Muscle Physiology

Front 1

Muscle System
~Functions (hint 3)

Back 1

~ motion,
~ maintenance of posture & joint stability
~ Heat Production

Front 2

Characteristics of Muscle:

Back 2

~ Excitability
~ Contractility
~ Extencibility
~ Elasticity

Front 3

Types of Muscle:

Back 3

~ Skeletal;stiated, voluntary
~ smooth; non-striated, involuntary
~ Cardiac; stiated, involuntary

Front 4

1 contractile unit =

Back 4

~ a sarcomere; this is from z line - z line

Front 5

Myosin has a binding site for
what?

Back 5

~ myosin has a binding site for actin

Front 6

Troponin has a binding site for?
~ also, troponin is a 3 subunit

Back 6

~ For Ca++

Front 7

Tropomyosin is a what type of filament ?

Back 7

Thin filament which runs along the F-actin and covers the binding site on the actin molecule

Front 8

Sarcoplasmic Reticulum:

Back 8

~Smooth ER in the muscle cell that stores Ca++
~ contains VOLTAGE SENSITIVE CA++ PUMPS

Front 9

T-Tubules- Transverse Tubules:

Back 9

~ Extensions of the Sarcolemma(Plasma Membrane) that are open to the outside
~ Runs transversley thru the muscle fiber

Front 10

Sliding Filament Theory of Muscle Contaction:
Thick and thin myofilaments
Requires three things in order to contract : ?

Back 10

~ Thick and Thin myofilaments
~ ATP
~ Calcium ions

Front 11

Contraction Cycle 2 Phases :

Back 11

~Phase one: Attach Stroke
requires CA++
~ Phase TWO: Release Cock
requires ATP

Front 12

Myosin has two binding sites:

Back 12

~ 1 st spot is for ATPase
~ 2nd Actin

Front 13

~ Major Events of Contraction
~ Steps 1-6 are ?

Back 13

Step 1:Skeletal Musc. stimulated via Nerve Impulse
Step 2:AP spreads over surface of muscle membrane
Step3: AP moves down into muscle fiber along T- Tubules
Step4: Depolarized T-Tubulesrelease of CA++ from SR
Step 5: CA++ TRIGGERS sliding of fillaments [ Contraction]
Step6: Relaxation occurs from ACTIVE TRANSPORT of CA++ back into SR

Front 14

~ End Plate Potential ( EPP)
Muscle Stim. Via Nerve Impulse:

Back 14

~ STEP 1- AP travels down from CNS along motor axon, releases ACh into synaptic cleft
~ STEP2- ACh binds to ACh receptors on muscle membrane called MOTOR END Plate
~ STEP3- OPENS Na+ gates INFLOW of NA+ Depolarization Event called End Plate Potential (EPP)
~ STEP 4- EPP, Threshold, AP across muscle membrane
~STEP5- ACh is Deactivated by AChase
located in muscle membrane

Front 15

~ Sliding Filament s CONTRACTION:

Back 15

1. CA++ binds to Troponin
2. Troponin changes shape> PULLS Tropomyosin OFF actin binding sites
3. Energized (ATP-bound) Myosin CROSS-Bridges attach to actin. Triggers release of energy stored in myosin head and allows production of STROKE (angular movement) of the Cross-Bridges.ADP & PO4 are released.
4. New ATP binds to myosin head > release.

Front 16

Regulation of Contraction
~ Muscle Cell Stimulation:

Back 16

~ ALWAYS With a Nerve Fiber(skeletal, smooth, cardiac)
~ Via hormones & or local chemical agent(smooth/cardiac
~ Spontaneous electrical activity within the membrane:(smooth, cardiac: within the walls the heart
~ Via MECHANOSENSITIVE RECEPTORS

Front 17

~ ALL NMJ's are ?

Back 17

~ EXCITATORY ~
~ ONLY ONE PER Muscle cell /fiber per skeletal muscle fiber

Front 18

~ MoTOR Unit:

Back 18

~ a motor unit is a motor neuron and all the muscle fibers it innervates
~Motor responces can be " graded" by special types of motor units
~ Fibers of one motor unit are scattered throughout the muscle- NOT ADJACENT to eachother
~ Motor units vary in the # of musc. fibers and SIZE of fibers
~ Small m. unots have FINER fibers & are more easily stimulated
~ Larger m. units have THICKER FIBERS

Front 19

~ CODING of SKELETAL MUSCLE CONTRACTION :

Back 19

~ To execute a specific response, THE MOTOR CORTEX CONTROLS: AMOUNT of FORCE developed-via # of motor units ativated
~ The maintenamce of sustained force or " MUSCLE TENSION" Via the Frequency of AP & asynchronous motor unit activation

Front 20

~ Excitation- Contraction Coupling: What is it ?

