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Flashcards in Muscles 1 Deck (36)
1

What are the three types of muscle that exist in the body?

Skeletal and cardiac (striated)
Smooth (blood vessels, airways, uterus, GI tract)

2

How are skeletal muscle fibres formed?

Groups of cells make a large chain which fuses to form a multinucleated fibre.
Formed by mononucleate myoblasts before birth

3

What makes up a muscle?

Groups of fibres encased in a connective tissue sheath

4

What is the function of satellite cells?

They replace damaged cells after injury, they then differentiate to form new muscle fibres

5

What is the Z line?

The border between sarcomeres

6

What does do the prefixes myo and sarco mean?

Muscle and flesh respectively

7

What is a myofibril?

The muscle strand that makes up a muscle cell

8

What type of filament is studded with crossheads?

(Thick Myosin)

9

What are the names given to the accessory proteins that cover actin?

Troponin and tropomyosin

10

What does troponin do to tropomyosin?

Holds the tropomyosin in a blocking position on actin

11

What is the effect of calcium on troponin?

Pulls away tropomyosin revealing binding sits on actin for crossheads.

12

Where are calcium ions released from?

The sarcoplasmic reticulum, which is studded with calcium pumps and surrounds each sarcomere

13

What is the function of the transverse tubules?

Conducts electrical signals and allows them to travel deep into the muscle fibre, ensuring the entirety of the muscle fibre receives the command to contract.

14

What causes the cross head to adopt a high energy configuration?

When it hydrolyses an ATP molecule

15

What causes the cross head to flip?

When it attaches to the actin and releases its ADP + Pi

16

What is the state of rigor?

When the cross head is in its low energy conformation whilst it is attached to the actin

17

What causes cross bridge dissociation?

ATP binding to the cross head (relaxation)

18

What is a motor unit?

Muscle fibres + motor neurone

19

Why do several motor neurones enter a large muscle group instead of one branched neurone?

Prevents paralysis of the large muscle group if the branched motor neurone becomes damaged. Allows small contraction, instead of every muscle fibre being innervated by the single branched neurone

20

What is tension?

The force exerted by a muscle

21

What is the load?

The force exerted on a muscle

22

What does an increase in the overlap of filaments in the sacromere result in?

Increased tension

23

What is the result of too much overlap?

The filaments interfere with one another

24

What does the A band measure?

The length of the myosin filament (remains unchanged during contraction)

25

What does the H band measure?

The distance between the actin filaments (reduced on contraction)

26

What does the I band measure?

The distance between the two myosin filaments

27

What is referred to as contraction with constant length?

Isometric

28

What is referred to as contraction with shortening length?

Isotonic

29

What is referred to as contraction with increasing length?

Lenghtening

30

What is a twitch?

The contraction of a single muscle fibre

31

What is the latent period?

The time before excitation contraction starts

32

What does contraction time depend on?

Calcium ion concentration

33

What happens to contraction velocity and the distance shortened by a muscle as the load increases?

Contraction velocity decreases and the distance shortened decreases

34

What is fused tetanus?

Constant stimulation by action potentials, no relaxation in the muscle

35

Why is tetanic tension greater than twitch tension?

Calcium concentration never gets the chance to decrease and allow troponin/tropomyosin to re-block myosin binding sites

36

What is the optimal length of a muscle?

Muscle length for greatest isometric tension.