12/4

• have your wp #1 out to be checked in.• Lecture on General muscles to

microscopic muscle• Building a muscle• HW: Quiz on muscle names & wp #2.

Finish coloring muscle sheets if not completed in class

B. Skeletal Muscle1. Attached to bones by tendons

2. Cells are multinucleate & large

a. Called muscle fibers due to long slender structure.

3. Striated – have visible banding of light and dark

4. Voluntary – subject to conscious control

5. Composition of skeletal muscle is: muscle fibers, connective tissue, blood vessels & nerves.

C. Smooth Muscle

1. Has no striations

2. Spindle-shaped cells

3. Single nucleus

4. Involuntary – no conscious control

5. Found mainly in the walls of hollow organs

a. Controls your pupil!

D. Cardiac Muscle

1. Shares features w/ skeletal & smooth

2. Has striations but smaller cells than skeletal

3. Usually has a single nucleus like smooth but can SOMETIMES have a double nucleus.

4. Involuntary like smooth muscle

5. Found only in the heart

Cardiac Muscle

1. The Organization of Skeletal Muscle.Skeletal muscle Fasicles (bundle of muscle

cells (fibers)) Muscle cells (aka: muscle

fibers) myofibril (a muscle cell organelle

composed of…) sarcomeres (units w/i the

myofibrils made of alternating…)

myofilaments (protein chains either THICK

(myosin) or THIN (actin)) Z lines (region of

separation between sarcomeres)

E. Microscopic Skeletal Muscle & Contractions

• NOTE: As we discuss muscle contractions, we are only going to discuss skeletal muscle contraction.

2. Micro-Anatomy of Skeletal Musclea.Myofibril

i. Bundles of myofilamentsii. Myofibrils are aligned to give distinct

bandsb. Sarcomere

i. Contractile unit of a muscle fiber

Figure 6.3b

c. Organization of the sarcomere

i. Thick filaments = myosin filaments

ii. Thin filaments = actin filaments

iii. Both composed of the protein

Figure 6.3c

d. Myosin filaments have cross-bridges

i. Myosin and actin layer and overlap w/ exception of H zone

ii. At rest, there is a H zone. When contracted this is closed Figure 6.3d

H

Go to Section:

Relaxed Muscle

Contracted Muscle

Z line Myosin Actin Z line

Sarcomore

Cross-bridges Z line

Movement of Actin FilamentActin

Binding sites

Cross-bridge

Myosin

Figure 36-8 Muscle Contraction

Section 36-2

Muscle model build

• Use the coloring sheets to help you figure out all of the parts. The coloring sheets should be colored, you can do this in conjunction of creating your model.

HW

• Quiz on muscle naming• Wp #2 on neuromuscular Junction &

Sliding filament model. Finish coloring muscle ws

12/8-9

• Have your wp #2 & coloring muscle / parts of muscle worksheet out- check answers with each other

• Quiz on muscle names• PPP on neuromuscular and sliding

filament• HW: WP #3-exercise & ws

Muscle controla. Skeletal muscles are directly connected to

the nervous system by neuromuscular junctions.i. Impulses from the nerve cell controls the

contractionsii. One nerve stimulates a few muscle cells

or hundreds

Pg 293

c. At the neuromuscular junction

i. The 2 cells never meet.

ii. The gap between them is a synaptic cleft

-filled with special interstitial fluid

Nerve Stimulus to Muscles

Figure 6.5b

d. When a muscle contracts…

i. Nerve releases acetylcholine (ACh)

ii. ACh diffuses across the synaptic cleft & meets the…

- sarcolemma: plasma membrane of the muscle cell.

iii. ACh causes sodium (Na+) to rush in and potassium (K+) to rush out of the muscle cell–BUT more Na+ gets in than K+ gets

out…

iv. This causes the muscle cell to change polarity passes the electrical current called Action Potential.

e. Once begun this can not stop and the current travels over the entire sarcolemma (like dominos)

i. the impulse moves & the muscle cell contracts

g. When the electrical pulse fires, the specialized sarcoplasmic reticulum (an organelle that covers the myofibril) releases calcium into the sarcomere.

i. Ca+ allows actin and myosin to interact and the cross-bridge is created.

h. The cell returns to a resting state when impulse ends

i. The sodium/potassium pump (active transport) restores original levels of Na & K and the calcium is reabsorbed by the specialized endoplasmic reticulum

• https://www.youtube.com/watch?v=7wM5_aUn2qs

The sliding filament modela. Myosin and Actin cause the muscle to

contract.b. Actin slides over the myosinc. Myosin forms a cross-bridge w/ actin. d. ATP changes the shape of the myosin cross-

bridge- this pulls the actin filament towards the

center of the sarcomere.-The crossbridge happens over and over until the contraction stops.

e. The distance between the Z line decreases & H zone is minimized.

