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physiology of contraction
what is a motor unit?
a single motor neuron and all of the musce fibers it supplies
what is nerve?
bundle of neurons or bundle of nerve cells
what is neuron?
single nerve cell
what is a muscle twitch?
is motor unit's response to a single to a single AP of its motor neuron
what are the 3 pahses in muscle twitch?
phases of muscle twitch) Latency
-period between the stimulus and initiation of the muscle twitch response
*myogram shows no response
phases of muscle twitch) Contraction (3)
-we have cross bridge connection
-onset of shortening of muscle
-reaches from onset to the peak of power
phases of muscle twitch) relaxation (2)
-calcium reenters the sarcoplasmic reticulum
-cross bridges let go
Is twitch duration the same with all types of muscles?
no, they differ by muscle fiber type
which type of muscles have a faster twitch?
muscles necessary for rapid response
which type of muscle is an exmaple of slow twtich muscles?
(increased muscle tension through graded muscle response) Summation- what is temporal?
increases the rate of stimulus delivery
(increased muscle tension through graded muscle response) summation- tetany?
(increased muscle tension through graded muscle response) what is multiple motor unit summation?
sequentially more motor units are recruited as stimulus intensity increases
*smalled motor units are recruited first followed by larger ones
**end result is smooth, steady increase in force generated
(increased muscle tension through graded muscle response) what is treppe?
warm up effect
(increased muscle tension through graded muscle response) why is treppe important?
as muscle warms up, enzymes become more efficient and stronger contractions occur
(increased muscle tension through graded muscle response) how does treppe differ from temporal summation?
treppe has complete relaxation periods
types of contraction) what is a contraction?
force generated by cross bridges formation
types of contraction) what is the force on object?
types of contraction) what is the weight of object?
types of contraction) what is isotonic contraction?>
types of contraction) 2 types of isotonic?
types of contraction) types of isotonic- concentric
*only type explained by Huxleys theory
types of contraction)types of isotonic- Eccentric
***occurs when we have a heavy object we lifted and then want to st it on a table carefully
*** short to long
***not backed by huxleys
types of contraction) isometric contraction? (2)
types of contraction) example of isometric
get out of chair and push against wall of house
*all of the muscles being used will not shorten or lengthen
types of contraction) isokinetic
-same speed with controlled angular velocity of joint
**ex) these happen in exercise machines
types of contraction) which two contractions are used in everyday lives?
isometric and isotonic
force of contraction) number of fibers and stimuli
temporal summation and recreuitment of fibers
force of contraction) size of muscle
larger the muscle the larger the force
force of contraction) having elastic elements
have to compensate for these structures because they do not contribute to the contraction
4 non-contractile elements of muscle cells?
force of contraction) tension- internal?
need to overcome non-contractile elements
*most of the tension is geared toward picking up the slack of non contractile elements
force of contraction) tension-external?
overcome the actual load
force of contraction) muscle length-length/tension relationship?
the overlap between thick and thin should around 80 to 120 percent of resting sarcomere length.
force of contraction) velocity and duration of contraction- load and duration (3)
the greater the load...
-the less the muscle shortens and
-the shorter the duration of contraction and
-the slower the contraction
force of contraction) velocity and duration of contraction- fiber type- fast glycolytic- 5 characteristics
-not depedent on oxygen
-high glycogen storages
**used for sprinting
force of contraction) velocity and duration of contraction- fiber type- fast oxidative glycolitic- 4 characteristics
-moderate glycogen stores
-some dependence on oxygen stores
force of contraction) velocity and duration of contraction- fiber type- Slow oxidative- 6 characteritics
-lots of myoglobin
-low glycogen stores
-used for endurance
function of smooth muscle
squeezing and pushing of material through a tube
what innervates the smooth muscle?
autonomic nervous system
what are the nerve endings called instead of terminal boutons?
what is the smooth muscles nueromuscular junction called?
histology of smooth muscle) how are the cells connected?
histology of smooth muscle) what surrounds each msucle cell?
histology of smooth muscle) what 2 things differ in sarcoplasmic reticulum of smooth from skeltal?
-it is less well developed
-touches plasma membrane
histology of smooth muscle) what does the plasma memebrane contain?
histology of smooth muscle) what are caveoli?
-cavities that contain calcium
histology of smooth muscle) where is teh calcium stored?
in sarcoplasic reticulum
histology of smooth muscle) does it contain t-tubules?
histology of smooth muscle) what is the ratio of thick to thin?
**skeltal is 1:2
histology of smooth muscle) what are the thick filaments made up off?
histology of smooth muscle) what are thin filaments made up off?
actin and tropomyosin
histology of smooth muscle) how are the thick and thin filaments oriented?
spiral down the long axis of a muscle cell
histology of smooth muscle) AP stimulus (4)
-NT release from bulbous varicosity
-SR receives the stimuls directly
-CA enters the cytoplasm from SR and the caveoli
-contraction can then occcur
histology of smooth muscle)how does AP spread ?
through the gap junctions
mechanism of smooth muscle contraction) 5 steps
-initiated by CA entry into cytoplasm
-CA binds to calmodulin
-calmodulin activates kinase
-kinase trasnfers phosphate to myosin head
-cross bridges form similarly to skeletal muscle
2 types of smooth msucle- single unit (3)
-cells contract as a unit
-gap junctions allow current flow directly
-found in organs
2 type of smooth muscle- multi unit charaterisitics (5)
-muscle cells are independent of one another
-rare gap junctions
-rare spontaneous APs
-respond to hormones
-innervated by autonomic nervous system
examples of multiunit smooth muscle?
-msucles that regulate pupil size, arrector pilli, alrge airways of lungs, and larger arteries
regulation of smooth muscle) What 2 NTs does it use?
regulation of smooth muscle) what 2 things does its receptors do?
either inhibit or excite
*depedning on organ system the receptor will increase or decrease contraction
**ex) when resting smooth msucle can increase contractions, when running they can inhibit contractions
regulation of smooth muscle) stretching?
when stretched, mre vigorous contractions occur
regulation of smooth muscle) hormone and local factors?
it depends on the receptors, which will dictate if they are going to be stimuate of inbit
unique features of smooth muscle) length tension
when stretching, it stimulates contraction
unique features of smooth muscle) hyperplasia
increase # of cells
unique features of smooth muscle) secretion (2)
-secretes elastin and collagen of connective tissues