how is it released ?

Answer 11

by diffusion

Question 12

where are the acetylcholine receptors ?

Answer 12

the sarcolemma

Question 13

are there inhibitary nerves at the neuromuscular junction ?

Answer 13

no , only excitatory ones.

Question 14

the acetylcholine released by nerves binds to what

Answer 14

nicotinic ACh-receptors

Question 15

what does this lead to ?

Answer 15

a Na+ influx and end-plate potential. The action potential propagates across plasma membrane and the action potential propagates into T-tubules

Question 16

then what?

Answer 16

The voltage-sensor activates Ryanodine Receptor on Sarcoplasmic Retiulum and Ca2+ released into cytosol

Question 17

then what ?

Answer 17

When calcium is released this binds to the troponin and this removes the blocking action of tropomyosin on the actin filament where myosin want to bind to.

Question 18

what does tropomysoin do ?

Answer 18

blocking action

Question 19

what does the ATP hydrolysis do ?

Answer 19

1. energises myosin and the cycle of ATP binding, hydrolysis, ADP/Pi release drives ratchets myosin towards Z-line.
2. Restoration of plasma-membrane ion gradients (Na+/K+-ATPase)
3. Removal of Ca2+ from cytosol back into sarcoplasmic reticulum (Ca2+-ATPase) ATP is required.

Question 20

whats the actin and mysoin cycle ?

Answer 20

The binding of calcium to troponin causes the tropomyosin to be removed and this exposes the myosin binding site on the actin. The mysoin then requires a molecule of ATP which is broken down to ADP and phosphate. This moves the myosin into an extended stretched position . The Phosphate is then lost and this allows the myosin to bind and slide past the actin , after this the ADP is lost.

Question 21

how much can ATP consumption be increased during muscle contraction ?

Answer 21

x100

Question 22

how can ATP be resupplied ?

Answer 22

1. phosphorylation of ADP by creatine phosphate
2. mitochondrial oxidative phosphorylation , requires oxygen (aerobic)
3. glycolysis: anaerobic metabolism of glucose supplied by
4. blood
5. catabolism of muscle glycogen

Question 23

why are some muscle fibres red ?

Answer 23

contain lots of mitochondria , and have lots of oxygen binding myoglobin proteins. There are many small blood vessels and they are red due to the oxidative fibres.

Question 24

why are some muscle fibres white ?

Answer 24

have few mitochondria and lots of glycolytic enzymes to increase ATP and stores of glycogen. They are white with glycolytic fibres ( chicken breast

Question 25

fast twitch muscle fibres ?

Answer 25

fibres contain very fast acting myosin ATPase and these are called fast twitch fibres

Question 26

slow twitch muscle fibres ?

Answer 26

contain slower acting myosin ATPase and are called slow twitch fibres.

Question 27

describe type I slow oxidative fibres ?

Answer 27

oxidative as their primary ATP source and they have many mitochondria for ATP. They receive their blood supply from high levels of myoglobin and capillaries. They have low levels of glycogen and glycolytic enzymes. They have slower myosin ATPase and contraction of speed. They muscle rate of fatigue is slow.

Question 28

type II fast glycolotyic fibres ?

Answer 28

have glycolytic as their primary source of ATP and they have few levels of mitochondira. They receive blood supply from low levels of myoglobin and few capillaries. They have high levels of glycogen and glycolytic enzymes. They have faster myosin ATPase and a fast contraction speed. The muscle rate of fatigue is fast.

Question 29

type IIa fast oxidative glycolotyic fibres ?

Answer 29

) fibres have oxidative as their primary source of ATP and they have many mitochondria. They also have high levels of myoglobin and many capillaries. They have intermediate levels of glycogen and glycolytic enzymes. The myosin ATPase faster and the contraction speed is intermediate. The rate of fatigue is intermediate

Question 30

is a whole skeletal muscle made up of many motor units or just one ?

Answer 30

many , never just one

Question 31

what is whole muscle tension a sum of ?

Answer 31

the recruitement of motor units

Question 32

recruitment speed of motor units in type I (slow)

Answer 32

fast

Question 33

recruitment speed of motor unit Type II ( fast)

Answer 33

slow

Question 34

motor neuron size in type I ?

Answer 34

small

Question 35

motor neuron size in type II ?

Answer 35

large

Question 36

what does the calcium rise allow ?

Answer 36

myosin-actin cross-bridge cycling to contract muscle