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Biology- topic 6 organisms respond to changes in their internal and external environments > Muscles > Flashcards

Muscles Flashcards

1
Q

What are the alternative names for each type of muscle?

A

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

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1
Q

What are the three types of muscle?

A

smooth, cardiac, skeletal

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2
Q

Describe the contractions of each type of muscle

A

smooth - slow
skeletal - rapid
cardiac - rapid/myogenic

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3
Q

Describe the speed of the fatigue of the muscle types

A

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

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4
Q

Describe the distribution of the different types of muscle

A

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

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5
Q

What is antagonistic muscle action?

A

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

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6
Q

Give an example of antagonistic muscles?

A

bicep and tricep

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7
Q

How is skeletal muscle controlled?

A

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

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8
Q

How do motor neurones interact with muscles?

A

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

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9
Q

Explain the process at a neuromuscular junction

A

-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

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10
Q

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

A

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

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11
Q

What are muscle fibres joined by?

A

tendons

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12
Q

What is a sarcomere?

A

the basic contractile unit

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13
Q

What is a muscle fibre?

A

a single muscle cell

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14
Q

How do myofibrils appear under a microscope?

A

banded structures

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15
Q

How are the insides of the myofibrils structured?

A

parallel filaments

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16
Q

What are the two types of filament in a myofibril?

A

thick - myosin
thin - actin

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17
Q

How are the two filaments linked?

A

intervals called crossbridges

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18
Q

Describe the structure of myosin

A

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

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19
Q

Describe the structure of actin

A

contains a binding site for myosin heads

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20
Q

Name the two proteins attached to actin

A

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

21
Q

What are the repeating units of a myofibril?

A

sarcomeres

22
Q

The ends of each sarcomere are joined by…

A

Z-lines

23
Q

What is the dark A-band?

A

thick myosin filaments

24
Q

What is the light I-band?

A

where thin filaments do not overlap with thick filaments

25
Q

What is the H-zone?

A

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

26
Q

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

A

reduces as thick and thin filaments slide past each other

27
Q

What happens to the dark and light bands during contraction?

A

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

28
Q

Where does the energy supply for muscle contraction come from?

A

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

29
Q

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

A

+33Kjmol-1

30
Q

Name three ways ATP is obtained?

A

-ATP phosphocreatine system
-aerobic respiration
-anaerobic respiration

31
Q

What does phosphocreatine do?

A

phosphorylates ADP to ATP to maintain the supply of ATP

32
Q

Describe the phosphocreatine system

A

-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

33
Q

How is the phosphocreatine store replenished?

A

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

34
Q

Describe anaerobic respiration when replenishing ATP

A

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

35
Q

Describe aerobic respiration when replenishing ATP

A

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

36
Q

Describe myoglobin

A

-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

37
Q

Name the two types of muscle fibre

A

fast twitch and slow twitch

38
Q

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

A

-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

39
Q

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

A

-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

40
Q

Fibres run…

A

the whole length of the muscle

41
Q

Describe the nuclei in a myofibril

A

they have many nuclei

42
Q

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

A

H-Zone - just thick filament

43
Q

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

A

dark band - overlap of thick and thin filament

44
Q

Compare fast vs slow twitch in terms of ATPase activity

A

slow - low , fast - high

45
Q

Compare fast vs slow twitch in terms of capillary density

A

slow - high , fast - low

46
Q

Compare fast vs slow twitch in terms of fibre colour

A

slow - dark red , fast - white

47
Q

Compare fast vs slow twitch in terms of glycolytic enzymes

A

slow - low , fast - high

48
Q

Explain the sliding filament theory

A

-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

49
Q

What happens when a muscle stops being stimulated?

A

-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

Biology- topic 6 organisms respond to changes in their internal and external environments (6 decks)

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