Download Connective Tissue Terminology

Connective Tissue
Terminology
• _________________- each
individual skeletal muscle
fiber is surrounded by this
delicate connective tissue
layer.
– _________________groups of skeletal muscle
fibers
• _________________connective tissue that binds
together fascicles.
• _________________- fibrous
connective tissue that
surrounds groups of fascicles.
Microscopic
• Muscle cells
Anatomy
– Are very large in size
of Skeletal Muscle
– Have a threadlike or fiberlike
shape.
– Usually are multi-nucleated
– Made up of smaller myofibrils
composed of
_______________ (thin) and
_____________ (thick)
filaments
• Network of
sarcoplasmic reticulum
(similar to ER)
– Stores ____________ for
muscle contraction
•A band- large dark band made up
of myosin filaments
•I Band- large light band made up
of actin filamaments
•Z line- dark band in center of I
band, disk that is viewed as a line
and is attachment site for actin
filaments.
•Sarcomere- area from one z line to
the next z line. Basic contracting
unit of skeletal muscle. When all
sarcomeres contract, leads to
overall muscle fiber shortening.
Neuromuscular
Junction
• Skeletal muscle is under voluntary
control
• If nerve supply is interrupted for
long period of time, muscle will
______________ (shrink down)
– Neuromuscular junctions- sites
where the ends of motor nerve
fibers connect to muscle fibers.
• The nerve is not actually
touching the muscle, there
is a space called the
synaptic space or cleft
between the nerve & the
muscle
Neuromuscular
Junction
• _______________________sacs at end of a nerve fiber;
contain neurotransmitter (e.g.,
acetylcholine)
– _______________neurotransmitter chemical that
travels across synapse to
activate muscle fiber
• Attaches to receptor on
sarcolemma
– __________________- enzyme
in the synaptic space that
removes acetylcholine
• If muscle is to contract again,
another impulse must be
sent
• Initiation of Muscle
Contraction and
Relaxation
– Nerve impulse comes down
motor nerve fiber, reaches
neuromuscular junction and
acetylcholine is released into
synaptic space.
– Acetylcholine binds to
receptors on surface of
sarcolemma (cell membrane)
of the muscle fiber.
– This starts impulse that
travels along sarcolemma
and through the T tubules to
the interior of the cell.
cont’d….
–Once impulse reaches
sarcoplasmic reticulum it
causes release of stored
calcium ions (Ca++) into the
sarcoplasm (cytoplasm).
–As Calcium diffuses into
myofibrils, initiates contraction
process which is powered by
ATP.
–As contraction occurs,
Calcium is pumped back out
of myofibrils which shuts down
contraction process.
• Both relaxation and
contraction requires energy
Mechanics of Muscle
Contraction
• When a muscle fiber is relaxed,
actin and myosin overlap a little.
• When stimulated _______
________ (levers on the myosin
filaments) ratchet back and forth
and pull the actin filaments on
both sides toward center of the
myosin filaments.
• Sliding of filaments shortens
sarcomere, thereby causing
contraction.
Motor Unit
• One nerve fiber and all muscle fibers it innervates
– Muscles that make small, delicate movements have only a few muscle
fibers per nerve fiber in each motor unit
– Large, powerful muscles may have a hundred or more muscle fibers per
motor unit
Characteristics of Muscle Contraction
• _____-____-_____________ principle
– An individual muscle fiber either contracts completely when it
receives an impulse or not at all.
– Movements can vary in strength due to number of muscle
fibers stimulated.
• small movements only require a few fibers to contract, whereas
larger, powerful movements require more fibers
• Nervous system sends out impulse based on muscle _______ or idea of how many fibers need to be stimulated for that
particular activity.
– ex: shooting a basketball vs. knitting a sweater
Phases of twitch contraction
(contraction of a single muscle)
• 1. _______________ phase
– Brief pause between nerve stimulus and beginning of actual
contraction (lasts about 0.01 seconds)
• 2. ________________ phase
– Actual contraction is taking place (lasts about 0.04 seconds)
• 3. ________________ phase
– When cells go back to a relaxed state (lasts about 0.05
seconds)
•
Some fibers are relaxing while others contract, so smooth muscle
contractions can occur