Part 3: Introduction to muscular tissue Flashcards
3 types of muscle tissue + (moves ___)
- Skeletal – moves body
- Cardiac – moves blood
- Smooth – moves food, liquid, air
muscle cells are ____
Specialized cells with contractile & conducting properties
muscle tissue provides ability to ____
1) move
2) regulate organ volumes
3) maintain posture
4) communicate
5) produce body heat
4 properties of muscle tissue
Excitability: ability to respond to stimulation (e.g., nerves, hormones)
Contractility: ability to shorten in response to an action potential
Extensibility: ability to contract over different lengths (range – without injury)
Elasticity: ability to regain original length after contraction
Major characteristics of skeletal muscle
1) somatic structures (under voluntary control though not always conscious)
2) innervated by spinal nerves & cranial nerves
3) contractile organs (long fibres that contract along longitudinal axis) that attach directly or indirectly onto bones
4) Their contractions produce motion of the body
Major functions of skeletal muscle
1) Produce movement at various joints of the skeleton
2) Maintain posture & body position (even at rest)
3) Support soft tissues
4) Regulate entering & exiting of material (sphincters in digestive & urinary systems)
5) Maintain body temperature
6) Communication (verbal & non-verbal expressions)
A skeletal muscle is surrounded by _____ (becomes continuous with ____)
an epimysium
periosteum
Muscle belly is composed of _______
bundles of muscle fascicles
A muscle fascicle is surrounded by ______ which does what?
an perimysium
protect from damage, contains capillaries & nerve fibres)
Each fascicle is composed of _______
bundles of muscle fibres (muscle cells)
A muscle fibre is surrounded by _______. Each fibre is composed of ______
an endomysium
bundles of myofibrils
Each myofibril is composed of _______
bundles of myofilaments (proteins responsible for muscle contraction)
Label
(left) Epimysium
Muscle fascicle
Endomysium
Perimysium
(right) Nerve
Muscle fibres
Blood vessels
Label
Perimysium
Muscle fibre
Endomysium
Label
(left) Mitochondria
Sarcolemma
Myofibril
Axon
Sarcoplasm
(right) Capillary
Endomysium
Myosatellite cell
Nucleus
sacrolemma (def.)
cell membrane of muscle fibre
sacroplasma (def.)
cytoplasm in muscle cell
Muscle fibres develop through the fusion of cells called _____
myoblasts
Myosatellite cells are ____
Only stem cells that remain; repair damaged muscle tissue
Muscle fibre length
40 cm
Myofibril (def.)
Contractile element composed of myofilaments (protein that exhibit striations)
Thin filament (def.)
actin
Thick filament (def.)
myosin
Mitochondrial activity + chemical breakdown of glycogen =
ATP power for muscle contraction
Myoglobin contains ____
stored oxygen
Sarcoplasmic reticulum stores _____
Ca2+ to promote muscle contraction
Transverse tubule conducts _____
electrical impulses (action potential) for muscle fibre contraction
_____is the basic contractile unit of a muscle (~ 10 000 per myofibril)
Sarcomere
Boundaries of a sarcomere are a _____
pair of Z-lines (protein discs repeated along myofibril)
Centre of a sarcomere is _____
an M-Line (middle – stabilize position of myosin)
elastic protein that connects myosin to Z lines
Titin
Label
top: titin
bottom (l to r): Z-line , M-line, Z-line
H-band contains ______
thick filaments only
I-band: (isotropic – light – uniform in each direction) contains ____
thin filaments only
A-band: (anisotropic – dark – directionally dependent) contains _____
both thin & thick filaments
Zone of overlap is where?
striations & where calcium ions are released
Label
top: I-band, H-band, I-band
bottom: A-band
Sliding Filament Theory contraction effects.
1) Actin slide toward each other
2) Width of the I-band & H-band decreases
3) Zone of overlap gets larger
4) Z lines move closer together
5) Width of the A-band remains constant
Sliding Filament Theory descr.
Cross-bridging between thick & thin filament ;Triggered by presence of calcium ions ; Requires ATP
nerve stimulating muscle steps
1) Muscle cells (fibres) are innervated by somatic motor neurons they penetrates epimysium, then perimysium, & ends at a muscle fibre through the endomysium.
2) Axon terminal at the tip of neuromuscular junction (NMJ) where it releases acetylcholine - Ach
3) signals the muscle cell to contract
4) Contraction is an all or none phenomenon
Steps That Initiate a Muscle Contraction
1) ACh released, binding to receptors in sarcolemma
2) Action potential reaches T tubule
3) Sarcoplasmic reticulum releases Ca2+
4) Active site exposure and cross-bridge
formation
5)Contraction Begins (power stroke)
Steps That End a Muscle Contraction
1) ACh removed by AChE (acetylcholinesterase – enzyme)
2) Sarcoplasmic reticulum recaptures Ca2+
3)Active sites covered, no cross-bridge interaction
4) Contraction ends – this still needs an ATP to occur
5) Relaxation occurs, passive
return to resting length (once myosin head is released)
All the muscle cells controlled by a single motor neuron constitute ______
a motor unit (1 neuron & all fibres it controls)
Smaller motor units control the contraction of a small number of fibres, therefore creates _____
smaller & more precise muscular contractions (eye muscles)
Types of skeletal muscle fibres
slow twitch
fast twitch
Slow fibres colour is ____ (due to numerous______)
red
mitochondria & myoglobin
diameter of slow twitch fibre
narrow
slow twitch fibres are ____to contract, resistant to ___, but _____ contractions.
