Ch 10-Muscles

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functions of skeletal muscle

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1

functions of skeletal muscle

body movement maintenance of posture protection and support-sphincter muscle regulating elimination of materials heat production-AP used

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2

characteristics of skeletal muscle

excitability conductivity contractility elasticity extensibility

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3

excitability

ability to respond to stimuli by changing membrane potential

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4

Condutivity

sending and electrical charge down the length of the plasma membrane

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5

Contractiility

proteins slide against one another-

muscle cells cause body movement

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6

Extensibility

ability to be stretched and lengthened

proteins slide and reduce overlap

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7

Elasticity

ability of cell to return to original length after shortened or lengthened

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8

what is elasticity dependent upon?

extensibility and contractiility

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9

why is skeletal muscle considered an organ?

many tissue types

CT, bv, nerves, muscle fibers

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10

fasicle

bundle of muscle fibers

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11

how many fascicles in muscle?

many

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12

muscle fibers

muscle cells

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13

Layers of skeletal muscle

epimysium perimysium endomysium

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14

epimysium

surrounds entire muscle

DENSE IRREG

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15

perimysium

surrounds fascicles bv and nerves

DENSE IRREG

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16

Endomysium

surrounds each muscle fiber insulation, support, binds neighboring cells

AREOLAR

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17

tendon

Connects muscle to bone

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18

common properties of tendons and aponeurosis

attachments of muscle to muscle, skin, bone

made from fibers of epi, peri, endo collective fibers

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19

what type of tissue is in tendons?

dense regular

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20

Aponeurosis

strong sheet of tissue that acts as a tendon to attach muscles to bone

btw frontal and occipital head

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21

what type of tissue is in aponeurosis?

dense irregular

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22

deep fascia

superficial to epimyisum

separates individual muscles, binds muscles with similar functions

bv, nerves, lymph

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23

what type of tissue is deep fasica made of?

dense irregular

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24

superficial fascia

separates muscle from skin

superficial to deep fascia

BARRIER

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25

what type of tissue is superficial fascia made of?

areolar/adipose

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26

blood vessel/nerve properties of skeletal muscle

vasculairzed-removes wastes, delivers oxygen

innervated by somatic neurons-voluntarily control of muscle

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27

sacroplasm

cytoplasm of a muscle cell

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28

what does the sarcoplasm contain?

organelles and cytosol

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29

how are muscle cells multinucleated?

myoblasts fuse together

some become satellite cells-support/repair

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30

sacrolemma

plasma membrane of a muscle cell

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31

T-tubules (transverse tubules)

deep invaginations of the plasma membrane

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32

channels in T-tuble and sacrolemma

VGC allow for electrical signals

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33

voltage sensitive calcium channels

responsive to the electrical signals (action potentials)

IN SARCOLEMMA

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34

myofibrils

bundles of myofilaments enclosed in sarcoplasmic reticulum

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35

How many myofibrils are in each muscle fiber?

100s-1000s

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36

sacroplasmic reticulum

internal membrane complex similar to smooth ER

contains Ca pumps/calcium release channels

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37

terminal cisternae

blind sacs of sarcoplasmic reticulum serve as reservoirs for Ca ions

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38

triad

two terminal cisternae and a T tubule

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39

calcium release channels

Triggered by electrical signal traveling down T-tubule

calcium released into sarcoplasm

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40

myofilaments

contractile proteins

thick/thin

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41

thick filaments

myosin

heads point towards end of filament

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42

thin filaments

actin, troponin, tropomyosin

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43

troponin

globular protein, Ca binding site, pulls tropomyosin off

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44

tropomyosin

covers myosin binding sites on the actin molecules

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45

f actin

G actins polymerized into a double helix

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46

g actin

myosin binding site

monomer of f actin

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47

sacromeres

myofilaments are organized into repeating functional units

thick/thin filaments

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48

z lines

The ends of the sacromeres that cause contractions of a muscle

ANCHOR FOR THIN FILAMENTS

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49

I bands

light bands

thin filaments b

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50

what are the I bands bisected by?

Z discs

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51

A band

dark area

thick filaments, some thin contains H zone and M line

CENTER OF SACROMERE

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52

H zone

Central region of A-band thick filaments

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53

M line

middle of H band

attachment site for thick filaments

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54

What anchors the thin filaments?

Z disc

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55

What anchors thick filaments together?

