1. Do now activity #1 What are the 3 types of muscle?
Which types of muscle are striated? Un-striated?
Which types of muscle are voluntary? Involuntary?
What are the physiological functions of the 3 types of muscle?

2. chapter 9-2: muscle contraction
Essential Question:
Describe the relationship between actin & myosin and how they work together to produce movement.
chapter 9-2: muscle contraction
Learning Targets
Define fascicle, muscle fiber, myofibril, sarcomere and myofilament.
Define actin and myosin.
Describe the sliding filament model of muscle contraction.
Describe how smooth muscle contracts.

3. Don’t forget to chunk your notes!

4. Myofibrils Elongated rod-like fibers in each muscle fiber
Contain the contractile elements of the muscle
These contain bands that create the striations of muscle
A (dark) bands and I (light) bands
The filaments of the sarcomere

6. Don’t forget to chunk your notes!

7. Sarcomeres Myofibrils contain many sliding pieces called sarcomeres
This is the smallest contractile unit of muscle
The actual functional unit of muscle

9. Sarcomeres Made of protein filaments Actin: thin Myosin: thick
The filaments slide past each other during contraction

10. Myosin (thick)

11. Thin (actin)

13. Don’t forget to chunk your notes!

14. Muscle Contraction
When muscles contract, one filament (actin) slides past the other (myosin)
Called the sliding filament model
Uses ATP for energy
ATP loses a phosphate to become ADP
ATP ADP + P
Molecules that receive the P are phosphorylated
This provides the energy

15. Relaxed

16. Contracted

17. Don’t forget to chunk your notes!

18. Sliding Model ATP is added to myosin
The ATP is broken down into ADP + P.
Myosin is phosphorylated
Myosin reaches out and attaches to actin
Myosin loses the P and ADP, causing the shape change
The changing of the shape causes actin to slide past the myosin
A new ATP is added causing myosin to let go of the actin
The process now starts all over

20. Don’t forget to chunk your notes!

21. Nerves & Muscle Contraction
Each muscle fiber has a junction with a neuron
A nerve impulse travels down the neuron and meets the muscle
This stimulates the neuron to allow Ca2+ into the cytoplasm
This causes the neuron to release a neurotransmitter called acetylcholine (ACh)
The ACh binds to the muscle and causes contraction

22. Don’t forget to chunk your notes!

23. The Role of Calcium Ions
Ca ions (Ca2+) are needed for contraction
They cause neurons to release neurotransmitters that trigger the sliding process
Ca2+ is also needed for the attachment of myosin to actin
The binding of calcium changes the shape of the actin allowing myosin to attach