Ex. Phys. Neuromuscular Physiology Flashcards Preview

Exercise Physiology > Ex. Phys. Neuromuscular Physiology > Flashcards

Flashcards in Ex. Phys. Neuromuscular Physiology Deck (68):
1

skeletal muscle general features

-attached to bones to produce movement
-comprised of long, multi-nucleated cells (fibers) arranged in series for maximum force production
-actin and myosin are the primary contractile filaments
-voluntarily controlled

2

skeletal muscle properties

-contractility: can generate tension
-irritability: responds to stimulation
-extensibility: can stretch
-elasticity: can return to original length

3

skeletal muscle structure (smallest to largest)

myofilament
myofibril
muscle cell/fiber
fascicle
whole muscle

4

myofilament
-composition
-filament relationship
-other important myofilaments

composition
-thin filaments
-thick filaments
filament relationship
-for every one thick filament there are six thin filaments surrounding it
other important myofilaments
-collagen
--structural myofilament
--arrangement and amount dictate how flexible or rigid the tissue is
-elastin
--stretchy protein that gives muscle its elastic property
-titin
--helps keep the myosin filaments aligned with one another inside the sarcomere
-nebulin
--protein that dictates the length of the actin filaments

5

thin filaments

actin
troponin
tropomyosin

6

thick filaments

myosin, which includes heavy and light chains

7

myofibril
-what is it?
-functional unit

bundle of myofilaments
functional unit
-sarcomere

8

sarcomere
-composition
-identifiable features

each sarcomere contains multiple thick and thin filaments
identifiable features
-Z-disk/line
-M-line
-I-band
-H-zone
-A-band

9

Z-disc/line

edges of the sarcomere

10

M-line

center "anchor" of the sarcomere

11

I-band

area where only actin filaments are present (no overlap with myosin)

12

H-zone

area where only myosin filaments are present (no overlap with actin)

13

A-band

area that spans the length of myosin filaments (includes areas of myosin and actin overlap)

14

muscle cell/fiber
-what is it
composition

bundle of myofibrils
composition
-sarcolemma
-satellite cells
-sarcoplasm
-transverse tubules
-sarcoplasmic reticulum
-terminal cisternae
-mitochondria
-nuclei
-myostatin
-dystrophin

15

sarcolemma
-what is it?

cell membrane

16

satellite cells
-function

regulate growth & adaptation

17

sarcoplasm
-what is it?
-contains

fluid part
contains
-ATP-CrP
-glycogen
-fats
-mitochondria

18

Transverse tubules (t-tubules)
-function

propagate action potentials inward from sarcolemma to myofibrils

19

sarcoplasmic reticulum
-location
-function

SR
network of longitudinal tubules that surround myofibrils for Ca2+ storage and release

20

terminal cisternae
-function

enlarged portion of SR for Ca2+ storage and release

21

mitochondria
-function

aerobic factories that produce ATP

22

nuclei
-function

control centers for the muscle fiber

23

myostatin
-function

negatively regulates muscle growth

24

dystrophin
-function

links cytoskeleton of muscle fiber to the extracellular matrix

25

contractile fibers within a skeletal muscle
-known as
-innervated by

known as extrafusal muscle fibers
innervated by alpha motor neurons

26

fascicle
-what is it?

bundle of muscle fibers

27

whole muscle
-what is it?

bundle of fascicles

28

connective tissues
-types (deep to superficial)
-what does each tissue type do?

types
-endomysium (surrounds fibers)
-perimysium (surrounds fascicles)
-epimysium (surrounds whole muscle)
function
-each tissue type connects to form bundles that ultimately fuse into the tendon

29

pennation
-what is it?
-types

the "architecture" of a muscle
types
-parallel
-pennate

30

parallel
-characteristics
-types

characteristics
-long fibers arranged parallel along the length of a muscle to produce large ranges of motion
types
-flat
-fusiform
-strap
-radiate
-sphincter

31

pennate
-characteristics
-types

characteristics
-fibers arranged obliquely to the central tendon to maximize cross-sectional area and force
types
-unipennate
-bipennate
-multipennate

32

fiber types (speed)

