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Anatomy > Muscle Physiology (Sept 19) > Flashcards

Muscle Physiology (Sept 19) Flashcards

1
Q

What are the three types of muscle?

A

-skeletal -cardiac -smooth

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2
Q

What type of muscle cell is this? What are some of this muscle type’s functions?

A
  • smooth muscle cell
  • storing and moving substances
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3
Q

What type of muscle cell is this? What are some of this muscle type’s functions?

A

-cardiac muscle

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4
Q

What type of muscle cell is this? What are some of this muscle type’s functions?

A
  • skeletal muscle
  • movement, stabilization
  • thermoregulation
  • contractions account for all body movements
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5
Q

Fill in the chart below

A
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6
Q

What are the layers of mysium and their functions?

A
  • endomysium: surrounds each individual muscle fibre
  • perimysium: surrounds a bundle of muscle fibres
    (fascicle: bundle of muscle fibres surrounded by perimysium)
  • epimysium: surrounds the entire muscle
  • all 3 layers contribute to the muscle sheath and become the tendon which connects 2 bones together
  • tendon becomes continuous with the periosteum (wrapping around bone)
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7
Q

Myocyte/myofibre structure

A
  • muscle fibre is composed of myofibrils: long tube-like structures, sarcomeres in series (collection of sarcomeres which allow muscles to contract)
  • sarcomeres: basic contractile unit of muscle
  • made up of a thick filament (myosin) and thin filament (actin)
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8
Q

Label the diagram

A
  1. Tendon
  2. Muscle
  3. Epimysium
  4. Perimysium
  5. Blood vessel
  6. Endomysium
  7. Muscle fibre
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9
Q

Label the diagram

A
  1. Myofibril
  2. Muscle fibre
  3. I band
  4. A band
  5. Sarcomere
  6. Z line
  7. thick filament (myosin)
  8. Thin filament (actin)
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10
Q

What happens when stressor is put on muscles?

A
  • hypertrophy!
  • muscles enlarge with use
  • exercise stimulates production of actin and myosin filaments
  • increased number of myofilaments expands the fibre causing muscle enlargement and definition
  • want more sarcomeres to handle that stress
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11
Q

What happens if you remove stress from muscle?

A
  • atrophy
  • have lots of metabolically active tissue but it’s not being used so it takes proteins and sarcomeres away to use for something else
  • aging, spinal cord injury, space flight all cause atrophy
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12
Q

What is the sliding filament theory?

A
  • contraction of sarcomeres happens through sliding of filaments
  • thin filament slides over thick filament (thick doesn’t move)
  • bring Z lines closer together
  • when sarcomere shortens, fill H zone and space between 1/2 I bands is being removed (distance between thick filament, A band, and Z line)
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13
Q

Label the diagram

A
  1. A band
  2. 1/2 I band
  3. H zone
  4. Relaxed
  5. Contraction
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14
Q

What is outlined in yellow? What are represented by dark black dots?

A
  • muscle fibre
  • thick filament (composed of myosin)
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15
Q

Label the diagram. What function does this structure serve?

A
  • it is a thick filament and the projections are cross bridges
  • the cross bridges are what makes the thick filament interact in 3D
  • each thick filament can interact with 6 thin filaments
  • each thin filament (actin) can interact with 3 thick filaments (myosin)
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16
Q

What is thick filament composed of?

A
  • several myosin molecules with their head sticking up
  • tail is lying down in parallel
  • wants to grab on to thin filament
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17
Q

What is thin filament composed of? What is the role of each component? Where does Ca2+ come in to play?

A
  • three proteins: actin, tropomyosin, troponin
  • actin: form 2 coiled chains (which is the “thin filament”)
  • tropomyosin: run along actin blocking cross bridge binding site (tropo: to turn or react)
  • troponin: holds tropomyosin in place
  • Ca2+ binds troponin and changes its conformation which pulls tropomyosin away from cross bridge binding site which allows for myosin-actin interaction to occur
  • when Ca2+ is removed, tropomyosin moves back to block cross bridge binding site (no actin-myosin interaction)
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18
Q

What is this diagram depicting?

A
  • cross bridge cycling
  • Ca2+ must be present
  • binds and releases
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19
Q

Complete the diagram

A

-if no ATP is present, can’t release cross bridge so there is tension in the muscle (rigor mortis)

20
Q

What is excitation?

A
  • motor neuron attaches to every muscle fibre
  • action potential comes, ACh comes across NMJ, hits muscle fibre
  • muscle fibre propogates action potential
  • action potential spreads over muscle fibre’s membrane
  • muscle fibres are large and have a large diameter
21
Q

What are T tubules? Terminal cisternae?

A
  • invaginations of the membrane
  • tunnels that go deep into muscle fibre and allow for synchronous release of calcium along the muscle fibre
  • T tubule wraps around myofilaments as it goes deep into muscle fibre
  • sarcoplasmic reticulum contains calcium in terminal cisternae
  • terminal cisternae is up against t tubule
  • triad consists of one t tubule with a terminal cisternae on either side
22
Q

What is the function of the DHP receptor?

A
  • located on t tubule membrane
  • reaches out and grabs “plug” on ryanodine receptor and pulls it open with arrival of action potential
  • electrically sensitive and undergoes confirmational change
  • ryanodine receptor located on terminal cisternae
  • calcium rushes out and follows concentration gradient (lots inside terminal cisternae so it rushes out)
23
Q

What are calcium ATPases?

