Unit 3- Muscular System

Skeletal: Where

mostly attracted to bone

Skeletal: Responds to

signals from somatic lower motor neurons

Skeletal: twitch speed

10-100 ms

Skeletal: appearence

long, striated, multinucleate

Smooth: where

around tubes + hallow organs

Smooth: responds to

ANS, hormones, local environment, stretched, inartistic

Smooth: twitch speed

4000-6000 ms or 4-6 seconds

Smooth: apearence

layered, small, non-striated, spindle-shaped

Cardiac: where

heart

Cardiac: responds to

intrinstic but influenced by ANS+ hormones

Cardiac: twitch speed

200-250 variable

Cardiac: appearence

striated, branched, interconnected

Antagonist

used to stabilize joint in movement

-allows to bend successfully to bend ligaments

Tendon

-attaches to membrane on surface of bone

-made of dense fibrous connective tissue

-lots of collagen

-works slowly

Fassicle

bundle of individual muscle fibers, each fiber is separate muscle cells

Motor Neuron 1

lower motor neuron and all the muscle fibers it controls

Small Muscle: about 10 fibers (eye)

-give you precise movements

Large Muscle: thousands at a time (quads)

-give you large movements

Contaction Mechanism

1) AP is lower motor neuron

2) release of ACh

3) Ach binds to NachR on muscle cell

4)Depolarizatio of muscle cells

5) triggers VG Na+ K+ channels

-muscle AP

6) muscle action propogated down t-tube

7) DHP receptor “twist” in response to AP

8) DHP pulls open RyR

9) CA2+ comes out through RyR 

-some holds RyR open

10) Ca2+ in sacroplasm gets into myofibrils, removing block and allowing contraction

DHP Receptor

nonfunctional VG CA+ channel

Ryanodine Receptor

(RyR)

CA2+-gated CA2+ channel

golgi- tendon organs

signal to CNS when tendon has too much stress

Miofibril

a structural unit of a muscle fiber composed of repeating sarcomeres.

sarcoplasmic reticulum

calcium pumped in and stays till needed —> myofibril

t-tubles

holes in membrane come next to sacroplasmic reticulum, allowing for rapid transmission of action potentials.

terminal cisterna

swelling at end of sarcoplasmic reticulum

myosin fibers

producers of force

CA fibers

how long the twitch can carry on

Oxidative Muscle Fibers

aerobic metabolism

-smaller , weaker

-requires 02

-lots of mitochondria + myoglobin 

-oxidative metabolism produces lots of ATP per glucose

-slow to fatigue

Mitochondria

organelle that have right structures and enzymes to do aerobic metabolism

Myoblobin

oxygen storage + transport protein 

-bright red

Glycolytic Muscle Fibers

anerobic metabolism

-no 02 needed

-few mitochondria and myoblobin

glycolytic metabolism is simpler and faster but generates less ATP

-fatigue quickly

larger much stronger

Oxidative Slow

weaker, slower,

very efficient

very fatigue resistant

slow to target

Type I (1)

Oxidative Fast

stronger, faster

fatigue resistant

weak to moderate

Type IIa (2A)

Glycolytic Fast

very strong and fast

fatigue quickly

Type IIX (2X)

Motor Unit Usage

ALL MUSCLES CONTAIN ALL 3 TYPES

motor units can use multiple types

-starts with 1

(not enough)

-add in IIA

(weight is very heavy)

-IIX

ATP breakdown

ATP—→ gets lots of energy when it is turned into ADP+ Pi

Glucose starting Equation

Glucose + 602—> 6CO2+ 6H20 + energy

GM- 1) Glycolysis

input- 1 glucose

useful output- 2 pyruvate'

waste- nothing

ATP- 2

NADH- 2

FADH2- nothing

GM- 2) Pyruvate Oxidation

input- 2 pyruvate

useful output- 2 acetylcholine

waste- 2 CO2

ATP- nothing

NADH- 2

FADH2- nothing

GM- 3) Krebs Cycle

Input- 2 achytocholine

useful output- nothing

waste- 4 CO2

ATP- 2

NADH- 6

FADH2- 2

GM- 4) Oxidative Phosphorolation

input- 6 02

useful output- nothing

waste- 6 H20

ATP- 28

NADH- -10

FADH2- -2

Lactic Acid Fermentation

at the end of the glycolysis stage, there are 2 pyruvate left

glycolysis can happen with no oxygen making 2 lactic acids

Glucose End Product

1 glucose + 602—> 6Co2+6H 20 +32

asynchronous recruitment

a pattern of motor unit activation where some units are activated while others are still at rest, allowing better force output and sustainment

-take turns twitching

Summation

one twitch adding to another

tetanus/tetonic contraction

sustained force overtime

Fused Tetinous

muscle contractions are as hard and as fast as they can be

always calcium present, myosin can have continuous contractive cycles

Unfused Tetanus

enough summation to hold force overtime with little relaxation between contractions

tetanus

enough summation to hold force overtime

optimum

the highest point in the length-tension relationship where there is the most generated force and the longest sarcomere length

Different Muscles

soleus- 80% type 1

quadracepts- 50% type 1

obicularis oculi- 15% type 1

Muscle Adaptation

muscles can evolve to add/ get rid of miochondria/ myofibrils

shifts to what the muscles are being used for

Phosphocreatine

allows rapid regeneration of ATP in short term (stores power)

