Chapter 9 quiz

Cardiac muscle tissue

• is found in hearts

• Makes up bulk of heart walls

• Striated

• Involuntary: cannot be controlled consciously

• Contracts at steady rate due to heart's own pacemaker, but nervous system can increase rate

1. Skeletal muscle tissue

is packaged into skeletal muscle: organs that are attached to bones and skin

Skeletal muscle fibers

are longest of all muscle and have striations (stripes)

Skeletal Muscle

Called voluntary muscle,  can be consciously controlled

• Contract rapidly; tire easily; powerful

Smooth Muscle Tissue

found in walls of hollow organs

• Examples: stomach, urinary bladder, and airways

• Not striated

• Involuntary: cannot  be controlled consciously

Muscle Cells

are Muscle fibers

Excitability (responsiveness)

• ability to receive and respond to stimuli

Contractility

ability to shorten forcibly when stimulated

Extensibility

ability to be stretched

Elasticity

• ability to recoil to resting length

• Four important functions

Produce movement: responsible for all locomotion and manipulation

• Example: walking, digesting, pumping blood

2. Maintain posture and body position

3. Stabilize joints

4. Generate heat as they contract

Three different features of skeletal tissues

• nerve and blood supply, connective tissue sheaths, and attachments

Nerve and Blood Supply

• Each muscle receives a nerve, artery, and veins

• Consciously controlled skeletal muscle has nerves supplying every fiber to control activity

• Contracting muscle fibers require huge amounts of oxygen and nutrients

• Also need waste products removed quickly

Connective Tissue Sheaths

• Each skeletal muscle, as well as each ACh, is covered in connective tissue

• Support cells and reinforce whole muscle

Epimysium

• Dense irregular connective tissue surrounding entire muscle; may blend with fascia

Perimysium

• fibrous connective tissue surrounding fascicles (groups of muscle fibers)

Endomysium

• fine areolar connective tissue surrounding each muscle fiber

Insertion

• attachment to movable bone

Origin

• attachment to immovable or less movable bone

Direct (fleshy)

• epimysium fused to periosteum of bone or perichondrium of cartilage

Indirect

connective tissue wrappings extend beyond muscle as rope like tendon or sheetlike aponeurosis

Skeletal muscle fibers (Microanatomy)

are long, cylindrical cells that contain multiple nuclei

Sarcolemma

muscle fiber plasma membrane

Sarcoplasma

• muscle fiber plasma

glycosomes

glycogen storage

myoglobin

• O2 storage

Modified organelles

• Myofibrils

• Sarcoplasmic reticulum

• T tubules

Myofibrils

• are densely packed, rodlike elements

• Single muscle fiber can contain 1000s

• Accounts for ~80% of muscle cell volume

• Striations

• stripes formed from repeating series of dark and light bands along length of each myofibril

A bands

• dark regions

H zone

• lighter region in middle of dark A band

M line

• Line protein (myomesin) that bisects H zone vertically

I bands

lighter regions

Z disc (line)

• coin-shaped sheet of proteins on midline of light I band

Sarcomeres

• Orderly arrangement of actin and myosin myofilaments within sarcomere

Actin myofilaments

• thin filaments

• Extend across I band and part way in A band

• Anchored to Z discs

Thick filaments

• composed of protein and myosin that contains two heavy and four light polypeptide chains