Muscles Flashcards

1
Q

What are the types of muscle and where are they found

A

Cardiac–in heart

Smooth - in walls of blood vessels and gut

Skeletal- attached to bone moving body

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2
Q

Describe the structure of a muscle

A
Whole muscle
Bundles of muscle fibres
Muscle fibre
Myofibril
Sarcomere
Actin and myosin
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3
Q

How are cells arranged in a muscle

A

Cells fused together in a long line

Myofibril run through the middle of the cells

Share cytoplasm (sarcoplasm) cell membrane (sarcollema) and endoplasmic reticulum (sarcoplasm reticulum) and nuclei

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4
Q

What is the advantage of the cell arangemnet in a muscle

A

Junctions would be a point of weakness so makes muscle stronger

Parralell Myofibril make them stronger

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5
Q

What is the function of the sarcoplasm reticulum

A

Store Ca2?+ for release for muscle contraction

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6
Q

What two proteins make up Myofibril

A

Actin and myosin

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7
Q

How is actin arranged

A

Actin molecules are soluble proteins arranged in a helix shape

Tropomysin follows shape of actin

Troponin attaches to Tropomysin

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8
Q

How is actin arranged

A

Actin molecules are soluble proteins arranged in a helix shape

Tropomysin follows shape of actin

Troponin attaches to Tropomysin

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9
Q

What is Tropomysin

A

Blocks actin mysoin binding sites

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10
Q

What is Troponin

A

Ca2+ binding site on Tropomysin

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11
Q

Describe the structure of myosin

A

Made of many parallel fibres of myosin made of insoluble tail and soluble head that stick out

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12
Q

Name the sections on a Sarcomere

A

Z line- middle of I band

I band - only actin

A band- actin and mysoin overlap

H zone- only myosin

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13
Q

What is a neuromuscular junction

A

Where a motor neurone meets a muscle fibre

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14
Q

Describe and explain the distribution of neuromuscular junctions across the muscle fibre

A

Regular intervals

Rapid and Simultaneous contraction

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15
Q

What is a motor unit

A

All muscle fibres supplied by one motor neurone acts a one unit

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16
Q

What is the advantage of having motor units

A

Allows control of force exerted (more units stimulted= more force)

17
Q

How is the sarcollema de polarised

A

Ap reaches the neuromuscular junction

Ca2+ voltage channels open allowing ca2+ to diffuse in.

Cause vesicles containing neurotransmitter to diffuse towards and fuse with postsynatic membrane, exocytosis

Acetylcholine diffuses across Synaptic left binding to Na+ receptors on sarcolemma.

Channels open Na+ Diffuse in = de polarisation

18
Q

Why is it important for acetyl choline to be broken down

A

To prevent over stimulation

19
Q

What are the similarities if a neuromuscular junction with a cholinergic synapse

A

Use acetyl choline through diffusion

Bind to na receptors causing them to open

Enzymes used to breakdown acetylcholine

Na/k pump used to repolarised

20
Q

What are the differences between neuromuscular junctions and cholinergic Synapses

A

Neuromuscular:
Only exhibitory not inhibitory
Only motor neurone not any other type
End of AP pathway

21
Q

What are the two types of muscle fibres

A

Slow and fast twitch

22
Q

Describe slow twitch fibres

A

Weak contractions over a long period of time

23
Q

How are slow twitch fibres adapted and for what

A

Adapted for endurance and aerobic Respiration

Low glycogen storage
Large myoglobin supply (oxygen store)
Good blood supply
Many mitochondria

24
Q

What are fast twitch fibres

A

Contract very rapid, powerfully for short amount of time

25
How and what are fast twitch fibres adapted for
Anaerobic Respiration, intense exercise Large glycogen storage (high rate resp because anaerobic = not efficient) Large phosphocreatin supply Thicker and more numerous myosin filaments Large conc of enzymes involved in anaerobic Respiration
26
By what mechanism do muscled contract
Sliding filament theory
27
What is the evidence for the sliding filament theory
A band stays same length (so filaments don't shorten) I band and H zone decrease causing overlap of filaments
28
How are muscles stimulated
Ap reaches neuromuscular junctions causing voltage gated Ca2+ channels to open so ions diffuse in Vesicles with acetylcholine diffuse and fuse with presynaptic membrane. Exocytosis Acetylcholine diffuses across the syntactic cleft Binds to Na+ channels on sarcolemma opening them. Ions diffuse in de polarising membrane.
29
How do muscles contract (starting from de polarisation of sarcollema)
Ap travels down t tubules to sarcoplasm reticulum Ca2+ channels open and ions are released from sarcoplasmic reticulum into cytoplasm. Ca2+ binds to Troponin causing Tropomyosin to change shape revealing binding sites for myosin on actin Actin myosin Cross Bridge forms ADP and pi released = power stroke= slide actin filament ATP attaches and is hydrolysed= myosin head detaches and is recocked to original position
30
What is the function of the sarcoplasmic reticulum in muscle contraction
Actively transports calcium ions fro cytoplasm for release via diffusion for muscle contraction.
31
What is the function of calcium ions in muscle contraction
Bind to Troponin changing shape of Tropomyosin allowing actin myosin Cross Bridges to form Activates ATP Hydrolyse for recock
32
How are muscles relaxed
No ap= calcium ion channels close and ions actively transported back in Less ions = Tropomyosin changes to original shape = blocks binding sites No actin myosin Cross Bridges so no sliding of filaments Antagonistic muscle pulls filaments apart
33
How are muscles relaxed
No ap= calcium ion channels close and ions actively transported back in Less ions = Tropomyosin changes to original shape = blocks binding sites No actin myosin Cross Bridges so no sliding of filaments Antagonistic muscle pulls filaments apart
34
What role does ATP play in muscle stimulation
Allows recock of myosin head Allows ca2+ to be actively Transported into to sarcoplasmic reticulum again for muscle relaxation Used to repolarise sarcollema