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Physiology (712) > Week 4 Review > Flashcards

Week 4 Review Flashcards

1
Q

distinguish between exercise and physical activity

A
  • PA = any movement of the body that requires energy expenditure
  • Exercise = planned, structures, repetitive, purposeful PA
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2
Q

How does bed rest affect muscle mass? Does this change reflect an adaptation to the stress of activity?

A
  • every time we sleep at night, our bodies begin to detrain (atrophy)
  • reflects an adaptation (or de-adaptation) to the decreased level of stress being placed on the muscle
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3
Q

List 6 functions of muscle and associate a type of muscle with that function

A
  • produces body movement (skeletal muscle)
  • helps maintain posture (skeletal muscle)
  • powers respiration (skeletal muscle)
  • produces body heat (skeletal muscle; shivering)
  • communicates w other organs/organ systems (smooth muscle)
  • regulates diameter of hollow organs and blood vessels (smooth muscle)
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4
Q

What are the 4 general properties of muscle?

A
  • contractility
  • excitability
  • extensibility
  • elasticity
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5
Q

What is contractility and how does it relate to PT?

A
  • ability of a muscle to shorten or attempt to shorten; expending energy and generating force in the process
  • strength exercises
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6
Q

what is excitability and how does it relate to PT?

A
  • capacity of a muscle to respond to a stimulus
  • skeletal muscle is excitable
  • e-stim
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7
Q

what is extensibility and how does it relate to PT?

A
  • ability to go from shortened muscle length to longer muscle length
  • ROM
  • rubber bands can only stretch to certain limits
  • muscles work the same way.. they can shorten/lengthen within a certain range
  • reduced ROM can reduce function
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8
Q

what is elasticity and how does it relate to PT?

A
  • ability of a muscle to recoil to its original resting length after being stretched
  • stretching
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9
Q

Identify essential differences between skeletal muscle and cardiac muscle

A
  • cardiac muscle = involuntary

- skeletal muscle = voluntary

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10
Q

how is the skeletal muscle in the brachialis different from the cardiac muscle in the heart?

A
  • when your heart beats, every cardiac muscle cell (myocyte) contracts
  • when you flex your elbow, not every skeletal muscle cell in the brachialis contracts
  • you don’t have control over your heartbeat, but you do have control over your brachialis
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11
Q

Identify essential differences between smooth muscle and striated muscle

A
  • smooth muscle: in organs, involuntary, single nucleus, low power output, fatigue resistant, low energy consumption; no sarcomeres
  • striated muscle: in skeletal muscle or cardiac muscle, involuntary or voluntary, contains sarcomeres
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12
Q

muscle contraction

A
  • when a muscle shortens or attempts to shorten

- actin and myosin moving past each other

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13
Q

tension

A

stretch on muscle when contracting or relaxed

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14
Q

resistance

A

force opposing the force of the muscle

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15
Q

force

A

measurable activation needed to overcome opposing resistance

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16
Q

isotonic contraction

A
  • muscle contraction in which the muscle changes length under a constant load
  • broad category including concentric and eccentric
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17
Q

concentric contraction

A
  • muscle shortens while contracting

- force generated > opposing force/resistance

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18
Q

Provide an example in daily life where one might make use of concentric contractions

A

biceps curl

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19
Q

eccentric contraction

A
  • muscle lengthens while contracting

- force generated < opposing force/resistance

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20
Q

Provide an example in daily life where one might make use of eccentric contractions

A
  • plyometrics

- walking down stairs = quads contract to keep your rear end from striking your heels

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21
Q

isometric contraction

A
  • muscle length does not change while actively contracting

- force generated = the resistance

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22
Q

Provide an example in daily life where one might make use of isometric contractions

A

weightlifter attempting to deadlift too much weight - his biceps are contracting but cannot overcome the opposing force

23
Q

isokinetic contraction

A

muscle shortens at constant speed

24
Q

Provide an example in daily life where one might make use of isokinetic contractions

A

isokinetic machine → creates different levels of resistance; movements are at a constant speed, no matter how much force is applied

25
Q

What is the function of satellite cells?

A
  • sits on the outside of a muscle cell and is called into play when a muscle is injured (regrows/replaces the damaged muscle cell)
  • lie adjacent to sarcolemma
  • Clinician: you will try to activate them as a clinician to try to repair the muscle
26
Q

define a sarcomere

A
  • basic contractile unit of muscle fiber; the z-lines define the lateral borders of the sarcomere
  • sarcomere will span from one z-line to the next
27
Q

Describe the connective tissue anatomy of a striated muscle (biceps) and explain how it is involved in joint movement

A
  • sarcolemma = plasma membranes of muscle cells
  • muscle cells are multinucleated; have many of the same organelles found in other cells
  • Endomysium surrounds fibers
  • Perimysium surrounds muscle fascicles
  • Epimysium surrounds fascicle bundles
28
Q

What is so unique about the 3 layers of connective tissue in striated muscle?

A
  • this connective tissue matrix allows contraction to be transmitted to the whole muscle
  • how we get joint movement
29
Q

How does building scaffolding relate to the anatomy of striated muscle?

