Muscle Physiology Slide Notes

Question 1

The limiting factor in muscle contraction

Answer 1

Calcium

Question 2

Utilize more extracellular Ca2+ than intracellular

Answer 2

Cardiac and smooth muscle

Question 3

Skeletal muscle function begins in the

Answer 3

Motor cortex (in cerebral cortex)

Question 4

Connect brain to regions of the spinal cord

-where motor signals leave the ventral root

Answer 4

Rubrospinal and reticulospinal tracts

Question 5

ACh receptors that are specific to skeletal muscle

Answer 5

Cholinergic-nicotinic receptors

Question 6

Allows for calcium to be released from the SR

-a voltage gated Ca2+ channel

Answer 6

DHPR-RyR complex

Question 7

Decreasing the amount of sarcoplasmic Ca2+ results in

Answer 7

Muscle relaxation

Question 8

Transports calcium out of the cell and sodium into the cell

-a secondary mechanism to move calcium out of the cell

Answer 8

NCX

Question 9

The biggest mechanism for sequestering Ca2+ back into the SR

Answer 9

SERCA

Question 10

In skeletal muscle, crossbridge cycling is driven by

Answer 10

Intracellular Ca2+

Question 11

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

Answer 11

Inotropic state

Question 12

Allows for influx of Ca2+ into the myocardium

Answer 12

Type L channel

Question 13

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

Answer 13

Parathyroid hormone (PTH)

Question 14

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

-can lead to muscle spasm

Answer 14

Hypocalcemia

Question 15

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

Answer 15

Hypercalcemia

Question 16

The opposition to displacing load

Answer 16

Afterlod

Question 17

Force generated to counter afterload

Answer 17

Preload

Question 18

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

Answer 18

Isotonic Contraction

Question 19

In cardiac muscle, the preload is the ability for

Answer 19

Ventricles to contract

Question 20

In cardiac muscle, the afterload is

Answer 20

Aortic BP and pulminary arterial pressure

Question 21

Blood only leaves the ventricles if

Answer 21

Preload > afterload

Question 22

The maximal force a muscle can generate

Answer 22

Muscle tetanus

Question 23

Phenomenon due to muscle elasticity

-stretch in muscle

Answer 23

Passive tension

Question 24

Reaches a maxima shortly after contraction and then declines

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

Answer 24

Active tension

Question 25

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

Answer 25

Lower than if it were at L0

Question 26

Greatest at intermediate loads where F and V are moderate

Answer 26

Power

Question 27

Describe the orderly recruitment principle

Answer 27

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

Question 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?

Answer 28

1. ) Golgi tendon organs | 2. ) Muscle spindles

Question 29

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

Answer 29

Golgi tendon organs (GTOs)

Question 30

Monitor change in muscle length and rate of change in length

Answer 30

Muscle spindles

Question 31

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

Answer 31

1. ) Bag fibers | 2. ) Chain fibers

Question 32

What are bag fibers innervated with? -Tells us about change in muscle length and provides us with proprioception

Answer 32

Type 1a afferents

Question 33

Tells us about static length

Answer 33

Type II afferents (in chain fibers)

Question 34

An increase in muscle fiber diameter -predomiant

Answer 34

Hypertrophy

Question 35

An increase in number of muscle fibers -less common

Answer 35

Hyperplasia

Question 36

Activated in response to stimuli induced by workload - stimulate myoblasts

Answer 36

Satellite cells

Question 37

The main source of muscle regeneration and growth

Answer 37

Satellite cells

Question 38

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

Answer 38

Myokines

Question 39

Myokines promote

Answer 39

Osteogenesis, anti-inflammatory interactions, and insulin secretion

Question 40

Have direct anabolic and anti-catabolic effects by Increasing: Satellite cell proliferation and GH and IGF-1 levels Decreasing: Glucocorticoid activity

Answer 40

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

Question 41

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

Answer 41

Growth Hormone (GH)

Question 42

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

Answer 42

IGF-1

Question 43

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

Answer 43

GH and IGF-1

Question 44

What are three catabolic factors?

Answer 44

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

Question 45

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

Answer 45

Glucocorticoids

Question 46

Stress induced hormones that decrease activity of IGF-1

Answer 46

Glucocorticoids

Question 47

Comes from the adrenal cortex and causes release of myostatin

Answer 47

Cortisol

Question 48

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

Answer 48

Myostatin

Question 49

Inhibition of myostatin results in

Answer 49

Unregulated muscle growth

Question 50

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

Answer 50

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

Question 51

Which type of muscle fiber is most affected by aging?

Answer 51

Type II fibers

Question 52

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

Answer 52

Visceral smooth muscle

Question 53

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

Answer 53

1. ) relaxation | 2. ) contraction

Question 54

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

Answer 54

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