BIOSCI 107 muscle tissue

Types of muscle tissue

skeletal, cardiac, smooth

What is muscle tissue made of?

Elongated cells known as myocytes, muscle cells or muscle fibers

Purpose of muscle tissue

movement, heat, posture

How do muscles generate force?

Hydrolysis of ATP

Skeletal muscle structure

striated, multiple nuclei per cell, long cylindrical shape

Skeletal muscle location

attached to bones by tendons

Skeletal muscle function

Voluntary motion, posture, heat, protection

Skeletal muscle control

Voluntary

Cardiac muscle structure

Striated, branched, single nucleated cells, intercalated disks

Intercalated disks

Branch and connect cardiac cells. Contain specialized gap junctions and desmosomes

Cardiac muscle function

pump blood

Cardiac muscle location

heart

Cardiac muscle control

involuntary

Smooth muscle structure

Non-striated, spindle shaped cells, centrally located nucleus

Smooth muscle function

motion of internal organs

Smooth muscle location

walls of hollow organs, iris

Smooth muscle control

involuntary

Striations

Stripes found on skeletal and cardiac muscle

Myofibrils

Filaments that run the length of muscles cells containing contractile mechanisms

myofilaments that make up myofibril

actin (thick) and myosin (thin)

What are myofilaments arranged into?

sarcomeres

What causes striation?

Organised arrangement of myofibrils

Z line/disk

Separate sarcomeres

A band

Contains all thick filaments, middle part

I band

thin filaments only

H zone

thick filaments only

M line

middle of sarcomere

actinins

Proteins that link thin filaments of adjacent sarcomeres

Titins

Molecular spring, extends from the Z-disc to the M-line

What happens to filaments in contraction

Thin filaments slide over the thick filaments

What happens to I band in contraction?

shortens

What happens to H zone in contraction?

shortens

What happens to A band in contraction?

stays the same

How does smooth muscle contract?

Sliding filaments contract in all directions toward the center of the cell, squeezing the cell.

Filaments in smooth muscle

thick, thin, intermediate

What are dense bodies in smooth muscle?

An attachment site for thin and intermediate filaments.

Major protein in dense bodies

Actinin

What happens to intermediate filaments during smooth muscle contraction?

Don't contract causing the cell to twist.