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Animal responses > Muscle contraction > Flashcards

Muscle contraction Flashcards

1
Q

what is the membrane of muscle fibres called?

A

Sarcolemma

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2
Q

what is the muscles cell’s cytoplasm called?

A

Sarcoplasm

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3
Q

What are the folds of sarcolemma called?

and what do they do?

A

Transverse tubules (T)

  • They help to spread electrical impulses throughout the sarcoplasm so they reach the muscle fibre
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4
Q

What is the sarcoplasmic reticulum?

and what does it do?

A

INTERNAL membranes of the sarcoplasm

  • They store and release the calcium ions that are needed for muscle contraction.
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5
Q

What does multinucleate mean?

A
  • Muscle fibres contain MANY nuclei
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6
Q

What are myofibrils?

A
  • Muscle fibres have these long cylindrical shaped organs called “myofibril” which are made up of proteins and are HIGHLY specialised for contraction.
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7
Q

What are the 2 types of filaments myofibrils consist of?

A

1) Thick myofilaments

2) Thin myofilaments

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8
Q

What are thick myofilaments made up of?

A

Myosin

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9
Q

What are thin myofilaments made up of?

A

Actin

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10
Q

what are the short units that make up myofibrils?

A

Sacromeres

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11
Q

Under a microscope what are the dark and light bands?

A

Dark bands are the - A bands- contain thick myosin filaments

Light Bands are the - I bands- contain thin actin filaments

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12
Q

What are the z lines?

A

The ends of the sarcomere

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13
Q

What is the M line?

A

Its in the middle of the sarcomere

The M- line is the middle of the myosin filaments

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14
Q

Where is the H zone and what does it contain

A
  • H zone is roughly in the middle

- The H zone ONLY consists of myosin filaments.`

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15
Q

When sarcomeres contract what gets shorter?

A

I band and h zone gets shorter
and the sarcomere size gets shorter

But A band stays the same length.

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16
Q

How do sarcomeres contract?

A

myosin filaments and actin filaments slide over one another.

sliding- filament theory

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17
Q

What does the myosin globular head do ?

A

Acts as a binding site for actin and ATP

  • The myosin globular head is hinged so it can move back and forth
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18
Q

what is the binding site for the myosin heads, on the actin filaments called?

A

Actin-myosin binding site

This is where the myosin globular head binds.

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19
Q

What do tropomyosin and troponin do and where are they found?

A

They help myofilaments move past each other

- these are found in between actin filaments.

20
Q

How does tropomyosin affect the actin-myosin binding site?

A
  • actin-myosin binding site is blocked by tropomyosin
    which is held up by troponin.
  • This means that myofilaments can not slide past each other.
21
Q

Muscle contraction triggered by an action potential process : ( 3 steps) just label the steps

A

1) Action potential triggers an INFLUX in Calcium ions
2) ATP provides the energy needed to move the myosin head
3) ATP provides energy to break the cross bridge

22
Q

1) The action potential triggers and influx in calcium ions:

A

1) action potential from a motor neurone stimulates a muscle cell, causing the sarcolemma to depolarise
- depolarisation spreads down transverse tubules to the sarcoplasmic reticulum

2) This causes sarcoplasmic reticulum to release the stored Calcium ions (Ca2+) into the sarcoplasm.
3) Calcium ions bind to troponin causing it to change shape, and this pulls tropomyosin out of the actin- myosin binding site, the binding site is now exposed and myosin globular head can bind to it.
4) Actin- myosin cross bridge is formed

23
Q

What is the bond called where a myosin head binds to an actin filament

A

Actin- myosin cross bridge

24
Q

2) ATP provides energy so that the myosin head can move:

A

1) Calcium ions also activate ATPase ( enzyme) which breaks down ATP -> ADP + pi
- to provide the energy needed for muscle contraction.

  • Energy released from ATP, allows the myosin head to move and it pulls the actin filament along in a “rowing kind of action”.
25
Q

3) ATP provides energy to break the cross bridge:

A

1) ATP provides energy to break the actin-myosin cross bridge, so the myosin head DETACHES from the actin filament.
2) The myosin head then binds to a different binding site on the actin filament, and a new actin- myosin cross bridge is formed.
- cycle repeats as long as there is calcium bound to the troponin.

26
Q

What happens if many cross bridges form?

A

If many cross bridges are forming and breaking rapidly,

this means that the sarcomere is getting shorter, causing the muscle to contract.

27
Q

what happens to calcium ions after muscles have stopped being stimulated? ( WHEN EXICITATION STOPS)

A
  • Calcium ions leave the troponin
  • calcium ions move back into sarcoplasmic reticulum by active transport
  • troponin returns to original shape and pulling the tropomyosin with it, causing tropomyosin to block the binding site again.
  • actin slides back to its relaxed position so the sarcomere becomes longer in length.
28
Q

What are the 3 ways in which ATP is continuously being regenerated?

A

1) Aerobic respiration- good for long period of low intensity exercise
2) Anaerobic respiration- ATP made rapidly by glycolysis.- good for short period of high intensity exercise
3) ATP- Creatine Phosphate (CP) system

29
Q

What is the ATP creatine phosphate system?

A

This system uses the phosphate from CP and gives it to ADP to form ATP.

  • This system is used during short periods of hard exercise as CP runs out very quickly

This system is anaerobic and alactic ( doesn’t produce lactate)

30
Q

What is the synapse between a motor neurone and a muscle cell called?

A

A neuromuscular junction

31
Q

What are the neuro transmitters at the neuromuscular junction?

A

Acetylcholine (ACh)

32
Q

What receptors does acetylcholine bind to ?

A

Nicotinic cholinergic receptors

33
Q

Does depolarisation cell cause contraction or relaxation?

A

CONTRACTION of muscle cells

IF the threshold is reached

34
Q

what does acetylcholinesterase do ?

A

AChE

Is released to break down acetylcholine after use

35
Q

where is AChE stored

A

Stored in the clefts of the postsynaptic membrane.

36
Q

What are the 3 types of muscle cells?

A

1) Skeletal muscle- voluntary muscles- consciously contract
2) Smooth muscle- involuntary muscles- unconsciously contract

3) Cardiac muscle- myogenic - contract on its own
- but rate of contraction controlled involuntarily by autonomic nervous system

37
Q

When skeletal muscles contract is it controlled consciously or unconsciously?

A

consciously

38
Q

DO skeletal muscles contain one nuclei or many nuclei

A

MANY nuclei

39
Q

When you look under a microscope and your observing skeletal muscle, what do you see?

A

cross- striations

These are the A bands and I bands

40
Q

Do skeletal muscles contract quickly or slowly?

A

They contract quickly for speed and strength but fatigue quickly

  • skeletal muscle fibres are many cm long
41
Q

DO smooth muscles contract consciously or unconsciously?

A

unconsciously

42
Q

What happens when blood vessel smooth muscle contracts

A

Flow of blood is reduced

43
Q

What are the shape of muscle fibres for smooth muscle cells?

A

Spindle- shaped

44
Q

Do smooth muscles and cardiac muscle only have one nuclei or many?

A

ONLY 1 nucleus in each muscle fibre

Each muscle fibre is 0.2mm long

45
Q

Does smooth muscle contract quickly or slowly

A

Contracts slowly and doesn’t fatigue

slow contractions are meant for endurance and posture

Animal responses (3 decks)

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