M line

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56

connectin

Extends from Z disc to M line

Stabilizes thick filaments

"springlike" properties (passive tension)

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57

dystrophin

Anchors some myofibrils to sarcolemma proteins Abnormalities of this protein cause muscular dystrophy

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58

Duchenne Muscular Dystrophy (DMD)

defective/insufficient dystrophin

sarcolemma damaged during contraction -ca enters cell, damage

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59

what age do most patients with DMD survive to?

30

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60

myoglobin

stores oxygen in muscle cells for ATP production

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61

where is glucose stored

liver and skeletal muscle

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62

creatine phosphate

phosphate from creatine phosphate can be removed and attached to an ADP to generate ATP quickly.

10-15 sec of energy

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63

catalyst in creatine phosphate

creatine kinase

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64

motor unit

A motor neuron and all of the muscle fibers it innervates

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65

small motor units

less than five muscle fibers -allow for precise control of force output

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66

large motor units

thousands of muscle fibers -allow for production of large amount of force but not precise control

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67

location of fibers of motor unit

dispersed throughout muscle

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68

synaptic knob

rounded areas on the end of the axon terminals

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69

synaptic vesicles

saclike structures found inside the synaptic knob containing AcH

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70

channels in synaptic knob

ca pumps, VGC Ca

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71

motor end plate

specialized part of a muscle fiber membrane at a neuromuscular junction

many AcH receptors

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72

synaptic cleft

separates knob from motor end plate

Acetylorichase resides here

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73

actetylcholinesterase

an enzyme that breaks down acetylcholine

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74

neuromuscular junction

Location where motor neuron innervates muscle

Has synaptic knob, synaptic cleft, motor end plate

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75

resting membrane potential skeletal muscle

-90mV

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76

Calcium entry at synaptic knob

•Nerve signal travels down axon, opens voltage-gated Ca2+ channels •Ca2+ diffuses into synaptic knob •Ca2+ binds to proteins on surface of synaptic vesicles

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77

Release of ACh from synaptic knob

-vesicles merge with cell membrane at synaptic knob: exocytosis -thousands of ACh molecules released from about 300 vesicles

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78

excitation-contraction coupling

sequence of events from motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's sarcomeres

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79

end plate potential (EPP)

  1. ach receptors open when Ach binds to them

  2. Na diffuses into cell, little K out

  3. EPP is local but is graded potential

  4. opens VGC

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80

How does EPP reach threshold?

by causing nearby voltage-gated Na+ channels to open

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81

depolarization of skeletal muscle

30 mV

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82

the release of Ca from the sarcoplasmic reticulum

Ca interacts with myofilaments triggering contraction

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83

crossbridge cycle

crossbridge formation: binding of myosin to myosin binding site and actin to actin binding site

power stroke: myosin pulls on actin, ADP and Pi released

release of myosin head: ATP binds to myosin head causing its release from actin

reset myosin head: ATP split ADP and Pi, cocks myosin head

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84

what is needed for crossbridge cycling?

Ca and ATP

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85

steps of cross bridge cycle

  1. cross bridge formation

  2. power stroke

  3. cross bridge detachment

  4. cocking of myosin head

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86

cross bridge formation

myosin heads attach to the active site on actin

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87

power stroke

action of myosin pulling actin inward (toward the M line)

ADP and P1 released

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88

what happens when ADP is released in crossbridge?

moves actin to m line

POWERSTROKE

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89

what happens when phosphate is released in crossbridge?

bonds get stronger

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90

cross bridge detachment

ATP attaches to myosin head, causing cross bridge to detach

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91

cocking of myosin head

As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high-energy, or "cocked" position

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92

hydrolize

break down (a compound) by chemical reaction with water.

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93

muscle relaxation

AP ends, electrical stimulation of SR stops

Ca2+ pumped back into SR Stored until next AP arrives Requires ATP

Without Ca2+, troponin and tropomyosin return to resting conformation Covers myosin-binding site Prevents actin-myosin cross-bridging

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94

storage of ATP in muscle cells

little

spent after 5 seconds of exertion

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95

myokinase

transfers Pi from one ADP to another, converting the latter to ATP

makes additional ATP rapidly

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96

Ways to generate ATP in skeletal muscle fiber

-Immediate supply via phosphate transfer -Short-term supply via glycolysis -Long-term supply via aerobic cellular respiration

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97

Glycolysis

NO OXYGEN NEEDED

breaks glucose into pyruvate in cytosol

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98

aerobic cellular respiration

REQUIRES OXYGEN

pyruvate oxidaized to CO2-NADH FADH

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99

How much ATP does glycolysis produce?

net gain of 2 ATP

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100

How much ATP does cellular respiration generate?

30

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