Muscles

Question 1

What are the alternative names for each type of muscle?

Answer 1

smooth - unstriped/involuntary
skeletal - striped/voluntary
cardiac - heart

Question 1

What are the three types of muscle?

Answer 1

smooth, cardiac, skeletal

Question 2

Describe the contractions of each type of muscle

Answer 2

smooth - slow
skeletal - rapid
cardiac - rapid/myogenic

Question 3

Describe the speed of the fatigue of the muscle types

Answer 3

smooth - slow
skeletal - rapid
cardiac - never/very slow

Question 4

Describe the distribution of the different types of muscle

Answer 4

smooth - tubular organs
skeletal - attached to skeleton/bones
cardiac - heart

Question 5

What is antagonistic muscle action?

Answer 5

muscle pairs that act in opposite directions, one contracts and the other relaxes

Question 6

Give an example of antagonistic muscles?

Answer 6

bicep and tricep

Question 7

How is skeletal muscle controlled?

Answer 7

-by the voluntary nervous system
-each muscle is controlled by a motor neurone

Question 8

How do motor neurones interact with muscles?

Answer 8

at a neuromuscular junction (specialised synapse between a motor neurone and muscle fibre)

Question 9

Explain the process at a neuromuscular junction

Answer 9

-an action potential arrives at the neuromuscular junction causing Ca2+ channels to open
-Ca+ diffuses into neurone
-this causes vesicles containing acetylcholine to fuse with the pre-synaptic membrane
-acetylcholine diffuses across the synaptic cleft and binds to sarcolemma receptor proteins on the post-synaptic membrane
-this causes Na+ to diffuse into the sarcolemma
-post-synaptic membrane depolarises and sends the an action potential along the sarcolemma and down T-tubules
-T-tubules channel the action potential towards the sarcoplasmic reticulum which releases Ca2+ ions into the cytoplasm
-increase in Ca2+ ions causes the muscle cell to contract

Question 10

Compare the neurotransmitter, post synaptic membrane, type of movement, effect, number of receptors, type of response of cholinergic synapse and NMJ

Answer 10

neurotransmitter - CS is acetylcholine, NMJ is acetylcholine
post synaptic membrane - CS is a neurone, NMJ is the sarcolemma in a muscle cell
type of movement - diffusion
effect - CS - action potential, NMJ - muscle contraction
number of receptors - CS - fewer, NMJ - more
type of response - CS - excitatory or inhibitory, NMJ - excitatory

Question 11

What are muscle fibres joined by?

Answer 11

tendons

Question 12

What is a sarcomere?

Answer 12

the basic contractile unit

Question 13

What is a muscle fibre?

Answer 13

a single muscle cell

Question 14

How do myofibrils appear under a microscope?

Answer 14

banded structures

Question 15

How are the insides of the myofibrils structured?

Answer 15

parallel filaments

Question 16

What are the two types of filament in a myofibril?

Answer 16

thick - myosin
thin - actin

Question 17

How are the two filaments linked?

Answer 17

intervals called crossbridges

Question 18

Describe the structure of myosin

Answer 18

-two heads called myosin heads
-each head contains an ATPase
-the heads stick out from the crossbridge

Question 19

Describe the structure of actin

Answer 19

contains a binding site for myosin heads

Question 20

Name the two proteins attached to actin

Answer 20

tropomyosin - wound around the actin
troponin - mound to the tropomyosin and contain calcium ion binding sites

Question 21

What are the repeating units of a myofibril?

Answer 21

sarcomeres

Question 22

The ends of each sarcomere are joined by…

Answer 22

Z-lines

Question 23

What is the dark A-band?

Answer 23

thick myosin filaments

Question 24

What is the light I-band?

Answer 24

where thin filaments do not overlap with thick filaments

Question 25

What is the H-zone?

Answer 25

the portion of the A-band where the thick and thin filaments do not overlap

Question 26

When a muscle contracts what happens to the length of the sarcomere?

Answer 26

reduces as thick and thin filaments slide past each other

Question 27

What happens to the dark and light bands during contraction?

Answer 27

dark bands - stay the same length light bands - reduce in length

Question 28

Where does the energy supply for muscle contraction come from?

