Muscle Tissue Flashcards
Cardiac muscle
- short, branched, and striated (usually have one nucleus)
- cells connected by intercalated discs
- have a pacemaker
- are involuntary
- can not regenerate
intercalated discs
where cardiocytes interlock and contain the gap junctions permit electrical coupling of cells
what is important about the nervous system on the pacemaker cells of the cardiac muscle
the nervous system can alter the rate in which the pace maker cells fire
smooth muscle
- short spindle shaped cells and non striated (usually one central nucleus)
- small cells with tapered ends
- can regenerate
- in the walls of blood vessels, digestive tract, urinary tract etc
- can move things, and regulates the diameter of blood and respiratory vessels
skeletal muscle
- long, cylindrical striated cells with multiple nuclei
- can regenerate with aid of satellite cells
four functions of skeletal muscle
- moves/stabiles the position of the skeleton
- guards the entrances and exits to the digestive, respiratory and urinary tract
- generates heat
- protects internal organs
excitability
ability to respond to stimulation
contractility
the ability to shorten actively and exert a pull or tension that is harnessed by connective tissue
extensibility
the ability to contract over a range of resting lengths
- for example: muscle cell can be stretched to several times its original length and still contract when stimulated
elasticity
the ability of a muscle to return to its original length
fascicles
this is a group of muscle fibers
is surrounded by perimysium
muscle fiber
- this is another term for a muscle cell
- long and cylindrical and span the entire length of the muscle
- this is surrounded by endomysium
myofibrils
cylindrical structures extending the entire length of the muscle fiber
myofilaments
- actin and myosin proteins
- organized into repetitive groupings of sacromeres that extend the length of the myofibril
epimysium
surrounds the entire muscle
perimysium
surrounds the fascles
endomysium
surrounds the muscle fibers
actin
this is the thin filament
myosin
this is the thick filament
sarcomere
this is how myofilaments are organized
-when many shorten together the muscle as a whole contracts
neuromuscular junction
this is where the motor neuron meets the muscle fiber
-where innervation occurs
motor unit
- single motor neuron and the muscle fibers it controls.
- it can innervate multiple muscle fibers
- the more muscle fibers it innervates the larger the motor unit is and the less individual/fine control the body has over it
all or nothing principal
the muscle fiber contracts completely or none at all
-all of the muscle fibers in one motor unit will contract or non at all
what has to happen is an area with small motor units wants to have a large coordinated movement?
Many motor units need to be signaled at once.
where are small motor units typically at?
-eyes, hands, etc
Slow oxidative Fibers (SO)
- these use oxygen as fuel
- these can contract for long periods of time
- these are aerobic and used for endurance
- have the greatest number of capillaries (blood supply)
fast oxidative fibers (FO)
these are intermediate fibers
Fast glycolytic fibers (FG)
- these are anaerobic, instantaneous power
- not for long periods of time
Every muscle has what type of fiber
every muscle has all three types of fibers but the ratio changes depending on which muscle you are looking at
-additionally different people will have different ratios when looking at the same muscle on both
muscle atrophy
this is a reduction in muscle size, tone, and power
-can be caused by lack of stimulation and happens with aging
muscle hypertrophy
- this is the increase of the size of the muscle fiber.
- the fiber itself gets bigger by the addition of more myofibrils and myofilaments but there is NOT an increase in the number of fibers.
What are the four main fascile arrangements?
- parallel
- convergent
- pennate
- circular
Parallel fibers
- all fibers run in one direction
ex. biceps, abs
convergent fibers
fanned out at the origin but converge at the tendon
-fibers run In different directions and different fibers have different functions due to the different angle and arrangement
pennate fibers
-these have fibers entering a tendon at an angle
-can be unipennate (one angle), bipennate (two angles),
and multipennate (many angels)
what is the benefit of being multipennate
this gives a larger cross-sectional area and increases the strength of the muscle.
circular fibers
there are used to make sphincters
