Muscle Structure Flashcards
Describe skeletal muscle tissue.
- considered an organ
- muscle fibres are striated (possessing stripes) when observed under a microscope
- there are over 700 skeletal muscles and together they form the muscular system
What are the 3 types of muscles in the body?
- skeletal
- cardiac
- smooth
What are the 5 functions of skeletal muscle tissue?
- body movement
- maintenance of posture
- temperature regulation
- storage and movement of materials
- support
What 7 things are taken into account when naming muscles?
- shape
- location
- attachment
- size
- orientation
- position
- function
What are fascicles?
a bundle of muscle fibres separated from other bundles of fibres by a dense irregular connective tissue covering
What do muscle fibers contain?
myofibrils
What are myofibrils composed of?
myofilaments
Name the organizational levels of skeletal muscle.
- muscle
- fascicle
- muscle fiber (muscle cell)
- myofibril
- myofilaments
What are muscle fibres (muscle cells)?
- elongated, multinucleated cylindrical finer (cell)
- contains myofibrils, separated from other fibres by delicate layer of areolar connective tissue
- has striations
What is a myofibril?
- long, cylindrical contractile element within muscle fibre
- as long as the muscle fibre itself
- composed of myofilaments
- has striations
What are myofilaments?
short contractile proteins of 2 types: thick (composed of myosin) and thin (composed of actin, tropomyosin, and troponin)
What are the 3 concentric layers of connective tissue composed of?
- collagen
- elastic fibres
What function do the 3 concentric layers of connective tissue serve?
- protection
- sites for blood vessel and nerve distribution
- attachment of the muscle to the skeleton
What are the 3 connective tissue layers?
- endomysium
- perimysium
- epimysium
Describe the endomysium.
innermost layer that surrounds and electrically insulates each muscle fibre
Describe the perimysium.
surrounds the fascicles
Describe the epimysium.
- surround the entire muscle
- deep fascia surrounds each muscle and separates muscles from each other
- superficial fascial separates muscle from skin
Connective tissue merges to form a _____. Define this.
- tendon
- attachment to the muscle to bone, skin, or another muscle
What is a aponeurosis?
sometimes, the tendon forms a thin, flattened sheet
Most muscles extend over a ______ and have attachments to both articulating bones.
joint
What happens upon contraction of the muscle in a muscle that extends over a joint?
one of the articulating bones moves and the other one does not
The point of attachment to the bone that does not move is called the _____.
origin
The point of attachment to the bone that does move is called the _____.
insertion
Describe the contraction of skeletal muscle fibres.
- muscle fibres shorten by myofilaments filament interaction within each functional unit of a muscle
- generates tension
The mechanism for contraction is explained by _______________.
the sliding filament theory
The neuromuscular junction = _____+______
neuron+muscle
How does muscle contraction begin?
a neuron impulse stimulates an impulse in a muscle fibre
Skeletal muscles are comprised of a mixture of 3 different types of muscle fibres. What are they?
- slow oxidative (SO) fibres (type I)
- fast oxidative (FO) fibres (type IIa)
- fast glycolytic (FG) fibres (type IIx or IIb)
Describe the ATP use of each type of skeletal muscle fibre.
type I: slow
type IIa: fast
type IIx: fast
Describe the capacity to make ATP for each type of skeletal muscle fibre.
type I: high, aerobic
type IIa: moderate, aerobic
type IIx: limited, anaerobic
Describe the concentration of capillaries in each type of skeletal muscle fibre.
type I: extensive
type IIa: moderately extensive
type IIx: sparse
Describe the colour of each type of skeletal muscle fibre.
type I: dark red
type IIa: lighter red
type IIx: white (pale)
Describe the contraction velocity of each type of skeletal muscle fibre.
type I: slow
type IIa: fast
type IIx: fast
Describe the resistance to fatigue of each type of skeletal muscle fibre.
type I: highest
type IIa: high
type IIx: low
Describe the distribution of each type of skeletal muscle fibre.
type I: found in greatest abundance in muscles of the trunk, especially postural muscles
type IIa: found in greatest abundance in muscles of the lower limbs
type IIx: found in greatest abundance in muscles of the upper limbs
Describe the diameter of each type of skeletal muscle fibre.
type I: smallest
type IIa: intermediate
type IIx: largest
Describe the number of mitochondria in each type of skeletal muscle fibre.
type I: many
type IIa: many
type IIx: few
Describe the amount of myoglobin in each type of skeletal muscle fibre.
type I: large
type IIa: medium
type IIx: small
Describe the primary function of each type of skeletal muscle fibre.
type I: endurance (ex. marathon running), maintaining posture
type IIa: medium duration, moderate movement (ex. walking, biking)
type IIx: short duration, intense movement (ex. sprinting, lifting weights)
