Skeleton muscle Flashcards
Myology?
Scientific study of muscle
Muscle cells (fibers) are the only cell in the body that have the property of ___________ which allow them to shorten and develop ________
1) contractility
2) tension
What are 3 types of muscle tissue?
1) Skeletal muscle
2) Cardiac muscle
3) Smooth muscle
Describe skeletal muscle
1) attaches to and moves the skeleton
2) contractile molecules are very organized giving skeletal muscle a striated (striped) pattern “striated pattern”
3) moves under voluntary control
Skeletal muscle comprises about _____ of the total body weight in women and _____ in men
women: 36%
men: 42%
_______ of the skeletal muscle is water and ________ is protein
water: 75%
protein: 20%
The remainder of skeletal muslce consists of…
1) pigments
2) carbohydrates
3) fats
4) inorganic salts
Describe smooth muscle
- found in walls of hollow organs and blood vessels
- contractile molecules are not aligned creating a smooth appearance
- moves under involuntary control
- connections between cells = syncytium which allows them to contract
Describe cardiac muscle
- the contractile tissue of the heart wall
- has characteristics of both smooth and skeletal muscle
What are the similarities cardiac muscle has with skeletal muscle
- have contractile molecules that are organized in striations
What are the similarities cardiac muscle has with smooth muscle
- under involuntary control
- connections between cells that allow them to contract together (syncytium)
- also facilitates the ejection of blood
Name 5 functions of the skeletal muscle
1) produce skeletal movement
2) maintain posture and body position
3) stabilize joints
4) chewing food and talking
5) generate heat to maintain body temperature
The criteria to name muscles
1) Shape
2) Action
3) Location
4) Divison
5) Size relationship
6) Directions of the fibers
Example of muscles with shape (4)
deltoid (triangle), latissimus (wide), trapezius, rhomboid
Action
various muscle names include flexor, extensor, adductor, or pronator (e.g adductor magnus)
Location
Tibialis anterior (to the front)
Intercostals (Inter=between, costals=ribs)
Divisions
Biceps brachii (bi-two)
Triceps brachii (tri-three)
Quadriceps femoris (quad-four)
Size relationship
gluteus maximus, gluteus medius, gluteus minimus
several name include the terms “brevis” (short) and “longus” (long)
Directions of fibers
tranvere (across): tranverse abdominus
rectus (straight): rectus abdominus
A bundle of muscle fibers is called…
Fasciculi
The movement of fasciculi
May run parallel to long axis of muscle (greater range of motion, less strength) or insert diagonally into a tendon running the length of muscle (smaller range of motion, greater strength.
What is unipennate and give an example
all fasciculi insert on one side of tendon (semimembranosus)
describe bipennate and give an example
fasciculi insert on both sides of the tendon (rectus femoris)
Describe multipennate and give an example
Convergence of several tendons (deltoids)
describe the longitudinal (strap) and give an example
fasciculi run parallel to the long axis of the muscle (sartorius, rectus abdominus)
describe radiate (convergent) and give an example
fibers fan out of a single attachment (pectoralis major)
What is a prime mover?
a muscle whose contraction is primarily responsible for a particular movement
What is an antagonist muscle?
- a muscle that opposes one another upon contraction
- (e.g. biceps brachii vs triceps brachii)
- antagonists are located on the other side of joint
What are fixators/stabilizers?
muscles that immobilize joint or bone near the origin of the prime mover, so that the prime mover can act more efficiently
When are more muscle stabilizers required?
