Skeletal Muscle

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created 6 years ago by hoovemaa
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Intro to the skeletal muscular system
Grade levels:
College: Second year, College: Third year
Subjects:
human anatomy
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1

3 types of muscle

skeletal, cardiac, smooth

2

skeletal

striated, voluntary

3

cardiac

straiated, involuntary

4

smooth

nonstriated, involuntary

5

contractibility

ability of a muscle to shorten

6

excitability

ability to respond to stimulus

7

how a muscle is "excited"

stimulus from neuron "excites" the muscle cell, causing contraction

8

how do contractions fire

all or none, they contract as hard as they can or not at all

9

motor unit

1 motor neuron and the muscle fiber/cell that it innervates

10

extensibility

ability of a muscle to be stretched

11

elasticity

ability of a muscle to return to its resting state

12

functions of muscle (4)

movement
opening and closing passageways
maintain posture and stabilize joints
heat generation

13

what surrounds the skeletal fibers/clls and muscles themselves?

sheaths of cartilaganous tissue

14

epimysium

surrounds the entire muscle

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perimysium

surrounds fasicles (bundles of fibers)

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endomysium

surrounds individual fibers

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perimysium, epimysium, and endomysium converge..

to form the tendon of the muscle

18

where does skeletal muscle cross?

movable joints

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origin

attachment of the muscle on the less movable bone

20

insertion

attachment of the muscle on the more movable bone

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what happens upon contraction?

insertion is pulled toward the origin

22

prefixes for "muscle" (3)

myo
mys
sarco

23

fibers are...

long cylindrical cells

24

why are muscle striated?

due to myofibril or contractile organelles

25

myofibril contain what?

myofilaments
aka specialize contractile proteins

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myofibril structure

composed of sarcomere
aka one unit of contraction

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z lines

boundaries at each end of sarcomere

28

thin filament/actin

myofibrils attach to z lines

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thick filament/myosin

myofibrils in the center of the sarcomeres
ends have myosin heads

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titin

springlike moleule that resists over stretching

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A-bands

dark bands from the presence of thick filament

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H-zone/band

central part of A-bands
no thin filament present

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M line

contains rods that hold thick filaments together

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I band

light bands because they contain only thin filament

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3 types of contractions

isometric
concentric
eccentric

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isometric contraction

muscle contracts but does not shorten

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concentric contraction

muscle shortens and does work
angle between origin and insertion is decrease

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eccentric contraction

muscle generates force as it lengthens
angle between origin and insertion increases
utilized in many movements when resisting gravity, muscle acts as brakes against gravity

39

sliding filament theory/mechanism

accepted theory for how concentric contractions occur
chemicals are needed to perform contractions

40

ATP

energy for muscles

41

calcium for muscles

alows actin and myosin to slide over each other

42

oxygen (o2)

allows for cell respiration for ATP production

43

acetylcholine

neurotransmitter for muscles

44

prcoess for acetylcholine

leaves the neauron and enters the spac between neuron and muscle fiber at neuromuscular junction
the stimulus causes calcium to be release from sarcoplasmic reticulum

45

sliding filament theory steps

1. troponin molecules hold the actin and myosin in place
2. nerve impulse reaches a muscle neuron causing the release of acetylcholine into the space between neuron and muscle fiber
3. acetylcholine stimulates receptors on muscle fiber which initiates impulse that travels along sarcolemma to the SR
4. calcium is released from the SR into the sarcoplasma
5. Ca binds with troponin in the actin causing moleules in the actin to shift and slide past myosin
6. ATP is broken down to relase energy which helps actin slide past myosin, shortening the muscle, causing contraction
7. Ca unbinds from troponin
8. myosin and actin slide apart and muscle relaxes

46

O2 debt

O2 is used to produce ATP in muscle fiber
ATP is used during muscle contraction so lots of O2 is neede
the more the muscle is the contracting the more O2 is needd
If O2 cannot be suplied fast enough the individual suffers from shortness of breath, this is O2 debt

47

prime mover

muscle that does most of the work

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synergist

assisting muscle in a movement

49

antagonist

muscle working in opposite direction of movement

50

muscle contract at different times, why?

to keep the movement smooth

51

how does strength of muscle contraction increase?

each muscle fiber contracts more often
or
more muscle fibers (not all) contract at the same time

52

tetany

a maximal sustain contraction
tension of msucle adds up until maximal contraction is sustained
if the muscle is not allowed to rest fatigue sets in due to no more available ATP

53

myosthenia gravis

autoimmune disease, affects eyelids, face, neck, and extremities
treated with immunosuppresants and muscle strengtheners

54

muscular dystrophy

progressive degeneration and weakening of muscles
as muscle fibers die fat and CT take their place

55

fibromyalgia

unexplainable chronic muscle pain
treatment-antidepressants, exercies, pain relievers