Muscle 1

Front 1

Myosin and Thick Filaments

Back 1

3 thick filaments have a 3D structure, within myosin molecules arrayed around the circumference of the thick filament

Front 2

Myosin Structure

Back 2

Long tail, 2 heads, all tails point towards center

Front 3

Even though each myosin has 2 heads, at any one time only one head can be bound and form a .....

Back 3

cross bridge

Front 4

Each Myosin Head has two binding sites:

Back 4

1 Actin Binding Site

1 ATP Binding Site: power the movement of myosin
(power the cross bridge cycle)

Front 5

The head of Myosin acts like a...

Back 5

ratchet.

binds to actin, then changes confirmation and slides the thin filaments towards center of sarcomere

Front 6

3 Proteins of a Thin Filament

Back 6

Globular-Actin: "twisted pearl strand"
chains of actin molecules twisted
into helices

Actin covered by:
Tropomyosin: regulatory protein
blocks myosin binding site on actin

Attached to tropomyosin:
Troponin: regulatory protein
a: troponin t - portin bound to tropomyosin
b: troponin c - portion of troponin that will bind to calcium

Front 7

Three subunits of Troponin

Back 7

TnT: portion bound to tropomyosin

TnC: portion that will bind to calcium

TnI:

Front 8

What happens to a thin filament in the absence of calcium?

Back 8

tropomyosin blocks the myosin binding site on the actin, preventing cross bridge attachment

Front 9

When can't myosin bind to actin?

Back 9

When tropomyosin blocks the cross bridge binding site on actin in a relaxed skeletal muscle

Front 10

When will muscle contraction occur?

Back 10

When you get calcium ions inside the cell to bind to troponin

this complex then pulls tropomyosin away from the cross bridge binding site, allowing myosin to bind to actin

Front 11

Absence of calcium vs presence of calcium

Back 11

absence: no binding

presence: myosin binds to actin

Front 12

Where is calcium stored?

Back 12

sarcoplasmic reticulum


*form of smooth endoplasmic reticulum

Front 13

Sliding Filament Theory

Back 13

filaments slide past one another

thin towards center of sarcomere, no change in length

Front 14

Calcium enters, binds to troponin, opening the binding site


Myosin binds, changes its confirmation in ratchets, slides thin filaments towards the center

Back 14

X

Front 15

Force exerted by each myosin head

Distance moved

Back 15

10 pN

10nm

Front 16

What does ATP do in the cross bridge cycle?

Back 16

breaks bond between myosin and actin

resets myosin head to prepare for another cycle

provides energy for "power stroke:" movement of myosin

Front 17

Neuromuscular Junction

Back 17

Where the motor nerve innervates the muscle fiber


similar structure to a synaptic cleft

Front 18

Motor Units

Back 18

motor nerve plus all of the muscle fibers that it innervates

Front 19

Where would you want a small motor unit? How about a large?

Back 19

Small: Eyes, fine control

Large: Limbs

Front 20

Unlike a nerve synapse... at the Neuromuscular junction:

Back 20

An AP in the motor nerve causes an AP in the skeletal muscle

1:1

Front 21

Action Potential in the motor neuron cause ______ release into the neuromuscular junction

Back 21

Acetylcholine (Excitatory NT)


Muscle contraction follows the delivery of ACh to the muscle fiber

Front 22

T-Tubule

Back 22

conduct electrical depolarization of the sarcolemma into the muscle cell interior

*Associated with the sarcoplasmic reticulum

Front 23

As an AP travels along the t-tubule, it opens what kind of channel?

Back 23

change in voltage activates a voltage gated receptor known as a DPH receptor

Front 24

DPH receptor senses the t-tubule voltage and causes, open this receptor:

Back 24

ryanodine receptor (essentially a modified calcium channel) on the sarcoplasmic reticulum


calcium ions released into the cytosol bind to troponin

Front 25

Tension of a Single Muscle Fiber Depends On:

Back 25

1. Number of cross bridges
2. Length at time of stimulation
3. Frequency of stimulation

Front 26

Single Fiber Force Production

Back 26

"All or none" principle

Either contracted (active) or relaxed

Front 27

The larger the CSA activated...

Back 27

The more force you can produce

Front 28

Increase whole muscle force by:

Back 28

Activate more motor units

Front 29

What is force directly proportional to?

Back 29

Cross Sectional Area

Front 30

Whole Muscle Force Depends on:

Back 30

- Contraction Type
- Velocity
- Muscle Fiber Type
- Muscle Architecture

Front 31

4 Types of Skeletal Muscle Contraction

Back 31

- Isotonic
- Isometric
- Eccentric
-Concentric

Front 32

Are concentric contractions and eccentric contractions isotonic?

Back 32

NO!

Front 33

Why are isotonic contractions studied in a lab?

Back 33

Can't do in a moving joint.

As you move through a range of motion, the force your muscle has to produce changes

Isotonic means "Same Force"

Front 34

Isometric Contraction

Back 34

Constant length contraction

Front 35

Eccentric Contraction

Back 35

Occurs when a muscle is active but being lengthed

Front 36

Concentric Contraction

Back 36

Occurs when a muscle is active and shortens

Front 37

How does an Isotonic contraction happen?

Back 37

attach muscle to a lever, then attach it to a weight, stimulate muscle

weight has to be light enough for muscle to shorten

force increases then levels out

force levels out: contraction begins, muscle shortens

Force the same, length changes

Front 38

Describe an Isometric Contraction

Back 38

Length doesn't change

Muscles are active, contracting, producing force

Front 39

Muscle Fiber Types

(Forms of Myosin)

Back 39

Fast Glycolytic (FG)

Slow Oxidative (SO)

Fast Oxidative Glycolytic (FOG)

Front 40

Fast Glycolytic Fibers

Back 40

White meat on the turkey

Produce high forces

low numbers of mitochondria, myoglobin, and blood capillaries


rely upon glycolysis for ATP: lactic acid build up = rapid fatigue

Front 41

Slow Oxidative Fibers

Back 41

Dark Meat Fibers

produce low levels of force

highly vascularized

abundant mitochondria

oxidative phosphorylation: slow fatigue

Front 42

Fast Oxidative Glycolytic Fibers

Back 42

Intermediate between FG and SO fibers

produce more force than SO, but

Front 43

Slow twitch, Red, Type I Fibers

Back 43

Slow Oxidative

Front 44

Fast twitch, White, Type II FIbers

Back 44

Fast Glycolytic

Front 45

A muscle that holds a bone still during a particular action is called:

Back 45

a fixator

Front 46

A fascicle is bounded and defined by:

Back 46

the perimysium

Front 47

What are the properties muscle cells must have to carry out their function?

Back 47

extensibility
elasticity
contractility
conductivity

Front 48

ACh receptor are found in:

Back 48

junctional folds