Chapter 10 Flashcards
approximately how many muscles are in the body that forms the muscular system
around 700 muscles
what are the three types of muscle in the body
- skeletal
- cardiac
- smooth
skeletal muscle
striated muscle under voluntary control
cardiac muscle
striated muscle under involuntary control
smooth muscle
non striated muscle under involuntary control
what does striated muscle mean
it has dark and light bands
what are the properties of muscle tissue
- exciatability
- contractility
- elasticity
- extensibility
excitability as a property of muscle tissue
muscle cells are responsive to input from stimuli
contractility as a property of muscle tissue
- stimulation of muscle fiber can lead to contraction and shortening of muscle fiber
- concentric movements
elasticity as a property of the muscle tissue
contracted muscle cells can treturn to resting length when applied tension is removed
extensibility as a property of muscle tissue
ability of muscle fiber to be stretched beyond its resting length
- eccentric movement
what are the characteristics of skeletal muscles
- each muscle is considered an organ
- striated: marked with long thin parallel streaks
- usually attached to bones
what are the functions of skeletal muscle
- support
- temperature regulation
- maintenance of posture
- body movement
- storage + movement of materials
gross anatomy of skeletal muscle tissue
- muscle fibers are organized into bundles called fascicles
- muscle fibers contain myofibrils
- myofibrils are composed of myofilaments
what are the components of the connective tissue of skeletal muscle
3 layers of concentric connective tissue composed of collagen and elastic fibers
what is the function of the connective tissue within skeletal muscles
- provide protection
- the sites for blood vessels and nerve distribution
endomysium
- areolar CT
- the innermost layer of connective tissue that surrounds and electrically insulates each muscle fiber
perimysium
- dense irregular CT
- surrounds the fasicles
epimysium
- dense irregular CT
- surrounds the entire muscle
- has deep fascia and superficial fascia
deep fascia
surrounds each muscle and separates muscel from each other
superficial fascia
separates muscle from skin
muscle attachments
at the ends of each muscle all CT merge to form a tendon
tendons
attaches muscles to bone, skin, or another muscle
what percentage of tendons are muscle to bone
90%
what percent of tendons are muscle to skin or another muscle
10%
what appearance to tendons have
- a cordlike appearance
- sometimes aponeurosis appearance
what is an aponeurosis appearance
appears as a flat sheet
upon contraction of the muscle what happens to the articulating bones
one articulating bone is moved the other does not move
origin
less moveable point of attachment
insertion
more moveable point of attachment
what is the microscopic anatomy of skeletal tissue
- sarcolemma
- sarcoplasmic reticulum
- myofibrils
- myofilaments (actin and myosin)
- sarcomere
sarcolemma
plasma membrane of the muscle fibers
sarcoplasm
cytoplasm of the muscle fibers
sarcoplasmic reticulum
smooth ER of the muscle fibers
myofibrils
cylindrical structures that extend the entire length of cell
myofilaments
- short bundles of proteins that comprise a myofibril
- organized of repetitive groupings
- two types (thick and thin filaments)
thick filaments
- composed of bundled molecules of myosin
- 11 nm in diameter
myosin
single molecule has a head and elongated tail
- heads are what forms the crossbridges with thing filaments during contraction
thin filaments
- composed of 2 strands of spherical molecules twisted around each other
- 5-6 nm in diameter
- has 2 regulatory proteins
what are the two types of actin molecules
F actin and G actin
sarcomere
functional contractile unit in skeletal muscle fibers
parts of a sarcomere
- A band
- I band
- H zone
- M line
- Z disc
A band
- region of the sarcomere that contains the myosin (thick filament) and overlapping part of actin
- dark
- has no change in length during contraction
I band
- region of the sarcomere that contains the actin filaments and actin filaments of adjacent sarcomeres
- light
- changes in length during contraction
H zone
- light central region of the A band that only consists of the myosin
- changes in length during contraction
M line
protein meshwork in the H zone that keeps the thick filaments aligned
Z disc
protein structure in the middle of the I band that serves as an attachment site for one end of thin filaments
how does a contraction occur
- muscle fibers shorten by interactions between thick and thin filaments
- generates tension
motor unit
a single motor neuron and the muscle fibers it controls
how many muscle fibers does a single motor unit control
typically controls only some
how are the size of motor units related to the degree of control
inversly
all or none principle
- muscle fibers contract completely or not at all
- if a motor unit is stimulated all fibers under its control will contract not just some
muscle tone
constant tension ina resting muscle
how do muscles avoid fatigue
- motor units are stimulated randomly
- a few at first then rotates with other motor units
