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HSC 215 - Exam #3 > Chapter 8-muscle Physiology > Flashcards

Chapter 8-muscle Physiology Flashcards

0
Q

Skeletal muscle

A

Striated and voluntary

Attached to bone

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1
Q

Functions of muscle

A

Generate force
Produce movement
Produce heat

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2
Q

Smooth muscle

A

No striated and involuntary

Ex. Peristalsis, vasodilation

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3
Q

Cardiac muscle

A

Striated and involuntary

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4
Q

Muscle consists of a number of muscle fibers lying parallel to one another held together by _________

A

Connective tissue

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5
Q

Muscle fiber

A

Single muscle cell

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6
Q

Multinucleated

A

May have >100

Formed from my oblasts (embryonic cells)

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7
Q

Sarcoplasmic

A

Cytoplasm within muscle cell

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8
Q

Sarcoplasmic reticulum

A
  • Modified Endoplasmic reticulum
  • Ends of segments expand to form saclike regions - terminal CISTERNAE
  • System of tunnels
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9
Q

Transverse tubules

A

Penetrate into muscle fiber from sarcolemma

- action potential on surface membrane spreads down into t-tubule

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10
Q

Transverse tubules - spread of AP down a t tubule triggers ________________

A

Release of calcium from SR into Sarcoplasm

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11
Q

Myofibrils

A

Contractile elements of muscle fiber

Contains the myofilaments

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12
Q

Thick filaments

A

Myosin

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13
Q

Thin filaments

A

Actin

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14
Q

Sarcomere

A

Functional unit of skeletal muscle

- found between two z-lines (connects thin filaments of two adjoining sarcomeres)

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15
Q

A band

A

Made up of thick filaments along with portions of thin filaments that overlap on both ends of thick filaments

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16
Q

H zone

A

Lighter area within middle of A band where thin filaments do not reach
Myosin only

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17
Q

M line

A

Extends vertically down middle of A band within center of H zone (middle)

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18
Q

I band

A

Consists of remaining portion of thin filaments that do not project into A band (actin only )

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19
Q

Proteins in muscle (list 3)

A

Contractile
Regulatory
Structural

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20
Q

Myosin

A
  • golf club
  • component of the thick filament
  • tails oriented toward center of filament and globular heads protrude outward at regular intervals
  • heads form cross bridges between thick and thin filaments
  • has two important sites critical to contractile process
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21
Q

Two critical sites for contractile process of myosin

A
  • actin binding site

- myosin ATPase site

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22
Q

ATPase of myosin

A
  • splits ATP into ADp and Pi
  • energy released is transferred to the myosin head
  • this causes the myosin head to be cocked
  • analogy - pulling back a rubber band
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23
Q

Actin

A
  • spherical in shape
  • contains two other regulatory proteins
  • each actin molecule has special binding site for attachment with myosin cross bridge (actin active site)
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24
Q

regulatory proteins - found on _______

A

thin filament

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25
Q

tropomyosin

A
  • thread-like molecules that lie end to end alongside groove of actin spiral
  • regulatory protein
  • covers actin active sites blocking interaction that leads to muscle contraction
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26
Q

troponin

A
  • thumb tack
  • regulatory protein
  • made of three polypeptide units:
  • binds to tropomyosin, actin, and calcium
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27
Q

troponin - when not bound to _____, troponin stabilizes tropomyosin in blocking position over actin’s cross-bridge binding sites

A

calcium

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28
Q

when calcium binds to _____, ________ moves away from blocking position

A

troponin

tropomyosin

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29
Q

with tropomyosin out of the way, _____ and ______ are free to interact

A

actin

myosin

30
Q

structural protein - ______

A

titin

extends in both directions from M line along length of thick filament to Z lines at opposite ends of sarcomere

31
Q

two important roles of titan

A
  1. stabilize myosin

2. acts like a spring to provide elasticity

32
Q

excitation - contraction coupling

A

how APs cause contraction

33
Q

sliding filament mechanism

A

how the sarcomere shortens

- how do myosin and actin interact to have this happen

34
Q

muscle contraction steps

A
  1. AP travels down motor neuron to NMJ where synaptic transmission occurs
  2. AP travels down T tubules
  3. Ca+ released from SR
  4. Ca+ binds with troponin and tropomyosin moves away from actin
  5. Actin active sites binding sites are exposed
  6. myosin crossbridges bind with actin
  7. ADP and Pi are released from myosin to change myosin’s shape
  8. myosin head bends toward center of sarcomere = power stroke
  9. actin slides over myosin
  10. new ATP binds to myosin to detach it from actin
  11. cycle is repeated
35
Q

contraction continues if ____ is available and ____ level in sarcoplasm is high

A

ATP

Ca+

36
Q

during shortening: Z lines ________

A

get closer

37
Q

during shortening: H zone ______

A

shortens

38
Q

during shortening: A _____

A

same

39
Q

shortening: I band _____

A

shortens (only actin)