When using free weights
Origin?
less moveable end of the muscle, usually proximal
Insertion?
more moveable end of the muscle, usually distal
Belly?
the widest portion of the muscle between its origin and the insertion
Most muscles controlling facial expression originate from ________ and insert in the __________
1) bone
2) skin
The three layers of connective tissue serve in part to maintain ________________ (2)
intramuscular pressure
which of the 3 layers surrounds the muscle
Epimysium
which of the 3 layers surround the bundle of muscle fibers (fasciculi)
Perimysium
which of the 3 surround muscle fibers
Endomysium
Tendons are extensions of connective tissue membranes beyond the end of the _________
muscle
Tendons transmit the force of contractile tissue to ________
bone
Tuberosity
a large roughened process on the bone
Which is stronger muscle or tendon
tendon as it can receive force from a larger number of muscle fibers
A muscle cell is a muscle _________
fiber
what is found within muscle cell/fibers?
myofibrils
What do myofibrils consist of?
Consists of a large array of contractile proteins (sarcomere) and is arranged repeatedly in a series which is what gives skelatal muscle its striated pattern of light and dark areas
Each repeated array of contractile proteins is called
a sarcomere
What are the two major contractile proteins of the sarcomere?
1) actin (thin filament)
2) myosin (thick filament)
Actin has binding sites for _________
myosin
What is the most prominent theory of muscle contraction?
The sliding filament theory
Explain the sliding filament theory
This theory suggests when the muscle is activated the protruding cross bridges on myosin attach to actin with the help ATP. The cross-bridge microstructure can “rotate”, thus causing the thin actin filament to slide over myosin. This causes the sarcomere to shorten.
What causes the sarcomere to shorten?
The rotation of the microstructure causes thin actin filaments to slide over myosin
How many capillaries surround each muscle fiber of a sedentary person?
about 3-4
How many capillaries surround each muscle fiber with training (angiogenesis)
up to 7
Muscles require good supply of __________ for continued _________ generation
1) blood
2) force
When muscle force increases does intramuscular pressure increase or decrease?
Increas
Increase in intramuscular pressure can….
restrict blood flow within the muscle
What does activation of muscle fiber, in the extreme, produce?
maximum force or maximum velocity
What do muscle fibers create in between the extremes
a combination of force and movement
What is the functional unit of a muscle?
a motor unit
The motor unit is the _________ unit of a muscle
functional
Where is the cell body of a motor neuron located
Spinal cord
The ________ of that _________ __________ extends from the spinal cord to the target which may be a few mm away or a few feet away
1) axon
2) motor neuron
An average motor unit the motor neuron will innervate _______ muscle fibers
200
If the body of the motor neuron receives a strong enough stimulus what will be generated?
An action potential
Motor units can be classifies as
slow twitch and fast twitch
muscle fiber types
Type I (slow twitch oxidative)
Type IIa (fast-twitch oxidative-glycolytic)
Type IIx (fast glycolytic)
Use the muscle ________ technique to determine fiber type proportions in humans
biopsy
Men, women and children generally have _________ slow twitch fiber
45-55%
All muscle fibers in a given motor unit will have identical ______ and ________ properties
1)contractile
2)metabolic
Endurance athletes have higher than the average __________ twitch muscle fibers
slow
Power athletes have a higher proportion of ________ twitch muscle fibers
fast
When velocity is positive muscle is _____
shortening (concentric contraction)
When velocity is negative muscle is ________
lengthening (eccentric contraction)
When velocity is 0…..
there is no shortening of muscle length (isometric)
The faster a muscle shortens the _______ __________ it produces
Less force
(T or F) The faster it lengthens in the eccentric phase, the more force it produces
TRUE
power = force x velocity
Three factors that affect the expression of strength by muscle
1) initial length of muscle fibers
2) speed of shortening
3) the angle of pull of the muscle on the bony skeleton
Sarcopenia
age-related decrease in skeletal muscle mass, strength and function
Physical characteristics of old age
-decrease in skeletal muscle mass and strength
-decrease in physical activity
-decrease in food intake
Sarcopenia is caused by
-food intake (insufficient protein)
-physical inactivity
-hormonal imbalance
Sarcopenia enhances
-loss of physical activity
-the risk of disability
-more dependency towards other people
-more medical costs
Prevention of sarcopenia
-strength training
-hormonal therapy
-dietary intervention
-reduction in sedentary time
