1. KEY CONCEPT Muscles are tissues that can contract, enabling movement.

2. Humans have three types of muscle.
The muscular system moves substances throughout the body.
bones of the skeletal system
food through digestive system
blood through circulatory system
fluids through excretory system

3. There are three types of muscle tissue. skeletal muscle smooth muscle
cardiac muscle
SKELETAL MUSCLE
SMOOTH MUSCLE
CARDIAC MUSCLE

4. Skeletal muscle attaches to the skeleton by tendons.
Tendons connect muscle to bone.
Skeletal muscles are mostly voluntary.
SKELETAL MUSCLE

5. Smooth muscle lines organs and is involuntary.
move food through digestive organs
empty liquid from the bladder
control width of blood vessels
Smooth muscle
around this artery allows the
artery to regulate blood flow
by shrinking and expanding.
SMOOTH MUSCLE

6. Cardiac muscle is found only in the heart. pumps blood throughout body
controlled by pacemaker
contains more mitochondria than skeletal muscle cells
CARDIAC MUSCLE

7. Muscle fibers are cells of the muscular system.
Muscles contract when the nervous systems causes muscle filaments to move.
Muscle fibers are cells of the muscular system.
muscle
muscle fiber

8. Myofibrils are long strands of protein in the muscle fiber.

9. Each myofibril is divided into sarcomeres.
Sarcomeres contain filaments that cause contraction.
myofibril
muscle fiber
muscle
sarcomere

10. Neuron stimulates muscle at the neuromuscular junction.

12. Each myofibril is divided into sarcomeres.
Sarcomeres contain filaments that cause contraction.
Actin filaments are pulled during contraction.
Myosin filaments pull actin during contraction.
CONTRACTION
RELAXATION
M line
myosin
Z line

13. Neuron stimulates muscle at the neuromuscular junction.
Neurotransmitters cause calcium channels in the sarcomere to open.
regulatory protein
Calcium exposes binding sites.
Myosin binds to actin and pulls it.
As the sarcomere shortens, the muscle contracts.
myosin
actin
Z line