what are the two types of muscle contractions
isometric and isotonic
isometric contraction
- length is constant, tension is changing
- muscle tension < resistance
isotonic contraction
- tension is constant and length is changing
- muscle tension >= resistance
- concentric and eccentric contraction
concentric contraction
muscle is shortening
eccentric contraction
- muscle is lengthening
- helps to slow down movements
types of skeletal muscle fibers
- slow oxidative (Type I)
- fast oxidative (Type IIa)
- fast glycolytic (Type IIb)
characteristics of Type 1 muscles fibers
- ATP use: slow
- capacity to make ATP: high, aerobic
- colors of fibers: dark red
- contractile velocity: slow
- fiber distribution: found in greatest abundance in muscles of the trunk especially postural muscle
- primary fiber function: endurance
characteristics of Type IIa
- ATP use: fast
- capacity to make ATP: moderate, aerobic
- colors of fibers: lighter red
- contractile velocity: fast
- fiber distribution: found in greatest abundance in muscles of the lower limbs
- primary fiber function: medium duration
characteristics of Type IIb
- ATP use: fast
- capacity to make ATP: limited, anaerobic
- colors of fibers: white
- contractile velocity: fast
- fiber distribution: found in greatest abundance in muscles of the upper limbs
- primary fiber function: short duration, intense movements
how many types of skeletal muscle fibers do muscles normally contain
usually contain all 3 muscle fiber types
how does a single motor unit control other muscle fibers
a single motor unit will control only muscle fibers of the same type
why do slow muscle fibers dominate postural areas
meant for longer duration periods
- postural muscles contract continuously to support body
how are muslce fibers organized
organized into fasicles
what are the different types of fascicle arrangement
- circular
- parallel
- convergent
- pennate
what is a circular fascicle arrangement
fibers arranged concentrically around an opening
what is the function of a circular arrangement
acts as a sphincter to open and close
what is an example of a circular fascicle arrangement
the orbicularis oris muscle
what is a parallel fascicle arrangement
- fascicles are paralllel to the long axis of the muscle
- upon contraction the body of the muscle will increase in diameter
- high endurance position not very strong
what is an example of a parallel fascicle arrangement
rectus abdominus
what is a convergent fascicle arrangement
triangular muslce with a common attachment site
- The direction of the pull can be changed
- does not pull as hard as equal-sized parallel muscle
example of a convergent fascicle arrangement
pectoralis major
what is a pennate fascicle arrangement
- muscle body has I or more tendon
- unipennate, bipennate, and multipennate
how are the fasicles arranged in a pennate arrangement and why
are attached in an oblique angle to a tendon that allows for a harder pull on muscle to occur compared to parallel muscle
- due to the relationship of pull vs stabilize axes
unipennate arrangement
all muscle fibers are on the same side of the tendon
example of a unipennate arrangement
extensor digitorum
bipennate arrangement
muscle fibers on both sides of the tendon
example of bipennate arrangement
rectus femoris
multipennate
tendon branches within muscle
example of a multipennate arrangement
deltoid
muscle atrophy
- wasting of muscle tissue that results in reduction of muscle size, tone, power
- cause by lack of stimulation
sarcopenia
excessive muscle atrophy
muscle hypertrophy
- increase in muscle fiber size, not # of muscle cells
- result of repetitive stimulation of muscle fibers
what occurs as a result of muscle hypertropy
- mitochondria increase in # = increase in ATP
- myofibrils and myofilaments increase in # = increase in muscle size
what are the 3 types of levers
- first class
- second class
- third class
what does the fulcrum represent in a lever
the joint
what does resistance represent in a lever
weight applied
what does effort represent in a lever
the muscle contracting
what is a first class lever
fulcrum is in the middle with weight and effort on the ends
example of first class lever
neck joint performing flexion and extension with the effort being trapezius muscle
what is a second class lever
fulcrum at one end, resistance in middle and effort upwards at the other end
what is an example of a second class lever
the foot
fulcrum: metatarsalphalangeal joint
effort: calf muscle and achilles tendom
resistance the mid foot
what is a third class lever
resistance in further from the fulcrum, effort upwards in the middle and fulcrum at the opposite end
what is the most common type of lever within the body
90% of levers are the third class
which type of lever is the most inefficient
third class
what are the actions of skeletal muscles
agonist
antagonise
synergist
stabilizers
agonist
produces specific movement when it contracts
- the prime mover
antagonist
muscle whose action opposes that of agonist
synergist
muscle that asists agonist in perfomring action
stabilizers
muscle that maintain area position to isolate needed muscles
