skeletal muscle contraction and neuromuscular junction

Question 1

what are striated muscles

Answer 1

muscles that convert chemical energy to physical work.

Question 2

what are the 6 components of muscle

Answer 2

epimysium
perimysium
blood vessel
muscle fibre
fasicle
endomysium

Question 3

what is the epimysium

Answer 3

dense connective tissue that surrounds the entire muscle and defines its volume

Question 4

whats the perimysium

Answer 4

connective tissue surrounding muscle bundles/fasicles and provides structure support to muscle

Question 5

whats the endomysium

Answer 5

separates single muscle fibres from one another

loose connective tissue that covers each muscle fibre

Question 6

what causes the skeletal muscle to contract

Answer 6

signal is sent via axon branch of somatic motor neurone causing it to contract (nervous system)

Question 7

what are slow twitch muscle fibres

Answer 7

fatigue resistant, and focused on sustained, smaller movements and postural control.

used for endurance

Question 8

what are the features of slow twitch fibres

Answer 8

• lots of mitochondria for ATP producetion
• lots of myoglobin
• extensive bloody supply (using oxygen to make energy aerobically)

Question 9

what are slow twitch muscle fibres adapted for

Answer 9

to provide for oxidative phosphorylation

Question 10

what are fast twitch muscle fibres

Answer 10

built for short, powerful bursts of energy

used for sprinting and weight lifting etc

Question 11

what are the features of fast twitch fibres

Answer 11

• contract quickly but fatigue fast
• high glycogen stores
• high anaerobic energy production (makes lactic acid)

Question 12

what are fast twitch fibres adapted for

Answer 12

immediate and non-oxidative phosphorylation

Question 13

what is a sarcolemma

Answer 13

cell membrane surrounding of myofibrils/ skeletal muscle fiber or a cardiomyocyte

Question 14

define neuromuscular junction

Answer 14

where a motor neurone and muscle fibre meet

Question 15

define motor unit

Answer 15

nerve fibre and muscle fibres it innervates

Question 16

what are t-tubules

Answer 16

deep invaginations within the sarcolemma with highly active ionic flow and cell depolarisation

Question 17

what is the triad

Answer 17

t-tuble bordered on either side by sarcoplasmic reticula

Question 18

what is the purpose of myoglobin in muscle cells

Answer 18

work as a store of oxygen for ATP productionpurp

Question 19

purpose of creatine in muscle cells

Answer 19

works as store of ATP

Question 20

what element does the sarcoplasmic reticulum have useful for muscle contractions

Answer 20

calcium that gets released

Question 21

explain the process of neuromuscular junction / how signal is sent to cause muscle contraction

Answer 21

• action potential at the nerve terminal causes influx of calcium which stimulates the release of acetyl choline
• Ach diffuses across synaptic cleft and binds with the acetylcholine receptors on the muscle membrane
• this binding stimulates an influx of positive sodium ions which causes the depolarisation of the sarcolemma (less negative in cell than outside)
• the difference in electric potential between inside and outside of cell caused by sodium influx generates a voltage
• this voltage opens gated calcium channels known as dihydropyridine
• activation of dihydropyridine is linked to activation of ryanodine receptors in the sarcoplasmic reticulum that are responsible for the release of calcium
• the increase in intercellular calcium causes filaments to slide and muscles to contract
• acetyl choline is removed when broken down by acetyl choline esterase and after muscle contraction calcium is actively pumped back into sarcoplasmic reticulum

Question 22

define sacromere

Answer 22

smallest functional unit of muscle contraction

Question 23

explain the filament sliding theory

Answer 23

calcium binds to troponin located on actin filament

causes it to change shape and move tropomyosin from the actin active site

the myosin filaments can now attach to the actin active site forming a crossbridge

the break down of ATP creates energy, enabling myosin to pull the actin filament inwards contracting the muscle

this occurs along the length of every myofibril in the muscle cell

when ATP binds to myosin head, it detaches from actin and cross bridge is broken

(when ATP breaks down again, the process can repeat along the actin filament)

Question 24

how do muscles that have big or fine movements differ

Answer 24

muscles that require fine movements have low number of muscle fibres innervated by each motor fibre

Question 25

what is concentric, isometric and eccertric

Answer 25

concentric= muscle shortens
isometric= muscle doesnt shorten nor does joint move
eccentric= muscle lengthens

Question 26

what are ways to weaken strength of muscle contraction

Answer 26

• inhibit ach release
• increase each breakdown
• damage nerve
• block each receptors
• block sodium influx
• inhibit protein synthesis
• deprive muscle of oxygen