ATP produced by _______ ( ____).
slow
fatigue
less powerful
mitochondria through aerobic metabolism
(slow mechanism)
slow twitch fibre blood flow
More extensive network of capillaries (greater blood flow to deliver oxygen)
slow twitch fibres are associated with ____
large muscles such as leg or gluteal muscles
Fast fibres colour is ____. _____diameter, has a ______reserve and ____mitochondria
_____contractions (_____amount of ATP), but _____rapidly.
white
Larger
large glycogen
few
Powerful
large
fatigue
fast twitch fibres: ATP generated by _____ . convert stored _____which results in _____ which interferes with )
anaerobic glycolysis
glycogen to lactic acid
acidic pH
contraction
fast twitch fibres are associated with _____
eye & hand muscles
muscle tone (resting tension) (def.)
Some motor units are always active (even at rest) but tension is not enough to cause movement
Isometric contraction (def.)
tension never exceeds the resistance/load (active muscle does not change in length with contraction)
Isotonic contraction (def.)
tension produced is equal or greater than resistance/load (results in a movement)
Two types of isotonic contraction
concentric
eccentric
concentric contraction (def.)
shortening of an active muscle (load is less than max tension of muscle)
eccentric contraction (def.)
lengthening of an active muscle
skeletal muscles attaches on ____
individual bones or soft tissue (skin = muscles of facial of expression)
skeletal muscles can cross ____
one or multiple joints
skeletal muscles pull a bone towards _____
another so that movement is produced at a joint
skeletal muscles can stabilize _____ so other muscles can _____
a joint
act & produce movement
(ex. wrist extensors stabilize the wrist joint when finger flexors contract to grasp firmly an object)
action (def.)
type of movement (function of muscle)
insertion (def.)
muscle attachment to moveable bone
origin (def.)
muscle attachment to stationary bone
A lever is _____
a rigid structure (a bone)
A lever moves on a fixed point known as ______
fulcrum (Fc) (a joint)
The lever moves a _____
weight (W) (any load/resistance that may oppose the muscle contraction)
Force (F) (_____) required to move weight generated by _____
muscle
muscle contraction
first class lever
First class lever increases _______ but requires ____
range & speed of movement
larger force
second class lever
second class lever increases ____ but at the expense of _____
force,
range & speed of movement (wheel-barrow)
third class lever
third class lever increase ______ but at the expense of ____
range & speed of movement
force
most common lever in body
third class lever
Types of primary muscle actions
Agonist (prime mover)
Synergist
Antagonist
Fixators
Agonist (def.)
contraction produces a particular movement (ex. biceps femoris muscle flexes the leg at knee joint)
Synergist (def.)
assists prime mover in performing an action (ex. semitendinosus muscle will also flex the leg at knee joint)
Antagonist (def.)
opposes the movement (ex. quadriceps femoris muscle extends the leg at knee joint, thus opposes movement of the biceps femoris & semitendinosus muscles)
Fixators (def.)
agonist & antagonist muscles contracting at the same time to stabilize a joint (all previous muscles contracting while standing up, stabilizing the knee joint)
muscle action & muscle function
muscle action is not always muscle function
parallel muscles have fascicles that are _____ to long axis of muscle
parallel
most common muscle types
parallel muscles
parallel muscles are either ____
flat band or spindle-shaped
spindle-shaped parallel muscles have a central portion called ____
a belly
during contraction, spindle muscles gets ___ & belly gets ___
shorter
wider
parallel muscles exert great force because _____
all fascicles pull in same direction
parallel muscles examples
biceps brachii (arm), rectus abdominis (abdomen)
Convergent muscles shape
fan-shaped
Convergent muscles: fascicles arrangement
originate over wide area, but converge at common attachment site
Convergent muscles: _____ can be changed by varying which fascicles contract
direction of pull
Convergent muscles do not _____
exert as much force because not all fascicles pull in same direction
Convergent muscles examples
pectoralis major (chest), trapezius (shoulder)
Pennate muscles: Tendons run ____
through body of muscle (like a feather)
Pennate muscles: Fascicles form _______
oblique angle relative to tendon
Pennate muscles contains more ____ than _____
muscle fibres
parallel muscle of same size
(generate more force)
Unipennate (def.)
muscle fibres on one side of the tendon; extensor digitorum (forearm)
Bipennate (def.)
muscle fibers on both sides of the tendon; rectus femoris (thigh)
Multipennate (def.)
tendon branches within the muscle; deltoid (shoulder)
circular muscles have their fibres arranged ____ (form ___)
concentrically around an opening or recess (form sphincters)
circular muscles contraction of muscle does what?
Examples: _____
reduces diameter of opening
orbicularis oculi (eye), orbicularis oris (mouth)