• https://www.youtube.com/watch?v=Ct8AbZn_A8A

Actin pulledCross-bridge releases actic

Cross-bridge changes shape

Myosin returns to original

shape

Myosin forms cross-bridge

with actin

2

1

34

5

Cycle Diagram

Section 36-2

Draw this: cycle of muscle contraction (5 minutes)

actin

Rest of class & HW

• Fill in the neuromuscular table• Fill in the neuromuscular worksheet.• You may work in pairs of your choice.• HW: WP #3, table, FITB & color WS

12/10-11

• 1. Have your WP #3 out and neuromuscular junction ws

• 2. Presentation• 3. Fatigue activity• HW: Dissection Prep & activity if you do

not finish.

Contraction of a Skeletal Muscle

• Muscle fiber contraction is “all or none”• Within a skeletal muscle, not all fibers may

be stimulated during the same interval• Different combinations of muscle fiber

contractions may give differing responses• Graded responses – different degrees of

skeletal muscle shortening

Types of Graded Responses• Twitch

–Single, brief contraction–Not a normal muscle function

• Tetanus (summing of contractions)

& Unfused/incomplete tetanus–One contraction is immediately followed by

another w/o returning to a resting state–The effects are added

Types of Graded Responses

• Fused (complete) tetanus–No relaxation between contractions–The result is a sustained muscle contraction

Figure 6.9c–d

Muscle Response

• Muscle force depends upon the number of fibers stimulated

• More fibers = more power• Can contract until cells run out of energy

Energy for Muscle Contraction

• First- used stored ATP for energy–Only 4-6 seconds worth of ATP is stored by

muscles!• THEN other pathways must be utilized to

produce ATP

• SECOND- Direct phosphorylation– Muscle cells use creatine

phosphate (CP), a high-energy molecule

– CP transfers energy to ADP, to regenerate ATP

– CP supplies are exhausted in about 20 seconds

• THIRD- Aerobic Respiration– Occur in the mitochondria

WITH OXYGEN– Glucose is broken down

to carbon dioxide and water, releasing LOTS OF ATP

– This is kinda slow…

• FOURTH- Anaerobic glycolysis–breaks down glucose

without oxygen–Glucose is broken

down and produces only few ATP & converted to lactic acid

–Not efficient but fast• Lactic acid produces

muscle fatigueFigure 6.10c

Effects of Exercise on Muscle

• Results of increased muscle use– Increase in muscle size– Increase in muscle strength– Increase in muscle efficiency–Muscle becomes more fatigue resistant

Exercise & Muscles1. Use it or lose it!

a. Muscle will quickly waste away if it is not used!

2. Types of Exercise

a. Aerobic exercise- increase strength, flexibility, & resilience to fatigue.

i. Increase blood supply, individual cells create more mitochondria to convert food to ATP

3. Anaerobic- force more muscle cells to contract w/ as much force as possible.

a. Increases muscle size b/c individual muscle cells become larger by making more contractile filaments

b. The cells do not multiply!

http://www.youtube.com/watch?v=kg6dovLasMI

How big can I get? http://www.youtube.com/watch?v=dChhzNGHgnA

Muscle Tone• Some fibers are contracted even in a relaxed

muscle• Different fibers contract at different times to

provide muscle tone• The process of stimulating various fibers is

under involuntary control1. At any given time some muscle cells, in

each muscle, are contracting.2. Muscle tone is why when resting you can

still sit up.3. Sleeping is the only time your muscles are

completely relaxed.

Muscle Fatigue and Oxygen Debt

• When a muscle is fatigued, it is unable to contract

• The common reason for muscle fatigue is oxygen debt–Oxygen is required to get rid of accumulated

lactic acid• Increasing acidity (from lactic acid) and lack of

ATP causes the muscle to contract less

4. Muscle Fatigue: Muscles become fatigued when cells are unable to contract even if still being stimulated.

a. Without rest active muscles tire and contractions begin to weaken.

b. Can stop working altogether (collapse) which is thought to be due to oxygen depletion

Fatigue Activity!

• Follow the directions• Ask if you need help.• Finish in class today…if you run out of

time then finish for HW.• Unit test is last day before break• There will be jeopardy• HW: Dissection prep & finish the Lab…• Also I recommend watching crash course

muscles.

crash course muscular system

• http://www.youtube.com/watch?v=jqy0i1KXUO4