A
  • bring calcium against its concentration gradient to pull it back into terminal cisternae
  • so it’s ready for next action potential and try to stop contraction
  • release is fast but this uptake is slower which allows for the contraction to last a certain amount of time
24
Q

Label the diagram

A
25
Q

What is occurring during latent period?

A

-time between action potential and muscle starting to shorten is the time taken that calcium is being released so there is enough pouring out to start contraction

26
Q

How do you adjust amount of force?

A
  • muscle length (easier to lift it when bicep is at optimal length rather than when it’s stretched)
  • action potential frequency (how many signals being sent to make calcium release)
  • number of fibres per motor unit and the cross sectional area of those muscle fibres (motor unit: one motor neuron and its branches and how many muscle fibres that innervates- if one branches 5 times it can active 5 muscle fibres)
27
Q

How does muscle length affect force?

A
  • optimal number of cross bridges that can form
  • L knot is in range where number of cross bridges that can attach to thin filament are at optimal length to produce maximal contraction
  • if muscle is too contracted, thin filaments start to overlap so you can’t get them to go more
  • if muscle is too stretched, thin filaments get pulled away from centre then have myosin heads that can’t reach thin filament and create cross bridge
28
Q

How does action potential frequency affect force?

A
  • one single action potential is a twitch
  • most movements require multiple action potentials to generate a sustained amount of calcium release
  • send multiple APs and it releases a certain amt of calcium
  • before calcium ATPase can take it all up, more calcium gets released with another AP
29
Q

Describe the graph

A

a) single AP
b) AP followed by another AP- summation of force
c) APs were spaced far enough apart that with each release of Ca, some Ca was taken up so force drops a bit then goes back up (unfused tetanus)
d) APs so closely spaced that Ca keeps pouring out (force is 3-5x greater than single AP)

30
Q

How do motor units affect force?

A
  • 3 types of motor units exist based on muscle fibre types
  • muscle fibre types differ in size and ease of activation
  • size determines the amount of force produced
31
Q

Slow versus fast muscle fibres

A
  • slow allow you to run marathons whereas fast give you power
  • differ on speed of contraction and what kind of energy they use
  • speed of contraction: dependent on rate of myosin ATPase action- slow fibre types contract more slowly but are more fatigue resistant, fast fibre types generate more power but fatigue rapidly
  • aerobic metabolism versus anaerobic metabolism
32
Q

Oxidative and glycolytic fibres

A
  • oxidative: primarly use O2 for ATP production (aerobic)
  • glycolytic: high capacity for ATP production without O2 (anaerobic)
33
Q

What is an isometric contraction?

A
  • muscle force=load
  • no movement of load
34
Q

Fill in characteristics of each fibre type and describe the size principle

A
  • motor units are recruited according to size
  • first to be recruited are slow oxidative, then fast oxidative glycolytic, then fast glycolytic
  • this way, fatigue resistant fibres are always first
  • the number of motor units recruited depends on the force required to perform the task
35
Q

What is an isotonic contraction?

A
  • muscle force does not equal load
  • force > load gives a concentric contraction
  • force < load gives eccentric contraction
36
Q

Identify the specimen and label the parts. Where is the specimen found?

A
  • smooth muscle
  • smooth muscle fibre
  • nucleus of smooth muscle fibre
  • lines the “hollow tubes of the body” (arteries, digestive system, respiratory, urinary and reproductive tracts)
  • can be electrically coupled by gap junctions
37
Q

Does smooth muscle contain thick and thin filaments? If so, do they differ from skeletal muscle?

A

Yes but they are less organized than skeletal muscle

  • no striations
  • filaments are anchored to dense bodies on the intermediate filament network
38
Q

Label the diagram

A
39
Q

What kind of contractions does smooth muscle make? What are the contractions regulated by?

A
  • very slow to contract
  • can maintain prolonged tension
  • contraction can be regulated by: ANS (NTs), hormones, stretching, other local factors (Nitric oxide), pacemaker cells
40
Q

What are some functions of smooth muscle?

A
  • storing and propelling substances (peristalsis)
  • mixing and churning
41
Q

Identify the specimen and label the diagram. What are some key features of the specimen?

A
  • cardiac muscle
  • cardiomyocytes generally have 1-2 nuclei and are branched
42
Q

How does cardiac muscle contract?

A
  • involuntary contraction
  • intrinsic conduction system (pacemaker cells)
  • regulated by ANS
43
Q

What are intercalated discs?

A
  • specialized areas where cardiomyocytes connect
  • contain desmosomes and gap junctions
  • desmosomes allow for interaction between cells (stabilize cell to cell contacts)
  • gap junctions allow electrical signal to pass (direct communication between adjacent cells)
44
Q

Label the diagram

A
45
Q

What is sarcolemma?

A
  • muscle cell membrane
  • t tubule is invagination of sarcolemma
46
Q

What is sarcoplasm?

A

-muscle cell cytoplasm (contains myoglobin and glycogen)

47
Q

What is sarcoplasmic reticulum?

A

-endoplasmic reticulum in muscle cell

Anatomy (27 decks)

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