Back 20

~ Process by w/c the AP in the Sarcolemma triggers OFF the Sequence of events leading to CROSS-Bridge activity and CONTRACTION

Front 21

MUSCLE RELAXATION:

Back 21

~ Results of ATP/CA2++ PUMPS ACTIVELY TRANSPORTING CA2++ back into SR AGAINST it's concentration gradient

Front 22

ROLE of ATP in the Muscle Contraction:

Back 22

~ During the contraction cycle-binding of ATP allows for the release of ACTIN from MYOSIN
~ATP used to actively transport CA++ back into the SR to allow for RELAXATION of the muscle
~ A relative deficit of ATP may lead to a mechanical fatigue. DECLINE IN MUSCLE TENSION
~ SECONDARY BY O2 delivery or nutrients

Front 23

What are Thick and thin myofilaments ?

Back 23

~ Thick are composed of Tthe protein, Myosin
~ myosin heads contain an actin binding site and an ATpase
~ Thin myofilaments: composed of the protein, F-actin along with 2 regulatory proteins, Troponin and Tropomyosin

Front 24

Troponin composed of 3 subunits :

Back 24

~ Which Bind to actin and tropomyosin along w/a binding site for Ca++ ion

Front 25

Tropomyosin:

Back 25

~ runs along the F-actin and covers the myosin binding site on the actin molecules

Front 26

F-actin :

Back 26

~ HELICAL CHAIN of G-actin units, with each containing a myosin binding site

Front 27

Myofibrils are bundels of myofilaments:

Back 27

~ each muscle fiber may contain 100's to 1000's of myofibrils
~ myofibrils may comtain up to 2500 myafilaments
~ each myofibril is partitioned into repeating units called sarcomeres

Front 28

Sarcomeres:

Back 28

~Repeating stuctural CONTRACTILE units of a myofibril

Front 29

Striations:

Back 29

~ Banding of myofibrils due to THICK and THIN myofilament arrangement in each sarcomere

Front 30

The Sliding Filament Model of Muscle Contraction:
Explain WHAT is Happening, in GENERAL !

Back 30

~ During shortening of muscle, the thin filaments within the myofibrils slide over the thick filaments

Front 31

What 3 things are needed for a contaction to occur ?

Back 31

~ Thick and Thin myofilaments
~ ATP
~ Calcium ions

Front 32

Functions of ATP:

Back 32

~ During the contractile cycle, binding of ATP allows for the Release of actin from myosin, as well as, the energy stored/released in the cock/stroke phases
~ ATP used to actively transport Ca++ back into the SR to allow for relaxation of the muscle

Front 33

Neuromuscular Junctions
(NMJ's)

Back 33

~ Area of contraction between a motor neuron and a muscle cell including the axon terminal and the motor end-plate
~ Most NMJ's are in the MIDDLE of a muscle fiber therefore, AP moves over entire muscle fiber in BOTH directions
~ ALL NMJ's are EXCITATORY; only one NM junction per muscle fiber
~ motor end-plate cont's: ACh receptors, ACHase molecules, Na+ chemical regulated gates
~ end-plate potential (EPP) is a GRADED response of HIGH MAGNITUDE ( one EPP may generate an action potential)

Front 34

What 3 things are needed for a contaction to occur ?

Back 34

~ Thick and Thin myofilaments
~ ATP
~ Calcium ions

Front 35

Functions of ATP:

Back 35

~ During the contractile cycle, binding of ATP allows for the Release of actin from myosin, as well as, the energy stored/released in the cock/stroke phases
~ ATP used to actively transport Ca++ back into the SR to allow for relaxation of the muscle

Front 36

Neuromuscular Junctions
(NMJ's)

Back 36

~ Area of contraction between a motor neuron and a muscle cell including the axon terminal and the motor end-plate
~ Most NMJ's are in the MIDDLE of a muscle fiber therefore, AP moves over entire muscle fiber in BOTH directions
~ ALL NMJ's are EXCITATORY; only one NM junction per muscle fiber
~ motor end-plate cont's: ACh receptors, ACHase molecules, Na+ chemical regulated gates
~ end-plate potential (EPP) is a GRADED response of HIGH MAGNITUDE ( one EPP may generate an action potential)