3.6 Skeletal muscles are stimulated to contract by nerves Flashcards

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1
Q

What is an antagonistic pair ?

A

One muscle contacts and the other relaxes

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2
Q

What is an antagonist ?

A

The muscle that is relaxing

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3
Q

What is an agonist ?

A

The muscle that is contracting

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4
Q

Name the 5 main structures of a muscle

A
  • Sarcolemma
  • Sacrcoplasmic reticulum
  • Mitochondria and nuclei
  • Myofibrils
  • Tubules
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5
Q

What is the structure/ function of the sarcolemma ?

A

It is the membrane of muscle fibres and folds inwards to the sarcoplasm (Membrane). These inward folds are called tubules and are important at initiating muscle contraction

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6
Q

What is the sarcoplasmic reticulum a store for and why is this important ?

A

Ca2+ ions that are important for contraction

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7
Q

Why do muscle fibres have lots of mitochondria ?

A

In order to provide lots of ATP for muscle contraction

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8
Q

What are myofibrils and why are they important ?

A

They are cylindrical organelles that run along the length of muscle fibres and are the site of muscle contraction

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9
Q

What is the A band ?

A

The total width of myosin (thick band)

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10
Q

What is the H zone ?

A

Just the parts where it is myosin only (In the centre). It overlaps the A band

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11
Q

What is the I band ?

A

Labels just where the actin is by itself. There is no overlap with myosin

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12
Q

What is the M line ?

A

The middle point of myosin

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13
Q

What do the Z lines indicate ?

A

The parameters of one sarcomere

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14
Q

On a micrograph does actin or myosin show up darker ?

A

Myosin will show up darker as it is a much thicker protein, Actin will show up a lot paler

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15
Q

What happens to the I band when the muscle contracts ?

A

It decreases in width

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16
Q

What happens to the H zone when a muscle contracts ?

A

It decreases in width

17
Q

What happens to the A band when a muscle contracts ?

A

It stays constant as the myosin does not move, only actin

18
Q

What is the sliding filament model ?

A

Explains how muscle contraction is coordinated in myofibrils

19
Q

How is muscle contraction initiated ?

A

When an action potential reaches the muscle cells which depolarises the sarcolemma

20
Q

What does depolarisation of the sarcolemma cause ?

A

Causes the myosin and actin filaments to slide over each other. This sliding movement causes the sarcomeres to contract

21
Q

What is the job or globular heads and where are they located ?

A

Globular heads are found on myosin filaments and they allow actin and myosin filaments to slide over each other in muscle contraction

22
Q

How many binding sites are there on a myosin head and what can they bind to ?

A

There are 2 binding sites that can bind to :
- ATP
- Actin

23
Q

What is tropomyosin ?

A

A protein located on actin filaments that blocks the actin-myosin binding site when muscles are at rest

24
Q

What are 3 ways ATP can be produced for muscles ?

A
  • Aerobic respiration
  • Anerobic respiration
  • Phosphocreatine
25
Q

How does phosphocreatine produce ATP ?

A

It donates a pi group to ADP to produce ATP, this leaves creatine

26
Q

What is the name for the bond between actin and myosin when the myosin head binds to the actin filament?

A

Actin-Myosin cross bridge

27
Q

Outline the steps followed by calcium ions in muscle contraction

A

1- Depolarisation of the sarcolemma
2- Influx of calcium ions by the SR
3- Movement of tropomyosin from the action-myosin binding sites
4- Formation of actin-myosin cross bridges

28
Q

How are calcium ions transported into the SR ?

A

By active transport

29
Q

Where are slow twitch fibres found ?

A

Found in muscles used for posture such as the back and neck

30
Q

Where are fast twitch fibres found ?

A

Found mainly in muscles such as the arms or legs

31
Q

What is the structure and function of slow twitch fibres ?

A

Function:
- Adapted for endurance and slow movement over long periods of time
Structure:
- Fibres are long and thin
- The muscles fatigue slowly and contract slowly

32
Q

What is the structure and function of fast twitch fibres ?

A

Function:
- Adapted for fast or strong movement over short periods of time
Structure:
- Fibres are short and wide
- The muscles fatigue quickly and contract quickly