-used to generate ATP quickly

muscle contains 8 twitches if we run out we use phosphocreatine

ATP Processing

phosphocreatine is used to generate ATP quickly, if you need more ATP, use glucose, take glucose and break it up, there is anaerobic or aerobic

Fatty Acids too make even more ATP but its a slow process

Muscles at Rest

if you have more ATP than needed can bring in creatine

can transfer a phosphate to creatine making ADP and phosphocreatine (lots of phosphate)

Muscle in Use

when muscle is in use gets lots of ADP from ATP breakdown—> ADP + phosphocreatine = transfer of phosphate to make ATP and phosphocreatine in plain creatine

enzyme creatine kinase

breaks down creatine phosphocreatine

Glucose Metabolism

extracted energy from glucose

we use energy to pump protons into inter membrane

allow protons to leave space through ATP synthase

we use movement of protons to put ADP and Pi to make ATP

ATP Number Breakdown

1 NADH- 2.4 ATP
1 FADH 2- 1.5 ATP

10 NADH x 2.5 ATP

2 FADH x 1.5 = 3 ATP

=28 ATP

Myosin

the thick filaments (A band)

-contains the protein titin

-200-300 myofibrils thick

-contains actin-binding region and ATPase binding site

Actin

the thin filaments (I band)

-twisted double helix

-each indiv. bead is an actin protein

-held on by tropomyosin with troponin

-held by nebulin

Sliding Filament Theory

bundles of protein filaments are sliding ontop of eachother is contraction

actin and myosin interact to produce muscle contraction.

Titin

shock absorber

acts as spring

Thin Filaments

that are primarily composed of actin and play a critical role in muscle contraction.

Thick Filaments

composed mainly of myosin and interact with thin filaments during muscle contraction.

sarcomere

distance of one z-disk to next

ATP

Adenosine Triphosphate

ADP

Adenosine Diphosphate

Pi

inorganic Phosphate

Contractile Cyle: 1

Rigor- myosin head bent back, bound to actin

ATPase entry

Contractile Cycle: 2

-ATP binds to myosin head

-causes release of myosin head(POP!)

-releases from Actin

Contractile Cycle: 3

hydrolysis ATP→ADP +P i

-energy is transffered to myosin head

both remain in ATPase

Contractile Cycle: 4

-uses energy it got from ATP to stretch out

-myosin head moves to extended position

-the muscle can wait at stage 4 until tropomyosin gets out of the way-blocked until ready to work

PS- Contractile Cycle: 5a

the myosin head grabs onto the actin filament and the phosphate is still attached

PS- Contractile Cycle: 5b

the myosin head comes off and the Pi (inorganic phosphate) comes off

PS- Contractile Cycle: 5c

the myosin head bends back (to vertical positon)

PS- Contractile Cycle: 5d

-the myosin head binds back to actin

-ATPase is empty

back to Rigor

Interrupting the Contractile Cycle

between step 4 and 5a, if tropomyosin is blocking, can’t bind—> once tropomyosin is out of the way can grab and continue contraction

Troponin

a protein that bocks myosin binding site

-troponin moves tropomyosin, exposing myosin binding sites on actin

-binding spot where Ca2 can bind

Actin Protein

has actin binding

myosin binding site outside chain

Nebulin

act as a core

holding the double helix straight

Excitation

having electrical potential

-electrical excitement of muscle fibers

Contracted

A- bands stay same

H- band disappears

I- band shrinks

Power Stroke

5a-5d

Action Potential

period of contraction but then tropomyosin binds and relaxation

Fast Twitch

-10 ms

-fast myosin ATPases and fast calcium ATPase

-myosin hydrolyzes ATP quickly

Slow Twitch

100 ms

-slow myosin ATPase and slow calcium ATPase

Fatty Acid

hydrocarbon chain with carboxyl group

8c Saturated Fatty Acid chain

Fatty Acid Metabolism Process

Beta-oxidation—> break off last 2 carbons in chain

becomes Acyl-unit

1 NADH+—→ NADH

1 FADH —→ FADH2

—→ Acetyl-CoA cycle

3 NAD+ —→ 3 NADH

1 FAD —→ 1 FADH2

& 1 ATP

Krebs Cycle

4 NADH x2.5= 10

2 FADH2 ×1.5= 3

+1 ATP

=14 ATP

Last 10 ATP without breakage

Krebs Cycle-

3 NADH—> 7.5 ATP
1 FADH2—> 1.5 ATP
1 GTP—> 1 ATP

=10 ATP

the end product

Fatty Acid- How many 2c pieces do you get?

1) ex. 18c =9c pieces

2) All but one give you 14 ATP

8×14= 112 ATP

3) last one give you 10

+10= 122 ATP

4) subtract 2 (# to start reaction) 122-2=120 ATP

Example of ATP use

hour and a half walk

-starts with aerobic glucose metabolism (30 min)

-in hour fatty acid metabolism kicks in

sustained lower impact exercise burns fatty acids

Smooth Muscle

-not striated

-contacts in all directions

-stretches without loosing strength

-can contract further

-musch stronger twitch

-can enter into latch-state

Types of Smooth Muscle

single unit and multi-unit

Single Unit

-connected with gap junctions

-has varicosities causes to trigger doc and release action potential

Multi-Unit

each cell contracts independently

produces contractions of varying amounts

-in between neurons to contract muscles more or less

MLCK

turns myosin on

enzyme is most involved in starting smooth muscle contraction

Myosin-Light Chain Kinase

Phosphotatse

turns myosin off