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
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
Maintain posture and body position
Stabilize joints
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