Answer 28

hydrolysis of ATP - movement of myosin heads and reabsorption of Ca2+ ions into the sarcoplasmic reticulum by active transport

Question 29

What is the number of energy released by hydrolysis of ATP?

Answer 29

+33Kjmol-1

Question 30

Name three ways ATP is obtained?

Answer 30

-ATP phosphocreatine system -aerobic respiration -anaerobic respiration

Question 31

What does phosphocreatine do?

Answer 31

phosphorylates ADP to ATP to maintain the supply of ATP

Question 32

Describe the phosphocreatine system

Answer 32

-acts a reserve supply of phosphate -generates ATP very quickly -used during short bursts of energy and runs out after a few seconds -anaerobic -no lactic acid made

Question 33

How is the phosphocreatine store replenished?

Answer 33

with rest - uses the phosphate from ATP when the muscle is relaxed

Question 34

Describe anaerobic respiration when replenishing ATP

Answer 34

-generates small amounts of ATP rapidly -used during short periods of hard exercise -lactic acid builds up which causes muscle fatigue

Question 35

Describe aerobic respiration when replenishing ATP

Answer 35

-most ATP is produced this way -only possible when oxygen is available -good for long periods of low-intensity exercise

Question 36

Describe myoglobin

Answer 36

-picks up oxygen very readily and is saturated at relatively low pO2 -if the pO2 falls to very low levels it will release all its oxygen

Question 37

Name the two types of muscle fibre

Answer 37

fast twitch and slow twitch

Question 38

Describe fast twitch muscle fibre (use/speed, thickness, by-product, ATP source, mitochondria/myoglobin)

Answer 38

-used for fast movements due to powerful and quick contractions -thicker more numerous myosin filaments -lactate produced cause them to become fatigued quickly -anaerobic respiration and store a lot of phosphocreatine -few mitochondria and little myoglobin

Question 39

Describe slow twitch muscle fibre (use/speed, thickness, by-product, ATP source, mitochondria/myoglobin)

Answer 39

-endurance activities as they contract slowly and can work for long periods of time, like maintaining posture -thinner/weaker contractions -no lactate -aerobic respiration - have a supply of glycogen and an excellent blood supply to deliver oxygen and glucose -large number of mitochondria and high conc of myoglobin

Question 40

Fibres run...

Answer 40

the whole length of the muscle

Question 41

Describe the nuclei in a myofibril

Answer 41

they have many nuclei

Question 42

When given a cross section of myofibrils, when it only has one type of thick dots what does this mean?

Answer 42

H-Zone - just thick filament

Question 43

When given a cross section of myofibrils, when it has two types of dots what does this mean?

Answer 43

dark band - overlap of thick and thin filament

Question 44

Compare fast vs slow twitch in terms of ATPase activity

Answer 44

slow - low , fast - high

Question 45

Compare fast vs slow twitch in terms of capillary density

Answer 45

slow - high , fast - low

Question 46

Compare fast vs slow twitch in terms of fibre colour

Answer 46

slow - dark red , fast - white

Question 47

Compare fast vs slow twitch in terms of glycolytic enzymes

Answer 47

slow - low , fast - high

Question 48

Explain the sliding filament theory

Answer 48

-when a nerve impulse arrives at a neuromuscular junction, calcium ions are released from the sarcoplasmic reticulum -the calcium ions diffuse and then bind to the troponin molecules causing them to move/change shape -the troponin displaces the tropomyosin on thin filaments and exposes the myosin binding sites -myosin heads bind to the myosin binding sites, forming cross bridges and causing ADP and Pi to be released -the myosin changes shape, causing the myosin head to nod forwards, sliding the actin over the myosin filament over each other -then ATP binds to myosin heads, causing the head to detach -ATP is then hydrolysed by ATPase, providing the energy to recock the heads to their normal position -cycle repeats

Question 49

What happens when a muscle stops being stimulated?

Answer 49

-calcium ions are actively reabsorbed into the sarcoplasmic reticulum -troponin reverts back to its normal shape and tropomyosin moves back to block the myosin binding sites