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Muscle Physiology > Lesson 2/3 > Flashcards

Lesson 2/3 Flashcards

1
Q

corticobulbar tract vs corticospinal tract

A

corticobular connects motor cortex to brain stem and controls motor for head, neck, and face. corticospinal controls motor for the rest of the body

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2
Q

a motor unit consists of…

A

one motor neuron and all the muscle fibers it innervates

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3
Q

a motor neuron determines _________

A

fiber types and only one fiber type per motor unit

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4
Q

explain the events at the NMJ and how an AP occurs

A

1 - AP reaches the terminal
2 - voltage gated Ca channels open
3 - Ca enters axon terminal
4 - ACh released into cleft
5 - ACh binds to postsynaptic recepts. Na+ enters muscle cell and K- exits cell following concentration gradient. membrane is now less negative so AP occurs
6 - ACh diffuses away or is broken up by acetylcholinesterase
7 - choline is reabsorbed by the axon for recycling

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5
Q

what protein allows the vesicle to dock to the cell membrane

A

SNARE/SM protein complex

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6
Q

what cell traps ACh in the synaptic cleft

A

kranocyte

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7
Q

ACh receptor is a ________- and therefore needs an ACh to dock on both sides to open

A

dimer

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8
Q

what type of Ach receptor do we only see in babies or denervated muscle? what is it replaced by when we are healthy adults?

A

gamma
epsilon

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9
Q

Acetylcholinesterase breaks down ACh and makes…

A

acetate
choline (recycled back into cell)
H+ ion

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10
Q

What starts excitation contraction coupling

A

1 - ACH released from axon terminal of a motor neuron and binds to receptors in the motor end plate. this binding elicits an end-plate potential, which triggers an action potential in the muscle cell.

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11
Q

1 - ACH released from axon terminal of a motor neuron and binds to receptors in the motor end plate. this binding elicits an end-plate potential, which triggers an action potential in the muscle cell.

What happens next?

A

2 - action potential propagates along the sarcolemma and down the T tubules.

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12
Q

2 - action potential propagates along the sarcolemma and down the T tubules.

What happens next?

A

3 - action potential triggers Ca+ release from SR

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13
Q

3 - action potential triggers Ca+ release from SR

What happens next?

A

4 - Ca+ binds to troponin C, exposing myosin binding sites

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14
Q

4 - Ca+ binds to troponin C, exposing myosin binding sites

What happens next?

A

5 - crossbridge cycle begins (muscle contracts)

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15
Q

5 - crossbridge cycle begins (muscle contracts)

What happens next

A

6 - Ca+ is actively transported back into lumen of SR following the action potential

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16
Q

6 - Ca+ is actively transported back into lumen of SR following the action potential

What happens next

A

7 - tropomyosin blocks myosin-binding sites (muscle fiber relaxes)

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17
Q

What is the steric hindrance model

A

Tropomyosin blocks the myosin binding site on actin until calcium binds to troponin C

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18
Q

How is force produced

A

crossbridge

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19
Q

What is the rate limiting step in the cross bridge cycle?

A

how fast ATP can be hydrolyzed by myosin

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20
Q

How does the cross bridge cycle begin?

A

1 - Tight binding between actin and myosin in the rigor state

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21
Q

1 - Tight binding between actin and myosin in the rigor state

What happens next

A

2 - ATP binds to myosin. Myosin disassociates from actin

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22
Q

2 - ATP binds to myosin. Myosin disassociates from actin

What happens next?

A

3 - myosin hydrolyzes ATP. ADP + Pi remain attached to myosin head

23
Q

3 - myosin hydrolyzes ATP. ADP + Pi remain attached to myosin head

What happens next

A

4 - energy of hydrolyzing ATP cocks myosin head and weakly binds to new actin molecule

24
Q

4 - energy of hydrolyzing ATP cocks myosin head and weakly binds to new actin molecule

What happens next

A

5 - release of Pi initiates power stroke

25
Q

5 - release of Pi initiates power stroke

What happens next

A

6 - myosin head releases ADP and returns to rigor state

26
Q

isotonic means

A

constant tension

27
Q

isokinetic means

A

constant velocity

28
Q

concentric means

A

shortening

29
Q

eccentric means

A

lengthening

30
Q

isometric means

A

constant length

31
Q

Po = ________ velocity and ______ load

A

zero
max

32
Q

Vmax = _______- velocity and _______ load

A

max
zero

33
Q

isometric force _____ Po

A

=

34
Q

concentric force _____ Po

A

<

35
Q

eccentric force ________- Po

A

>

36
Q

is Vmax or force changing as a result of strength training on a force velocity curve

A

force moves to the right with strength training

37
Q

What is the strength of a muscle contraction influenced by?

A
  • size of muscle
  • # and size of motor units recruited
  • # and size of fibers within motor unit
  • total amount of contractile protein
  • amount of force per individual actin-myosin (crossbridge) interactions
  • fraction of crossbridges bound and producing force
38
Q

What is a motor unit

A

one motor neuron and all the fibers innervated by that neuron

39
Q

explain all or nothing principle

A

one AP induces all fibers within that motor unit to contract

40
Q

all fibers within a motor unit are the ______ type

A

same

41
Q

_______ motor units for fine motor skills, _______ motor units for gross skills

A

small
large

42
Q

motor units are recruited via the _______

A

size principle

43
Q

what is the skeletal muscle recruitment order according to the size principle

A

1, 2a, 2x

44
Q

gross motor = _______ innervation ratio
fine motor = _______ innervation ratio

A

low
large

45
Q

what is the optimal overlap measurement for sarcomeres

A

2.2-2.25um

46
Q

what does the length tension curve illustrate?

A

there is an optimal amount of overlap between sarcomeres

47
Q

power = _______ x ______

A

force x velocity

48
Q

peak power occurs at ______ of Po and about ________ of Vmax

A

30-40%
30%

49
Q

relaxed muscle is elastic, force is required to stretch it. this is ___________

A

passive tension

50
Q

_________ contributes to passive tension

A

connective tissue

51
Q

________ provides passive elasticity

A

titin

52
Q

what happens with AP is successful?

A

fusion of twitches to make tetanus

53
Q

what are some velocity parameters to measure muscle twitches

A
  • contraction time (CT)
  • relaxation time (RT)
  • one half RT (1/2 RT)
54
Q

what does the one half RT parameter measure?

A

the efficiency of SERCA

Muscle Physiology (19 decks)

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