Type IIx (fast glycolytic)
Type IIa (fast oxidative glycolytic)
Type I (slow oxidative)
-all of the muscle fibers have the same stuff, just in different amounts
-there is shifting between Type IIx and Type IIa
-lower extremity and larger muscles have more Type II

33

Type IIx
-anatomical properties

-little myoglobin, mitochondria, and blood capillaries
-a lot of glycogen and
CrP in sarcoplasm
-fast form of myosin ATPase enzyme

34

Type IIx
-physiological/functional properties

-can anaerobically generate and hydrolize ATP at a high rate
-fatigue easily
-speed of contraction in 5-6x faster than Type I fibers
-contraction force is much higher than Type I fibers
-great for speed/power activities

35

Type IIa
-anatomical properties

-moderate amounts of myoglobin, mitochondria, and blood capillaries
-a lot of glycogen and CrP in sarcoplasm
-fast form of myosin ATPase enzyme

36

Type IIa
-physiological/functional properties

-decent capacity for generating ATP via anaerobic AND aerobic metabolism, therefore these fibers can hydrolyze ATP at a high rate (slower than Type IIx, but still fast)
-faster contraction velocity than Type I, but slower than Type IIx
-higher contraction force than Type I, bull tell than IIx
-more resistant to fatigue than Type IIx, but less resistant than Type I
-good compromise for all activities

37

Type I
-anatomical properties

-a LOT of myoglobin, mitochondria, and blood capillaries
-slow form of myosin ATPase enzyme

38

Type I
-physiological/functional properties

-can aerobically generate loads of ATP, but at a slow rate
-most resistant to fatigue
-slowest contraction velocity
-lowest contraction force
-great for endurance activities

39

muscle receptor types

muscle spindles
Golgi Tendon Organs (GTOs)

40

muscle spindles
-function
-knows as
-rapid lengthening of whole muscle...

function
-provide feedback on muscle length and rateof change in length to the CNS
known as
-intrafusal muscle fibers, which are innervated by gamma motor neurons
rapid lengthening of whole muscle (feedback sent to CNA) elicits the "stretch (myostatic) reflex" (response)

41

stretch reflex

-lengthening of the intrafusal fibers (muscle spinles) stimulate Ia efferent (sensory) neurons
-sensory feedback is received in the CNS and inhibits a-motor neuron for the antagonist muscle (reciprocal inhibition)
-motor feedback from A-motor neuron stimulates extrafusal muscle fiber contraction in the agonist muscle

42

muscle spindle note

gamma-motor neurons regulate the sensitivity of the muscle spindle by stimulating the intrafusal fibers to contract, thereby shortening the spindle
consequently, only a small stretch is required to activate the stretch reflex

43

Golgi Tendon Organs (GTO's)
-function
-location

function
-provide feedback on muscle tension and rate of change in tension to the CNS
location
-located in tendinous connective tissue at ends of skeletal muscle

44

autogenic inhibition reflex
-what is it?

response elicited by tension placed on several motor units within a muscle (feedback sent to CNS)

45

autogenic inhibition reflex
-process

-deformation of 10-20 motor units (due to tension) within the GTO stimulates 1b afferent (sensory) neurons
-sensory feedback is received in the CNS and inhibits a-motor neuron for the agonist muscle and excites a-motor neuron for the antagonist muscle (reciprocal excitation)
-inhibited motor feedback from A-motor neuron for agonist muscle inhibits or reduces extrafusal muscle fiber contraction

46

autogenic inhibition and reciprocal excitation function

play critical roles in the timing of muscle activation during locomotion

47

two processes of skeletal muscle contraction

excitation-contraction coupling
sliding filament theory

48

excitation-contraction coupling steps

1. nervous stimulus in the form of an action potential (AP) is delivered to muscle via a-motor neuron
2. at the neuromuscular junction, acetlycholine (Ach) is released from the pre-synaptic membrane of the a-motor neuron into the synaptic cleft
3. Ach binds to nicotinic receptors on the post-synaptic membrane of the muscle fiber
4. an AP is generated across the sarcolemma of the muscle fiber and down the T tubules
5. the AP activates DHP receptors, which transmit electrical signal through triadic feet to ryanodine receptors located in the SR
6. ryanodine receptors signal CA2+ release from the SR into the muscle sarcoplasm

