Transcript 33.2 Muscular System

33.2 Muscular System
KEY CONCEPT
Muscles are tissues that can contract, enabling
movement.
33.2 Muscular System
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
33.2 Muscular System
• There are three types of muscle tissue.
– skeletal muscle
– smooth muscle
– cardiac muscle
SKELETAL MUSCLE
SMOOTH MUSCLE
CARDIAC MUSCLE
33.2 Muscular System
• Skeletal muscle attaches to the skeleton by tendons.
– Tendons connect muscle to bone.
– Skeletal muscles are mostly voluntary.
SKELETAL MUSCLE
33.2 Muscular System
• 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
33.2 Muscular System
• Cardiac muscle is found only in the heart.
– pumps blood throughout body
– controlled by pacemaker
– contains more mitochondria than skeletal muscle cells
CARDIAC MUSCLE
33.2 Muscular System
Muscles contract when the nervous systems causes
muscle filaments to move.
• Muscle fibers are cells of the muscular system.
muscle fiber
muscle
33.2 Muscular System
• Myofibrils are long strands of protein in the muscle fiber.
myofibril
muscle fiber
muscle
33.2 Muscular System
• Each myofibril is divided into sarcomeres.
• Sarcomeres contain filaments that cause contraction.
muscle fiber
myofibril
sarcomere
muscle
33.2 Muscular System
• Neuron stimulates muscle at the neuromuscular junction.
neuromuscular
junction
neuron
MUSCLE
33.2 Muscular System
33.2 Muscular System
• Each myofibril is divided into sarcomeres.
• Sarcomeres contain filaments that cause contraction.
– Actin filaments are pulled during contraction.
– Myosin filaments pull actin during contraction.
RELAXATION
myosin
M line
CONTRACTION
Z line
33.2 Muscular System
• Neuron stimulates muscle at the neuromuscular junction.
– Neurotransmitters
cause calcium
regulatory protein
channels in the
sarcomere to
open.
– Calcium exposes
binding sites.
– Myosin binds to
actin and pulls it.
actin
– As the sarcomere
shortens, the
muscle contracts.
myosin
Z line