Muscle Contractions Flashcards

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1
Q

What is the sacolemma

A

Membrane

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2
Q

What is the myofibril

A

Block of protein, some thick some thin

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3
Q

What is the sarcomere

A

Single unit of muscle

The distance between adjacent Z-lines

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4
Q

What is the sarcoplasmic reticulum

A

Sack filled with calcium

Form of adaptation of the muscles

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5
Q

What 2 proteins are involved

A

Actin (thick)

Myosin (thin)

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6
Q

Why do myofibrils appear striped

A

Altering light coloured and dark coloured bands

A band = dark
(I band = light)

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7
Q

Why do A bands appear darker

A

Actin and myosin filaments overlap in this region

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8
Q

What is the H zone

A

Part of A band which is exclusively myosin

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9
Q

Why is the Z-line

A

Centre of each I band

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10
Q

What happens when the muscle contracts

A

Sacromeres shorten so pattern of dark and light bands change

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11
Q

What proteins are in actin’s structure

A

Actin
Tropomyosin
Troponin

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12
Q

What is a neuromuscular junction

A

Where motor neurone meets skeletal muscle fibre

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13
Q

Why are there many neuromuscular junctions spread through the muscle

A

Means can be quick muscle contractions as they simultaneously, making it powerful

This is essential for survival

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14
Q

What is the role of tropomyosin

A

Covers up myosin binding sites then shifts out of place to expose them and allow myosin to bind

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15
Q

Describe the cycle of muscle contraction

A
Calcium arrives, bonds to Troponin
Causes Tropomyosin to pull away
Myosin binding sites exposed
Myosin binds to actin
Myosin head pivots, causes actin to move
ATP attaches, causing head to detach 
ATP hydrolysis provides energy for head to reposition
Cycle continues as long as calcium present
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16
Q

What happens when nerve meets neuromuscular junction

A

Synaptic vesicles fuse with membrane and release acetylcholine
This diffuses into membrane changing permeability
Causes sodium ions to enter
Sodium ions depolarise membrane
Enzyme breaks acetylcholine which diffuses back

17
Q

What happens after sodium ions enter muscle membrane

A

Action potential travels down T-tubules
Tubules contract with sarcoplasmic reticulum
Causes calcium ion channels to open
(Then muscle contraction cycle occurs)

18
Q

What happens when muscle relaxes

A

Nervous stimulation stops
Calcium ions actively transported back to sarcoplasmic reticulum
Using energy from ATP hydrolysis
Tropomyosin blocks actin filament
Myosin heads no longer able to bind to actin filament
Contraction stops

19
Q

What is the role of calcium

A

Stimulates ATPase in myosin heads

Binds calcium sites

20
Q

How is ATP required in muscle contractions

A

Detaches myosin head

Transport calcium back into sarcoplasmic reticulum

21
Q

Why do dead bodies muscles stay contracted

A

When dead no ATP

So myosin head can’t detach

22
Q

What are the 2 types of muscle fibre

A

Slow-twitch

Fast-twitch

23
Q

What are slow-twitch fibre

A

Contract slowly as less powerful contraction over long period of time
(Adapted for endurance work)

Also adapted for aerobic respiration to avoid build up of lactic acid (this would affect their efficiency)

24
Q

What are the 4 main characteristics of muscle tissue

A

Excitable
Contractile
Elastic
Extensible

25
Q

What are fast-twitch muscle fibres

A

Contract rapidly
Produce powerful contractions over a short period of time

Adapted for intense exercise

26
Q

What are the adaptations of slow-twitch fibres

A

Large store of myoglobin (stores oxygen)
Supply of glycogen (source of metabolic energy)
Many bloody vessels (to deliver oxygen and glucose)
Many mitochondria (produce ATP)

27
Q

What are the adaptations of fast-twitch fibres

A

Many thick myosin filaments
Many enzymes involved in anaerobic respiration
Store of phophocreatine (supply energy for muscle contraction as can rapidly generate ATP from ADP in anaerobic respiration)