49

Sliding filament theory steps

1. Ca2+ binds to troponin, pushing tropomyosin off from active binding sites on actin
2. myosin heads bind to actin at a 45 degree angle
3. ATP binds to myosin heads causing myosin to dissociate from actin
4. ATP is hydrolyzed into ADP and Pi by myosin ATPase, which cocks the myosin heads
5. myosin binds weakly to actin again, this time at 90 degrees
6. Pi is released from myosin heads, which initiates the power stroke
7. myosin ehads rotate back to a 45 degree position relative to actin, dragging actin closer to the M-line
8. ADP is released after the power stroke and myosin remains bound to actin
9. repeat... the resultant ratcheting movement of myosin head and repeated coupling and uncoupling with actin produces muscle shortening/lengthening under tension

50

what happens when muscular contraction is no longer desires?

Ca2+ is resequestered into the SR, tropomyosin covers binding sites and actin slides back to original resting position

51

types of muscle contraction

isotonic
isometric
isokinetic

52

isotonic
-what happens
-types of isotonic contractions

muscle produces force while moving at any velocity
types
-concentric
-eccentric

53

concentric

muscle produces force while shortening

54

eccentric

muscle produces force while lengthening

55

isometric

muscle produces force statically

56

isokinetic

muscle produces maximal force at a fixed velocity

57

motor unit
-what is it?
-types of movement
-what dictates muscle fiber type?

an a-motor neuron and all the muscle fibers it innervates
types
-gross: single neuron innervating several fibers
-fine; single neuron innervating a few fibers
motor neuron dictates muscle fiber type

58

three strategies for neuromuscular recruitment

All or None Principle
Size Principle
rate coding

59

All or None Principle
-what is the principle?
-application

when a motor unit is recruited, all innervated fibers contract to their full potential
application
-when few motor units are recruited little force is produced
-when lots of motor units are recruited lots of force is produced

60

size principle
-what is it?
-application

low threshold motor units recruited first and higher threshold motor units are recruited as more force is needed
application
-Type I motor units are easier to recruit, so they are recruited first
-Type II motor units are recruited later

61

rate coding
-what is it?
-types of stimulus

a motor unit can exert varying levels of force dependent on the frequency at which it is stimulated
types
-single stimulus = twitch (little force)
-repeated, rapid stimuli = summation (more force)
-continued stimulation = tetanus (max force)

62

additional factors that influence muscle force output

fiber cross-sectional area (CSA)
muscle pennation
muscle receptor sensitivity & feedback
velocity of muscle contraction
muscle length
muscle elasticity
type of muscle action
concurrent-activation potentiation (CAP)
post-activation potentiation (PAP)

63

velocity of muscle contraction
-faster means...
-note

the fast a muscle fiber contracts, the less force it can produce

64

muscle length
-sarcomere too short
-ideal sarcomere length
-note

when the sarcomere is too short or too long, the number of actin-myosin cross-bridges decreases, so force output is limited
the ideal sarcomere length maximizes the number of actin-myosin cross-bridges for maximum force output
note
-the effective use of levers and body position can overcome deficiencies in sarcomere length to maximize practical force output

65

muscle elasticity

there is an elastic component of force output that can be augmented when a muscle is stretched (like a rubber band)

66

type of muscle action
-concentric
-isometric
-eccentric
-note

concentric is typically the weakest due to dynamic cross-bridging and actin-myosin overlap at shorter muscle lengths
isometric action can produce more force than concentric action probably because of static cross-bridges
eccentric (strongest) action can produce the most force because of the additional contribution of stored elastic energy
note
-eccentric action followed immediately by concentric action can induce what's knows as the Stretch Shortening Cycle

67

concurrent-activation potentiation (CAP)

remote voluntary contractions (RVC) or the H-reflex may induce a MOTOR OVERFLOW that excites target motor units, which in turn increases force output
-grit your teeth when lifting a heavy weight

68

post-activation potentiation (PAP)

30-sec to a few minutes after a high intensity muscle contraction, the activated motor units may be more easily excitable and, therefore, more easily recruited for greater force production