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Biology 116 > Topic 21: Musculoskeletal System > Flashcards

Topic 21: Musculoskeletal System Flashcards

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1
Q

What does contractile tissue lead to?

A

movement

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2
Q

What does motor output lead to?

A

mechanical force

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3
Q

What are functions of muscle?

A

locomotion
manipulation of environment
blood circulation
feeding, peristalsis

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4
Q

What are skeletal muscles sometimes called and what does this mean?

A

striated muscle

it’s striped

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5
Q

What does the skeletal muscle do?

A

moves skeleton

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6
Q

How are the skeletal muscles attached to the bones?

A

through tendons: cords of connected tissue

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7
Q

What is the most abundant tissue in the body?

A

tendons

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8
Q

What is the motor unit and what does it do?

A

motor neuron connected to about 150 muscle fibers

they all contract at once

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9
Q

What is each synapse in motor unit considered?

A

a neuromuscular junction

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10
Q

What is another name for the muscle fiber?

A

muscle cell

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11
Q

What is the muscle fiber?

A

a long cylindrical cell

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12
Q

What does multinucleate mean?

A

many nuclei

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13
Q

What is multinucleate?

A

the muscle fibers

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14
Q

What are the T (transverse) tubules?

A

extension of PM

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15
Q

What is the sarcoplasmic reticulum?

A

specialized ER of muscle cells

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16
Q

What are myofibrils

A

longitudinal fibers within a cell

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17
Q

What 2 types of filaments do myofibrils contain?

A

thin and thick

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18
Q

What are thin filaments composed of? What is wrapped around it and what else does it contain?

A

composed of mostly actin
tropomyosin is wrapped around actin
troponin complex on tropomyosin

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19
Q

What does the thick filaments have?

A

about 350 myosin molecules
each has a head and tail - heads stick out
tails bundle together - form thick filament

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20
Q

How are filaments arranged and what does it look like?

A

they are arranged in a regular pattern

striped appearance

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21
Q

What is a sarcomere?

A

basic contractile unit - overlaps thick and thin filaments

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22
Q

What is a myofibril in relation to sarcomeres?

A

myofibrils are hundreds of sarcomeres end to end

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23
Q

What does the Z-line mark?

A

the beginning and end of each sarcomere

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24
Q

What does the M-line mark?

A

only the thick filament

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25
Q

What happens during contraction?

A

thick and thin filaments slide past each other

  • > increase overlaps
  • > sarcomere gets shorter
26
Q

Do the lengths of the filaments change during contraction?

A

No! only the amount of overlap between them changes

27
Q

Explain the overlap in a fully contracted muscle

A

Z-lines get closer the more contracted it is

thick and thin are COMPLETELY overlapped in a fully contracted muscle

28
Q

What is the simple pathway of a contraction?

A

CNS -> motor neuron -> muscle fiber contraction

29
Q

What are the steps for skeletal muscle contraction?

A 
muscle fiber at rest
message from motor neuron
getting APs to myofibril
contraction
muscle relaxation
30
Q

What happens when the muscle fiber is at rest?

A

tropomyosin covers myosin binding sites of actin

31
Q

What happens when the message is being sent from the motor neuron?

A

AP reaches synaptic terminal of motor neuron
-> Acetylcholine is released into synaptic cleft
Binds receptors on muscle fiber PM -> depolarization
if strong enough -> AP in muscle fiber

32
Q

What happens when the APs are going to the myofibrils?

A

muscle fibers are thick - APs only travel on membranes
Solution - T tubules
AP travels along PM
-> goes down T tubules
-> reaches sarcoplasmic reticulum (SR)
-> SR reaches Ca2+ into cytosol

33
Q

What happens during the contraction?

A

Ca2+ binds troponin
exposes myosin binding sites on actin
-> contraction can occur

34
Q

What happens during muscle relaxation?

A

one motor neuron is no longer signaling the motor unit:
Ca2+ in cytosol actively pumped into SR
Without Ca2+ to bind troponin, tropomyosin moves back to covering myosin binding sites on actin

35
Q

What happens during the sliding filament model?

A

cyclical process in sarcomeres

-> muscle contracts when this occurs in many muscle fibers at the same time

36
Q

What is the process of sarcomere contraction?

A
  1. myosin head with ATP - low energy configuration
  2. ATP hydrolysis -> myosin head in high E configuration
  3. myosin head binds to binding site on actin
    cross bridge formed:
    myosin head of thick filament bound to actin of thin filament
  4. myosin head released ADP and Pi - but still bound to actin
    -> myosin head returns to low energy configuration
    -> power stroke
  5. new ATP molecule binds myosin head
    -> breaks cross-bridge
    Cycle can now begin again
37
Q

How does the energy from contraction happen?

A

each myosin head forms about 5 cross-bridges/second

only enough ATP present for a few seconds of activity

38
Q

What do muscles store?

A

creatine phosphate - transfers P to ADP -> ATP
provides about 15 seconds of AP
glycogen - broken down to glucose
glucose broken down via aerobic respiration -> ATP
provides about 1 hour of ATP

39
Q

What are the other types of muscle? Voluntary or involuntary?

A

skeletal
smooth
cardiac
involuntary

40
Q

Where are cardiac muscles located?

A

in the walls of heart

41
Q

What kind of muscles are the cardiac muscles?

A

striated

42
Q

What is the function of cardiac muscle?

A

can generate APs without nervous system input

spread APs to adjacent cells via intercalated discs

43
Q

Where are smooth muscles located? Voluntary or involuntary?

A

walls of digestive tract, bladder, uterus, blood vessels

involuntary contractions

44
Q

What are some characteristics of the smooth muscle?

A 
not attached to bone
not striated
no t tubules
not well developed SP
less efficient
slow contraction
slow relaxation
45
Q

What are the 3 functions of the skeleton?

A

support body
protect internal organs
movement

46
Q

How are we able to move?

A

using NS signals and antagonistic muscle pairs

47
Q

What are the 3 types of skeletons?

A
  1. hydrostatic skeleton
  2. exoskeleton
  3. endoskeletons
48
Q

What is the hydrostatic skeleton?

A

a fluid filled cavity

fluid under pressure in closed environment

49
Q

What animals is the hydrostatic skeleton present in?

A

cnidarians, nematodes, annelids

50
Q

What is peristalsis?

A

movement produced by rhythmic waves of contractions

51
Q

What animals are hydrostatic skeletons good for?

A

small, aquatic animals

52
Q

What are some characteristics of exoskeletons?

A

external

non-living - does not grow

53
Q

What animals are exoskeletons present in?

A

arthropods - chitin - protection, movement

mollusks - CaCO3 - protection

54
Q

Where are endoskeletons present? What animals have endoskeletons?

A

internal
echinoderms, chordates
living, able to grow

55
Q

What are the 2 components of endoskeletons?

A

cartilage

bone

56
Q

What is cartilage?

A

flexible skeletal tissue

57
Q

What is bone?

A

rigid, mineralized skeletal tissue

58
Q

Why is physical activity important?

A

muscles and bones develop

59
Q

How often is the adult human skeleton completely replaced?

A

every 10 years

60
Q

What are osteoblasts?

A

bone - building cells

61
Q

What are osteoclasts?

A

break down bone, overactivity -> osteoporosis

Biology 116 (24 decks)

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