A
  • Epimysium pulls on perimysium, which pulls on endomysium as muscle contracts
  • if you pull on one layer, you’re going to pull on the other layers too
30
Q

What happens when the connective tissue layers are compromised?

A
  • Extensibility becomes compromised
  • Connective tissue repairs very slowly. If it is not repaired correctly, it can impact movement and limit functionality.
  • Depending on how injured an athlete gets, they may not heal all the way to return to the athletic level they had before injury.
31
Q

What is a muscle fascicle?

A
  • Bundle of fibers wrapped in perimysium

- Like a bundle of firewood

32
Q

Describe anatomic changes in a skeletal muscle that might develop into a contracture

A

Rigid muscles fixed and at a particular length, there is a lack of extensibility

33
Q

Which sarcomeric band keeps the same length or width during an isotonic muscle contraction?

A
  • A band
  • thick filaments (myosin)
  • dark part of striations
34
Q

The length of which sarcomeric zone shortens during an isotonic muscle contraction?

A
  • I band move closer together -H zone shortens in width

* thin filaments moves and crawls on the A Band*

35
Q

Describe the myotendinous junction (MTJ)

A
  • bridging structure between muscle and tendon

- when a skeletal muscle cell shortens/attempts to shorten, it pulls on the MTJ which in turn is pulling on the tendon

36
Q

True or false: the myotendinous junction is a weak point

A
  • true
  • if the tendon cannot match the strength of the muscle cell, there’s a tendency for the muscle cells to be pulled away from the tendon, causing injury
  • MTJ can adapt to greater force, particularly with resistance training
37
Q

What is a costamere?

A
  • component of striated muscle cells that connects sarcomere to cell membrane
  • forces are transmitted laterally through the costamere within the cytoskeleton of the fiber into the ECM and neighboring skeletal muscle
38
Q

force production by muscle is not just transmitted ____ but also ____ thanks to the costamere

A

longitudinally; laterally

39
Q

What happens to the sarcomere during an eccentric contraction?

A

lengthens

40
Q

What happens to the A band during an eccentric contraction?

A

stays the same length

41
Q

What happens to the I band during an eccentric contraction?

A

widens

42
Q

What happens to the H zone during an eccentric contraction?

A

widens

43
Q

Is there force production with an eccentric contraction?

A
  • Force production declines; is predicated in part by the amount of overlap between the thick and thin filaments
  • If there is little overlap, fewer cross bridges link the thick and thin filaments
44
Q

What happens when a muscle is supracontracted?

A
  • there is too much overlap b/w thick and thin filaments
  • m-line disappears due to the overlapping of the thin filaments
  • force production will also decline at this point (Atrial de-fibrillation device)
45
Q

What happens to the amount of overlap between the thick and thin filaments during an eccentric contraction?

A
  • amount of overlap decreases
  • z lines move further apart
  • thin filaments move away
  • fewer opportunities for cross bridges to form b/w thin and thick filaments
46
Q

What happens to the amount of overlap between the thick and thin filaments during an isometric contraction?

A

nothing, stays the same

47
Q

What happens to the amount of overlap between the thick and thin filaments during hyperextension?

A

even less overlap than normal

48
Q

What happens to the amount of overlap between the thick and thin filaments during a supra-maximal skeletal muscle contraction?

A
  • z lines move closer together
  • thin and thick filaments overlap
  • thin filament move towards center and M line ultimately disappears
  • thin filaments overlap to where no more optimal contraction can occur
  • outermost thin filament cannot form cross bridge, so force production goes down
49
Q

What is the role of troponin in muscle contraction?

A

Covers up binding site for myosin head when muscle is relaxed

50
Q

What role(s) does Ca+ play in striated muscle contraction?

A
  • Binds to troponin and reveals the myosin binding sites

- once muscle relaxes, Ca unbinds from Troponin, which blocks the active sites again (ex: Rigor Mortis)

51
Q

In skeletal muscle, the source of the Ca+ that drives contraction is found in what organelle?

A

sarcoplasmic reticulum

52
Q

What roles does ATP play in muscle contraction?

A
  1. ) Ca 2+ binds to the troponin C, active site revealed, cross bridge forms b/w myosin and actin
  2. ) The myosin head serves as a myosin ATPase enzyme, splitting ATP into ADP & Pi
  3. ) Pi & ADP released and the cross bridge is flexed
  4. ) Release of Pi introduces a powerstroke that pulls the thin filament (z-disks move toward the center)
  5. ) After the powerstroke the myosin head straightens out and binds a new ATP molecule which is then split into ADP & Pi
  6. ) Ca2+ is actively removed from cytoplasm
  7. ) The action is repeated tens of thousands of times
53
Q

Why is the use of a tug-of-war match a poor analogy for sarcomeric shortening?

A
  • There is only muscle action in one direction; no counter force being produced by actin; myosin binds and pulls the actin inward on the sarcomere
  • Sk. Musc. move the z-discs together
  • Muscle contraction brings the z-discs closer together
  • When ATP binds there is flexion in cross-bridge; if there is one cross-bridge on one side, it pulls the z-line in one direction (towards the midline) and the other side pulls it in the opposite direction, pulling the Z-line together

Physiology (712) (9 decks)

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