Lab #9 Effector Systems: Muscles Muscle Mechanisms Physiology

Front 1

Skeletal muscle
4

Back 1

• Striated
• Long, parallel fibers
• Several fused cells make multinucleated fibers
• Voluntary contraction

Front 2

2 skeletal muscle groups
How they work together

Back 2

1) Flexor = contracts and shortens
2) Extensor = relaxes and elongates

They work antagonistically, as one contracts the other relaxes

Front 3

Tendons
What?
Made of?
Extension of?

Back 3

• Connects skeletal muscle to bone
• Fibrous dense connective tissue
• Extension of the epimysium (facia) layer which wraps around the muscle

Front 4

Smooth muscle
4

Back 4

• No striations
• Spindle shaped
• Found amongst the internal organs
• Involuntary peristalsis

Front 5

Cardiac muscle
4

Back 5

• Striated
• Branched
• Intercalated disks (gap junctions) separate myocytes
• Involuntary contractions

Front 6

Muscle anatomy
4

Back 6

1) Muscle = organ
2) Muscle fiber = cell
3) Myofibril = organelle
4) Sarcomere = contractile unit

Front 7

A bands vs. I bands

Back 7

A bands:
• Thick segment of myofilaments
• Made up of horizontal thick myosin proteins, and thin actin proteins projecting in between the myosin

I bands:
• Thin segment of myofilaments
• Made up of the vertical zig-zagging Z line with the horizontal actin proteins attached to it

Front 8

Z line

Back 8

The vertical actin protein disk dividing I bands in half

Front 9

Sarcomere

Back 9

• Repeating contractile units
• 1 sarcomere = Z line - Z line

Front 10

Myosin structure
2

Back 10

• many golf-club shaped protein filaments twisted together
• has heads which protrude out to walk along the actin

Front 11

Actin structure
2

Back 11

• double helixed proteins
• has myosin binding sites covered by tropomyosin until troponin binds to unveil them

Front 12

Sarcoplasmic reticulum

Back 12

Smooth ER of a myocyte which stores Ca+2

Front 13

Where is the concentration gradient of Ca+2 in a myocyte?
When and how is it built?

Back 13

• Concentration gradient is inside the sarcoplasmic reticulum
• It is built when the muscle fiber is at rest
• Ca+2 pumps actively transports Ca+2 inside the SR

Front 14

What is contraction?
2

Back 14

• Myosin heads walk along the actin filaments, pulling in the Z line
• Actin and myosin do not shorten, rather they glide past one another shortening the sarcomeres

Front 15

Mechanism of contraction
5 steps

Remember 4 chemicals involved minus ATP

Back 15

1) Motor neurons secrete the neurotransmitter acetylcholine
2) ACh ignites an impulse that travels to the sarcoplasmic reticulum
3) Impulse opens Ca+2 channels, allowing Ca+2 to rush out into the cytoplasm
4) Ca+ bind to troponin, causing the tropomyosin to uncover actin's myosin binding sites
5) Mysoin heads can now bind to actin to walk along it

Front 16

ATP's role in contraction
4

Back 16

1) High energy state: ATP bound to myosin & detached from actin
2) Myosin hydrolysizes ATP → ADP + P, thrusting the head forward to bind to the myosin binding site
3) ADP + P is released from head, and head pivots (power stroke), pulling myosin filament along actin
4) ATP binds to head, releasing it from actin

Front 17

Back 17

Orbicularis oculi

Front 18

Back 18

Zygomaticus

Front 19

Back 19

Masseter

Front 20

Back 20

Orbicularis oris

Front 21

Back 21

Platysma

Front 22

Back 22

Trapezius

Front 23

Back 23

Deltoids

Front 24

Back 24

Triceps brachii

Front 25

Back 25

Biceps brachii

Front 26

Back 26

Pectoralis major

Front 27

Back 27

Intercostals

Front 28

Back 28

Rectus abdominis

Front 29

Back 29

Latissimus dorsi

Front 30

A

Back 30

Gluteus medius

Front 31

B

Back 31

Gluteus maximus

Front 32

Back 32

Sartorius

Front 33

Back 33

Rectus femoris

Front 34

Back 34

Vastus lateralis

Front 35

Back 35

Vastus medialis

Front 36

Back 36

Gastrocnemius

Front 37

Back 37

Biceps femoris

Front 38

Back 38

Calcaneal (Achilles) tendon