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Flashcards in Muscle Physiology Slide Notes Deck (54):
1

The limiting factor in muscle contraction

Calcium

2

Utilize more extracellular Ca2+ than intracellular

Cardiac and smooth muscle

3

Skeletal muscle function begins in the

Motor cortex (in cerebral cortex)

4

Connect brain to regions of the spinal cord

-where motor signals leave the ventral root

Rubrospinal and reticulospinal tracts

5

ACh receptors that are specific to skeletal muscle

Cholinergic-nicotinic receptors

6

Allows for calcium to be released from the SR

-a voltage gated Ca2+ channel

DHPR-RyR complex

7

Decreasing the amount of sarcoplasmic Ca2+ results in

Muscle relaxation

8

Transports calcium out of the cell and sodium into the cell

-a secondary mechanism to move calcium out of the cell

NCX

9

The biggest mechanism for sequestering Ca2+ back into the SR

SERCA

10

In skeletal muscle, crossbridge cycling is driven by

Intracellular Ca2+

11

Changes in Ca2+ are directly proportional to changes in contractility. These different levels of contraction are called the

Inotropic state

12

Allows for influx of Ca2+ into the myocardium

Type L channel

13

Targets bone and the kidneys and increases bone resorption, which increases plasma concentration of Ca2+

Parathyroid hormone (PTH)

14

Causes motor neuron and skeletal muscle hyperexcitability an Na+ channel stabiity

-can lead to muscle spasm

Hypocalcemia

15

Raises the threshold for voltage-gated Na+ channels which leads to muscle and neuron hypoexcitability

Hypercalcemia

16

The opposition to displacing load

Afterlod

17

Force generated to counter afterload

Preload

18

The preload is greater than the afterload and work is performed in

Isotonic Contraction

19

In cardiac muscle, the preload is the ability for

Ventricles to contract

20

In cardiac muscle, the afterload is

Aortic BP and pulminary arterial pressure

21

Blood only leaves the ventricles if

Preload > afterload

22

The maximal force a muscle can generate

Muscle tetanus

23

Phenomenon due to muscle elasticity

-stretch in muscle

Passive tension

24

Reaches a maxima shortly after contraction and then declines

-shows us that muscle generates most of its power early in contraction

Active tension

25

If muscles are not starting from L0, but rather from a shorter length, the power the muscle can generate will be

Lower than if it were at L0

26

Greatest at intermediate loads where F and V are moderate

Power

27

Describe the orderly recruitment principle

We want to move a load, so type 1 fibers are recruited and we are in a stage of isometric contraction, then some type 2 fibers are recruited and we get an isometric to isotonic conversion. Then a large amount of type 2 fibers are recruited and we reach maximal force of muscle contraction. But then after 50msec or so, we recruit type 1 fibers because they are the only ones with the oxidative capacity to sustain prolonged contraction

28

Musculotendon assessment mechanisms tell us if it is ok to keep contracting or if we need to stop. What are the two systems we have in place for this assessment?

1.) Golgi tendon organs
2.) Muscle spindles

29

Stress sensors that will decrease muscle contraction via type 1b afferent fibers if necessary

Golgi tendon organs (GTOs)

30

Monitor change in muscle length and rate of change in length

Muscle spindles

31

What are the components of the intrafusal fibers of muscle spindles?

1.) Bag fibers
2.) Chain fibers

32

What are bag fibers innervated with?

-Tells us about change in muscle length and provides us with proprioception

Type 1a afferents

33

Tells us about static length

Type II afferents (in chain fibers)

34

An increase in muscle fiber diameter

-predomiant

Hypertrophy

35

An increase in number of muscle fibers

-less common

Hyperplasia

36

Activated in response to stimuli induced by workload

- stimulate myoblasts

Satellite cells

37

The main source of muscle regeneration and growth

Satellite cells

38

Released due to anaerobic and aerobic work and function in autocrine and paracrine hypertrophy myogenesis

Myokines

39

Myokines promote

Osteogenesis, anti-inflammatory interactions, and insulin secretion

40

Have direct anabolic and anti-catabolic effects by

Increasing: Satellite cell proliferation and GH and IGF-1 levels

Decreasing: Glucocorticoid activity

Anabolic androgen steroids (i.e. testosterone and dihydrotestosterone)

41

Induces increase in nitrogen balance, proteogenesis, and increased hepatic IGF-1

Growth Hormone (GH)

42

Ubiquitously expressed in skeletal muscle and increases proteogenesis and regeneration of muscle

IGF-1

43

Are less effective without eachother, i.e. they are synergists

GH and IGF-1

44

What are three catabolic factors?

1.) Excess Ca2+
2.) Glucocorticoids
3.) Myostatin

45

Released as part of the immune/anti-inflammatory response and function to increase proteolysis and type II fiber atrophy

Glucocorticoids

46

Stress induced hormones that decrease activity of IGF-1

Glucocorticoids

47

Comes from the adrenal cortex and causes release of myostatin

Cortisol

48

Expressed within satellite cells where it blocks cell cycle progression and inhibits proliferation of satellite cells

Myostatin

49

Inhibition of myostatin results in

Unregulated muscle growth

50

Muscle fatigue will prevent cross-bridge cycling. What are two factors that will lead to muscle fatigue?

1.) Decreased pH (affects type II fibers)
2.) K+ efflux

51

Which type of muscle fiber is most affected by aging?

Type II fibers

52

Has slow wave and spike potentials and is innervated by autonomic nerve fibers

Visceral smooth muscle

53

In visceral smooth muscle, what is the effect of the following stimulation:
1.) Sympathetic
2.) Parasympathetic

1.) relaxation
2.) contraction

54

In vascular smooth muscle, epinephrine and norepinephrine activate α1 adrenoreceptors which lead to

Inhibition of SERCA, resulting in increased sacoplasmic Ca2+ and thus vasoconstriction

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