40
Q

muscle relaxation steps

A
  1. motor neuron AP stops
  2. AChE breaks down ACh at NMJ
  3. muscle fiber AP stops
  4. reuptake of Ca+ into SR
  5. TT complex cover actin active sites
41
Q

rigor mortis

A

state of muscle rigidity post death

  • there is no ATP being produced
  • Ca+ leaks out of SR
  • sliding filament mechanism begins
  • no ATP to break crossbridges
42
Q

length tension relationship

A

sarcomeres can generate the most tension when the overlap of filaments is optimal

43
Q

tension generated is determined by _______

A

the number of crossbridges that can be formed

44
Q

finely controlled movement

A

contain fewer fibers per motor unit

45
Q

coarsely controlled movement

A

have larger number of fibers per motor unit

46
Q

twitch

A
  • brief, weak contraction
  • produced from single AP
  • too short and too weak to be useful
  • normally does not take place in body
  • ex. gastrocnemius in frogs
47
Q

twitch summation

A

if the muscle fiber is stimulated before it has completely relaxed
- results from sustained elevation of cytostolic calcium

48
Q

tetanus

A

sustained contraction

  • occurs if muscle fiber is stimulated so rapidly that it does not have a chance to relax between stimuli
  • contraction is usually 3 to 4 times stronger than a single twitch
  • caused by greater crossbridge cycling
  • maximum calcium release and prolonged removal
49
Q

what causes power stroke?

A

when ADP and Pi leave

50
Q

isotonic muscle contraction

A

muscle tension remains constant as muscle changes length

ex. angle changes

51
Q

isometric contraction

A

muscle length remains constant to generate force

ex. when you plant your foot

52
Q

steps requiring ATP

A

splitting of ATP by myosin
binding of ATP to myosin
active transport of Ca+

53
Q

steps requiring ATP: splitting of ATP by myosin

A

provides energy that leads to power stroke (cock the head)

54
Q

steps requiring ATP: binding of ATP to myosin

A

to detach from actin

55
Q

steps requiring ATP: active transport of Ca+

A

back into SR during relaxation depends on energy derived from breakdown of ATP

56
Q

3 biochemical pathways: transfer of high-energy phosphate from ______ to ADP

A

PC

  • < 1 minute (amount of ATP that lasts)
  • first energy at onset of x - used for short-burst, high-intensity x
57
Q

creatine

A

molecule capable of storing ATP energy

- creatine + ATP –> PC + ADP

58
Q

creatine phosphate

A

molecule with stored ATP energy

59
Q

3 biochemical pathways: oxidative phosphorylation

A

(CAC and ETC)

  • takes place within muscle mitochondria IF sufficient O2 is present
  • fuel from glucose/glycogen or fatty acids
  • relatively slow to generate ATP
  • aerobic exercise - sustainable, non-fatiguing, system working most to produce ATP
60
Q

3 Biochemical pathways - Glycolysis

A
  • supports high-intensity exercise, burst of power, quick to fatigue (anaerobic exercise)
  • much faster than oxidative phosphorylation
61
Q

muscle fatigue

A

when exercising muscle can no longer respond to stimulation

  • defense mechanism that protects muscle from reaching point at which it can no longer produce ATP
  • underlying causes of muscle fatigue are unclear
62
Q

slow oxidative fibers (type 1)

A

dark (red meat)

  • low myosin ATPase activity
  • slow
  • high to fatigue
  • high oxidative phosphorylation
  • many mitochondria
  • many capillaries
  • high myoglobin content
63
Q

fast oxidative fibers (type IIa)

A
  • high myosin ATPase activity
  • fast
  • high oxidative phosphorylation capacity
  • many mitochondria
64
Q

fast glycolytic fibers (type II x)

A
  • high myosin ATPase activity
  • fast
  • low to fatigue
  • few mitochondria
  • few capallaries
65
Q

produce ATP by ________

A

oxidation phosphorylation

66
Q

smooth muscle: found in ______

A

walls of hollow organs and tubes

67
Q

smooth muscle characteristics

A
  • spindle shaped cells
  • no sarcomeres
  • circular and longitudinal fibers to allow for peristalsis
  • thin filaments contain tropomyosin, but lack troponin
68
Q

smooth muscle: Ca+ binds to _______

A

calmodulin

69
Q

smooth muscle: muscle contractions are _______

A

slow and sustained

70
Q

2 types of smooth muscle: multiunit

A
  • in large blood vessels
  • in large airways to lungs
  • function independantly
  • must be stimulated by nerves
  • in order to get contraction, a nerve has to talk to it
71
Q

2 types of smooth muscle: single unit

A
  • visceral smooth muscle (in guts)
  • contract as a single unit
  • exhibit pacemaker activity
  • arranged in sheets
  • will still contract if no nerves stimulate it
72
Q

steps in smooth muscle contraction

A
  1. AP causes voltage gated Ca+ channels to open
  2. Ca+ in the cell interacts with calmodulin
  3. Ca+ calmodulin complex activates enzymes
  4. causes myosin head to be phosphorylated
  5. myosin interacts with actin
  6. contractions are slow and sustained

HSC 215 - Exam #3 (2 decks)

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