Muscular System 2 Flashcards
total tension a fiber can produce depends on:
the rate at which nerve impulses arrive at the neuromuscular junction
The more rapidly a muscle is stimulated, but ______ force it exerts
more
Muscle fibers of a motor unit are dispersed:
throughout the entire muscle
Muscles with precise movements have:
many small motor units
The somatic motor neuron and all the skeletal muscle it stimulates:
Motor Unit
A brief contraction of all the muscle fibers in a motor unit
Twitch Contraction
*A response to a single action potential in its motor neuron
Shows how long a muscle contraction lasts:
Myogram
A twitch lasts:
20-200 msec
the “line” drawn by a myogram is a _____
tracing
Stages of a twitch contraction:
- Latent Period
- Contraction Period
- Relaxation Period
- 2 mseconds
- CA++ are released from the SR and filaments begin to exert tension
- There isn’t a contraction yet
Latent Period
-10-100 mseconds
Contraction Period
- 10-100 mseconds
- CA++ return to SR, which results in relaxation
Relaxation Period
A second stimuli will cause a contraction:
wave summation
*Frequency of stimulation
Stimulation of the skeletal muscle at a rate of 20-30x 1 sec
Unfused Tenanus
- Stimulation rate of 80-100 stimuli/sec
- generate a sustained contraction where individual twitches cannot be discerned
Fused Tenanus
Process by which the number of active motor units is increased
-only some motor units are active at a time to delay the period of muscle fatigue
Motor Unit Recruitment
Why do only some motor units activate at a time?
To delay the period of muscle fatigue
Some involuntary activated motor units that produced sustained contraction of the muscle fibers that generate muscle
Muscle Tone
Contractions that are not long enough to generate actual movement
Muscle Tone
A muscle shortens and pulls on another structure to produce movement
Concentric Isotonic Contractions
The overall length of a muscle increases during a contraction
Eccentric Isotonic Contractions
Tension is generated without shortening the muscles
Isometric Contractions
*Apply Pressure with hands on the table
Muscle fibers differ in the content of _____
myoglobin
*Giving white and red muscle fibers
Skeletal muscle fibers are classified into 3 main types:
- Slow Oxidative
- Fast Oxidative
- Fast Glycolytic
- Are the smallest in diameter
- the least powerful of the muscle fibers
- dark red because they contain large amounts of myoglobin
- They have many mitochondria so they usually generate ATP through aerobic respiration
- Have a low concentration velocity, but rarely fatigue
Slow Oxidative Fibers
- Are Intermediate in diameter
- Have large amounts of myoglobin
- Generate lots of ATP through aerobic respiration and aerobic glycolysis
- Are able to contract at a higher velocity
Fast Oxidative Fibers
The ATPase in the myosin heads hydrolyzes ATP faster than the ATPase in slow oxidative fibers
Fast Oxidative Fibers
- The largest in diameter
- Have the most myofibrils (highest #)
- Can generate the most powerful contractions
- Have low myoglobin content and few mitochondria
- Are white
- Hydrolyze ATP rapidly to help cause fast and strong fiber contraction
Fast Glycolytic Fibers
*Cannot contract for long (not as vascularized)
- Principle tissue of the heart
- Has actin and myosin, banding, and Z discs
- The ends of these cells are attached to subsequent cells through intercalated discs
- Require a constant supply of oxygen
- Mitrochondria are larger
Cardiac Muscle Tissue
- Usually activated involuntarily
- Has thick and thin filaments but they are not arranged in orderly sarcomeres (thus no striations)
- Lack T-Tubules and few SR
- Has two types
Smooth Muscle Tissue
Two types of smooth muscle tissue:
- Visceral Smooth Muscle Tissue
2. Multiunit Smooth Muscle Tissue
Forms parts of walls of arteries and veins and hollow viscera
Visceral Smooth Muscle Tissue
- Made of individual fibers
- found in the walls of large arteries, in airways to lungs, arrector pili, in iris, and the ciliary body
Multiunit Smooth Muscle Tissue
What causes “Muscle Growth” after development?
Due to the increase in size of current muscle fibers
Divide slowly and fuse to existing fibers of damaged fibers
Satellite Cells
Replacement of muscle fibers by fibrous scar tissue
Fibrosis
Additional cells can migrate from ____ to participate in muscle regeneration
red bone marrow
all muscles are derived from the _____
mesoderm
Somites are formed on the:
20th day of development
Paired, blocklike masses of mesoderm, arranged segmentally alongside the neural tube of the embryo, forming the vertebral column and segmental masculature
somites
What do somites form?
- ) vertebral column
2. ) segmental masculature
Around ___, humans begin to loose skeletal muscle mass and it is replaced by fibrous connective tissue and adipose tissue
30
Around age 30, what replaces skeletal muscle?
fibrous connective tissue and adipose tissue
Around age 30, there is a decrease in:
Maximal strength
Why are endurance and strength training programs so effective in older people?
They can slow or reverse age-associated decline in muscular performance
Skeletal muscles work together or in opposition to:
create movement
Muscles only:
pull
What happens when muscles shorten?
The insertion usually moves toward the origin
Whatever a muscle does, another muscle _____
counteracts
Provides the major force for producing a specific movement:
prime movers
oppose a movement
Antagonist
- Add force to a movement
- Reduce undesired or unnessesary movements
Synergists
Synergists that immobilize a bone or muscle origin
Fixator
Bone or body region associated with the muscle
Location of a muscle
*E.g., rectus femoris, temporalis
Deltoid
Shape
Maximus, minimus, longus
Relative Size
Rectus, Transverse, Oblique
Direction of Fibers
biceps and triceps
Number of origins
The point of origin or insertion (e.g., sternocleidomastoid)
Location of Attachments
Flexor/extensor
Action
