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Biology 116 > Topic 21: Musculoskeletal System > Flashcards

Topic 21: Musculoskeletal System Flashcards

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
What happens during contraction?
thick and thin filaments slide past each other - > increase overlaps - > sarcomere gets shorter
26
Do the lengths of the filaments change during contraction?
No! only the amount of overlap between them changes
27
Explain the overlap in a fully contracted muscle
Z-lines get closer the more contracted it is | thick and thin are COMPLETELY overlapped in a fully contracted muscle
28
What is the simple pathway of a contraction?
CNS -> motor neuron -> muscle fiber contraction
29
What are the steps for skeletal muscle contraction?
``` muscle fiber at rest message from motor neuron getting APs to myofibril contraction muscle relaxation ```
30
What happens when the muscle fiber is at rest?
tropomyosin covers myosin binding sites of actin
31
What happens when the message is being sent from the motor neuron?
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
What happens when the APs are going to the myofibrils?
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
What happens during the contraction?
Ca2+ binds troponin exposes myosin binding sites on actin -> contraction can occur
34
What happens during muscle relaxation?
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
What happens during the sliding filament model?
cyclical process in sarcomeres | -> muscle contracts when this occurs in many muscle fibers at the same time
36
What is the process of sarcomere contraction?
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
How does the energy from contraction happen?
each myosin head forms about 5 cross-bridges/second | only enough ATP present for a few seconds of activity
38
What do muscles store?
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
What are the other types of muscle? Voluntary or involuntary?
skeletal smooth cardiac involuntary
40
Where are cardiac muscles located?
in the walls of heart
41
What kind of muscles are the cardiac muscles?
striated
42
What is the function of cardiac muscle?
can generate APs without nervous system input | spread APs to adjacent cells via intercalated discs
43
Where are smooth muscles located? Voluntary or involuntary?
walls of digestive tract, bladder, uterus, blood vessels | involuntary contractions
44
What are some characteristics of the smooth muscle?
``` not attached to bone not striated no t tubules not well developed SP less efficient slow contraction slow relaxation ```
45
What are the 3 functions of the skeleton?
support body protect internal organs movement
46
How are we able to move?
using NS signals and antagonistic muscle pairs
47
What are the 3 types of skeletons?
1. hydrostatic skeleton 2. exoskeleton 3. endoskeletons
48
What is the hydrostatic skeleton?
a fluid filled cavity | fluid under pressure in closed environment
49
What animals is the hydrostatic skeleton present in?
cnidarians, nematodes, annelids
50
What is peristalsis?
movement produced by rhythmic waves of contractions
51
What animals are hydrostatic skeletons good for?
small, aquatic animals
52
What are some characteristics of exoskeletons?
external | non-living - does not grow
53
What animals are exoskeletons present in?
arthropods - chitin - protection, movement | mollusks - CaCO3 - protection
54
Where are endoskeletons present? What animals have endoskeletons?
internal echinoderms, chordates living, able to grow
55
What are the 2 components of endoskeletons?
cartilage | bone
56
What is cartilage?
flexible skeletal tissue
57
What is bone?
rigid, mineralized skeletal tissue
58
Why is physical activity important?
muscles and bones develop
59
How often is the adult human skeleton completely replaced?
every 10 years
60
What are osteoblasts?
bone - building cells
61
What are osteoclasts?
break down bone, overactivity -> osteoporosis

Biology 116 (24 decks)

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